micro-implants biomechanics a comparative...

MICRO-IMPLANTS BIOMECHANICS – A COMPARATIVE STUDY TO

ASSESS VARIATIONS IN ANTERIOR TOOTH MOVEMENT USING

DIFFERENT HEIGHT OF RETRACTION HOOKS

Dissertation submitted to

THE TAMILNADU DR. M.G.R.MEDICAL UNIVERSITY

In partial fulfillment for the degree of

MASTER OF DENTAL SURGERY

BRANCH V – ORTHODONTICS AND DENTOFACIAL ORTHOPAEDICS

APRIL - 2011

CERTIFICATE

This is to certify that this dissertation titled “MICRO-IMPLANTS

BIOMECHANICS – A COMPARATIVE STUDY TO ASSESS VARIATIONS

IN ANTERIOR TOOTH MOVEMENT USING DIFFERENT HEIGHT OF

RETRACTION HOOKS” is a bona fide record of work done by Dr. RATHI

AMEY JAYANT under my guidance during his postgraduate study period 2008–

2011.

This dissertation is submitted to THE TAMIL NADU Dr. M.G.R.

MEDICAL UNIVERSITY, in partial fulfillment for the degree of Master of Dental

Surgery in Branch V – Orthodontics and Dentofacial Orthopaedics.

It has not been submitted (partially or fully) for the award of any other degree

or diploma.

Acknowledgement

I would l ike to acknow ledge and thank my beloved Professor and Head, Dr. N.R.

KRISHNASWAMY, M .D . S . , M .O r t ho ( RC S, E d i n ) , D . N .B . ( O r t ho ) , D i p lom a t o f I nd i an bo a rd o f

O r t h o d o n t i c s , Department of Orthodont ics, Ragas Dental Col lege and Hospital , Chennai. I

cons ider myself extremely fortunate to have had the oppor tun ity to t rain under h im. His

enthusiasm, integral view on research, t ireless pursuit for perfection and mission for providing

‘high quality work’, has made a deep impression on me. He has always been a source of

inspiration to strive for better not only in academics but also in life. His patience and technical

expertise that he has shared throughout the duration of the course has encouraged me in many

ways.

I would l ike to express gratefulness to my respected guide, Professor Dr. ASHWIN

GEORGE, M . D . S D . N . B . ( O r t h o ) , D i p l o m a t o f I n d i a n b o a r d o f O r t h o d o n t i c s , for his undying

enthusiasm and guidance which helped me complete this study. His everlasting inspirat ion,

incessant encouragement, construct ive cri t icism and valuable suggestions conferred upon me

have encouraged me. He has been an integral part of my post graduate course during which I

have come to know his outlook towards l ife and wish to inculcate it someday.

I e x p r e s s m y d e e p s e n s e o f g r a t i t u d e a n d i n d e b t e d n e s s t o P r o f e s s o r , Dr. S.

VENKATESWARAN, M.D.S. D .N.B. (Or tho) , Dip l omat o f Ind ian board o f Or thodont ics , f or always

being a pi l la r of suppor t and encouragement . H is s imp l ic i ty, i nnovat ive approaches and

impetus throughout the duration of my course has encouraged me in many ways. He has helped

me to tune myself to the changing environment in our profession and his guidance wil l a lways

be of paramount importance to me.

M y s i n c e r e t h a n k s g o o u t t o P r o f e s s o r Mr. KANAKARAJ C h a i r m a n e t Dr.

RAMACHANDRAN, Pr inc ipa l , Ragas Denta l Col lege for prov id ing me with an oppor tun i t y

to ut il ize the faci l it ies avai lable in this institut ion in order to conduct this study.

I would also l ike to acknowledge Dr. SHAHUL,( Asso . P ro fessor ) , Dr. JAYAKUMAR

( R e a d e r ) , Dr. ANAND ( R e a d e r ) , Dr. SHAKEEL ( R e a d e r ) , Dr. REKHA, Dr. RAJAN, Dr.

SHOBANA, Dr. PRABHU and Dr. BIJU fo r the i r s uppor t , ent hus iasm et prof es s i ona l

assistance throughout my post graduate course.

M y h ea r t f e l t t h a nk s t o m y w o n d e r f u l b a t c h m a t es , Dr. Goutham Kalladka,

Dr.Shailendra Vashi, Dr. Fayyaz Ahmed, Dr. Kavitha Iyer, Dr. Subu Thomas, Dr. Geetha T,

Dr. Ritika Kailey, who were cheer ful ly avai lable at a l l t imes to help me. I wish them a

successful career ahead.

I also extend my grat itude to my juniors Dr. Ayush, Dr. Ashwin, Dr. Sheel, Dr.

Sreesan, Dr. Vinoth, Dr. Saravanan, Dr. Sabitha, Dr. Mahalaxmi, Dr. Vijayshri Shakti, Dr.

Deepak, Dr. Ashwin, Dr. Ravanth K, Dr. Siva S, Dr. Manikandan, Dr. Noopur Aarthi, Dr.

Vijay Anand for lending me their patients and their support.

I thank Mr. Bhoopathi K , for helping me with the statistical analysis and Mr. Ashok,

Mr. Rajendran and Mr. Kamaraj for helping me with the photographs.

I would like to thank Sister Lakshmi, Sister Rathi, Sister Kanaka, Ms. Haseena, Mr.

Mani, Mr. Bhaskar, Ms. Shalini, and Ms. Divya for their co-operation and help during my

course.

And to My parents, I am forever indebted. They have always been there to show me the

right path and to correct me when I have strayed. Life, as I see it is only because of the love,

guidance and support they have given me. I would l ike to thank my beloved wife Dr. Shipra

Rathi, for her support and understanding.

Last but not the least ; I would l ike to thank GOD for guiding me through this chapter

of my life.

CONTENTS

Title Page Number

1. Introduction 1

2. Review of Literature 4

3. Materials and Methods 49

4. Results 58

5. Discussion 63

6. Summary and Conclusion 71

7. Bibliography 73

Introduction

Introduction

1

INTRODUCTION

Absolute anchorage represents a new orthodontic paradigm and it may be the

most important advancement in recent times, because it offers the orthodontics of

“action without reaction", practically eliminating the third principle of Newton.

Although extraoral appliances like head gears have proved its worth, patient

compliance is very susceptible and intra-oral appliances like TPA cannot be

considered as a source of absolute anchorage [there is bound to be anchor loss].

Over the past years, orthodontic micro-implants have become a standard in

modern orthodontic practice, and the ability to move teeth in a never-before fashion

has been demonstrated in many articles. Therefore, it appears that there are great

benefits to this new treatment approach.

The efficacy of micro-implants has proven itself indispensible in the

orthodontic armamentarium, because orthodontist have realized that no current intra

oral treatment philosophy, no matter how intelligent and complicated it be, cannot

prevent all reciprocal effects, and this is one area where the micro-implants stands

out. Among the newer concepts introduced to the fraternity in the latter half of this

decade, micro-implants have definitely proved its worth.

Introduction

2

The simplicity of the clinical procedure involved in the placement of the

micro-implant has rendered it a popular choice of orthodontists, which in turn has

facilitated its rise in clinical practice these days. However, clinicians are in complete

ignorance of the variations in the biomechanical principles of tooth movement when

using micro-implants.

The very fact micro-implants come under the category of stationary

anchorage, should make one question the considerable variations involved when

compared to conventional modes of anchorage using the dentition. Another important

factor to be considered is that micro-implants are placed at various heights in the

alveolus. This variation in change in the height of placement, in relation to the center

of resistance of the dentition as a whole, and an individual tooth, would definitely

bring about changes in its biomechanical principles. Thus the biomechanics involved

with micro-implants is quite different and challenging when compared to

conventional biomechanics, a fact which cannot be ignored.

This study was therefore undertaken while considering such biomechanical

variations and the concept of changing the height of the retraction hook to bring about

different types of anterior teeth retraction depending on the clinical needs.

Finite element studies have shown conflicting reports with regards to the

concept of varying height of retraction hook, when using micro-implants for the

purpose of anterior teeth retraction

Hee-Moon Kyung et al 37 used different anterior hook heights from 2mm to

6mm and showed that when the micro-implant height was 8mm and the anterior hook

Introduction

3

height was 2mm, the anterior teeth were tipped lingually, but on the contrary when the

anterior hook height was long more of bodily tooth movement occurred.

Sang-Jin Sung et al 67 showed contradictory results, they found no bodily

retraction of anterior teeth in high mini implant traction with 8-mm anterior retraction

hook condition, after applying retraction force vector above the center of resistance of

six anterior teeth.

Therefore this in-vivo study was done to bring about conclusive evidence with

regard to the contradictory finite element reports, which could be of substantial

implication for a practicing orthodontist.

AIMS AND OBJECTIVES:

a) To determine the optimum height of the retraction hook when bringing about

anterior tooth retraction.

b) To evaluate the feasibility of such variations in clinical practice.

Review of Literature

Review Of Literature

REVIEW OF LITERATURE

IMPLANTS USED IN RETRACTION

Kim CN 37 (2003) The purpose of this FEM study was to investigate the micro-

implant height and anterior hook height to prevent maxillary six anterior teeth from

lingual tipping and extruding during space closure. Bracket was .022" x .028" slot size

and attached to tooth surface. Wire was .019" x .025" stainless steel and .032" x .032"

stainless steel hook was attached to wire between lateral incisor and canine. The

heights of them were 4, 6, 8, 10mm starting from wire. They analyzed initial

displacement of teeth by various force application points, applying force of 150gm to

each micro-implant and anterior hook. The conclusions of this study are as follows: 1.

when the micro-implant height was 4mm and the anterior hook height was 5mm and

below, anterior teeth were tipped lingually. When the anterior hook height was 6mm

and above, anterior teeth were tipped labially. 2. When the micro-implant height was

6mm and the anterior hook height was 5mm and below, the anterior teeth were tipped

lingually. When the anterior hook height was 6mm and above, the anterior teeth were

tipped labially. But lingual tipping of anterior teeth decreased and labial tipping

increased when the micro-implant height was 6mm, compared with 4mm micro-

implant height. 3. When the micro-implant height was 8mm and the anterior hook

height was 2mm, the anterior teeth were tipped lingually. When the anterior hook

height was 3mm and above, labial tipping movement of the anterior teeth increased

proportionally.4. When the micro-implant height was 10mm and the anterior hook

height was 2mm and above, labial tipping of the anterior teeth increased


5

proportionally. 5. As the anterior hook height increased, anterior teeth were tipped

more labially. But extrusion occurred on canine and premolar area because of the

increase of wire distortion. 6. Movement of the posterior teeth was tipped distally

during maxillary six anterior teeth retraction using micro-implant because of the

friction between bracket and wire.

Sheau Soon Sia 73 (2006) conducted a study to determine the location of centre of

resistance and the relationship between height of retraction force on power arm

(power-arm length) and movement of anterior teeth (degree of rotation) during sliding

mechanics retraction .The results suggested that different heights of retraction forces

could affect the direction of anterior tooth movement. They concluded that the higher

the retraction force was applied, the lower the degree of rotation (crown-lingual

tipping) would be. The tooth rotation was in the opposite direction (from crown-

lingual to crown-labial) if the height of the force was raised above the level of the

centre of resistance .During anterior tooth retraction with sliding mechanics,

controlled crown-lingual tipping, bodily translation movement, and controlled crown-

labial movement could be achieved by attaching a power-arm length that was lower,

equivalent, or higher than the level of the centre of resistance, respectively. The

power-arm length could be the most easily modifiable clinical factor in determining

the direction of anterior tooth movement during retraction with sliding mechanics.

Chung.K.R 18 (2007) this article describes the orthodontic treatment of a 14.5-year-

old girl with severe bidentoalveolar protrusion. Specially designed sandblasted, large-

grit, acid-etched (SLA) orthodontic microimplants (C-implants, C-implant Co, Seoul,


6

Korea) were placed in the alveolar bone in all 4 quadrants to provide anchorage for

en-masse retraction without the help of banded or bonded molars. The

osseointegration potential of these microimplants allows them to resist rotational force

moments and control 3-dimensional movements of the anterior teeth during retraction.

Facial aesthetics improved for the patient, fullness of the upper and lower lips was

reduced, and the interdental relationship was corrected. Biomechanical

considerations, efficacy, and potential complications of the treatment technique are

discussed.

Barlow M 2 (2008) reviewed recent literature to determine strength of clinical

evidence concerning the influence of various factors on the efficiency (rate of tooth

movement) of closing extraction spaces using sliding mechanics .Of these ten trials on

rate of closure, two compared arch wire variables, seven compared material variables

used to apply force, and one examined bracket variables. Other articles which were

not prospective clinical trials on sliding mechanics, but containing relevant

information were examined and included as background information. The results of

clinical research support laboratory results that nickel-titanium coil spring produce a

more consistent force and a faster rate of closure when compared with active ligatures

as a method of force delivery to close extraction space along a continuous arch wire;

however, elastomeric chain produces similar rates of closure when compared with

nickel-titanium springs. Clinical and laboratory research suggest little advantage of

200 g nickel-titanium springs over 150 g springs. More clinical research is needed in

this area.


Mimura H. 57 (2008) conducted a study to describe the treatment of severe

bimaxillary protrusion with the aid of miniscrews and to discuss the complications

encountered during treatment. Following extraction of the four first premolars,

miniscrews were placed bilaterally in both jaws to permit maximum retraction of the

anterior teeth, and intrusion of the posterior and upper anterior teeth. The mandible

rotated forward and upward, the face height reduced and the facial aesthetics

improved. During treatment an irregular ridge of bone developed labial to the upper

incisors, bone was deposited in the incisive fossae and the apices of the upper incisors

were resorbed. They concluded that absolute anchorage provided by miniscrews may

become an effective alternative to orthognathic surgery for treatment of severe

bimaxillary protrusion. During extensive retraction, the teeth may contact structures

not normally encountered during conventional orthodontic treatment.

Tae-Woo Kim 39 (2008) in their study have used miniscrews for anterior retraction

with sliding mechanics. They have found that using conventional anchorage causes

the molar to move forward by 3.6-3.8mm and also causes the anterior and posterior

segments to rotate around the centre of rotation causing bowing of the archwire. They

have suggested that the use of miniscrews produces a force which is not reciprocal

hence avoiding the bowing effect .They have also recommended the use of short

hooks (2-3mm) on the archwire in open bite cases and long hooks (10mm) for

translator movement of anterior teeth.

Madhur Upadhyay 78 (2008) conducted a study to determine the efficiency of

mini-implants as intraoral anchorage units for en-masse retraction of the 6 maxillary


8

anterior teeth when the first premolars are extracted compared with conventional

methods of anchorage reinforcement.: In the first group (G1), mini-implants were

used for en-masse retraction; in the second group (G2), conventional methods of

anchorage preservation were followed. They concluded that Mini-implants are

efficient for intraoral anchorage reinforcement for en-masse retraction and intrusion

of maxillary anterior teeth. No anchorage loss was seen in either the horizontal or the

vertical direction in G1 when compared with G2. However, a statistically significant

decrease in intermolar width was noted in G1.

Upadhyay M 79 (2009) conducted a study to examine the skeletal, dental, and soft

tissue treatment effects of retraction of maxillary anterior teeth with mini-implant

anchorage in non-growing Class II division 1 female patients. Twenty-three patients

(overjet > or =7 mm) were selected on the basis of predefined selection criteria.

