university of glasgow

Anterior open bite & high angle case

Personal notes

Dr. Mohammed Almuzian

1/1/2013

.

Table of Contents

Definition.........................................................................................................................................2

Incidence..........................................................................................................................................2

True rotation, matrix rotation & apparent total rotation as described by Bjork 1969.....................5

Predictors of skeletal open bite........................................................................................................6

Features of high angle or long face syndrome.................................................................................8

Overbite and Open bite..................................................................................................................10

Indication of treatment...................................................................................................................11

The etiology can be classified into................................................................................................11

Treatment is dependent on the.......................................................................................................14

Methods of treatment.....................................................................................................................14

In details.........................................................................................................................................15

1. For sucking habit....................................................................................................................15

Prevention of digit-sucking sucking habits, BOS guidelines 2000..........................................16

Treatment of digit-sucking habits, BOS guidelines 2000.........................................................16

Correction of Problems Caused by Habit.................................................................................17

2. For mouth breather.................................................................................................................17

3. For tongue thrust....................................................................................................................17

4. Myofunctional Therapy..........................................................................................................18

5. Extraoral Traction...................................................................................................................20

6. Fixed Appliances....................................................................................................................20

8. Molar intrusion using skeletal anchorage...............................................................................22

9. Repelling magnets..................................................................................................................23

10. Orthognathic Surgery..........................................................................................................23

11. Adjunctive procedure..........................................................................................................23

Stability of AOB............................................................................................................................23

Management of relapse..................................................................................................................24

Difficulty associated with the treatment of AOB, Burford 2003 Sandler 2011............................24

Posterior open bite.........................................................................................................................25

Caused by.......................................................................................................................................25

Treatment.......................................................................................................................................25

Summary of the evidences.............................................................................................................25

Anterior open bite & high angle case

Definition

Dental AOB: It is present when there is no incisor contact and no vertical overlap of the lower

incisors by the uppers (Houston, 1996). The severity varies, from almost an edge-to-edge

relationship to a severe handicapping open bite.

The skeletal AOB is mainly due to growth problem that is associated with un-balanced growth

between the AFH and PFH leading to posterior growth rotation and AOB. It characterized by

increased in AFH, shortened PFH, steep MP, divergent facial profile and antegonial notch.

Classification (worms 1971)

Pseudo pen bite which means that there is positive vertical overlap between U and L incisors

with no contact.

True open bite: loss of vertical overlap

Incidence

In children is 4% at age 9 years, falling to 2% by the early teenagers (O’Brien, 1993).

One measure of the importance of the inherited characteristics is the incidence of AOB in

black and white individuals in the USA.

Blacks are 8 times more likely to have an AOB.

Worms 1971 showed 50% reduction from age of 7 till 12 (from 13.5% to 3.7%)

Type of growth of the mandible

Nielsen et al 1991

1. Normally

A. The direction of condylar growth is vertical, with some anterior component,

B. Always there is a balance between APH and PFH growth to achieve normal FH. If this is

lost then either long or short face might develop

C. AFH depend on the

1. Eruption of the maxillary and mandibular posterior teeth

2. Growth at the posterior dentoalveolar area

3. The amount of sutural lowering of the maxilla.

4. Surface remodelling at the anterior region of the mandible

D. PFH depend on the

1. Downward growth of posterior cranial fossa

2. Lowering of the temporomandibular fossae

3. Condylar growth.

4. Surface remodeling at the posterior region of the mandible

2. In anterior or forward rotation

If the incisor occlusion is stable, the overbite remains unchanged during the

growth period & the fulcruming point is located at the front teeth.

If the incisor occlusion is unstable, the fulcruming point is located further back

along the occlusal plane. In this situation the bite normally becomes increasingly deep

over time as the result of greater posterior face height increase in combination with lack

of anterior tooth contact. This deterioration of the occlusion is most pronounced during

puberty when growth intensity is at its greatest, but continues throughout the growth

period. Patients with a pronounced tendency to anterior growth rotation and a deep bite

should therefore be treated early and the occlusion supported throughout the growth

period. Retention, especially in the mandibular arch, must also be maintained until

mandibular growth is completed.

