A New Maxillary Anterior Ridge Classification According to Ideal Implant Restorative Position

Determined by Computerized Axial Tomographic Analysis

Department of Dentistry

The Graduate School, Yonsei University

A New Maxillary Anterior Ridge Classification According to Ideal Implant Restorative Position

Determined by Computerized Axial Tomographic Analysis

Directed by Professor Yong-Keun Lee

The Doctoral Dissertation

Submitted to the Department of Dentistry,

the Graduate School of Yonsei University

in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

Young-Sang Park

June 2007

This certifies that the Doctoral Dissertation of ‘Young-Sang Park’ is approved.

___________________________ Thesis Supervisor: Yong-Keun Lee

___________________________ [Kyoung-Nam Kim: Thesis Committee Member #1]

___________________________ [Kwang-Mahn Kim: Thesis Committee Member #2]

___________________________ [Seong-Ho Choi: Thesis Committee Member #3]

___________________________ [Hong-Seok Moon: Thesis Committee Member #4]

The Graduate School Yonsei University

June 2007

ACKNOWLEDGEMENTS

낯설고 어렵게만 느껴졌던 출발점에서 시작하여 어느덧 세월도 흐르고 아직도

어설프지만 여러 사람들의 관심과 도움으로 마지막 골인 지점으로 들어오고

있습니다. 이것이 끝이 아니고 새로운 또 하나의 시작이란 것을 알고 있습니다.

대학원 생활 내내 만났던 좋은 사람과의 인연을 감사히 여기며, 앞으로의 삶에

있어서 초심을 잃지 않고 정진하는 사람이 될 수 있도록 노력하기로 다짐하며 이

글을 씁니다.

본 논문이 완성되기까지 끝없는 지도와 관심을 기울여 주신 이용근 지도

교수님과 많은 도움과 격려로 여기까지 이끌어주신 김경남 교수님과 김광만

교수님께 깊은 감사를 드립니다. 아울러 부족한 논문을 정성으로 세심하게

살펴주신 최성호 교수님, 문홍석 교수님께도 감사드립니다.

그리고 한결같은 사랑으로 저를 기르시고 용기를 주신 부모님과 장인어른,

장모님께도 감사의 마음을 전하며 언제나 환한 웃음으로 격려해 준 사랑하는 아내

정아와 귀여운 소현, 병진에게도 감사의 마음을 전합니다.

2007년 7월

박 영 상 드림

I

TABLE OF CONTENTS LIST OF FIGURES ·····················································································Ⅳ

LIST OF TABLES ························································································Ⅳ

ABSTRACT ··································································································V

I. INTRODUCTION ········································································································1

II. MATERIALS AND METHODS

1. CAT-scans selection······························································································6

2. Characteristics of the measurements ·····································································6

A. Position ···········································································································7

B. In the mesio-distal direction············································································7

C. In the bucco-lingual direction ·········································································7

3. Proposal of a new classification system of ridge deformities································7

A. Class I··············································································································7

B. Class II ············································································································7

C. Class III ···········································································································7

D. Class IV···········································································································7

III. RESULTS·····················································································································8

IV. DISCUSSION············································································································15

V. CONCLUSION ·································································································21

REFERENCES·······································································································22

ABSTRACT (IN KOREAN) ···············································································25

II

LIST OF FIGURES

Figure 1. Class I: implants were surrounded by bone, no dehiscence and no

fenestrations. Class І-A : ≥ 2 mm of facial plate of thickness. Class І-B :

< 2 mm of facial plate of thickness···························································8

Figure 2. Class II: dehiscence was detected but no fenestrations. Class II-A: only

buccal or palatal dehiscence was noticed··················································9

Figure 3. Class II: dehiscence was detected but no fenestrations. Class II-B: both

buccal and palatal dehiscence was noticed ·············································10

Figure 4. Class III-A: fenestrations were detected but no dehiscence························11

Figure 5. Class IV: both dehiscence and fenestrations were detected························12

Figure 6. Distribution of ridge deformities of 144 CAT images································13

Figure 7. Proper thickness of bone on buccal side of interproximal peak··················17

LIST OF TABLES

Table 1. Clinical conditions presenting tissue deficiencies in the anterior maxilla······3

Table 2. Classification of ridge defects (Soft/hard tissue defects) ·······························3

Table 3. Classification of ridge defects (Hard tissue defects) ······································4

Table 4. HVC classification and treatment options······················································4