Treatment mechanics consisted of retraction of anterior teeth by placing mini-

implants in the interdental bone between the roots of the maxillary first molar and

second premolar. The upper anterior teeth showed significant retraction (5.18 +/- 2.74

mm) and intrusion (1.32 +/- 1.08 mm). The upper first molar also showed some distal

movement and intrusion, but this was not significant. They concluded that mini-

implants provided absolute anchorage to bring about significant dental and soft tissue

changes in moderate to severe Class II division 1 patients and can be considered as

possible alternatives to orthognathic surgery in select cases.

Kuroda S 43 (2009) in this study, they compared treatment outcomes of patients with

severe skeletal Class II malocclusion treated using miniscrew anchorage (n = 11) or


9

traditional orthodontic mechanics of headgear and transpalatal arch (n = 11). Both

treatment methods, miniscrew anchorage and headgear, achieved acceptable results as

indicated by the reduction of overjet and the improvement of facial profile. However,

incisor retraction with miniscrew anchorage did not require patient cooperation to

reinforce the anchorage and provided more significant improvement of the facial

profile than traditional anchorage mechanics (headgear combined with transpalatal

arch). They concluded that orthodontic treatment with miniscrew anchorage is simpler

and more useful than that with traditional anchorage mechanics for patients with Class

II malocclusion.

Martins RP 53 (2009) The objective of this study was to analyze rates of canine

movement over the first 2 months of continuous retraction, when rate changes are

expected. Ten patients with bone markers placed in the maxilla and the mandible had

their canines retracted over a 2-month period. Retraction was accomplished with beta-

titanium alloy T-loop springs. The maxillary cusp was retracted 3.2 mm, with less

movement during the first (1.1 mm) than during the second 4 weeks (2.1 mm). The

maxillary apices did not move horizontally. There were no significant vertical

movements in the cusps and apices of the maxillary canines. The mandibular cusp

was retracted 3.8 mm-1.1 mm during the first and 2.7 mm during the second 4 weeks.

The mandibular apices were protracted 1.1 mm. The cusps and apices were intruded

0.6 and 0.7 mm, respectively. The only difference between jaws was the greater

protraction of the mandibular apices during the second 4 weeks and in overall

movement. They concluded that the rate of canine cusp retraction was greater during

the second than the first 4 weeks. The mandibular canines were retracted by


10

uncontrolled tipping whereas the maxillary canines were retracted by controlled

tipping.

Sia S 71 (2009) This study was designed to determine the optimum vertical height of

the retraction force on the power arm that is required for efficient anterior tooth

retraction during space closure with sliding mechanics. Three adults (1 man, 2

women) with Angle Class II Division 1 malocclusions were selected for this study. In

each subject, the maxillary right central incisor was the target tooth. The tooth's

motion trajectories on the midsagittal plane were studied. The location of the centre of

rotation of the target tooth varied according to the different heights of the retraction

forces. Controlled anterior tooth movement (ie, lingual-crown tipping, lingual-root

movement) can be predicted, simulated, or even manipulated by different heights of

retraction forces on the power arm in the sliding mechanics force system. A power

arm length of 3 to 5 mm is estimated to produce controlled lingual-crown tipping

(with the apex as the centre of rotation) for efficient anterior tooth retraction during

sliding space closure in adults with Angle Class II Division 1 malocclusion. They

concluded that knowing and applying the correct height of retraction force on the

power arm is the key to efficient anterior tooth retraction.

Ghouse B A 25 (2010) The purpose of this study was to measure and compare the

difference between rate of en-masse retraction with mini-implant and molar

anchorage. The study consisted of 14 patients (all females) randomized into 2 groups.

Seven in group I (nonimplant) molar was used as anchor for en-masse retraction of


11

anterior teeth. In group II (implant), mini-implant of 1.3mm diameter and 8mm length

was used as anchorage to retract the anterior teeth, which were immediately loaded

with force of 2N. In both groups, all first premolars were extracted. Rate of retraction

and anchor loss were measured by using pterygoid vertical in maxilla. The stability of

surgical steel in this study was 71.4%. Mini-implants provided absolute anchorage in

patients requiring maximum anterior retraction. No differences in the mean retraction

time were noted between 2 groups.

Sang-Jin Sung 67 (2010) This study was a finite element analysis to examine

effective en-masse retraction with orthodontic mini-implant anchorage. Base models

were constructed from a dental study model. Models with labially and lingually

inclined incisors were also constructed. The center of resistance for the 6 anterior

teeth in the base model was 9 mm superiorly and 13.5 mm posteriorly from the

midpoint of the labial splinting wire. The working archwires were assumed to be

0.019 X 0.025-in or 0.016 X 0.022-in stainless steel. The amount of tooth

displacement after finite element analysis was magnified 400 times and compared

with central and lateral incisor and canine axis graphs. The tooth displacement

tendencies were similar in all 3 models. The height of the anterior retraction hook and

the placement of the compensating curve had limited effects on the labial crown

torque of the central incisors for en-masse retraction. The 0.016 X 0.022-in stainless

steel archwire showed more tipping of teeth compared with the 0.019 X 0.025-in

archwire. For high mini-implant traction and 8-mm anterior retraction hook condition,


12

the retraction force vector was applied above the center of resistance for the 6 anterior

teeth, but no bodily retraction of the 6 anterior teeth occurred.

STABILITY OF MICRO-IMPLANTS

Heidemann W 28 (1998) The aim of his study was to enlarge the drill size up to a

critical pilot hole size, exceeding of which leads to a rapid decrease of the screw's

holding power. Titanium screws of diameter 1.5 and 2 mm were inserted in discs of

PVC, wood and porcine mandibular bone with different thickness between 2 to 4 mm,

using pilot hole sizes of 66-95% of the screw's external diameter. The maximum

torque was recorded and pull-out tests were performed. A multiphase regression

analysis was performed to calculate the critical pilot hole size (CPHS). In torque

measurements, the CPHS of microscrews were between 83% and 85% of screw outer

diameter (SOD) and the CPHS of miniscrews were between 80% and 90% of SOD. In

pull-out analysis the CPHS of microscrews were between 83% and 89% of SOD and

the CPHS of miniscrews were between 79% and 91% of SOD. The CPHS was thus

found to be around 85% of the screw's external diameter. He concluded that up to this

critical point the pilot hole size may be increased without affecting the holding power

of the screws.

Douglas 40 (2003)conducted a study that hypothesizes that early loading (decreased

implant healing time) leads to increased bone formation and decreased crestal bone

loss. Radiographic and histological assessments were made of the osseointegrated

bone changes for 3 healing times (between implant insertion and loading), following 5


13

months of loading. The effect of loading on crestal bone loss depended on the healing

time. Early loading preserved the most crestal bone. Delayed loading had significantly

more crestal bone loss compared with the non-loaded controls (2.4 mm vs. 0.64 mm).

The histological assessment and biomechanical analyses of the healing bone

suggested that loading and bioactivities of osteoblasts exert a synergistic effect on

osseointegration that is likely to support the hypothesis that early loading produces

more favourable osseointegration.

Liou E J 49 (2004) conducted a study to determine whether the miniscrews are

absolutely stationary or move when force is applied. Sixteen adult patients with

miniscrews (diameter = 2 mm, length = 17 mm) as the maxillary anchorage were

included in this study. Miniscrews were inserted on the maxillary zygomatic buttress

as a direct anchorage for en masse anterior retraction. Nickel-titanium closed-coil

springs were placed for the retraction 2 weeks after insertion of the miniscrews.

Cephalometric radiographs were taken immediately before force application (T1) and

9 months later (T2).The miniscrews were also evaluated clinically for their mobility

(0: no movement, 1: < or = 0.5 mm, 2: 0.5-1.0 mm, 3: >1.0 mm).On average, the

miniscrews tipped forward significantly, by 0.4 mm at the screw head. The

miniscrews were extruded and tipped forward (-1.0 to 1.5 mm) in 7 of the 16 patients.

He concluded that miniscrews are a stable anchorage but do not remain absolutely

stationary throughout orthodontic loading. They might move according to the

orthodontic loading in some patients.


14

Oyonarte R 63 (2005) conducted a study of bone response to orthodontic loading and

compared it histomorphometrically around 2 different types of osseointegrated

implants (porous surfaced and machined threaded) to determine their suitability for

orthodontic anchorage. Five beagles each received 3 implants of each design in contra

lateral mandibular locations. After a 6-week initial healing period, abutments were

placed, and, 1 week later, the 2 mesial implants on each side were orthodontically

loaded for 22 weeks. Porous-surfaced implants had higher marginal bone levels and

less relative implant displacement than threaded implants. They concluded that

differences in implant surface design can lead to differences in peri-implant bone

height and bone-to-implant contact. Porous-surfaced implants might be successful as

orthodontic anchorage units.

Lang NP 51 (2006) conducted a study to investigate the significance of the initial

stability of dental implants for the establishment of osseointegration in an

experimental capsule model for bone augmentation. Sixteen male rats were used in

the study. In each rat, muscle-periosteal flaps were elevated on the lateral aspect of

the mandibular ramus on both sides, resulting in exposure of the bone surface. On one

side of the jaw, the implant was placed through the hole in such a way that its apex

did not make contact with the mandibular ramus (test). This placement of the implant

did not ensure primary stability. On the other side of the jaw, a similar implant was

placed through the hole of the capsule in such a way that contact was made between

the implant and the surface of the ramus (control). This provided primary stability of

the implant. After placement of the implants, the soft tissues were repositioned over

the capsules and sutured. The findings of the present study indicate that primary


15

implant stability is a prerequisite for successful osseointegration, and that implant

instability results in fibrous encapsulation, thus confirming previously made clinical

observations.

Wilmes B 85 (2006) conducted a study to quantitatively analyze the factors

influencing primary stability: bone quality, implant-design, diameter, and depth of

pilot drilling. To determine the primary stability, they measured the insertion torque

of five different mini-implant types (tomas-pin [Dentaurum, Ispringen, Germany] 08

and 10 mm, and Dual Top [Jeil Medical Corporation, Seoul, Korea] 1.6 x 8 and 10

mm plus 2 x 10 mm). Twenty-five or 30 implants were inserted into each pelvic bone

segment following preparation of the implant sites using pilot drill diameters of 1.0,

1.1, 1.2 and 1.3 mm and pilot drill depths of 1, 2, 3, 6 and 10 mm. He concluded that

compact thickness, implant design and implant site preparation have a strong impact

on the primary stability of mini-implants for orthodontic anchorage. Depending on the

insertion site and local bone quality, the clinician should choose an optimum

combination of implant and pilot-drilling diameter and depth.

Wu JC 90 (2006) conducted a study to evaluate the potential anchorage of bicortical

microimplant for tooth movement. Five bicortical microimplants were inserted in the

interradicular area of the second premolar (P2) in one side of the mandible (test side),

5 monocortical microimplant in the contra lateral region (control side) in 5 beagle

dogs. A total of 100 g force was generated between the implant and the fourth

premolar (P4) in two sides. Analysis showed no difference of the BIC between the

bicortical microimplants and the monocortical microimplants. The bicortical


16

microimplant may be used as orthodontic anchorage for mesial movement of posterior

tooth.

Wu J 89 (2006) conducted a study to evaluate the stability of mini-screw implant

during different healing periods in the unloaded conditions. Sixty titanium mini-

screws were used in this study. He concluded that the Fourth-week is a critical time

point in the progress of osseointegration. Within 8 weeks of healing process, the

stability of implant was significantly correlated with healing time.

Motoyoshi M 61 (2007) conducted a study to examine the relationship between

cortical bone thickness, inter-root distance (horizontal space), distance from alveolar

crest to the bottom of maxillary sinus (vertical space) at the prepared site, and implant

placement torque and the success rate of mini-implants placed for orthodontic

anchorage. After computerized tomography examination, mini-implants 1.6 mm wide

and 8 mm long were placed in the posterior alveolar bone. The mini-implant was

judged a success when orthodontic force could be applied for at least 6 months

without pain or clinically detectable mobility .A relationship between stability after

implant placement and the width and height of the peri-implant bone was not

demonstrated. They conclude that the prepared site should have a cortical bone

thickness of at least 1.0 mm, and the placement torque should be controlled up to 10

Ncm.

K. Chaddad 9 (2007) in his study evaluated the hypothesis that the surface

characteristics of mini-implants influence their survival rates and permit immediate


17

orthodontic activation. Seventeen machined titanium (MT) and 15 sand-blasted, large

grit acid-etched (SLA) mini- implants were placed in 10 patients. These were

immediately loaded with forces of 50 to 100g for the first 2 weeks; the force was later

increased to 250 g. The patients were examined at 7, 14, 30, 60, and 150 days after

placement. The survival rate appears to be significantly influenced by torque value at

placement. All fixtures with torque values greater than 15 N per centimetre were

successfully loaded immediately compared with mini-implants with less than 15 N

per centimetre, for a survival rate of only 69.2%

José Nibo O. Freire 23 (2007) The purpose of this study was to evaluate the bone

response to statically loaded 2.5-mm diameter mini-implants of 6 and 10 mm lengths

activated after various healing periods in a dog model. Seventy-eight machined-

surface Ti-6Al-4V mini-implants were bilaterally placed in the mandibular premolar

and molar regions of 6 beagle dogs. Experimental mini-implants healing periods of 0

days (immediately activated), 1 week, and 3 weeks were followed by a 12-week load

activation period (250 g between parallel implant pairs). Control (non-loaded) mini-

implant groups were placed for 12 weeks, 3 weeks, and 1 week before the dogs were

killed .The control groups showed classic bone-healing events, and the experimental

groups showed mature bone morphology after 12 weeks in vivo regardless of

placement time before load activation. These results showed that low-intensity

immediate or early orthodontic static loads did not affect mini-implant performance.

Seong-Hun Kim 38 (2007) described a clinical application of a new surgical guide

system that uses cone-beam computed tomography(CBCT) images, an implant


18

positioning program and stereo-lithography to make a surgical guide for accurate

placement of orthodontic mini-implants. In selected patients CBCT image slices for

the posterior maxilla were obtained .The surgical guide was fabricated from the

transported CBCT data. The completed surgical guide was easily placed intra-orally

and permitted simple and rapid placement of the mini-implant. They concluded that a

post placement CBCT demonstrated accurate placement of the min-implant on the left

and a minor discrepancy between the simulated mini-implant position and clinical

position on the right.

Baek SH 4 (2008) conducted a study to determine the difference in the success rate

for two types of oral installed mini-implants (OMIs): one type of initially installed

OMI and a new implant of the same type that is reinstalled. The subjects consisted of

58 patients (19 male, 39 female; mean age = 21.78 +/- 5.85 years) who had received

at least one OMI (self-drilling type, conical shape with 2.0-mm upper diameter and 5-

mm length) in the attached gingiva of the upper buccal posterior regions for

maximum anchorage during en-masse retraction. If an OMI failed, a new one was

immediately inserted in the same area after 4 to 6 weeks or in an adjacent area

immediately. The total number of initially installed OMIs (II-OMI) was 109 and the

total number of reinstalled OMIs (RI-OMI) was 34. He concluded that the success

rate of the II-OMI was not statistically different from that of the RI-OMI. Sex and

ANB angle might be more important factors for better II-OMI results.

Ito Y 32 (2008) conducted a study to explain this discrepancy and to clarify the

relation between RF and histological implant-bone contact, we conducted the present


19

study. A hydroxyapatite-coated implant, 4 mm diameter and 10 mm length, was used.

Twenty-four implants were placed in the tibiae of four mini-pigs. The animals were

sacrificed 1, 2 and 4 weeks after the placement, and the RF of each implant was

measured. Loosening the screw at the neck region of the implant remarkably

decreased RF compared with the screws of the other regions. Correlation between RF

and implant-bone contact, which was measured all around the implant, was not

significant (r=0.221, P=0.299).They concluded that although RF did not correlate

with histological implant-bone contact, the present results demonstrated that a

connection between the implant and bone at the neck region of the implant affects RF

the most effectively, further suggesting the superiority of RFA in the process of

implant treatment and the follow-up. The present results could explain the

discrepancy between RFA and other parameters of implant stability.