The erupting dentition in this type of mandibular growth characteristically

undergoes a considerable amount of mesial migration of both the maxillary and

mandibular teeth with some degree of proclination of the mandibular incisors. Where the

amount of mesial migration of the lower posterior teeth does not equal the advancement

of the incisors by proclination (due to trapping behind upper incisors), secondary

crowding of the front teeth frequently develops.

3. In posterior rotation of the mandible

If dentoalveolar growth is greater than vertical condylar growth, the resulting

change in mandibular position is back ward or posterior rotation of the mandible. The

increase in AFH is greater than in PFH, the mandible rotates posteriorly with the fulcrum

at the condyle.

This posterior growth rotation may result in an anterior open bite, depending on

the extent of vertical dentoalveolar compensation.

The associated dental eruption pattern of the posterior teeth is generally distal &

vertical and in some instances the anterior teeth may even become more retroclined with

time. Late crowding is common finding in this pattern of growth due to soft tissue

maturation.

Because the centre for the growth rotation is located near the mandibular

condyles, treatment should be postponed until after puberty or at least until the potential

for backward or posterior rotation is reduced. The reason for late treatment is that

A. The tendency to extrude the posterior teeth decreases when there is less active growth.

B. In addition when treated orthodontically these patients are at increased risk for further

mechanically induced posterior rotation by acceleration of their molar eruption and

require careful control.

C. The increased risk of extrusion in these patients is associated with their weaker

masticatory musculature making vertical control an important consideration.

True rotation, matrix rotation & apparent total rotation as described by Bjork 1969

The actual rotation or total rotation in humans is generally masked on average by

50% surface modelling within the jaws.

In a recent study of non-human primates, it was found that this modelling or

intramatrix rotation in the Rhesus monkey masked the rotations by about 75% in the

maxilla and 90% in the mandible.

This surface modelling causes, in most instances, the lower border of the

mandible to appear almost unchanged in its inclination to the cranial base and has led to

misinterpretations of the actual growth changes and tooth movements in humans.

An example of this is seen in Figure below

where the change in mandibular lower border

inclination over time, the so-called matrix rotation,

was -7.3° whereas the actual, or true rotation, was

as much as -16.4° anteriorly

Predictors of skeletal open bite

A. Bjork's structural signs (Bjork, 1969)

B. PFH:AFH ratio (Jarabak ratio)

C. UAFH-LAFH ratio : Nahoum (1975)

D. Molar and incisor dentoalveolar (Neilsen, 1991).

E. Dung and Smith technique

F. The degree of dentoalveolar compensation or dysplatic compensation Bjork 1969

A. Bjork's structural signs help to predict type of growth rotation , (Skieller and Bjork, 1969)

1. A backward inclination of the condyles;

2. A flat mandibular canal;

3. A lower border that is thinner anteriorly and convex, due to minimal remodelling along the lower

border of the mandible and bony deposition at the posterior border of the ramus;

4. The symphysis is inclined backward within the face and the chin is receding;

5. The interincisor angle decreased

6. Interpremolar and intermolar angles are all decreased;

7. The lower anterior face height is increased and there is an anterior open bite.

The authors reported that a combination of four variables ccounted for 86% of the variability

observed.

B. PFH:AFH ratio (Jarabak ratio)

Jarabak, 1972

PFH:AFH, 59 – 63% is normal;

if 64 low angle case, deep OB;

58 high angle case, reduced OB

C. UAFH-LAFH ratio: Nahoum (1975) believed that patients with a dental open bite and a UAFH-

LAFH ratio of less than 65% (normally they are equal) are considered to be poor risks for

conventional orthodontic treatment alone.

D. Increased dentoalveolar height in molar region and reduced dentoalveolar height in incisor

region due to strong muscle allowing molar eruption. (Neilsen, 1991).

E. Dung and Smith

Dung and Smith’s sample (1988).

SN/MP angle 40º or greater

OP/MP angle 22º or greater

MxP/MnP angle 32º or greater

AOB negative overbite

PFH/AFH (Jarabak ratio 58% or less

UFH/LFH (Nahoum ratio) 0.65 or less

A seventh measurement was used, namely, the overbite depth

indicator (ODI)

68

This was described by Kim in 1974, and is described as the angle the A-B plane makes with the

mandibular plane combined with the angle of the palatal plane to the Frankfort horizontal. PP-

FH is positive it is added this value from AB-MP and vice versa. A value of less than 68º is said

to indicate an open bite tendency. The value of this analysis is that it

proposes to identify those patients who have an open bite tendency

and identifies open bite patients who have a good potential for

orthodontic correction.