Table 5. Clinical classification of bone defects····························································5

Table 6. Distribution of ridge deformities of 144 CAT images ·································14

Table 7. Treatment Options based on New Classification ·········································20

III

ABSTRACT

A New Maxillary Anterior Ridge Classification According to Ideal Implant Restorative Position Determined by

Computerized Axial Tomographic Analysis

Young-Sang Park

Department of Dentistry The Graduate School, Yonsei University

(Directed by Associate Professor Yong-Keun Lee, PhD)

Deformed partially edentulous ridges may compromise ideal implant placement

and survival. Deformities of the alveolar ridge may be caused by traumatic extraction,

facial trauma, clefts from birth defects, endodontic surgeries, removal of teeth with

advanced periodontal disease, or implant failures. Several published reports classified

ridge defects to help plan the treatment regimen for clinical correction. To date, no

published report has classified ridge deformities according to the position of the

projected implant restoration. Currently, 3-dimensional radiographic images are

available to evaluate hard tissue and to plan implant placement prior to surgery. The

purpose of present study was to classify ridge deformities utilizing Computerized

Axial Tomographic (CAT) scan images based on the ideal implant restorative

position as determined by implant simulation.

Clinical and CAT-scan data in this study were obtained from the Implant Dentistry

Database (IDD) established at the Department of Periodontology and Implant

Dentistry at New York University College of Dentistry. CAT-scans were selected

with the following criteria.

1) Only maxillary anterior missing teeth were included.

2) At least two consecutive missing teeth were required.

3) Images had to show at least one remaining anterior tooth, which was used as a

guide for angulation.

4) Radiographic templates used during taking of the CAT-scan were a prerequisite

for this study.

One thousand and five hundred CAT-scans were screened from the NYUCD

Department of Periodontology and Implant Dentistry IDD. Fifty five cases satisfied

the selection criteria. In these 55 subjects, 144 implant sites were evaluated.

IV

All the measurements were performed and documented using CAT-scan software

(Simplant 8.0, Materialise, Glen Burnie, MD, USA). In all CAT-scan images, one

3.25×10 mm parallel side simulated implant was positioned for every single

edentulous area.

In the new proposed classification system ridges were categorized into seven

different classes as follows.

1) Class І : The implant is completely surrounded by bone. No dehiscence and no

fenestration present.

(1) Class I-A : ≥2 mm of facial plate of thickness

(2) Class І-B : < 2 mm of facial plate of thickness

2) Class II : Dehiscences are detected but no fenestrations are present.

(1) Class ІІ-A : only buccal or palatal dehiscence is present.

(2) Class ІІ-B : both buccal and palatal dehiscences are present.

3) Class ІІІ : Fenestrations are detected but no dehiscence is present.

(1) Class ІІІ-A : only buccal or palatal fenestration is present.

(2) Class ІІІ-B: both buccal and palatal fenestrations are present.

4) Class ІV : Both dehiscences and fenestrations are present.

The following represents the findings in our study utilizing 144 CAT-scan images

to classify maxillary anterior ridge deformities. 19.4% (28) of our locations were

classified as Class І-A ridge deformities; 10.4% (15) were Class I-B; 20.8% (30) were

Class II-A alveolar defects; Class II-B were present on 12.5% (18) of our samples;

6.3% (9) of sites were fenestrations without dehiscences (Class III), and all were in

the Class III-A category (buccal or palatal fenestration). Finally, 30.6% (44) of the

potential implant site showed both dehiscences and fenestrations (Class IV). This

high number of Class IV deformities may be due to the fact that when these patients

were evaluated at the time of intra-oral examination the treating clinician noting the

ridge defect subsequently sent the patient for CAT-scan evaluation. Based on the

number of ridge deformity complications documented in the present study, a

knowledge and training in procedures for ridge augmentation may be necessary for

clinicians to obtain predictable results and manage surgical complications.

Keywords: dental, implant, ridge, classification, dehiscences, fenestrations,

augmentation

1

A New Maxillary Anterior Ridge Classification According to Ideal Implant Restorative Position Determined by

Computerized Axial Tomographic Analysis

Young-Sang Park

Department of Dentistry The Graduate School, Yonsei University

(Directed by Associate Professor Yong-Keun Lee, PhD)

I. INTRODUCTION

When considering the various modalities of treatment for the prosthetic

replacement of teeth following tooth loss, the end goal of therapy is to provide a

functional restoration that is in harmony with the adjacent natural dentition. To

achieve this goal of therapy, it is desirable to provide treatment that will aim at

preservation of the natural tissue contours in preparation for the proposed implant

prosthesis (Tarnow et al. 1996).