Ji GP 34 (2008) conducted a study to summarize the clinical failure rate of 286 self-

drilling microimplant anchorages and to investigate the relationship between the

stability of microimplant anchorages and the patient's gender and age. The failure rate

of 286 self-drilling microimplants placed in the maxillary posterior region for anterior

teeth retraction was analyzed. The difference of failure rates was compared between

male group and female group, as was done between children group and adult group.

Besides, the incidence of failure in both sides of one patient was also compared

between children group and adult group. In this study, the average failure rate of 286

self-drilling microimplants is 17.5%. There is no significant relationship between the

stability of microimplants and gender. It seems more possible for microimplants

placed in children to fail than those in adults.


20

Cheol-Hyun Moon 59 (2008) conducted a study to determine the success rate and the

factors related to the success rate of orthodontic miniscrew implants (OMI) placed at

the attached gingiva of the posterior buccal region. Four hundred eighty OMI placed

in 209 orthodontic patients were examined. The placement site was divided into three

interdental areas from the first premolar to the second molar in the maxilla and

mandible. Dislodgement of the OMI occurred most frequently in the first 1–2 months,

and more than 90% of the failures occurred within the first 4 months. Sex, age, jaw,

soft tissue management, and placement side did not show any difference in the

success rate. Placement site, however, showed a significant difference in the mandible

of adult patients. There was no difference in the success rate in the maxilla. They

concluded that placement site is one of the important factors for success rate of OMI.

Benedict Wilmes 86 (2008) conducted a study to analyze the implant of insertion

angle on the primary stability of mini-implants. A total of 28 Ilium bone segments of

pigs were used.2 different min-implant sizes(dual top screw 1.6mm X 8mm and

2.0mm X 10mm) were inserted at 7 different angles(30°, 40°, 50°, 60° , 70° , 80°

and 90°).The insertion torque was recorded to assess primary stability. The results

indicated that the angle of the mini-implant insertion had a significant impact on

primary stability. The highest insertion torque values were measured at angles

between 60° and 70°.Very oblique insertion angles (30°) resulted in reduced primary

stability .They concluded that to achieve the best primary stability an insertion angle

ranging from 60° and 70° is advisable. If the available space between adjacent roots is


21

small a more oblique direction of insertion seems to be favourable to reduce the

amount of risk contact.

Gracco 26 (2008) conducted a study to analyse the stress distribution developing

around an orthodontic miniscrew(OM) inserted into the maxilla and to determine the

stress field changes for different screw lengths and for different levels of

osseointegration occurring at bone/screw interface. They concluded that photoelastic

analysis showed that stress distribution does not change significantly for moderate

initial orthodontic loads. The optimal screw length seems to be 9 mm, increasing the

screw length to 14mm increases the stress concentration.

Wilmes B 84 (2008) conducted a study to quantitatively analyze the impact of implant

design and dimension on primary stability. Forty-two porcine iliac bone segments

were prepared and embedded in resin. To evaluate the primary stability, we

documented insertion torques of the following mini-implants: Aarhus Screw,

AbsoAnchor, LOMAS, Micro-Anchorage-System, ORLUS and Spider Screw. We

observed wide variation in insertion torques and hence primary stability, depending

on mini-implant design and dimension; the great impact that mini-implant diameter

has on insertion torques was particularly conspicuous. Conical mini-implants

achieved higher primary stabilities than cylindrical designs. They concluded that the

diameter and design of the mini-implant thread have a distinctive impact on primary

stability. Depending on the region of insertion and local bone quality, the choice of

the mini-implant design and size is crucial to establish sufficient primary stability.


22

Leung MT 45 (2008) conducted a study to examine the primary stability of connected

miniimplants and miniplates. Three different skeletal anchorage systems were

investigated: (1) two 1.5 mm diameter cylindrical mini-implants connected with a

0.021 x 0.025 inch stainless steel (SS) wire, (2) two 1.6 mm diameter tapered mini-

implants connected with a 0.021 x 0.025 inch SS wire, and (3) two 2.0 mm diameter

cylindrical mini-implants connected by a titanium locking miniplate. Both the

titanium miniplate and SS wire connection systems showed severe deformation at the

screw head, which broke before the mini-implants failed. This in vitro study

demonstrated that the connection of two mini-implants with a miniplate resulted in

higher pull-out force, stiffness, and yield force to resist pulling force and deformation.

Such a set-up could thus provide a stable system for orthodontic skeletal anchorage.

Ozkan Dilek 21 (2008) conducted a study to measure the primary stability, minimum

placement, and removal torque values of mini dental ımplants which were originally

designed for immediate loading. Therefore, mini dental ımplants (10, 13, 15, and 18

mm length and 1.8 and 2.4 mm diameter) were inserted into nonviable femoral bovine

bone with a physiodispenser which can show the torque values digitally. Finally, 3

related tables were created, which show the match of the 3 different values (primary

stability, placement, and removal torque) for each implant. They concluded that the

selection of the Periotest value ranges and their related placement and removal torque

values should decide for immediate loading of the mini dental implants. Mini dental

implants, which are especially designed for immediate loading, can only be loaded

immediately if their Periotest values (and their related placement and removal torque

values) are measured to be between the ranges of -8 to +9.


23

Chen Y 13 (2009) conducted a study to evaluate the stability of machined

microimplant anchorage after immediate orthodontic loading in dogs and to ascertain

clinical and histologic features. Sixty microimplants were placed in the buccal sides

of the maxillae and mandibles of 4 dogs, including the interradicular area.

Superelastic nickel-titanium coil springs were activated between 24 pairs of

reciprocally loaded implants, producing a force of 200 g, and the remaining 12

unloaded implants served as controls. The distance between 2 microimplants was

measured at the beginning and the end of loading. Extrusion and tipping were seen in

areas of thin cortical bone in both jaws. Histologic analysis showed remodelling at the

periosteal bone was slightly more active in the loaded specimens than in the controls.

There was no statistically significant difference in bone and implant contact values of

the 2 groups. He concluded that the immediate loading does not affect

osseointegration of orthodontic microimplants, but the anchorage unit is not always

absolutely stationary.

Apel S 1 (2009) conducted a study to evaluate the colonization of implants with

pathogenic bacteria. Therefore, the microflora associated with successful and failed

mini-implants has been screened. Material and methods: A total of 76 mini-implants

collected from 25 patients were observed during regular orthodontic treatment.

Bacterial samples of eight failed and - exemplarily - four successful (control) cases

were subjected to a universal Bacteria-directed real-time quantitative polymerase

chain reaction for quantification in combination with a microarray-based

identification of 20 selected species. However, A. viscosus was found in four (100%)


24

and Campylobacter gracilis in three (75%) stable controls, whereas both species were

rarely found (12.5%) in failed implants. They concluded that in the present study, the

peri-implant sulcus surrounding failed orthodontic mini-implants did not show a

specific aggressive bacterial flora.

Cesare Luzi 52 (2009) conducted an investigation to evaluate tissue reaction to

immediate loading in animal model.50 orthodontic titanium mini implants were

inserted in 4 adult male monkeys at 4 time intervals.42 devices were loaded with

50cN super elastic coil springs immediately after insertion while eight were left

unloaded and served as controls .Bone volume (BV/TV) , bone to implant contact

(BIC) ,mineralizing surface (MS) and erosion surface (ES/BS) were evaluated .They

concluded that BV/TV did not show any particular trend while BIC was a time

dependent factor.MS/BS and ES/Bs demonstrated opposite trends during the healing

period . Immediately loading with light forces did not negatively affect the bone

healing pattern.

P.W.Woods 87 (2009) conducted a study to evaluate the effect of timing and force of

loading as well as implant location ,on bone to implant contact (BIC) of loaded and

control miniscrew implants(MSI) .7 mature beagle dogs were selected and divided

into groups with immediate and delayed loading. Mobility was detected in 3 of the 56

MSIs. The mobile implants were all unloaded controls and showed no BIC. All

remaining stable MSIs showed some BIC. There was no significant differences in

BIC associated with timing of force application, amount of force applied or implant

location. They concluded that timing and amount of force loading and location of


25

implant placement do not affect BIC and only a limited amount of osseo-integration is

necessary for implant stability.

Wu TY 91 (2009) conducted a study to evaluate failure rates and factors associated

with the stability of mini-implants used for orthodontic anchorage. They enrolled 166

patients (35 male patients and 131 female patients) who had consecutively received

mini-implants for orthodontic anchorage at the Section of Orthodontics and Paediatric

Dentistry, Taipei Veterans General Hospital. Differences in overall failure rates for

the maxilla and mandible (9.3% and 16.3%, respectively) were not statistically

significant. A lower failure rate was found for the maxilla with implant diameters

equal to or less than 1.4 mm (P = .036). The left side had a lower failure rate than the

right (6.7% vs. 13.9%, P = .019).They concluded that careful diameter selection for

different locations is essential. In the maxilla an implant diameter equal to or less than

1.4 mm is recommended. In the mandible an implant diameter larger than 1.4 mm is

suggested for better orthodontic anchorage. Hygienic care of implantation sites should

also be emphasized for long-term success of mini-implant.

Wilmes B 83 (2009) conducted a study to test the hypothesis that the impact of the

insertion depth and predrilling diameter have no effect on the primary stability of

mini-implants. Twelve Ilium bone segments of pigs were embedded in resin. After

implant site preparation with different predrilling diameters (1.0, 1.1, 1.2, and 1.3

mm), Dual Top Screws 1.6 x 10 mm (Jeil, Korea) were inserted with three different

insertion depths (7.5, 8.5, and 9.5 mm). The insertion torque was recorded to assess


26

primary stability. He concluded that the hypothesis is rejected. Higher insertion

depths result in higher insertion torques and thus primary stability. Larger predrilling

diameters result in lower insertion torques.

Veltri M 81 (2009) conducted a study to evaluate the soft bone primary stability of 3

different orthodontic screws by using the resonance frequency analysis. Aarhus mini-

implan (Aarhus Mini-implant, Charlottenlund, Denmark) (A), Mini Spider Screws

(HDC, Sarcedo, Italy) (S), and Micerium Anchorage System (Micerium, Avegno,

Italy) (MAS) were investigated. Four screws per system were tested. Each screw was

placed in 5 excised rabbit femoral condyles, providing experimental models of soft

bone. Placement was drill-free for the A screw, whereas the MAS and S screws

required a pilot hole through the cortical layer. After each placement procedure,

resonance frequency was assessed as a parameter of primary stability. They concluded

that the resonance frequency analysis is applicable to comparatively assess the

primary stability of orthodontic miniscrews. The 3 systems had similar outcomes in

an experimental model of soft bone.

Kang YG 36 (2009) conducted a study to examine the stability of mini-screws that

invade a dental root by measuring the retention period/failure rate, and to illustrate

their effects on paradental tissues. Three adult male beagle dogs received 48

orthodontic mini-screws. Half of the mini-screws were implanted to invade the roots,

and the rest were placed in the middle of the alveolar bone. Half of the mini-screws

were loaded immediately. The application of force had little effect on the failed mini-

screws. Moderately injured roots were repaired with osteoid and/or cementoid tissues


27

with normal periodontal ligaments, followed by recovery of the original

configuration. They concluded that the orthodontic mini-screws had a higher failure

rate when placed to invade the dental roots. However, minimally damaged dental

roots do not adversely affect the healing process.

Eliades T 22 (2009) conducted a study to characterize the morphologic, structural, and

compositional alterations and to assess any hardness changes in used orthodontic

miniscrew implants. Eleven miniscrew implants (Aarhus Anchorage System, Medicon

eG, Tuttlingen, Germany) placed in 5 patients were retrieved after successful service

of 3.5 to 17.5 months; none showed signs of mobility or failure. The materials

precipitated on the surfaces were sodium, potassium, chlorine, iron, calcium, and

phosphorus from the contact of the implant with biologic fluids such as blood and

exudates, forming sodium chloride, potassium chloride, and calcium-phosphorus

precipitates. They concluded that used titanium-alloy miniscrew implants have

morphologic and surface structural alterations including adsorption of an integument

that is calcified as a result of contact of the implants with biologic fluids. Randomly

organized osseointegration islets on these smooth titanium-alloy miniscrew surfaces

might be enhanced by the extended period of retention in alveolar bone in spite of the

smooth surface and immediate loading pattern of these implants

Buschang P H 66 (2010) The purpose of this study was to determine the effect of

miniscrew implant orientation on the resistance to failure at the implant-bone

interface. Methods: Miniscrew implants (IMTEC) were placed in 9 human cadaver

mandibles, oriented at either 90° or 45° to the bone surface, and tested to failure in


28

pull-out (tensile) and shear tests. The line of applied force and the orientation of the

implants aligned at 45° were either parallel or perpendicular to the maximum axis of

bone stiffness. In the shear tests, the implants aligned at 45° were angled toward and

opposing the axis of shear force. The implants aligned at 90° had the highest force

(342N) at failure of all the groups. In the shear tests, the implants that were angled in

the same direction as the line of force were the most stable and had the highest force

(253N) at failure. The implants angled away from the direction of force were the least

stable and had the lowest force (87N) at failure. They concluded that more closely the

long axis of the implant approximates the line of applied force, the greater the

stability of the implant and the greater its resistance to failure.

IMPORTANCE OF TRANS PALATAL ARCH IN BIOMECHANICS

Jager A 33 (1992) an in-vitro study was performed analysing the forces and moments

produced by the transpalatal arches of the Goshgarian type (0.036" x 0.032" stainless

steel and of the "Precision Lingual Arch System" advocated by Burstone (0.032" x

0.032" stainless steel and 0.032" x 0.032" TMA) using an electronic force-moment

gauge recently developed by Planert. The palatal bars were adapted passively, and in

addition, molar expansion, symmetrical molar rotation, and buccal root torque were

applied. It was found that under clinical conditions it was impossible to fabricate an

absolutely passive arch wire with any of the arch types under investigation. The

highest precision in applying forces and moments together with the least side-effects

was possible using the low stiffness TMA version of the Burstone system.


29

McNamara JA 93 (2008) conducted a retrospective cephalometric study to test an

additional function of the TPA: its ability to enhance orthodontic anchorage during

extraction treatment. All patients were white and had 4 first premolars extracted as

part of their treatment protocol. Patients were treated either with or without a TPA of

the soldered Goshgarian design .Analysis of the changes from pre-treatment to post-

treatment for the TPA and the no-TPA groups showed no statistically significant

differences in any of the variables examined. The net difference for both vertical and

mesial movement of the maxillary first molar in relation to the maxilla between the 2

groups was 0.4 mm, with the no-TPA group in a more downward and forward

position. Although the usefulness of the TPA for the abovementioned functions is not

negated, it does not provide a significant effect on either the antero-posterior or the

vertical position of the maxillary first molars during extraction treatment.

Liu YH 50 (2009) The purpose of this study was to compare the differences in

cephalometric parameters after active orthodontic treatment applying mini-screw

implants (G1) or transpalatal arches (G2) as anchorage in adult patients with

bialveolar dental protrusion needing extraction of four premolars. A total of 34

Chinese patients (18-33 years) with bialveolar dental protrusion were randomly

assigned to G1 and G2. Sliding mechanics and en-masse retraction of anterior teeth

were applied to close extraction spaces. Mini-screw implants provide absolute

anchorage in vertical and sagittal directions. Better dental, skeletal and soft tissue

changes could be achieved by mini-screw implants especially in hyperdivergent

patients. Skeletal anchorage should be routinely recommended in patients with

bialveolar dental protrusion.