The only measurements that were statistically significant were the

overbite depth indicator (ODI) and the presence of an open bite at

the start of treatment.

F. The degree of dentoalveolar compensation or dysplatic

compensation

First described by Bjork 1969 and later discussed by Solow. These

can be measured through the following:

In the maxilla, the maxillary zone, measured as the angle between

the palatal plane (ANS-PNS) and the maxillary occlusal plane (mean

10°±3 ), describes the extent of compensatory or dysplastic development.

In the mandible, the mandibular zone, measured between the mandibular plane (GO-GN)

and the mandibular occlusal plane (mean 20°±4°), similarly describes possible

compensation.

If one or both of these measurements are increased in a patient with an increased vertical

jaw relation, favorable dentoalveolar compensation is indicated.

On the other hand, if these measurements are normal or reduced in the same patient,

either no compensation or dysplastic development has taken place.

This will help in determine the type of treatment. Eg. If the high angle case has no

compensation or has dysplastic development, then treatment can be achieved through

orthodontic treatment to initiate this compensation, but if the compensation is already

present then the case is surgical.

Features of anterior open bite angle and/or long face syndrome

A. Skeletal feature

1. Tapered facial type.

2. Long lower third of the face,

3. Long maxilla

4. Short mandible

5. Short ramus

6. Class II skeletal relationship

B. Cephalometric feature.

1. Enlarged adenoid seeing in the ceph

2. Increased dentoalveolar height in molar region and reduced dentoalveolar height in incisor

region due to weak muscle allowing molar eruption. (Neilsen, 1991)

3. Bjork’s seven features of posterior growth rotation (Bjork, 1969)

4. Jarabak ratio: 58 high angle case, reduced OB

5. UAFH-LAFH ratio: less than 65%

6. The overbite depth indicator (ODI) less than 68 degree

C. Soft tissue features

1. Long lower third of the face,

2. Narrow nose

3. Narrow alar bases

4. Decreased nasolabial angle

5. Incompetent lip

6. VME & excessive exposure of maxillary anterior teeth and gingiva at rest and smiling which is

due to dentoalveolar compensation of the anterior part of the maxilla to compensate for AOB.

7. Retruded chin

D. Intraoral features

1. Open bite

2. Class 2 tendency

3. Increased overjet

4. Narrow upper arch

5. Crowded LLS

E. Growth feature

Usually posterior growth rotation

F. Path of closure

Usually normal or may be associated with unilateral cross bite and mandibular displacement

G. IOTN and OB

Overbite measured from any of the lateral or central incisors with the largest

vertical discrepancy is recorded.

Overbite and Open bite

Overbite Open bite

Grade and

qualifier

Grade and

qualifier

2f Increased greater Than Or equal to 3.5

mm

2e Anterior or posterior open

bite 0-2mm

3f Deep overbite complete on labial or

palatal 'issues but no Trauma

3e Anterior or posterior open

bite 2.1 mm — 4 mm

4f Increased and complete overbite with

labial or palatal trauma

4e Extreme lateral open bites

greater than 4 mm

Indication of treatment

1. Difficulty with incision of food

2. Speech problems like lisping

3. Dental and facial appearance

The etiology can be classified into

1. Transitional physiological factors

2. Skeletal factors

3. Soft tissue factors

Muscle of mastication

Neurological disturbances

Chronic nasal obstruction

Adenoids

4. Habits,

Digit Sucking Habits.

Endogenous (primary) thrust

5. Pathology

Inflammatory

Hormonal

6. Traumatic

7. Local Dental factors

8. Iatrogenic factors

9. Combination

In details

1. Transitional physiological causes, as the permanent incisors are erupting

2. Skeletal factors

A. Genetic

Vertical growth pattern more genetically correlated than horizontal one; if you had the long face

in one generation then chances are high that you would have a long face in the next generation.