Implant therapy in the anterior maxilla is challenging for the clinician because of

the esthetic demands of patients and difficult pre-existing anatomy. In this area of the

mouth, the clinician is often confronted with tissue deficiencies caused by various

conditions. These conditions can be divided into 2 categories: anatomic and

pathologic (Table 1) (Buser et al. 2004).

In the anterior maxilla, unsuccessful treatment outcomes can lead to disastrous

clinical situations that can only be corrected with removal of the implant and

subsequent tissue augmentation procedures.

Several published reports classified ridge defects to help plan the treatment

regimen for clinical correction (Table 2, 3). Seibert classified ridge deformities into

three broad categories. A class I defect has bucco-lingual loss of tissue with normal

ridge height in an apico-coronal direction. A class II defect has apico-coronal loss of

tissue with normal ridge width in a bucco-lingual direction. A class III defect has a

combination bucco-lingual and apico-coronal loss of tissue resulting in loss of height

2

and width (Seibert 1983). Allen et al. proposed 3 different types of ridge deformities

and also further described the ridge deformity by assessing the depth of the defect

relative to the adjacent ridge (1985). Recently, Wang and Al-Shammari described a

new system, HVC classification, which is a modification of Seibert’s classification

(2002). These H (horizontal), V (vertical), and C (combination) defects were

subdivided into S (small), M (medium), and L (large) subcategories. They also

described treatment options based on this HVC classification (Table 4).

The advent and widespread use of dental implants mandated careful evaluation of

available bony ridge volume and dimensions. Lekholm and Zarb’s classification

includes five stages of bone resorption, from minimal to severe (1985). Misch and

Judy’s classification describes four divisions of available bone with treatment options

based on the amount of available bone height, width, and angulation (1987). Tinti and

Parma-Benfenati introduced a clinical classification of bone defects. They focused on

the “envelope of bone,” or likelihood of the remaining bone housing protecting the

organized blood clot. They assumed that the envelope of bone will direct the

treatment methods and be a significant factor in determining the prognosis for future

site development to place implants. They categorized “the envelope of bone” into five

categories: extraction wounds, fenestrations, dehiscences, horizontal ridge

deficiencies, and vertical ridge deficiencies (2003). They also proposed treatment

based on this classification (Table 5).

To date, no published report has classified ridge deformities according to the

position of the projected implant restoration. Currently, 3-dimensional radiographic

images are available to evaluate hard tissue and to plan implant placement prior to

surgery. Clinicians must focus on the 3-D bone-to-implant relationship to establish the

basis for an ideal and harmonic soft tissue situation that is stable over a long period.

Furthermore, many authors discussed the importance of at least 2 mm of facial plate

thickness (Spray et al. 2000, Grunder et al. 2005). When the facial plate is less than

this critical thickness, the clinician may expect frequent and greater loss of vertical

height of the facial plate.

The purpose of present study was to classify ridge deformities utilizing

Computerized Axial Tomographic (CAT) scan images based on the ideal implant

restorative position as determined by implant simulation.

3

Table 1. Clinical conditions presenting tissue deficiencies in the anterior maxilla

Etiology Conditions Remarks

Anatomic Narrow alveolar crest and/or facial undercut of alveolar process

Congenitally missing teeth

Dental trauma Tooth avulsion with fracture of the facial bone plate

Posttraumatic conditions Root ankylosis with infraocclusion, root resorption, root fractures

Acute or chronic infections Periodontal disease, periapical lesions, endo/perio lesions

Pathologic

Disuse bone atrophy Long-standing tooth loss

Table 2. Classification of ridge defects : Soft/hard tissue defects

Study Classification

Siebert 1983

* Class I : buccolingual loss of tissue with normal apicocoronal ridge height

* Class II : apicocoronal loss of tissue with normal buccolingual ridge width

* Class III : combination-type defects (loss of both height and width)

Allen 1985

* A : apicocornal loss of tissue * B : buccolingual loss of tissue * C : combination Mild: <3 mm ; Medium: 3-6 mm; Severe: >6 mm

4

Table 3. Classification of ridge defects : Hard tissue defects

Lekholm & Zarb 1985

* Virtually intact alveolar ridge * Minor resorption of alveolar ridge * Advanced resorption of alveolar ridge to base of dental

arch * Initial resorption of base of dental arch * Extreme resorption to base of dental arch