30

SELF DRILLING AND SELF TAPPING

Massif L 54 (2007) the goal of his experimental study was to show that the realization

of a before-hole limits the intraosseous constraints during screwing. This having

short-term effects on the primary stability of the mini-screws and long-term effects on

their maintenance. Two self-drilling and self-tapping mini-screws (Aarhus Medicon)

of 1.6 and 1.3 mm diameters are screwed with a manual screwdriver, without a

before-hole, in a plate of cortical bone fixed on a sensor measuring the forces and the

couple. They concluded that screwing without before-hole led to the alteration of the

osseous surface layer caused by micro fractures which limit the possibilities of

blocking of the mini-screws.

Yan Chen 14 (2008) conducted a study to compare the influences of different implant

modalities on orthodontic microimplants and surrounding tissues biomechanically and

histologically.56 samples were tested. They found that success rate was higher in the

self-drilling group than in the predrilled group. Higher peak insertion torque values

were seen in the self drilling group both in the maxilla and mandible. They concluded

that self-drilling microimplants can provide better anchorage than predrilled screws.

Wang 82 (2008) conducted a retrospective cephalometric study to compare the

loading behaviour of predrilled and self-drilling miniscrews placed in the

infrazygomatic crest of the maxilla. The subjects were 32 women who had

miniscrews in the infrazygomatic crest of the maxilla as skeletal anchorage for en-

masse anterior retraction and intrusion; 16 had predrilled miniscrews, and 16 had the

self-drilling type. The miniscrews were all 2 mm in diameter and 10 to 17 mm long.


31

They were loaded with nickel-titanium closed-coil springs 2 weeks after placement.

The predrilled and self-drilling miniscrews were all significantly displaced in

accordance with the force direction of the nickel-titanium coil springs. The amounts

of miniscrew displacement were similar between the predrilled and self-drilling

miniscrews, and were correlated to the length of the loading period. The

displacements were 0.0 to 1.6 mm with extrusion, 1.5 mm with forward or backward

tipping at the screw tail, and 1.5 mm with forward tipping at the screw head. He

concluded that the loading behaviours of predrilled and self-drilling miniscrews were

similar in the infrazygomatic crest of the maxilla.

TORQUE OF IMPLANTS

Chen YJ 15 (2006) conducted a study to measure the removal torque of immediately

loaded miniscrews after clinical usage and to determine the possible factors associated

with this value. From 29 patients with malocclusions, 46 miniscrews were removed,

and removal torque was measured with a torque gauge. Removal torque values were

significantly higher in the mandible than in the maxilla. The removal torques of 15

mm and 17 mm miniscrews was significantly higher than those of 13-mm miniscrews.

They concluded that the removal torque values of the majority of miniscrews in this

study population when loaded immediately as orthodontic anchorage were greater

than 0.89 kg x cm, and this was sufficient for these implants to fulfil their purpose as

anchors in 3-dimensional tooth movements.

M. Motoyoshi 61 (2007) conducted a study to determine the success rate of mini-

implants in adolescents, and also whether a latent period is necessary and the


32

optimum placement torque in an attempt to improve the success rate in adolescent

patients. When a mini-implant endured an orthodontic force applied for 6 months or

more without any mobility, it was considered a success. The success rate was 63.8%

in the early-load group (less than 1-month latent period) of adolescents, 97.2% in the

late load group (3-month latent period) of adolescents and 91.9% in the adult group.

In measurements of the placement torque in adolescents, the success rate of the 5–10

Ncm groups was significantly higher than the other groups only in the maxilla of the

early-load group. They concluded that although the optimum torque could not be

defined, a latent period of 3 months before loading is recommended to improve the

success rate of the mini-implant when placed in the alveolar bone in adolescent

patients.

Seon-A Lim 48 (2008) conducted a study to determine the variation in the insertion

torque of orthodontic miniscrews according to the screw length, diameter, and shape.

Cylindrical and taper type of miniscrews with different lengths, diameters, and pitches

were tested. In particular, there was a significant increase in torque with increasing

screw length and diameter. An analysis of the serial insertion torque of miniscrews

revealed the cylindrical type screw to have much higher insertion torque at the

incomplete screw thread, while the taper type screw showed a much higher insertion

torque at the final inclination part of the screw thread. The insertion torque was

affected by the outer diameter, length, and shape in that order. They concluded that an

increase in screw diameter can efficiently reinforce the initial stability of the

miniscrew, but the proximity of the root at the implanted site should be considered.


33

Kimak Selmoria 70 (2008) conducted a study to evaluate the insertional torque axial

pull out strength and to determine the initial and perimplant cortical bone thickness.60

microimplants were used. They found that there was a regular correlation between

pullout strength and perimplant cortical bone thickness .They concluded that pull-out

strength is greater immediately after placement of MI(microimplant), cortical bone

thickness decreases because of bone resorption and insertional torque is not an

efficient method for predicting the retention of the microimplant.

Brantley WA 30 (2008) compared four brands of miniscrew implants (A-D) with 1.6-

mm diameters with implants having diameters of 1.2 to 2.0 mm. The miniscrews were

loaded to failure in torsion, and the mean moment and twist angle were determined

for each group (n = 8).Miniscrew A and C implants were pure titanium, whereas

miniscrew B and D implants contained small amounts of vanadium, aluminium, iron,

and manganese. Only alpha-titanium peaks were detected for all implants by micro x-

ray diffraction, but beta titanium was observed in the microstructures of miniscrew B

and D implants, which had significantly higher torsional moments at failure. They

concluded that addition of small amounts of other elements to titanium yielded

significantly improved torsional performance for miniscrew implants. Research to

develop optimum compositions for mechanical properties and biocompatibility is

needed.

Glaucio Serra 72 (2008) The purpose of his study was to analyze interfacial healing

1, 4, and 12 weeks after the placement of titanium mini-implants in New Zealand

rabbits by removal torque test (RTT) and scanning electron microscopy (SEM).


34

Eighteen animals were used in the experiment, in which 72 titanium grade 5 mini-

implants 2.0 mm in diameter and 6.0 mm long, were placed. Each animal received 4

mini-implants; 2 were immediately loaded with 1N. The immediate 1N load did not

cause significant changes in the fixation of the mini-implants after 1 and 4 weeks of

bone healing. Nevertheless, after 12 weeks, the loaded group had significantly lower

RTT values than the unloaded group without compromising the stability of the

mini-implants.

Toru Shigeeda 76 (2010) In this study the placement and removal torques of mini-

implants were evaluated as an index of implant stability and also examined factors

affecting the initial and long-term stability of mini-implants. They measured the

placement and removal torques of 134 mini-implants placed in buccal posterior

alveolar bone and assessed the relationships among placement and removal torques,

placement period, age, sex, and cortical bone thickness. The mini-implants were

machine-surfaced, 1.6 mm in diameter and 8 mm long. A torque screwdriver was used

to measure the peak torque values. The placement and removal torques averaged

approximately 8 N cm and 4 N cm, respectively. A torque of 4 N cm suggests

sufficient anchorage capability for mini-implants. They found no significant

correlation between placement and removal torques. Placement torque was

significantly related to age and cortical bone thickness in the maxilla, whereas

removal torque was not significantly related to placement period, age, sex, or cortical

bone thickness.


35

DENSITY OF ALVEOLAR BONE AND SOFT-TISSUE THICKNESS

Marissa Schnelle 69 (2004) conducted a study to determine radiographically the most

coronal interradicular sites for placement of miniscrews in orthodontic patients and to

determine if orthodontic alignment increases the number of sites with adequate

interradicular bone for placement of miniscrews. Interradicular sites were examined

with a digital calliper for presence of 3-4mm of bone. If 3-4mm bone existed then a

vertical measurement from the cementoenamel junction (CEJ) to the first

measurement was made. They concluded that bone stock for placement of screws was

found to exist primarily in the maxillary (mesial to first molars) and mandibular

(mesial and distal to first molars) posterior regions. Typically adequate bone was

located more than halfway down the root length which is likely to be covered with

movable mucosa

Isidor F 31 (2006) presented a paper dealing with the relationship between forces on

oral implants and the surrounding. Randomized controlled as well as prospective

cohorts studies were not found. Although the results are conflicting, animal

experimental studies have shown that occlusal load might result in marginal bone loss

around oral implants or complete loss of osseointegration. In clinical studies an

association between the loading conditions and marginal bone loss around oral

implants or complete loss of osseointegration has been stated, but a causative

relationship has not been shown.

Deguchi T 19 (2006) conducted a study to quantitatively evaluate cortical bone

thickness in various locations in the maxilla and the mandible. In addition, the


36

distances from intercortical bone surface to root surface, and distances between the

roots of premolars and molars were also measured to determine the acceptable length

and diameter of the miniscrew for anchorage during orthodontic treatment. Three-

dimensional computed tomographic images were reconstructed for 10 patients.

Significantly less cortical bone thickness was observed at the buccal region distal to

the second molar compared with other areas in the maxilla. These data show that the

safest location for placing miniscrews might be mesial or distal to the first molar, and

an acceptable size of the miniscrew is less than approximately 1.5 mm in diameter

and approximately 6 to 8 mm in length.

Hyo Sang Park 65 (2008) conducted a study to quantitatively evaluate density of the

alveolar bones of the maxilla and mandible. The sample consisted of 23 men and 40

women. Cortical and cancellous bone densities at the alveolar and basal bones at the

incisor ,canine ,premolar ,molar and maxillary tuberosity/retromolar areas were

measured using CT software .The findings of this study suggested that the highest

bone density in the maxilla was observed in the canine premolar region and the

maxillary bone density showed the lowest bone density. Density of the cortical bone

was greater in the mandible than in the maxilla and showed a progressive increase

from the incisor to retromolar area.

Bong-Kuen Cha 8 (2008) conducted a study to evaluate area- and gender-related

differences in the soft tissue thickness of potential areas for installing miniscrews in

the buccal-attached gingiva and the palatal masticatory mucosa. An ultrasonic

gingival thickness meter was used to measure the soft-tissue thickness in the buccal-


37

attached gingiva just adjacent to the mucogingival junction of the upper and lower

arches and 4 mm and 8 mm below the gingival crest in the palatal masticatory

mucosa. Significantly thicker soft tissue occurred in the anterior areas in the upper

arch and in the posterior areas in the lower arch. In the palatal masticatory mucosa,

significantly thicker soft tissue was found 4 mm below the gingival crest in the

anterior areas and 8 mm below the gingival crest in the posterior areas. The areas

between the canines and the premolars showed higher values than other areas 4 mm

below the gingival crest. They concluded that measurements of the soft-tissue

thickness using an ultrasonic device could help practitioners select the proper

orthodontic miniscrew in daily clinical practice.

A.Ono 62 (2008) performed a study to investigate cortical bone thickness in the

buccal posterior region mesial and distal to the first molar, where mini-implants are

often placed, and determine any differences according to location, age and sex.

Cortical bone thickness was measured from 1 to 15 mm below the alveolar crest at 1-

mm intervals. The average cortical bone thicknesses ranged from 1.09 to 2.12 mm in

the maxilla and 1.59 to 3.03 mm in the mandible. The greater the height, the thicker

the cortical bone tended to be, and the mandibular cortical bone was significantly

thicker than that of the maxilla. The cortical bone was thinner in females than in

males in the region of attached gingiva in the maxilla mesial to the first molar. The

mandible suffices as a preparation site for mini-implants, while the maxilla might be

insufficient at shallow locations. Regardless of age, the initial stability of mini-

implants in shallow locations in the maxilla of women should be considered.


38

Chun YS 17 (2008) conducted a study to evaluate bone density differences between

interradicular sites. Computed tomographic (CT) images were obtained from 14 M/F

.Bone density in Hounsfield units (HU) was measured at 13 interradicular sites and

four bone levels. Bone densities in both maxilla and mandible significantly increased

from the alveolar crest toward basal bone in posterior areas, while the opposite was

observed in anterior areas. There were statistically significant differences in bone

densities between the maxilla and mandible in posterior areas. Bone densities

progressively increased from anterior to posterior areas in the mandible. The results

suggest that mini-implants for orthodontic anchorage may be effective when placed in

most areas with equivalent bone density up to 6mm apical to the alveolar crest. Site

selection should be adjusted accordingly.

Chun YS 16 (2009) conducted a study to determine whether the tip of the interdental

gingiva can serve as a visible guide for placement of mini-implant. Computer

tomography (CT) images from 15 males and 15 females (mean age 27 years, range:

23–35 years) were used to evaluate the distance from the tip of the interdental gingiva

to the alveolar crest from the central incisor to the 1st molar. There was no significant

difference in the distance from the tip of interdental gingiva to the alveolar crest

between maxilla and mandible. The distance between the tip of interdental gingiva

and the alveolar crest at the central ⁄ lateral incisors was the shortest compared with

that of other sites. They concluded that the tip of interdental gingiva appears a

reasonable visual guide for the placement of mini-implants for orthodontic anchorage.


39

Baumgaertel S 5 (2009) in his study, investigated the buccal cortical bone thickness

of every interdental area as an aid in planning mini-implant placement. From the

cone-beam computed tomography scans of 30 dry skulls, 2-dimensional slices

through every interdental area were generated. On these, cortical bone thickness was

measured at 2, 4, and 6 mm from the alveolar crest. Buccal cortical bone thickness

was greater in the mandible than in the maxilla. Whereas this thickness increased with

increasing distance from the alveolar crest in the mandible and in the maxillary

anterior sextant, it behaved differently in the maxillary buccal sextants; it was thinnest

at the 4-mm level. He concluded that the interdental buccal cortical bone thickness

varies in the jaws. Knowledge of this pattern and the mean values for thickness can

aid in mini-implant site selection and preparation.

Santiago RC 68 (2009) conducted a study to correlate the clinical and radiographic

stability of titanium miniscrews when used as orthodontic anchorage for maxillary

canine retraction and to assess bone quality. Thirty titanium miniscrews were placed

in 15 consecutive patients (8 male, 7 female; age range, 12 years 5 months-32 years

11 months) as orthodontic anchorage. Orthodontic loads were applied immediately

after miniscrew placement (T1) with a nickel-titanium closing coil spring. The initial

estimated load was 200 g. The bone quality in each region of interest was determined

by multi-slice computed tomography. He concluded that the regions between the

maxillary second premolars and first molars, and mesial to the maxillary second

premolars, are safe as far as bone quality is concerned for miniscrew placement

during the first 90 days of canine distalization. A good surgical technique and

appropriate planning for miniscrew placement, inflammation control, and adequate


40

oral hygiene are fundamental to the success of this new anchorage system during

maxillary canine distalization.

Tae-Min Yoon 75 (2010) This study was aimed to determine the effect of bone

mineral density (BMD), cortical bone thickness (CBT), screw position, and screw

design on the stability of miniscrews. Ninety-six miniscrews of both cylindrical and

tapered types were placed in 6 beagle dogs. The BMD and CBT were measured by

computerized tomography and correlated with the placement and removal torque and

mobility. The placement torque showed a positive correlation in the order of removal

torque (0.66), BMD of the cortical bone (0.58), and CBT (0.48). They found that

placement and removal torque values were significantly higher in the mandible

compared with the maxilla. Tapered miniscrews had higher placement torque than did

the cylindrical type (P<0.001). However, the removal torque was similar in both

groups. Placement torque was affected by screw position, screw type, and BMD of

cortical bone, in that order. BMD of cortical bone, screw type, and screw position

significantly influence the primary stability of miniscrews.