(Hunter 1968)

B. Environmental which subdivided into:

I. Inflammatory: Juvenile rheumatoid arthritis An inflammatory arthritis occurring before the age

of 16 years and involving the temporomandibular joints can result in the development of a severe

class II malocclusion and AOB due to restricted growth of the mandible

II. Hormonal: Excessive growth hormone Overproduction of growth hormone from an anterior

pituitary tumour causes gigantism in children and acromegaly in adults. In both circumstances,

the patient presents with a worsening class III malocclusion characterized by mandibular excess

and AOB.

III. Traumatic:The condyle is the commonest site of fracture in the mandible during childhood and

many go undiagnosed. In severe cases with bilateral fracture and dislocation from the glenoid

fossa, an anterior open bite can be one of the presenting features due to a loss in ramus height. A

long-term sequelae of early trauma to the mandibular condyle can be asymmetry, with an

ipsilateral decrease in ramus height and deviation of the chin point to the affected side.The

severity of outcome is in part related to the age at the time of injury. However, a high percentage

of children sustaining a condylar fracture have normal mandibular growth due to the reparative

capacity of the condyle, even when displaced from the glenoid fossa.

3. Soft tissue factors

I. Muscle of mastication: Hunt 1997 & Benington 1999 showed large muscle fibres in deep bite

and small size muscle fibres in AOB. This again is classified under the genetic effect

II. Neurological disturbances and Muscle weakness

III. Chronic nasal obstruction (Solow & Tallgren 1976)

IV. Adenoids (Aronson, 1979). However, Vig (1985) that “ the magnitude of the morphological

difference attributed to adenoid removal was far too small to be of any clinical significance”

4. Habits,

I. Digit Sucking Habits.

The incidence of digit sucking is around 30% at 1 year of age, reducing to 12% at 9 years and

2% by 12 years. Most persistent suckers are female (Brenchely, 1992).

The severity of the malocclusion depends on the age of the patient, the intensity, frequency and

duration of the habit. Larsson, 1987

II. Long term pacifier (Larsson 1987)

III. Endogenous (primary) thrust

Very rare & affects 1% of population

Usually associated with lack of neuromuscular control e.g. Downs syndrome

May cause AOB which is difficult to close

Usually associated with a lisp, bimaxillary proclination, reverse COS in the lower and deep COS

in the upper. The diagnosis is therapeutic which means the high tendency to relapse after

treatment.

5. Local Dental factors

Localized failure of development of anterior teeth

Over eruption of posterior teeth

Proclination of incisors

6. Idiopathic factors Idiopathic like idiopathic condylar resorption

7. Combination

Treatment is dependent on the

1. Age

2. Family history

3. Medical condition

4. Growth

5. Concerns

6. Profile

7. Etiology

8. Severity

9. Intra and intermamaxillary relationship

10. Compliance

11. Clinician philosophy

Methods of treatment

For sucking habit

For mouth breather

For tongue thrust

Myofunctional Therapy Muscle exercise

Vertical holding appliance

Spring-loaded bite block

Passive posterior bite-blocks

The functional regulator appliance (FR IV)

Myofunctional+EOA

combination Therapy

Teuscher activator

BIS

MIS

Concorde appliance

Van Beek appliance

Twin block appliance modifications including:

1. TB with high-pull headgear inserted in the flying spring

2. Thick Twin block appliance

3. TB with occlusal stopper

4. Avoid trimming the appliance

Extraoral Traction Vertical pull chin-cup

High-pull headgear

Fixed Appliances Extraction of terminal molars

Bracket set up

Wire bending

Tongue timer which act as a tongue thrust breaker

Vertical intermaxillary elastics

Segmental arch mechanics

Kim mechanics

Modified Kim mechanics

Molar intrusion using skeletal anchorage

Repelling magnets

Orthognathic Surgery

Adjunctive procedure

In details

1. For sucking habit

Please refer to my summary about Digit sucking & dummy-sucking habit

Prevention of digit-sucking sucking habits, BOS guidelines 2000

1. If a dummy is provided, there appear to be fewer problems in the long-term, because the majority

of dummy sucking habits are self-limiting and stop before eruption of the permanent teeth. Any

persistent dummy sucking habit is easily broken by removal of the dummy.