Misch & Judy 1987

* Abundant bone * Barely sufficient bone * Compromised bone

� C-h : compromised height; � C-w : compromised width

* Deficient width

Table 4. HVC classification and treatment options

Class Defect Size Treatment modality

Small (≤ 3 mm) Ridge expansion procedures, Inlay/onlay monocortical grafts, GBR

Medium (4-6 mm) Inlay/onlay monocortical grafts, GBR H

orizontal Large (≥ 7 mm) Inlay/onlay monocortical grafts, GBR

Small (≤ 3 mm) Orthodontic extrusion, GBR

Medium (4-6 mm) Orthodontic extrusion, GBR Onlay osseous grafts, Distraction osteogenesis

Vertical

Large (≥ 7 mm) GBR, Onlay osseous grafts, Distraction osteogenesis

Small (≤ 3 mm) Inlay/onlay monocortical grafts, GBR

Medium (4-6 mm) Combination of GBR, Monocortical inlay/onlay grafts, Distraction osteogenesis

Com

bination Large (≥ 7 mm) Difficult to correct, Large extraoral block grafts (tibia, rib, calvaria), Multiple procedures needed

5

Table 5. Clinical classification of bone defects

Extraction wounds Class I : the envelope of bone is intact Class II : the envelope of bone is not intact

Fenestrations

Class I : the implant surface penetrates the wall of bone by an insignificant amount and located within the envelope of bone

Class II : there is a convexity and a significant portion of the implant is exposed outside the envelope of bone

Dehiscence

Class I : the implant surface resides within the envelope of bone

Class II : the implant surface resides outside the envelope of bone

Horizontal ridge deficiencies

Class I : the exposed implant surface resides within the envelope of bone

Class II : the exposed implant surface resides outside the envelope of bone

Vertical ridge deficiencies Class I : the vertical insufficiency is < 3 mm Class II : the vertical insufficiency is > 3 mm

6

II. MATERIALS AND METHODS

Clinical and CAT-scan data in this study were obtained from the Implant Dentistry

Database (IDD) established at the Department of Periodontology and Implant

Dentistry at New York University College of Dentistry (NYUCD) Kriser Dental

Center. This data set was extracted as de-identified information from the routine

treatment of patients. The IDD was certified by the Office of Quality Assurance at

NYUCD. This study is in compliance with the Health Insurance Portability and

Accountability Act (HIPAA) requirements.

1. CAT-scans selection

CAT-scans were selected with the following criteria.

� Only maxillary anterior missing teeth were included.

� At least two consecutive missing teeth were required.

� Images had to show at least one remaining anterior tooth, which was used as a

guide for angulation.

� Radiographic templates used during taking of the CAT-scan were a prerequisite

for this study.

� Unclear CAT-scan images were excluded from this study.

One thousand and five hundred CAT-scans were screened from the NYUCD

Department of Periodontology and Implant Dentistry IDD. Fifty five cases satisfied

the selection criteria. In these 55 subjects, 144 implant sites were evaluated.

2. Characteristics of the measurements

All the measurements were performed and documented using CAT-scan software

(Simplant 8.0, Materialise, Glen Burnie, MD, USA) in a IDD by two independent

investigators. In all CAT-scan images, one 3.25×10 mm parallel side simulated

implant was positioned for every single edentulous area. Every simulated implant was

placed in the ideal tooth position according to following protocol and without regard

to the bone anatomy.

7

A. Position: The implants were placed according to the tooth position outlined by the

radiographic template.

B. In the mesio-distal direction: The implants were placed according to the adjacent

existing tooth position.

C. In the bucco-lingual direction: The implants were placed using the adjacent

existing tooth/teeth and the tooth position outlined by the radiographic template

allowing a variation of long axis ending either in the incisal edges or the cingulum.

In the apico-coronal direction: The implants were placed 3 mm below the buccal

cemento-enamel junction (CEJ) of the tooth position outlined by the radiographic

template.

3. Proposal of a new classification system of ridge deformities

In the new proposed classification system ridges were categorized into seven different

classes as follows.

A. Class І : The implant is completely surrounded by bone. No dehiscence or

fenestration present (Fig. 1).

(A) Class І-A : ≥ 2 mm of facial plate of thickness

(B) Class І-B : < 2 mm of facial plate of thickness

B. Class II : Dehiscences are detected but no fenestrations are present.

(A) Class ІІ-A : only buccal or palatal dehiscence is present (Fig. 2).