IMPLANTS AS POTENTIAL ANHCORAGE

Buchter A 7 (2005) The purpose of this study was to determine the clinical and

biomechanical outcome of two different titanium mini-implant systems activated with

different load regimens. A total of 200 mini-implants (102 Abso Anchor and 98 Dual

Top) were placed in the mandible of eight Göttinger minipigs. Two implants each

were immediately loaded in opposite direction by various forces (100, 300 or 500 cN)

through tension coils. Additionally, three different distances between the neck of the


41

implant and the bone rim (1, 2 and 3 mm) were used. Clinical implant loosing was

only present when load exceeded 900 cN mm. No movement of implants through the

bone was found in the experimental groups, for any applied loads .They concluded

that the dual Top implants revealed a slightly higher removal torque compared with

Absoanchor implants. Based on the results of this study, immediate loading of mini-

implants can be performed without loss of stability when the load-related

biomechanics do not exceed an upper limit of TM at the bone rim.

Chae JM 10 (2006) has concluded in his study that Tweed-Merrifield directional force

technology with microimplant anchorage is a useful treatment approach for a patient

with a Class I or Class II dentoalveolar-protrusion malocclusion. It can create a

favourable counter clockwise skeletal change and a balanced face without patient

compliance. In contrast, headgear force with high-pull J-hook can obtain similar

results but depends on patient cooperation. Good facial balance was obtained by

Tweed-Merrifield directional force technology with microimplant anchorage, which

provided horizontal and vertical anchorage control in the maxillary and mandibular

posterior teeth, and intrusion and torque control in the maxillary anterior teeth,

resulting in a favourable counter clockwise mandibular response.

Y.-C. Tseng 12 (2006) the aim of this study was to explore the use of mini-implants

for skeletal anchorage, and to assess their stability and the causes of failure. Forty-five

mini-implant were used in orthodontic treatment. The diameter of the implants was 2

mm, and their lengths were 8, 10, 12 and 14 mm. The drill procedure was directly

through the cortical bone without any incision or flap operation. Two weeks later, a


42

force of 100–200 g was applied by an elastometric chain or NiTi coil spring. The

average placement time of a mini-implant was about 10–15 min. Four mini-implants

loosened after orthodontic force loading. The overall success rate was 91.1%. The

location of the implant was the significant factor related to failure. In conclusion, the

mini-implants are easy to insert for skeletal anchorage and could be successful in the

control of tooth movement.

Kokitsawat S 42 (2008) conducted a study to measure the clinical effects associated

with miniscrew anchorage used to retract the upper anterior teeth, specifically the

positional changes associated with the miniscrews, the upper anterior teeth and the

first upper molar. After orthodontic alignment, miniscrews were inserted in the

maxillary zygomatic buttresses as anchorage for en masse retraction of the upper

anterior teeth. Following premolar extractions, nickel-titanium closed coil springs,

stretched between the miniscrews and upper archwire, were used for retraction.

Three-dimensional changes in the upper anterior teeth, the upper first molars and the

heads of the miniscrews were measured on study models taken before a 300 g force

was applied and seven months later, or when retraction was completed if less than

seven months. They concluded that miniscrews provide satisfactory anchorage for

retraction of the upper anterior segment, but do not remain absolutely stationary under

orthodontic loads. Because of coincidental mesial movement of the upper molars,

there must be sufficient clearance mesial to the molars to avoid the molar roots

contacting the miniscrews.


43

Hoste S 29 (2008) The aims of this review are twofold, firstly, to give an overview of

the general and local risk factors when using temporary anchorage devices (TADs)

and the prerequisites for placement and, secondly, to illustrate the orthodontic

indications of various TADs. They concluded that temporary anchorage devices have

a place in modern orthodontics. Careful treatment planning involving radiographic

examination is essential. Consultation with an oral surgeon is advisable if a soft tissue

flap is required. Excellent patient compliance, particularly avoidance of inflammation

around the implant, is an important consideration for successful use of TADs.

Lee C. K. 46 (2008) conducted a study to determine patients’ expectations,

acceptance, and experience of pain with microimplant surgery compared to other

orthodontic procedures. Seventy-eight microimplants were placed in 37 patients as an

anchorage unit. Patients were asked to rate anticipated pain and pain experienced with

various orthodontic procedures (tooth extraction, insertion of separators, initial tooth

alignment, and microimplant surgery) on a visual analog scale (VAS) over a 7-day

period. Unlike other orthodontic procedures, patients expected to experience a

significantly higher level of pain with microimplant surgery than they experienced.

The postoperative pain experienced decreased continuously from day 1 to day 7 for

all orthodontic procedures. The total area under the curve (AUC) of pain experienced

over the 7-day period was significantly larger for initial tooth alignment than for

microimplant surgery. They concluded that patients tended to overestimate the pain

anticipated with microimplant surgery.


44

Justen E 35 (2008) conducted a study to evaluate clinical success and longevity of

mini-screws during orthodontic treatment and to assess the patient's opinion. Fifty

mini-screws were inserted in the mandible and maxilla of 21 patients with a flapless

technique under local anaesthesia. Thirty-three mini-screws (64%) remained stable

sufficiently long enough to obtain the effect during the orthodontic movement. The

survival was comparable in mandible or maxilla, and not related to the orthodontic

forces applied or time of activation of the load. The results do suggest that a waiting

period of 1 week before loading improves success, and mini-screws inserted into the

anterior region score better also compared to the posterior region. Initial periodontal

parameters, which are very important in prognosis of orthodontic treatment, are not

influencing the success rate in the examined group. They concluded that the mini-

screw implant is an easy and an inexpensive method for temporary anchorage of

orthodontic appliances.

Garfinkle 24 (2008) conducted a study to determine the success rate, positional

stability , and patient evaluation of orthodontic mini-implants(OMI).13 patients were

selected .The right and left arch was randomly selected for immediate loading up to

250g of direct force. The contra lateral side was loaded 3-5 weeks later. They found

that the combined success rate of loaded OMIs was significantly higher than that of

unloaded OMIs. They concluded that OMIs are a predictable, effective and well

tolerated anchorage source for adolescents. The orthodontic forces can be applied

immediately to OMIs.


45

Badris T 3 (2008) conducted a study to measure and compare the rates of canine

retraction with titanium microimplant anchorage and conventional molar

anchorage.12 patients were selected. After the levelling and aligning, titanium

microimplants 1.2mm in diameter and 9mm in length were placed between the roots

of the second premolar and 1st molar in the maxilla and mandible. A brass wire guide

and a peri-apical radiograph were used to determine the implant position. After 15

days the implants and the molars were loaded with closed coil springs with a force of

100g for canine retraction. They concluded that the canine retraction proceeds at a

faster rate when titanium microimplants were used as anchorage.

Bryan Brettin 6 (2008) conducted an in-vitro study to test the hypothesis that

bicortical miniscrew placement gives the orthodontist superior force resistance and

stability compared with monocortical placement. 44 titanium alloy screws, 1.5 X 15.0

mm were placed in 22 hemisected maxillae and mandibular specimens between the

1st and 2nd premolars .Half were placed monocortically , half were placed bi-cortically

and all were subjected to tangential force loading perpendicular to the miniscrew

through a lateral displacement of 1.5mm.Their results indicated that the deflection

force values were significantly greater for bicortical than for a monocortical screws

placed for both the maxilla and mandible. Furthermore force values at mandibular

sites were significantly greater than those at maxillary sites for both the screws. They

concluded that bi-cortical miniscrews provide the orthodontist superior anchorage

assistance, reduced cortical bone stress and superior stability.


46

Motoyoshi 62 (2008) conducted a study to examine the relationship between cortical

bone thickness, inter-root distance (horizontal space), distance from alveolar crest to

the bottom of maxillary sinus (vertical space) at the prepared site, and implant

placement torque and the success rate of mini-implants placed for orthodontic

anchorage. After computerized tomography examination, mini-implants 1.6 mm wide

and 8 mm long were placed in the posterior alveolar bone. The mini-implant was

judged a success when orthodontic force could be applied for at least 6 months

without pain or clinically detectable mobility. The success rate was significantly

higher in the group with an implant placement torque of 8 to 10 Ncm (100%) as

compared to implants with higher or lower placement torques. The odds ratio for

failure of the mini-implant was 6.93 (P = .047) when the cortical bone thickness was

less than 1.0 mm relative to 1.0 mm or more. They concluded that a relationship

between stability after implant placement and the width and height of the peri-implant

bone was not demonstrated. The prepared site should have a cortical bone thickness of

at least 1.0 mm, and the placement torque should be controlled up to 10 Ncm.

Eddie Hsiang-Hua Lai 44 (2009) conducted a retrospective study on dental models to

compare the orthodontic outcomes of maxillary dentoalveolar protrusion treated with

headgear, miniscrews, or miniplates for maximum anchorage. The 40 subjects were

divided into 3 groups according to the type of anchorage used. The 3D analysis of

serial dental models demonstrated that, compared with headgear, skeletal anchorage

achieved better results in the treatment of maxillary dentoalveolar protrusion. Greater

retraction of the maxillary anterior teeth, less anchorage loss of the maxillary

posterior teeth, and the possibility of maxillary molar intrusion all facilitated


47

correction of the Class II malocclusion, especially for patients with a hyperdivergent

face.

Chang CS 11 (2009) conducted a study to investigate the effects of two different

microrough surface treatments on miniscrews with loading over different time periods

in vivo. Twenty-four New Zealand white rabbits were selected. One hundred and

forty-four miniscrews with a machined (MA), sandblasted and acid-etched (SLA) or

sandblasted and alkaline-etched (SL/NaOH) surface were implanted into the tibia of

the rabbits. Then, orthodontic forces with Ni-Ti coils were applied immediately to two

of the three miniscrews in each tibia, with the centre one serving as the control. After

2, 4, 8 and 12 weeks, the rabbits were sacrificed. The removal torque value (RTV)

was tested and bone-to-implant contact (BIC) was examined. In most groups, there

were no differences between the RTV in the unloaded and loaded conditions at

different time periods. In the loaded condition, the RTV of the SLA groups increased

significantly after 4 weeks of healing. They concluded that there were no differences

between the loaded and unloaded conditions in most groups. The RTV and BIC

increased with time. In the loaded condition, the RTV of the SLA surface increased

earlier, at 4 weeks, while the SL/NAOH group showed the highest RTV after 8

weeks.

ANCHORAGE LOSS

Priscilla Denny 20 (2006) conducted a retrospective study to determine the effects of

soldered transpalatal arches (TPA) on the first maxillary molars during orthodontic

treatment involving extraction of maxillary first bicuspids. Group A consisted of 20


48

patients treated with extraction of maxillary first bicuspids and TPAs soldered to the

maxillary first molar bands during space closure. Group B received the same

treatment without TPAs .This study questioned the effect of a soldered TPA on the

anchorage of the maxillary first molars in the horizontal and vertical planes of space.

However a soldered TPA might influence the vertical movement of the maxillary

incisors. Based on these results the soldered TPA had an intrusive effect on the

anterior maxillary incisors.

Thiruvenkatachari B 74 (2006) conducted a study to compare and measure the

amount of anchorage loss with titanium microimplants and conventional molar

anchorage during canine retraction. After levelling and aligning, titanium

microimplants 1.3 mm in diameter and 9 mm in length were placed between the roots

of the second premolars and the first molars. Implants were placed in the maxillary

and mandibular arches on 1 side in 8 patients and in the maxilla only in 2 patients. A

brass wire guide and an intraoral periapical radiograph were used to determine the

implant positions. After 15 days, the implants and the molars were loaded with

closed-coil springs for canine retraction. The amount of molar anchorage loss was

measured from pterygoid vertical in the maxilla and sella-nasion perpendicular in the

mandible. Mean anchorage losses were 1.60 mm in the maxilla and 1.70 mm in the

mandible on the molar anchorage side; no anchorage loss occurred on the implant

side. They concluded that titanium microimplants can function as simple and efficient

anchors for canine retraction when maximum anchorage is desired.

Materials and Methods


49

MATERIALS AND METHODS

The aim of this study was to compare the effects of short and long hooks in en-masse

retraction of anterior teeth using two (right and left ) micro-implants placed in the

maxillary arch between the roots of the second premolar and first molar.

The study comprised of 10 patients divided into 2 groups: Group A and Group B, of 5

patients each. Patients in group A had long hooks and group B had short hooks. A

stringent inclusion criterion was maintained for this study. Records were taken from

individuals undergoing orthodontic treatment in department of Orthodontics, Ragas

Dental College.

INCLUSION CRITERIA:

The basic difference in the inclusion criteria in the two groups selected in this study

was:

a. Long hooks in patients with U1-NA (INCISAL ANGULATION) = 20° -

30°(GROUP A), needing more of bodily movement.

b. Short hooks in patients with U1-NA (INCISAL ANGULATION) = 30°-

40°(GROUP B), needing more of controlled tipping.


50

The other inclusion criteria which were similar for both the groups were:

Full permanent dentition

Extracted first pre-molar

Average mandibular angle

Fully levelled and aligned arches with 0.019” X 0.025” SS wires

Banded 2nd molars with TPA.

Patients with sound gingival and periodontal health and maintaining good oral

hygiene.

ARMAMENTARIUM

1. Abso-Anchor Micro-Implant Anchorage system from Dentos Inc.,Korea.

2. Screwdriver for the Micro-implants(DENTOS)

3. TMA stent. (0.017” x 0.025” TMA)

4. Micro-motor with reduction gear hand piece.

5. Round surgical bur (2 mm)

6. Mouth mirror, Explorer and Periodontal probe, Tweezers.

7. Surgical blade no.11 and handle

8. Geometry box.

9. Normal Saline

10.Topical anaesthetic spray

11. Local anaesthetic with vasoconstrictor adrenaline.

12.Photography mirror.

13.Betadine solution


51

MICRO-IMPLANT SPECIFICATION:

This system consists of micro-implants of 1.3 mm diameter and 8mm length with

a hole of 0.8mm in the implant neck and is fabricated from a Titanium alloy

(Titanium 90%, Aluminium 6% and Vanadium 4%).

They are threaded so as to mechanically interlock with the bone without

osseointegration. The site of placement was 10mm from the archwire between 1st

molar and 2nd premolar.

HOOK SPECIFICTAION:

Long Hook – 8mm (modified S shaped hook)

Short Hook – 2 mm

MATERIALS:

NiTi coil springs (13mm and 8mm in length,0.5mm diameter)

0.09 inch ligature wire

Brass wire for making soldered hooks.

Solder material (0.05mm)

Soldering torch

Dontrix gauge


52

PRE-SURGICAL PREPARATION:

A written consent was obtained from both the patients as well as their parents after

explaining in detail about the treatment and its effects. Prior to the surgical procedure

the instruments were sterilized using an autoclave. One hour prior to surgery all the

patients were given prophylactic antibiotic and 0.2% Chlorhexidine mouthwash to

create an antiseptic insertion site. The upper and lower lips were cleaned with

betadine solution prior to placement.

To assess the placement of the micro-implant a TMA stent was fabricated of height

10mm from the archwire slot with 0.017 X 0.025 TMA wire. A wire was welded on

the stent individually for each patient to determine the point of insertion of the micro-

implant. With the stent in place an IOPA (Paralleling cone tech.) was taken. This

IOPA was then used to actually determine the point of insertion.


53

SURGICAL PROCEDURE:

Following the assessment of ideal implant position the buccal mucosa was

anesthetised first with a lignocaine topical spray and then later injected with 2ml of

2% lignocaine with vasoconstrictor adrenaline. The stent was placed intra-orally and a

point was marked on the attached gingiva/mucosa using a sharp sterilised probe. A

surgical blade was then used to place an incision in the buccal mucosa if required. A 2

mm round bone cutting surgical bur attached to a reduction gear hand piece and

operated at low speed of 400rpm was used to drill 2mm into the bone along with

copious saline irrigation to avoid overheating and thereby preventing osseous and

tissue necrosis.