(B) Class ІІ-B : both buccal and palatal dehiscences are present (Fig. 3).

C. Class ІІІ: Fenestrations are detected but no dehiscence is present.

(A) Class ІІІ-A: only buccal or palatal fenestration is present (Fig. 4).

(B) Class ІІІ-B: both buccal and palatal fenestrations are present.

D. Class ІV: Both dehiscences and fenestrations are present (Fig. 5).

8

III. RESULTS

The following represents the findings in our study utilizing 144 CAT-scan images to

classify maxillary anterior ridge deformities.

Fig. 1. Class I: implants were surrounded by bone,

no dehiscence and no fenestrations.

Class I-A : ≥≥≥≥ 2 mm of facial plate of thickness

Class I-B : < 2 mm of facial plate of thickness

9

Fig. 2. Class II: dehiscence was detected but no fenestrations,

Class II-A: only buccal or palatal dehiscence was noticed.

10

Fig. 3. Class II: dehiscence was detected but no fenestrations,

Class II-B: both buccal and palatal dehiscence was noticed.

11

Fig. 4. Class III-A: fenestrations were detected but no dehiscence.

12

Fig. 5. Class IV: both dehiscence and fenestrations were detected.

13

Table 6. Distribution of ridge deformities of 144 CAT images

Group Number (rate %)

Class I-A 28 (19.4 %)

Class I-B 15 (10.4 %)

Class II-A 30 (20.8 %)

Class II-B 18 (12.5 %)

Class III 9 (6.3 %)

Class IV 44 (30.6 %)

Fig. 6. Distribution of ridge deformities of 144 CAT images.

0000

5555

10101010

15151515

20202020

25252525

30303030

35353535

I-A I-B II-A II-B III IV

14

19.4% (28) of our locations were classified as Class І-A ridge deformities; 10.4%

(15) were Class I-B; 20.8% (30) were Class II-A alveolar defects; Class II-B were

present on 12.5% (18) of our samples; 6.3% (9) of sites were fenestrations without

dehiscences (Class III), and all were in the Class III-A category (buccal or palatal

fenestration). Finally, 30.6% (44) of the potential implant site showed both

dehiscences and fenestrations (Class IV). Class IV ridge deformities had the highest

incidence followed by Class II- A, Class I-A, II-B, I-B, and Class III.

Other findings showed that 28 Class I-A deformities were in 17 cases; 15 Class I-B

deformities were in 14 cases; 30 Class II-A deformities presented in 21 cases; 18

Class II-B deformities were found in 9 cases; 9 Class III deformities were observed in

5 cases, and 44 Class IV deformities were noted in 18 cases. Class II-A was the most

common ridge deformities followed by Class IV, Class I-A, Class I-B, Class II-B and

Class III.

There were 34 patients (61.8%) with more than one class of ridge deformities

present and the remaining 21 patients (38.2%) showed only one class of deformity.

15

IV. DISCUSSION

The ultimate goal of implant treatment is to surgically place implants in the most

desirable position compatible with esthetics, phonetics, and function. Identification of

the “optimal final tooth position” allows the restorative dentist and surgeon to analyze

the impact of pathologic alterations and to determine if soft or hard tissues need to be

reconstructed to maximize function and esthetics (Mecall & Resenfeld 1996). The

esthetic replacement of anterior teeth is a difficult challenge, especially in the

maxillary arch. This situation can be further complicated by the presence of a ridge

deformity. These anatomic defects may seriously compromise the esthetics of the

final restoration. The defect should be carefully examined and classified before any

attempt at restoration. The treatment modality used will depend to a great extent upon

the type of deformity (Abrams et al. 1987).

Alveolar ridge defects and deformities can be the results of trauma, periodontal

disease, surgical treatment or congenital maldevelopment. Resorption after tooth loss

has been shown to follow a certain pattern: the labial site of alveolar crest is primarily

resorbed, which first reduces its width and later the height (Truhlar et al. 1997,

Atwood 1983, Cawood & Howell 1988). Atwood described six residual alveolar ridge

stages after tooth extraction, ranging from initial to severe ridge resorption.

Longitudinal cephalometric studies have provided excellent visualization of the gross

patterns of the bone loss (1971).

Alveolar bone is resorbed after tooth extraction or avulsion most rapidly during the

first years. Extraction of anterior maxillary teeth is associated with a progressive loss

of bone mainly from the labial side (Cawood & Howell 1988). The loss is estimated

to be 40-60 % during the first 3 years and decreases to 0.25-0.5 % annual loss

thereafter (Ashman & Rosenlicht 1993). The cause for resorption of alveolar bone has

been assumed to be due to disuse atrophy, decreased blood supply, localized

inflammation or prosthesis pressure (Ashman 2000).

The osseous topography of the anterior sextants, and their relation in space relative

to the cranium, plays a leading role in shaping dentofacial aesthetics. In health, the

alveolus in these regions not only serves as the foundation for the natural dentition

and associated gingival tissues but is also responsible for supporting the lips as well

16

as directly affecting the facial profile.

Much more prevalent in everyday practice are patients with normal skeletal pattern

who have lost a substantial degree of their original osseous dimensions due to tooth

loss or trauma. Reconstructing any resulting aesthetic deficiencies through purely

prosthetic means often proves impossible or, at best, inadequate for patients with high

smile lines and those demanding a fixed restorative option. If the fixed restoration is

to be implant supported, reconstructing the deformed osseous ridge may be necessary

to allow for functionally and esthetically oriented placement of the implants.

The minimal requirements for predictable success in implant therapy include an

edentulous ridge that manifests an osseous dimension capable of fully housing the

diameter of the fixture buttressed by 1mm of bone bucally and lingually. Although

gingival augmentation procedures are capable of significantly enhancing soft tissue

ridge profiles for conventional pontics in fixed prosthodontics, they are ineffective in

preparing deficient osseous ridges for implant placement. If the potential implant

receptor sites are thus compromised, alternative osseous augmentation techniques

need to be used.

Soft and hard tissue ridge deformities are prevalent in areas of tooth loss and trauma

and significantly compromise aesthetics outcomes. Only a full understanding of the

severity of the dimensional defects, the surgical techniques available and the aesthetic

and functional needs of the final implant or fixed prosthetic restoration will allow the

design of a treatment approach that will achieve the desired outcome (Seibert 1996).

Pre-operative estimation of the width and height of alveolar bone before

implantation is important. Computerized tomography (CT) scans have been used in

estimating bone quality and quantity before implantation and the gain of new bone in

sinus floor augmentations as well as in integration of interpositional bone grafts. The

analysis requires multiple thin axial CT slices through the jaws. The data obtained is

reformatted with special software packages to produce cross-sectional and panoramic

views (Oikarinen et al. 2003).

To achieve a long-lasting, ideal esthetic result with implants, in light of

circumferential bone resorption that usually occurs as part of the healing response

around the implant head, the thickness of the bone on the buccal side of an implant

should be at least 2 mm (Fig. 7) (Grunder et al. 2005). Having a facial bone wall of

17

sufficient height and thickness is important for long-term stability of harmonious

gingival margins around implants and adjacent teeth. Attempts to place implants in

sites with facial bone defects in the absence of reconstruction will frequently result in

soft tissue recession, potentially exposing implant collars and leading to loss of the

harmonious gingival margin.

Fig. 7. Proper thickness of bone on buccal side of interproximal peak.

2 mm2 mm2 mm2 mm

18

Deficient alveolar crest width and /or facial bone atrophy require a bone

augmentation procedure so that the implant can be positioned in a correct orofacial

position. Depending on the extent and morphology of the bone defect, a simultaneous

or staged approach is necessary. Clinical sounding and sophisticated radiographic

techniques such as conventional tomograms, dental computerized tomograms (CTs)

or volume CTs can assist in diagnosing deficiencies in this dimension (Buser et al.

2004).

The bone augmentation technique employed to reconstruct these different ridge

defects is dependent on the horizontal and vertical extent of the defect. The

predictability of the corrective reconstructive procedures is influenced by the span of

the edentulous ridge and the amount of attachment on the neighboring teeth; typically,

reconstructive procedures are less favorable in defects that exhibit horizontal and

vertical components. The extent of the anticipated bone resorption varies between the

mandible and maxilla and at sites within the arches (McAllister & Haghighat 2007).

Using the proposed new classification system, ridge classification of the bone

defects may be identified and complications avoided due to more accurate treatment

planning of implant size and position (Table 7). The relationship between the adjacent

teeth and bone can also be observed by utilizing the radiographic template, which was

worn by the patient when taking the CAT-scan.