The 1.3 mm diameter and 8 mm length micro-implant was removed from the

autoclaved pouch and held with a long head screw drive without touching the part that

had to be inserted into the bone. The implant was inserted into the bone with the head

of the screwdriver being turned in the clockwise direction. Simultaneously the

position of insertion was determined with the help of a reflective mirror held in the

oral cavity. Since the micro-implant was self-drilling in nature, it was gently threaded

into the remaining unprepared bone. The implant stability was assessed clinically by

evaluating with tweezers to check for any mobility. Same procedure was followed on

right and left side of patient. IOPA radiographs were taken both before and after

placement of the implant to confirm the implant location in the bone.

Patients were prescribed with antibiotics and analgesics. 0.2% chlorhexidine

mouthwash was also prescribed to maintain the oral hygiene. Peri-implant tissues

were allowed to heal for a week. After a week’s time the implants were loaded.


54

METHOD

A total of 10 cases were selected and divided into group A (LONG HOOK) and

group B (SHORT HOOK). Group A had long hooks of 8mm soldered on 0.019 x

0.025 inch SS wire between the upper lateral incisor and canine. Group B had short

hooks of 2mm soldered on 0.019 x 0.025 inch SS wire between the upper lateral

incisor and canine.

En-masse retraction was done for both the groups using a micro-implant (Dentos

no.1312-08) placed at the standard height of 10mm from the arch wire between the

roots of the upper first molar and second premolar.

The micro-implants were checked for stability after a week with tweezers and then

loaded with an initial force of 150g using a NiTi- coil spring (Dentos-13mm length)

for both the groups. After one month the force levels were increased to 250g and

subsequently to 300g in further appointments using a shorter NiTi- coil spring

(Dentos-8mm length). The amount of force was measured by Dontrix gauge.

Pre-stage T1 and Post-stage T2 cephalograms were superimposed to differentiate the

type of tooth movement achieved (Bodily or Tipping movement). Different angular

and linear cephalometric values were compared at the start (Pre-stage,T1) and after

the correction of overjet (Post-stage,T2). The results were then statistically analysed.


55

RECORDS:

Records were taken at start of retraction using implants (Pre-stage,T1) and after

overjet correction(Post-stage,T2).

The records consisted of,

a) Lateral Cephalogram (Pre-stage T1 and Post-stage T2)

b) Orthopantomogram (OPG) (Pre-stage T1 and Post-stage T2)

c) Intra oral peri-apical radiographs (IOPA) ( Before and after implant placement)

d) A set of intra-oral photographs were taken at (Pre-stage T1 and Post-stage T2)

CEPHALOMETRIC ANALYSIS

Lateral cephalograms were traced on matt acetate film of 50 micron thickness and

were traced by the same operator using 0.5mm lead pencil respectively. The right and

left structures were averaged and the usual landmarks for cephalometric analysis were

identified on the averaged tracing and linear measurements and angular measurements

were taken.


56

CEPHALOMETRIC MEASUREMENTS:

Following angular and linear cephalometric measurements were compared

ANGULAR MEASUREMENTS LINEAR MEASUREMENTS

1. U1-NA(°) 1. U1-NA(mm)

2. U1-SN(°) 2. U6-PTV(mm)

3. U1-PALATAL PLANE(°) 3. OVERJET(mm)

4. OCCLUSAL- PALATAL

PLANE(°)

5. PALATAL PLANE –SN(°)

6. OCCLUSAL PLANE –SN(°)

The initial and final measurements for all cephalometric variables were assessed and

the changes were calculated.


57

Armamentarium

TMA Stent Dentos MicroImplants [1312-08],Implant Driver, Anthogear

Dentos NiTi coil spring [8 mm and 13 mm]

Gesults

Results

58

RESULTS

The study comprised of 10 patients divided into 2 groups of 5 patients each. Patients

in group A had long hooks (8 mm) and group B had short hooks (2 mm). A stringent

inclusion criterion was maintained for this study. Records were taken from individuals

undergoing orthodontic treatment in department of Orthodontics, Ragas Dental

College.

INCLUSION CRITERIA:

The basic difference in the inclusion criteria in the two groups selected in this study

was:

1) Long hooks in patients with U1-NA (INCISAL ANGULATION) = 20°-30°

(GROUP A), needing more of bodily movement.

2) Short hooks in patients with U1-NA (INCISAL ANGULATION) = 30°-40°

(GROUP B), needing more of controlled tipping.

Cephalometric records were taken at the start of retraction (Pre-stage, T1) and after

the closure of overjet (Post-stage, T2).

Results

59

STATISTICAL ANALYSIS:

All statistical analysis were performed by using SPSS software package (SPSS for

Windows XP, version 16.0, Chicago).For each variable measured on the lateral

cephalogram, the mean and standard deviation were calculated.

Mann Whitney U test: It is a statistical test which is done when the sample size is

less than 30. In our study the sample size was 10.

Wilcoxon Signed Ranks Test: The Wilcoxon Signed Ranks test is generally used

when measurements are taken from the same subject before and after treatment. In our

study the cephalometric variables were recorded in Pre-stage (T1) and after

completion of retraction in Post-stage (T2).

Wilcoxon Signed Ranks test was used to determine treatment changes between T1

and T2 for both the groups. Mann Whitney U test was done between the difference

values of T1 and T2 and compared for both the groups (A and B). All cephalograms

were exposed with standardized settings.

The data in this study were evaluated and comparisons were made between the incisor

cephalometric variables between T1 and T2 for both the groups. Differences with the

probabilities less than 5% (P < 0.05) were considered statistically significant and (P <

0.001) was considered as highly statistically significant.

Results

60

CEPHALOMETRIC FINDINGS:

1. U1-NA (INSICAL ANGULATION): The upper incisal angulations for T1

and T2 for group A(LONG HOOK) were 26.40° and 21.80° (Table 1) and for

group B (SHORT HOOK) were 34.20° and 24.00° (Table 2) respectively. The

mean difference between T1 and T2 were 4.60° for group A and 10.20° for

group B (Table 3 and 4). These values suggest that the difference in degree of

retractions between both groups A (LONG HOOK) and B (SHORT HOOK)

were found to be statistically significant.(P < 0.05) (Table 5)

2. U1-SN (INCISAL ANGULATION): The upper incisal angulations with

respect to S-N plane for T1 and T2 for group A (LONG HOOK) were 111.6°

and 107.0° and for group B(SHORT HOOK) were 114.60° and 104.40°

(Table 1 and 2) respectively. The mean difference between T1 and T2 were

4.60° and 10.20° for group A and group B respectively (Table 3 and 4). These

values suggest that the difference in degree of retractions between both groups

A (LONG HOOK) and B (SHORT HOOK) were found to be statistically

significant (P<0.05) (Table 5).

3. U1-PALATAL PLANE (INCISAL ANGULATION): The upper incisal

angulations were measured with respect to the palatal plane. The values for T1

and T2 for group A were 67.0° and 71.6° and for group B were 59.80° and

70.0° (Table 1 and 2). The mean difference between T1 and T2 were -4.60°

and -10.20° for group A and group B respectively (Table 3 and 4). These

Results

61

values suggest that the difference in degree of retractions between both groups

A (LONG HOOK) and B (SHORT HOOK) were found to be statistically

significant (P<0.05) (Table 5).

4. Occlusal plane – Palatal plane: The values for group A (LONG HOOK) for

T1 and T2 were 9.60° and 9.40° respectively (Table 3) and for group B

(SHORT HOOK) for T1 and T2 were 9.20° and 9.20° respectively (Table 4).

These values were found to be statistically insignificant.

5. PALATAL PLANE – SN: The values for group A (LONG HOOK) for T1

and T2 were 6.40° and 6.00° respectively (Table 3) and for group B (SHORT

HOOK) for T1 and T2 were 7.40° and 7.40° respectively (Table 4). These

values were found to be statistically insignificant.

6. OCCLUSAL PLANE-SN: The values for group A (LONG HOOK) for T1

and T2 were 17.60° and 17.20° respectively (Table 3) and for group B

(SHORT HOOK) for T1 and T2 were 17.80° and 17.60° (Table 4)

respectively. These values were found to be statistically insignificant.

7. OVERJET (mm): The values for T1 and T2 6.6 mm and 3.0 mm for group A

(LONG HOOK) (Table 3) and for group B (SHORT HOOK) were 9.2 mm

and 3.6 mm (Table 4). The mean difference between group A and group B

were 3.60 mm and 5.60 mm. These values were found to be statistically

significant with a P value of 0.033 (Table 5).

Results

62

8. U6-PTV (mm): The values for T1 and T2 for group A (LONG HOOK) were

19.40 mm and 19.40 mm (Table 3) and for group B (SHORT HOOK) were

18.60 mm and 18.60 mm (Table 4). As micro-implants were used for

anchorage there was no anchorage loss observed. Hence this variable was

found to be insignificant for both groups.

9. U1-NA (mm): The values for T1 and T2 were 7.2 mm and 3.2 mm for group

A (LONG HOOK) (Table 3) and for group B (SHORT HOOK) were 9.6 mm

and 4.2 mm (Table 4). The mean difference value between T1 and T2 were

4.0 mm and 5.4 mm, were however found to be insignificant with a P value of

0.230 (Table 5). This indicates that there is not much difference in the linear

retraction of the central incisors when compared for both the groups.

The results in this study indicate that that maximum lingual tipping of anterior teeth is

seen when the height of the retraction hook is as low as possible as determined by the

variable U1-NA (Group B)(P< 0.05). In cases where torque control and bodily

movement is the criteria, the hook length should be at the maximum height possible

(Group A). As micro-implants were used in this study the U6-PTV value remained

constant for both the groups indicating that there was no mesial movement of the

upper molars and hence this value was found to be statistically non-significant. The

study also shows that there is not much difference in the linear retraction of the

central incisors when compared for both the groups.

Results

Table 1: LONG HOOK – GROUP A: Mean Values

Group A LONG HOOK Mean

Case 1 Case 2 Case 3 Case 4 Case 5

1 U1- NA (°) Pre 25° 28° 24° 29° 26° 26.4

Post 18° 22° 20° 25° 24° 21.8

2 U1 -SN (°) Pre 110° 116° 104° 112° 116° 111.6

Post 103° 110° 100° 108° 114° 107.0

3 U1 - Palatal Plane (°) Pre 63° 60° 63° 79° 70° 67.0

Post 70° 66° 67° 83° 72° 71.6

4 Occlusal Plane - PalatalPlane (°)

Pre 11° 5° 8° 12° 12° 9.6

Post 12° 5° 7° 11° 12° 9.4

5 Palatal Plane -SN (°) Pre 5° 10° 5° 8° 4° 6.4

Post 3° 10° 5° 8° 4° 6.0

6 Occlusal Plane - SN (°) Pre 22° 17° 13° 20° 16° 17.6

Post 21° 18° 12° 19° 16° 17.2

7 Overjet (mm) Pre 5 mm 6 mm 9 mm 7 mm 6 mm 6.6

Post 3 mm 2 mm 4 mm 3 mm 3 mm 3.0

8 U6 - Ptv (mm) Pre 21 mm 15 mm 18 mm 18 mm 25 mm 19.4

Post 21 mm 15 mm 18 mm 18 mm 25 mm 19.4

9 U1 - NA (mm) Pre 8 mm 8 mm 7 mm 7 mm 6 mm 7.2


Results

Table 2: SHORT HOOK – GROUP B: Mean Values

Group B SHORT HOOK Mean

Case 1 Case 2 Case 3 Case 4 Case 5

1 U1- NA (°) Pre 34° 32° 34° 36° 35° 34.2

Post 22° 22° 25° 26° 25° 24.0

2 U1 -SN (°) Pre 108° 112° 116° 120° 117° 114.6

Post 96° 102° 107° 110° 107° 104.4

3 U1 - Palatal Plane (°) Pre 55° 58° 71° 61° 54° 59.8

Post 67° 68° 80° 71° 64° 70.0

4 Occlusal Plane - PalatalPlane (°)

Pre 8° 11° 8° 7° 12° 9.2

Post 11° 11° 7° 6° 11° 9.2

5 Palatal Plane -SN (°) Pre 9° 8° 8° 6° 6° 7.4

Post 9° 8° 8° 6° 6° 7.4

6 Occlusal Plane - SN (°) Pre 21° 21° 16° 13° 18° 17.8

Post 22° 20° 15° 12° 19° 17.6

7 Overjet (mm) Pre 9 mm 10 mm 8 mm 12 mm 7 mm 9.2


8 U6 - Ptv (mm) Pre 19 mm 16 mm 15 mm 22 mm 21 mm 18.6

Post 19 mm 16 mm 15 mm 22 mm 21 mm 18.6

9 U1 - NA (mm) Pre 10 mm 7 mm 11 mm 13 mm 7 mm 9.6


Results

Table 3: Group A - Long hook (Wilcoxon Signed Ranks Test)

Pre stage Post stage MeanDiff

P-Value SignificanceMean SD Mea

nSD

U1- NA (°) 26.4 2.07 21.8 2.86 4.6 0.042 *

U1 -SN (°) 111.6 4.98 107.0

5.57 4.6 0.042 *

U1 - Palatal Plane (°) 67.0 7.65 71.6 6.80 -4.6 0.042 *

Occlusal Plane - Palatal Plane(°)

9.6 3.05 9.4 3.21 0.2 0.564 NS

Palatal Plane -SN (°) 6.4 2.51 6.0 2.92 0.4 0.317 NS

Occlusal Plane - SN (°) 17.6 3.51 17.2 3.42 0.4 0.317 NS

Overjet (mm) 6.6 1.52 3.0 0.71 3.6 0.042 *

U6 - Ptv (mm) 19.4 3.78 19.4 3.78 0.0 1.000 NS

U1 - NA (mm) 7.2 0.84 3.2 0.84 4.0 0.041 *

NS: Not significant; *p < 0.05 (statistically significant); **p < 0.001 (statistically highlysignificant)

Table 4: Group B - Short hook (Wilcoxon Signed Ranks Test)

Pre stage Post stage MeanDiff

P-Value SignificanceMean SD Mean SD

U1- NA (°) 34.2 1.48 24.0 1.87 10.2 0.039 *

U1 -SN (°) 114.6 4.67 104.4 5.51 10.2 0.039 *

U1 - Palatal Plane (°) 59.8 6.83 70.0 6.12 -10.2 0.039 *


9.2 2.17 9.2 2.49 0.0 0.705 NS

Palatal Plane -SN (°) 7.4 1.34 7.4 1.34 0.0 1.000 NS

Occlusal Plane - SN (°) 17.8 3.42 17.6 4.04 0.2 0.655 NS

Overjet (mm) 9.2 1.92 3.6 0.89 5.6 0.042 *

U6 - Ptv (mm) 18.6 3.05 18.6 3.05 0.0 1.000 NS

U1 - NA (mm) 9.6 2.61 4.2 1.30 5.4 0.042 *

Results

Table 5: Mann Whitney U test to compare the difference in mean values between

groups A (long hook) and B (short hook)

LONGHOOK

SHORTHOOK

P-Value Significa-nce

Mean SD Mean SDU1- NA (°) 4.6 1.95 10.2 1.10 0.008 *

U1 -SN (°) 4.6 1.95 10.2 1.10 0.008 *

U1 - Palatal Plane (°) -4.6 1.95 -10.2 1.10 0.008 *


0.2 0.84 0.0 1.73 0.735 NS

Palatal Plane -SN (°) 0.4 0.89 0.0 0.00 0.317 NS

Occlusal Plane - SN (°) 0.4 0.89 0.2 1.10 0.811 NS

Overjet (mm) 3.6 1.14 5.6 1.14 0.033 *

U6 - Ptv (mm) 0.0 0.00 0.0 0.00 1.000 NS

U1 - NA (mm) 4 1.22 5.4 1.67 0.230 NS

NS: Not significant; *p < 0.05 (statistically significant); **p < 0.001 (statistically highlysignificant)

Results

LONG HOOK

PRE TREATMENT (T1)

POST TREATMENT (T2)

PRE TREATMENT CEPHALOGRAM (T1)

PRE TREATMENT OPG (T1)

POST TREATMENT OPG (T2)

POST TREATMENT CEPHALOGRAM (T2)

SHORT HOOK

PRE TREATMENT (T1)

POST TREATMENT (T2)

PRE TREATMENT CEPHALOGRAM (T1)

PRE TREATMENT OPG (T1)

POST TREATMENT CEPHALOGRAM (T2)

POST TREATMENT OPG (T2)

Long Hook (Group A) Superimposition of Pre-stage T1 and Post-stage T2

Short Hook (Group B) Superimposition of Pre-stage T1 and Post-stage T2

Discussion

Discussion

63

DISCUSSION

Successful orthodontic treatment depends on maximising the desired tooth movement

and minimising the undesirable side effects by evaluating and controlling reactionary

effects of orthodontic force systems. Conventional intraoral anchorage has been

modified in several ways to improve anchorage potential. These include moving less

number of teeth pitting the anchorage against a larger group of teeth – for eg.

independent canine retraction.

Although extraoral appliances like head gears have proved its worth, patient

compliance is very susceptible and intra-oral appliances like transpalatal arches,

cannot be considered as an absolute anchorage. All these drawbacks have necessitated

the introduction of an intraoral stationary anchorage and implant assisted anchorage

system, which is now considered as a highly accepted form of anchorage preservation

with its many fold advantages have become a standard part of an orthodontist

armamentarium. It produces good treatment results with no need of patient co-

operation, saves time and convenient to use.

Innovations in the field of “implant assisted orthodontics” were performed which led

to the development of the miniscrews and micro-implants. The screws were available

in varying lengths and diameters and are fabricated from various materials with

Discussion

64

titanium being the first choice among them. These screws could be placed in the

buccal as well as palatal regions according to Hee Moon Kyung et al.37.

Although the anchorage concept of micro-implant is not debatable there is always

been much speculation as far as the biomechanics with regard to the height of

retraction hooks. It is also known that different hook lengths will cause different kinds

of moments to be produced during retraction, but not much clinical in-vivo studies

have been done so far.

Two finite element studies have shown conflicting reports. H.M. Kyung 37 in his

FEM study has used different implant placement heights with different hook lengths

and has concluded that maximum lingual tipping of anterior teeth is seen when the

position of the implant is at the maximum height within anatomic limits possible and

the height of the retraction hook the least possible. In cases where torque control and

bodily movement is the criteria, the hook length should be at the maximum height

possible and the implant position should be as low as possible.

Although Sang-Jin Sung 67 in his FEM study showed contradictory results, he found

no bodily retraction of anterior teeth in high mini implant traction with 8-mm anterior

retraction hook condition after retraction, when the retraction force vector was

applied above the center of resistance for the 6 anterior teeth,

Discussion

65

Therefore this in vivo study was done in which we varied the height of retraction

hook between 2 mm and 8 mm keeping a stable position of implant between second

premolar and first molar at the height of 10 mm from the archwire to ascertain if any

difference in the type of retraction [tipping or bodily retraction] occurred between

them. The patients were divided into 2 groups, 5 cases of short hook (2 mm) and 5

cases of long hook (8 mm). Retraction in patients was started after a week with

minimum loading force of 150g, measured by dontrix gauge.

Although it has been proved that implants can be immediately loaded upto 200g 60,

we loaded the implants after a week’s interval with forces upto 150g. Primary

stability, according to Melsen and Costa 55, is an important factor for micro-implant

success. It expresses the initial stability of a recently placed micro-implant. Primary

stability is a function of the mechanical retention of the implant obtained by the

friction and close contact with the bone 85.

Hans-Peter Bantleon et al 27 found that longer healing periods did not provide

additional stability and higher success rate at forces upto 200g. Therefore micro-

implants can be loaded within days after placement with forces upto 200g. Tseng Y C

et al 77 found a success rate of 85.7% when micro-implants were loaded after 7 days

at forces upto 100–300 g

Discussion

66

Before the micro-implants were loaded, we checked the mobility of micro-implants

with help of tweezers. Any absence of mobility was considered as a successful and

stable implant. The study by Motoyoshi 60 used absence of mobility as the definition

of success, since any mobility means lack of absolute anchorage.

The teeth were retracted with the help of NiTi-coil springs (Dentos) of two different

lengths. Initially a 13mm long (Dentos) NiTi - coil spring was used from the implant

head to the hooks, to provide a retraction force of 150g, which was measured by

dontrix gauge. Only after 4-6 weeks of micro-implant placement, secondary stability

occurs and only then maximum forces can be applied, so after 2 appointments we

further increased the force to 250g and subsequently 300g using the 8mm short

(Dentos) NiTi coil – spring. This is in accordance with the study done by Barlow et

al 2, who recommend the use of initial force of 150g by using NiTi-coil springs and

have found it to be superior to use of e-ties for retraction.

This study deals with the placement of the micro-implants between the roots of the

second premolar and molar on the buccal side. The obvious advantage over the other

available sites is it ease of insertion and removal of the implant, better hygiene control

by the patients and ease in tying the NiTi-coil springs (used in the study) by the

operator. Also it has been shown that the inter-radicular space between the second

premolar and first molar is widest in the maxilla and this site is first choice for micro-

implant placement on the buccal side for anterior retraction in maxilla 64. In this study

a TMA stent was custom fabricated for patients to enable the operator to use it as a

clinical guidance tool.

Discussion

67

Micro-implants of length 8mm and diameter 1.3mm have been used in this study. As

length is considered an important factor in stability and success rate of micro-

implants, Tseng Y C et al 77 showed increased success rate from 72% to 90% by

using 8mm micro-implants instead of 6 mm micro-implants. He recommends micro-

implant of length 8mm and diameter 1.2 – 1.3mm, have sufficient stability with a

minimum risk of root damage.

Miyawaki 58 observed an 85% success rate of micro-implants and evaluated the

relative risk of the failure of micro-implant anchorage in subjects with peri-implant

inflammation and concluded that preventing peri-implant inflammation is important

for preventing failure of the implant anchor. To prevent postoperative infection in

long term, antibiotics were prescribed to the patients in this study, and the peri-

implant inflammation was effectively controlled by regular oral rinsing with 2%

chlorhexidine mouthwash. Peri-implant tissues were allowed to heal for a week.

In our study we have used stabilising trans-palatal arches joining the maxillary molars

to provide vertical control during retraction process. In this study the retraction of

anterior teeth was done en-masse instead of the traditional two step retraction of the

canine and incisors. Individual canine retraction often results in rotations and

mesiodistal tipping of canine. However with en-masse retraction no such problems are

encountered.

Discussion

68

This study has compared the incisor inclination changes occurring during retraction of

anterior teeth using short hooks (2mm length) and long hooks (8mm length). All the

implants were removed at the completion of the study and cephalometric records were

taken along with cast impressions .The results in this study are in accordance with the

FEM study done by H.M.Kyung et al.37. The results in this study indicate that

maximum lingual tipping of anterior teeth occurred in Group B where the height of

retraction hook was the least at 2mm and the difference in U1-NA was 10.2° between

T1 and T2.

On the other hand, more torque control and bodily movement occurred in Group A

where the height of retraction hook was the maximum at 8 mm and the difference in

U1-NA was 4.6° between T1 and T2. Superimpositions also confirmed the finding,

which shows more of bodily movement in long hook (Group A) and lingual tipping in

short hook (Group B). As micro-implants were used in this study the U6-PTV value

remained constant for both the groups indicating that there was no mesial movement

of the upper molars and hence this value was found to be statistically non-significant.

The study also indicates that there is not much difference in the linear retraction of the

central incisors when compared for both the groups.

Discussion

69

There was however some practical difficulties faced in this study .The most common

were:

1. Implant failure due to soft tissue over-growth, because of lack of oral hygiene

being the most common.

2. Operators implant placement errors.

Implant failure due to the above mentioned causes was seen in 3 cases which was not

included in the final sample (10 patients).

Anchorage reinforcement is most commonly needed in patients with severe

protrusion. In conventional retraction with sliding mechanics after first premolar

extractions, the molars typically move forward 3.6 - 3.8 mm (anchorage loss) 41.

Anchorage reinforcement can allow more retraction of the incisors while reducing

forward movement of the molars and the use of micro-implants have proved its worth

as reliable method of intraoral stationary anchorage. However since the anchorage is

not taken from the dentition and as the micro-implants are placed at varying heights in

the alveolus, there is bound to be substantial biomechanical variations when using the

retraction force from the micro-implants.

Results of this study clearly indicate that if lingual tipping is required the height of

retraction hook should be small in anterior teeth retraction and in cases where more of

torque control and bodily movement is required the height of retraction hook should

be long. The centre of resistance of anterior six teeth is located 6.76 mm above the

cervical area between the roots of the lateral incisor and canine 47 or at the level of the

root tip 80 and as it is know that when force is passed along the centre of resistance of

Discussion

70

a tooth, it causes bodily movement, so the height of retraction hook should be as close

to the centre of resistance as possible to bring bodily movement of anterior segment,

which can be 8mm as proved in our study. The short hooks bring about difference in

the U1-NA angulations (10.2°) when compared to the long hooks (4.6°) which

indicates that there is much of lingual tipping seen when short hook is used for

anterior retraction.

Thus we can summarize that these biomechanical variations achieved by altering the

height of retraction hook can bring about substantial changes in the type of tooth

movement. The clinician can put into practical application of these principles which

could bring about significant improvement in the quality of orthodontic treatment

results.

Summary and Conclusion


71

SUMMARY AND CONCLUSION

This clinical study was undertaken to determine the optimum height of the retraction

hook when bringing two basic types of anterior tooth movement i.e. bodily movement

and tipping movement when retracting from a buccal implant and to take advantage of

these variations and apply them in various clinical situations of retraction. A total of

10 cases were selected and divided into two groups of 5 cases each.

Group A had long hooks (8mm) soldered on 0.019 x 0.025 inch SS wire between the

upper lateral incisor and canine. Group B had short hooks (2mm) soldered on 0.019 x

0.025 inch SS wire between the upper lateral incisor and canine.

En-masse retraction was done for both the groups using a microimplant (Dentos

no.1312-08) placed at the standard height of 10mm from the arch wire between the

roots of the upper first molar and second premolar.

Initially a force of 150gm measured with dontrix gauge was given using a NiTi- coil

spring (Dentos-13mm length) for both the groups and after one month the force levels

were increased to 250gm and 300gm in subsequent appointments using a shorter

NiTi- coil spring (Dentos-8mm length).

Different angular and linear cephalometric values were compared at the start (Pre-

stage,T1) and after the correction of overjet (Post-stage,T2) and the results were

statistically analysed.


72

Results of this study showed that maximum lingual tipping of anterior teeth is seen

when the height of the retraction hook is as low possible (Group B). In cases where

torque control and bodily movement is the criterion, the hook length should be at the

maximum height possible (Group A). The molar position in both the groups however

remained unchanged .The results found in our study correlate to the results of the

FEM study of H.M. Kyung et al.37

From this study it can be concluded that that implant biomechanics has a substantial

variation from the biomechanics used in standard retraction and different types of

tooth movement can be achieved by varying the height of the retraction hook.

Thus microimplant assisted anchorages have not only stretched the boundaries of

camouflage treatment but also have forced the orthodontist to inspect the variation in

biomechanics which have been proved to be substantially different from conventional

orthodontic biomechanics.

Further long-term in vivo studies with more number of subjects will be forthcoming

to further evaluate this approach of treatment.

Bibliography

Bibliography

73

BIBLIOGRAPHY

1. Apel S, Apel C, Morea C, Tortamano A, Dominguez GC, Conrads G .

Microflora associated with successful and failed orthodontic mini-implants.

Clin Oral Implants Res 2009.

2. Barlow M, Kula K . Factors influencing efficiency of sliding mechanics to

close extraction space: a systematic review. Orthod Craniofac Res 2008;11:65-

73.

3. Badri T, Ammayappan P. Comparison of rate of retraction with conventional

molar anchorage and titanium implant anchorage .AJO-DO 2008;134(1):30-

35.

4. Baek SH, Kim BM, Kyung SH, Lim JK, Kim YH. Success rate and risk

factors associated with mini-implants reinstalled in the maxilla. Angle Orthod

2008; 78:895-901.

5. Baumgartel S, Hans MG. Buccal cortical bone thickness for mini-implant

placement. Am J Orthod Dentofacial Orthop.2009; 136:230-5.

6. Brettin B, Qian F. Bicortical .vs. Monocortical skeletal anchorage. AJO-DO

2008; 134(5):625-635.

Bibliography

7. Büchter A, Wiechmann D, Koerdt S, Wiesmann HP, Piffko J, Meyer U .

Load-related implant reaction of mini-implants used for orthodontic

anchorage. Clin Oral Implants Res 2005; 16:473-9.

8. Cha BK, Lee NK, Choi DS. Factors influencing primary stability of miniplate

anchorage: a three dimensional finite element analysis .Korean J Orthod

2008;38(5):304-30.

9. Chaddad K, Geurs N, Reddy MS. Influence of surface characteristics on

survival rates of mini-implants under immediate orthodontic loading.AJO

2007;131:569.

10. Chae JM. New protocol of Tweed –Merrifield directional force technology

with micro-implant anchorage. AJO-DO 2006;130:100-9

11. Chang CS, Lee TM, Chang CH, Liu JK. The effect of microrough surface

treatment on miniscrews used as orthodontic anchors. Clin Oral Implants Res.

2009.

12. Chen CH, Chang CS, Hsieh CH, Tseng YC, Shen YS, Huang IY et al. The

use of microimplants in orthodontic anchorage. J Oral Maxillofac Surg

2006;64:1209-13.

Bibliography

13. Chen Y, Kang ST, Bae SM, Kyung HM. Clinical and histologic analysis of

the stability of microimplants with immediate orthodontic loading in dogs. Am

J Orthod Dentofacial Orthop 2009;136:260-7.

14. Chen Y, Shin HI, Kyung HM.Biomechanical and histological comparison of

self-drilling and self-tapping orthodontic microimplants in dogs. Am J Orthod

Dentofacial Orthop 2008;133:44-50.

15. Chen YJ, Chen YH, Lin LD, Yao CC. Removal torque of miniscrews used

for orthodontic anchorage--a preliminary report. Int J Oral Maxilfac Implants

2006;21:283-9.

16. Chun YS, Lee SK. The interdental gingiva, a visible guide for placement of

mini-imlants.Orthod Craniofac Res 2009;12(1):20-4

17. Chun YS, Lim WH. Bone density at interradicular sites: implications for

orthodontic mini-implant placement. Orthod Craniofac Res 2009;12(1):25-32.

18. Chung KR, Nelson G, Kim SH, Kook YA. Severe bidentoalveolar protrusion

treated with orthodontic microimplant-dependent en-masse retraction. Am J

Orthod Dentofacial Orthop 2007;132:105-15.