The advantages of this new Implant Oriented Classification System (IOCS)

include: 1) more accurate evaluation of the clinical situation prior to surgery to

determine treatment options. 2) the ability to evaluate the need for hard tissue

augmentation and simulate the necessary augmentation prior to surgery. 3) allowing

selection of appropriate implant type and size before surgery. 4) using the

radiographic template as a surgical guide. 5) ability to communicate with restorative

dentists and patients concerning treatment procedures and the expected outcomes.

19

Table 7. Treatment Options based on New Classification

Suggested Treatment Options

Class I-A Implant placement in ideal restorative position

Class I-B Implant placement without dehiscence or fenestration

Class II-A Staged GBR; Simultaneously GBR and implant placement;

Ridge expansion; Ridge splitting

Class II-B Staged GBR; Simultaneously GBR and implant placement;

inlay/onlay block graft; distraction osteogenesis

Class III Staged GBR; Simultaneously GBR and implant placement;

inlay/onlay block graft, Taper implants; Shorter implants

Class IV Distraction osteogenesis + Staged GBR or onlay graft;

block graft

A 3.25×10 mm implant was selected as a guide implant for the new IOCS because,

according to the literature, this is the smallest permanent implant with a high success

rate (Andersen et al. 2001, Lekholm et al. 1999). This study indicated that narrow-

diameter implants used in the anterior region of the maxilla as support for single-tooth

replacements show results that are comparable to standard-diameter implants placed

the same region (Andersen et al. 2001). The reason for the use of the smallest

permanent implant in this study was to avoid any ridge augmentation procedures. A

variety of successful grafting techniques have been developed, but they often require

multiple surgical procedures and prolonged healing time.

Evaluation of a residual ridge deformity begins with the determination of the

optimal final tooth position. An assessment of ridge alteration can only be made by

completing a clinically tested diagnostic wax-up in which the parameters of tooth size

and coronal form have been established. Implant diagnostic methods using computed

tomography with barium-coated templates have revealed the relationship between the

20

optimal final tooth position and the residual alveolar process or ridge. This

information can assist the implant team in the development of realistic treatment

objectives and in more accurately addressing the needs and concerns of the patient

during presurgical treatment planning (Mecall & Rosenfeld 1996).

The ideal implant position in this study was based on the radiographic template.

The simulated implants were placed 3 mm below the ideal CEJ as a determined from

the wax-up and radiographic template in order to provide enough apicocoronal room

for esthetic prosthetic replacement (Buser et al. 2004).

The results reported in the present study revealed that 29.8 % of the deformities

were classified as Class I. Almost 66 % of Class I deformities were classified as Class

I-A. The remaining 34 % of the Class I defects would require some form of bone

augmentation procedure for a successful long term prognosis. On the other hand 30 %

of the deformities were classified as Class IV according to the CAT-scan simulation.

This high number of Class IV deformities may be due to the fact that when these

patients were evaluated at the time of intra-oral examination the treating clinician

noting the ridge defect subsequently sent the patient for CAT-scan evaluation.

Nevertheless, these findings indicate that a significant number of implant cases would

require ridge augmentation for implant placement or a modification in the treatment

plan which may preclude the use of an implant in these sites.

According to our IDD CAT-scan data, 81 % (116 of the total 144) of the implant

sites and 92.7 % (51 of 55) of the cases studied were identified as requiring grafting

procedures. This may be due to the pre-existing anatomy and ridge resorption pattern

in the maxillary anterior area (Atwood 1971, Atwood & Coy 1971). However,

deformities in the anterior part of the maxilla may be related to the tooth biotype,

genetic disorders, trauma, iatrogenic damage of the bone, or other reasons

independent of the maxillary resorption. The limited number of cases present in our

study that did not require graft procedures with the 3.25 mm diameter template may

be of importance for clinicians placing implants in the maxillary anterior area.

Moreover, the use of conventional diameter implants would have resulted in a greater

number of ridge defects and complications than that reported in the present study

population. In addition this may have increased the number of patients with more

advanced classifications of deformities. Based on the number of ridge deformity

21

complications documented in the present study, a knowledge and training in

procedures for ridge augmentation may be necessary for clinicians to obtain

predictable results and manage surgical complications.

V. CONCLUSION

The present report proposed a new classification system for maxillary anterior

alveolar ridge deformities based on CAT-scan implant simulation as a useful concept

in order to more precisely predict treatment outcomes and the necessity for ridge

augmentation prior to implant placement. The results indicate that a high number of

cases in the maxillary anterior area would require augmentation procedures in order

to achieve ideal implant placement and restoration.