Bibliography

19. Deguchi T, Nasu M, Murakami K, Yabuuchi T, Kamioka H, Takano-

Yamamoto T Quantitative evaluation of cortical bone thickness with

computed tomographic scanning for orthodontic implants.Am J Orthod

Dentofacial Orthop.2006;129:721.e7-12.

20. Denny P. Retrospective cephalometric investigation of the effects of soldered

transpalatal arches on the maxillary first molars during orthodontic treatment

involving extraction of maxillary first bicuspids .AJO-DO 2006;129(1):81-82.

21. Dilek O , Dincel M. Required minimum primary stability and torque values

for immediate loading of mini dental implants: An experimental study in

nonviable bovine femoral bone .Oral Surg Oral Med Oral Pathol Oral Radiol

2008;105:e20-e27

22. Eliades T, Zinelis S, Papadopoulos MA, Eliades G. Characterization of

retrieved orthodontic miniscrew implants. Am J Orthod Dentofacial Orthop

2009;135:e1-7.

23. Freire JN, Silve N, Giljos JN. Histomorphologic and histomorphometric

evaluation of immediately and early loaded mimi-implants for orthodontic

anchorage. AJO-DO 2007;131(6):704.

Bibliography

24. Garfinkle JS, Cunningham LL Jr, Beeman CS, Kluemper GT, Hicks EP,

Kim MO. Evaluation of orthodontic mini-implant anchorage in premolar

extraction therapy in adolescents. Am J Orthod Dentofacial Orthop

2008;133:642-53.

25. Ghouse B A, Shantaraj R, Mogegowda S B. Comparative study between

conventional en-masse retraction (sliding mechanics) and en-masse retraction

using orthodontic micro implant. Implant Dentistry: Basic and Clinical

Research Apr 2010; 19; 2; 128-136.

26. Gracco A, Cozzani M, Vitale G. Numerical/experimental analysis of the

stress field around miniscrews for orthodontic anchorage. Eur J orthod

2009;31(1):12-20

27. Hans-Peter Bantleon, Adriano G. Crismani, Michael H. Bertl, Ales G.

Celar, , and Charles J. Burstonec Miniscrews in orthodontic treatment:

Review and analysis of published clinical trials. Am J orthod Dento Orthop

2010; 137:108-13

28. Heidemann W, Gerlach KL, Gröbel KH, Köllner HG . Effect of the

diameter of various bore holes on retention of osteosynthesis screws. Mund

Kiefer Gesichtschir 1998;2:136-40.

Bibliography

29. Hoste S, Vercruyssen M, Quirynen M, Willems G. Risk factors and

indications of orthodontic temporary anchorage devices: a literature review.

Aust Orthod J 2008;24:140-8.

30. Iijima M, Muguruma T, Brantley WA, Okayama M, Yuasa T, Mizoguchi

I. Torsional properties and microstructures of miniscrew implants. Am J

Orthod Dentofacial Orthop 2008;134:e1-6.

31. Isidor F.Influence of forces on peri-implant bone. Clin Oral Implants Res

2006;17:8-18.

32. Ito Y, Sato D, Yoneda S, Ito D, Kondo H, Kasugai S .Relevance of

resonance frequency analysis to evaluate dental implant stability:simulation

and histomorphometrical animal experiments. Clin Oral Implants Res

2008;19:9-14.

33. Jäger A, Planert J, Modler H, Gripp L. An in-vitro study of the use of

palatal arches in controlling the position of the upper molars. Fortschr

Kieferorthop 1992;53:230-8.

34. Ji GP, Yu Q, Shen G.The relationship between the stability of microimplants

and factors of gender and age. Shanghai Kou Qiang Yi Xue 2008;17:360-3.

Bibliography

35. Justens E, De Bruyn H. Clinical outcome of mini-screws used as orthodontic

anchorage. Clin Implant Dent Relat Res 2008;10:174-80.

36. Kang YG, Kim JY, Lee YJ, Chung KR, Park YG.Stability of mini-screws

invading the dental roots and their impact on the paradental tissues in beagles.

Angle Orthod. 2009;79:248-55.

37. Kim CN, Sung JH, Kyung HM. Three-dimensional finite element analysis of

initial tooth displacement according to force application point during

maxillary six anterior teeth retraction using skeletal anchorage. Korean J

Orthod. 2003 Oct;33(5):339-350.

38. Kim SH, Choy YS, Chung KR. Surgical positioning of orthodontic mini-

implants with guides fabricated on models replicated with cone-beam

computed tomography. AJO-DO 2007;131(4):S82-9.

39. Kim Tae-Woo, Jung MH. Biomechanical considerations in treatment with

miniscrew anchorage, part 1:the sagittal plane.JCO 2008;42(2)

40. Ko CC, Douglas WH, DeLong R, Rohrer MD, Swift JQ, Hodges JS.

Effects of implant healing time on crestal bone loss of a controlled-load dental

implant. J Dent Res 2003;82:585-91.

Bibliography

41. Kocadereli, I.: The effect of first premolar extraction on vertical dimension,

Am. J. Orthod. 116:41-45, 1999.

42. Kokitsawat S, Manosudprasit M, Godfrey K, Chatchaiwiwattana C .

Clinical effects associated with miniscrews used as orthodontic anchorage.

Aust Orthod J. 2008 Nov;24(2):134-9.

43. Kuroda S, Yamada K, Deguchi T, Kyung HM, Takano-Yamamoto T .

Class II malocclusion treated with miniscrew anchorage: comparison with

traditional orthodontic mechanics outcomes. Am J Orthod Dentofacial Orthop

2009;135:302-9.

44. Lai EH, Yao CC, Chang JZ, Chen I, Chen YJ. Three-dimensional dental

model analysis of treatment outcomes for protrusive maxillary dentition:

comparison of headgear, miniscrew, and miniplate skeletal anchorage.Am J

Orthod Dentofacial Orthop 2009;135:559.

45. Leung MT, Rabie AB, Wong RW. Stability of connected mini-implants and

miniplates for skeletal anchorage in orthodontics. Eur J Orthod 2008;30:483-9.

46. Lee C.K, Colman P.J. Patient’s perceptions regarding micro-implant as

anchorage in orthodontics.Angle Orthod 2008;78(2):228-33.

Bibliography

47. Lee, H.K. and Chung, K.R.: The vertical location of the center of resistance

for maxillary six anterior teeth during retraction using three dimensional finite

element analysis, Kor. J. Orthod. 31:425-438, 2001.

48. Lim SA, Cha JY, H CJ. Insertion torque of orthodontic miniscrews according

to changes in shape, diameter and length. Angle Orthod 2008;78:234-40.

49. Liou EJ, Pai BC, Lin JC. Do miniscrews remain stationary under orthodontic

forces? Am J Orthod Dentofacial Orthop 2004;126:42-7.

50. Liu YH, Ding WH, Liu J, Li Q . Comparison of the differences in

cephalometric parameters after active orthodontic treatment applying mini-

screw implants or transpalatal arches in adult patients with bialveolar dental

protrusion. J Oral Rehabil 2009;36:687-95.

51. Lioubavina-Hack N, Lang NP, Karring T.Significance of primary stability

for osseointegration of dental implants.Clin Oral Implants Res 2006;17:244-

50.

52. Luzi C, Verna C, Melsen B. Immediate loading of orthodontic mini-

implants: a histomorphometric evaluation of tissue reaction. Eur J Orthod

2009;31:21-9.

Bibliography

53. Martins RP, Buschang PH, Gandini LG Jr, Rossouw PE . Changes over

time in canine retraction: an implant study. Am J Orthod Dentofacial Orthop

2009k;136:87-93.

54. Massif L, Frapier L, Micallef JP.Insertion of min-screws: with or without

pre-drilling? Orthod Fr 2007;78:123-32.

55. Melsen B, Costa A. Immediate loading of implants used for orthodontic

anchorage. Clin Orthod Res 2000;3:23-8.

56. Melsen, B.; Fotis, V.; and Burstone, C.J.: Vertical force considerations in

differential space closure, J. Clin. Orthod. 24:678- 683, 1990.

57. Mimura H. Treatment of severe bimaxillary protrusion with miniscrew

anchorage: treatment and complications. Aust Orthod J 2008;24:156-63. \

58. Miyawaki S, Koyama I, Inoue M, et al. Factors associated with the stability

of titanium screws placed in the posterior region for orthodontic anchorage.

Am J Orthod Dentofacial Orthop. 2003;124:373–378.

59. Moon CH, Lee DG, Lee HS. Factors associated with the success rate of

orthodontic mini-screws placed in the upper and lower posterior buccal region.

Angle Orthod 2008;78(1):101-6.

Bibliography

60. Motoyoshi M, Hirabayashi M, Uemura M, Shimizu N. Recommended

placement torque when tightening an orthodontic miniimplant. Clin Oral

Implants Res 2006;17:109-14.

61. Motoyoshi M, Yoshida T, Ono A, Shimizu N .Effect of cortical bone

thickness and implant placement torque on stability of orthodontic mini-

implants. Int J Oral Maxillofac Implants.2007;22:779-84.

62. Ono A, Motoyoshi M, Shimizu N.Cortical bone thickness in the buccal

posterior region for orthodontic mini-implants.Int J Oral Maxillofac

Surg.2008;37:334-40.

63. Oyonarte R, Pilliar R, Woodside D . Peri-implant bone response to

orthodontic loading: Part 1.A histomorphometric study of the effects of

implant surface design. AJO-DO 2005;128(2):173-81.

64. Park HS. An anatomical study using CT image for the implantation of micro

implants. Korean J Orthod 2002;32:435-41.

65. Park HS, Lee YJ, Geong SH, Kwon TG. Density of the alveolar and basal

bones of the maxilla and the mandible. AJO-DO 2008;133(1):30-37.

66. Peter H. Buschang, Michael B. Pickard, Paul Dechow, P. Emile Rossouw.

Effects of miniscrew orientation on implant stability and resistance to failure.

Am J Orthod Dentofacial Orthop 2010;137:91-9

Bibliography

67. Sang-Jin Sung, Gang-Won Jang, Youn-Sic Chun, Yoon-Shik Moon.

Effective en-masse retraction design with orthodontics mini-implant

anchorage : A finite elemt analysis. Am J Orthod Dentofacial Orthop 2010;

137:648-57

68. Santiago RC, de Paula FO, Fraga MR, Picorelli Assis NM, Vitral RW.

Correlation between miniscrew stability and bone mineral density in

orthodontic patients. Am J Orthod Dentofacial Orthop 2009;136:243-50.

69. Schnelle M, Beck FM, Janes RM, Hooja SS. Radiographic evaluation of the

availability of bone for placement of miniscrews.Angle Orth 2004;74:830-7.

70. Selmoria K, Tanaka OM, Maruo H. Insertional torque and axial pull out

strength of mini-implants in mandibles of dogs.AJO 2008;133(6):790.

71. Sia S, Shibazaki T, Koga Y, Yoshida N. Experimental determination of

optimal force system required for control of anterior tooth movement in

sliding mechanics. Am J Orthod Dentofacial Orthop 2009;135:36-41.

72. Serra G, Morais LS, Meyers MA.Sequential bone healing of immediately

loaded mini-implants.AJO 2008;134(1):44-52.

Bibliography

73. SheauSoon Sia; Yoshiyuki Koga; Noriaki Yoshida. Determining the Centre

of Resistance of Maxillary Anterior Teeth Subjected to Retraction Forces in

Sliding Mechanics. The Angle Orthodontist 2006 ;77:999–1003.

74. Thiruvenkatachari B, Pavithranand A, Rajasigamani K, Kyung HM .

Comparison and measurement of the amount of anchorage loss of the molars

with and without the use of implant anchorage during canine retraction. Am J

Orthod Dentofacial Orthop 2006;129:551-4.

75. Tae-Min Yoon, Jung-Yul Cha, Jae-Kyoung Kil, Chung-Ju Hwang.

Miniscrew stability evaluated with computerized tomography scanning. Am Jo

Orthod Dentofacial Orthop 2010;137:73-9

76. Toru shigeeda, Kumiko Okazaki, Mitsuru Motoyoshi, Miwa Uemura,

Noriyoshi Shimizu. Factors affecting long term stability of oethodontic mini

implant AJO-DO 2010;137:588e1-e5

77. Tseng YC, Chen CH, Chang CS, Hsieh CH, Shen YS, Huang IY, et al. The

use of microimplants in orthodontic anchorage. J Oral Maxillofac Surg

2006;64:1209-13.

78. Upadhyay M, Yadav S. mini-implants anchorage for en-masse retraction of

maxillary anterior teeth : A clinical cephalometric study.AJO-DO

2008;134:803-10

Bibliography

79. Upadhyay M, Yadav S, Nagaraj K, Nanda R. Dentoskeletal and soft tissue

effects of mini-implants in Class II division 1 patients. Angle Orthod

2009;79:240-7.

80. Vanden Bulcke, M.M.; Dermaut, L.R.; Sachdeva, R.C.; and Burstone,

C.J.: The center of resistance of anterior teeth during intrusion using the laser

reflection technique and holographic interferometry, Am. J. Orthod. 90:211-

220, 1986.

81. Veltri M, Balleri B, Goracci C, Giorgetti R, Balleri P, Ferrari M.Soft bone

primary stability of 3 different miniscrews for orthodontic anchorage: a

resonance frequency investigation. Am J Orthod Dentofacial Orthop.2009

;135:642-8.

82. Wang YC, Liou EJ. Comparison of the loading behaviour of self-drilling and

predrilled miniscrews throughout orthodontic loading. Am J Orthod

Dentofacial Orthop 2008;133:38-43.

83. Wilmes B, Drescher D.Impact of insertion depth and predrilling diameter on

primary stability of orthodontic mini-implants.Angle Orthod.2009;79:609-14.

84. Wilmes B, Ottenstreuer S, Su YY, Drescher D. Impact of implant design on

primary stability of orthodontic mini-implants. : J Orofac Orthop 2008;69:42-

50.

Bibliography

85. Wilmes B, Rademacher C, Olthoff G, Drescher D.Parameters affecting

primary stability of orthodontic mini-implants.J Orofac Orthop 2006;67:162-

74.

86. Wilmes B, Su YY, Drescher D. Insertion angle impact on primary stability of

orthodontic mini-implants. Angle Orthod. 2008 Nov;78(6):1065-70.

87. Woods PW, Owens PH. The effect of force , timing , and location on bone-

to-implant contact of miniscrew implants.Eur J Orthod 2009;31(3):232-40

88. Wu J, Bai YX, Wang BK.Biomechanical and histomorphometric

characterizations of osseointegration during mini-screw healing in rabbit

tibiae. Angle Orthod.2009 ;79:558.

89. Wu J, Bai YX, Wang BK, Gao XH.Stability of the miniscrew implant during

healing period. Zhonghua Kou Qiang Yi Xue Za Zhi 2006 Apr;41:226-7.

90. Wu JC, Huang JN, Zhao SF. Effect of bicortical orthodontic microimplant

on tooth movement in dogs. Zhejiang Da Xue Xue Bao Yi Xue Ban

2006;35:491-5.

91. Wu TY, Wu CH. Factors associated with the stability of mini implants for

orthodontic anchorage. J Oral Maxillofacial Surg 2009;67(8):1595-9.

Bibliography

92. Yao CC, Lai EH, Chang JZ, Chen I, Chen YJ. Comparison of treatment

outcomes between skeletal anchorage and extraoral anchorage in adults with

maxillary dentoalveolar protrusion. Am J Orthod Dentofacial Orthop

2008;134:615-24. .

93. Zablocki HL, McNamara JA Jr, Franchi L, Baccetti T . Effect of the

transpalatal arch during extraction treatment. Am J Orthod Dentofacial Orthop

2008;133:852-60

micro-implants biomechanics a comparative...

Documents