22

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Andersen E, Saxegaard E, Knutsen BM, Haanaes HR (2001). A prospective clinical

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25

ABSTRACT (in Korean)

컴퓨터컴퓨터컴퓨터컴퓨터 단층촬영단층촬영단층촬영단층촬영 분석을분석을분석을분석을 이용한이용한이용한이용한 이상적이상적이상적이상적 임임임임플플플플란트란트란트란트 수복수복수복수복 위치에위치에위치에위치에

따른따른따른따른 상악상악상악상악 전치부전치부전치부전치부 치조제의치조제의치조제의치조제의 새로운새로운새로운새로운 분류분류분류분류

< 지도교수 이용근 >

연세대학교 대학원 치의학과

박 영 상

이상적인 위치로의 임플란트 식립 뿐 아니라 성공율 면에서도 손상된 부분

무치악제는 여러 가지 어려움이 있다. 이런 치조제의 손상은 외상성 발치, 안면 외상,

치근단 수술, 만성 치주염으로 인한 발거, 임플란트 실패 등으로 기인한다. 특히 상악

전치부의 경우 좋지 않은 치료 결과로 인하여 임상가와 환자 모두에게 크나큰 좌절을

유발할 수도 있다.

지금까지 여러 논문에서 치조제 손상에 대한 분류 및 임상적 대처 방법에 대해

보고하였으나, 임플란트의 이상적인 수복 위치에 따른 분류법은 소개된 적이 없었다.

실제로 수술에 앞서 3차원적 방사선 영상을 통해 경조직을 평가하고 심미적이고

연조직과 조화스러운 임플란트 시술이 되도록 주의해야 한다. 이 논문의 목적은

컴퓨터 단층촬영 분석을 이용하여 이상적 임플란트 수복위치에 따른 상악 전치부

치조제의 손상을 분류하는 것이다.

이 연구에 이용된 데이터는 뉴욕대학교 치주�임플란트과의 데이터를 이용했으며

아래와 같은 경우에 한하여 자료를 수집하였다.

(1) 상실된 상악 전치부 증례만 포함

(2) 최소 2개의 인접 치아가 상실된 증례

(3) 원래의 치아 각도를 알 수 있는 최소 1개의 잔존 치아 존재

(4) 치아외형 형판을 컴퓨터 단층 촬영시 착용

26

이를 근거로 1500개의 필름을 검토한 뒤 55개의 증례와 144개의 임플란트 수복

부위를 평가하였다.

모든 측정은 특정 소프트웨어 (Simplant 8.0) 를 이용하였으며, 3.25×10 mm

크기의 가상 임프란트를 이용하였다.

먼저 이 연구에서 제시한 새로운 치조제 분류방법은 제 1군-A는 2 mm 이상의

순측골을 가지며 열개나 창이 없고, 제 1군-B는 2 mm 이하의 순측골을 가지며

열개나 창이 없고, 제 2군-A는 한쪽편의 열개를 가지고 있고 창은 없으며, 제 2군-

B는 협, 설측 모두 열개를 보이며 창은 없고 제 3군-A는 열개는 없고 한쪽편의 창을

보이며, 제 3군-B는 열개는 없고 협, 설측 모두 창을 보이고 제 4군은 열개, 창을

모두 보이는 것으로 분류하였다. 본 연구 결과 제 4군이 30.6 %로 가장 많았으며 그

뒤로 제 2군-A (20.8 %), 제 1군-A (19.4 %), 제 2군-B (12.5 %), 제 1군-B

(10.4 %), 제 3군 순이었다. 제 4군 변형이 가장 많은 숫자를 나타낸 것은 초진 당시

이미 치조제 변형을 감지하여 컴퓨터 촬영이 필요한 것으로 의뢰하였기 때문으로

여겨진다. 또한 본 연구에서 사용한 임플란트보다 큰 일반적 크기의 임플란트 적용시

더 많은 숫자의 치조제 손상을 보일 것으로 예상된다. 따라서 임상가들은 이런 손상된

치조제 증례에서도 좋은 예후를 보일 수 있도록 정확한 진단과 골 증대술과 같은

수술적 접근법에도 익숙해질 수 있도록 노력해야 할 것이다.

핵심되는핵심되는핵심되는핵심되는 말말말말:::: 치과, 임플란트, 치조제, 분류, 열개, 창, 골 증대술