2. It has been suggested that if a digit-sucking habit is noticed, a dummy should be given to the

child.

3. If a dummy is used, it must not be sweetened. After the age of 2, to prevent problems with

speech development, it should be used as little as possible during the day

Treatment of digit-sucking habits, BOS guidelines 2000

1. The child must want to stop otherwise any approach is likely to be unsuccessful.

2. A child who is undergoing severe psychological trauma is unlikely to respond to habit breaking.

A psychologist’s input may be required

3. The use of orthodontic pacifiers which is oval shape and has a vent to reduce the effect of

dummies.

4. The following methods for breaking the habit are listed in the order in which they should be

used:

A. Non-physical methods

Explanation

Reward

Habit reversal

Teach the child to carry out alternative activities when they have the urge to suck the digit

B. Physical methods

Reminder therapy like finger bandage, finger paint or thermoplastic finger post

C. Intra-oral appliances

These deterrent appliances have been shown to be effective within 10 months.

They must be fitted with the full understanding and co-operation of the child and must not

compromise compliance with any future orthodontic treatment.

Fixed appliance like palatal appliance with crib or Blue grass appliance (Huang 1990)

Removable appliance

Functional appliance can stop habit

Correction of Problems Caused by Habit

Active orthodontic treatment should not be attempted until the habit is broken. Fortunately, most

of the problems created by the habit are reversible once the habit is eliminated. It has been

suggested that digit-sucking beyond the age of 7 has been associated with an increased risk of

root resorption during orthodontic treatment

2. For mouth breather

Although prolonged mouth breathing may be a contributory factor for malocclusion, it is not

necessarily the main etiological factor. Therefore, adenoidectomy or tonsillectomy is not

recommended in the prevention of malocclusion and should be done for medical purposes only.

Another justification for not performing elective adenoidectomy in mouth breather is the high

risk of prion disease transmission.

3. For tongue thrust

Parker (1971) used spurs soldered to upper central incisor bands to produce dramatic changes in

anterior open bite and posterior crossbite by altering tongue posture. The suggestion is that

anterior tongue posture is responsible for anterior open bites in cases of normal skeletal

proportions with no history of a digit sucking habit. The tongue spurs should be placed

approximately 3-4 mm behind the upper incisors and should be angled backwards and

downwards so that they establish a positive overlap with the lower incisors. Tongue spurs might

cause psychological problems Haryett et al (1967, 1970). Careful explanation of the purpose of

tongue spurs is therefore essential before embarking on treatment. Huang et al (1990) showed a

similar results. Tongue cribs or spurs should be worn for six months after a positive over bite is

achieved; careful patient motivation is required and sharpened spurs are preferred to smooth

ones. The spurs may be carried over to the retainer if desired.

Sometime for primary tongue thrust glossotomy is recommended.

4. Myofunctional Therapy

1. Muscle exercise described by Laurie Park 2007 (Patients were instructed to clench their teeth

together as hard as possible for 15 seconds and to repeat this process at least four times for a total

of one minute; this one-minute exercise was to be performed as often as possible throughout the

day).

2. Vertical holding appliance (TPA with acrylic pad that kept away from palate and rely on the

tongue force to intrude the posterior teeth.

3. Spring-loaded bite block, the spring-loaded bite block has helical springs that are placed both

lingually and buccally between the first premolar region and the last molar region. The ends of

the springs are embedded occlusally in the molar regions of the acrylic part of the device. The

upper and lower acrylic occlusal blocks are connected by palatal and lingual wires, which are

activated to a force of 450 g bilaterally. Patients are instructed to use the appliance for an average

of 16 h daily

4. Passive posterior bite-blocks are functional appliances that are used to open the bite 3–4 mm

beyond the rest position. In growing patients, this inhibits the increase in height of the buccal

dentoalveolar processes, thus preventing a downwards and backwards rotation of the mandible. It

also allows differential eruption to occur as the labial segments can erupt unhindered, hence

closing the AOB.

5. The functional regulator appliance (FR IV) It works by allowing vertical eruption of upper and

lower incisors and retraction of the maxillary incisors, and may also encourage upward and

forward mandibular rotation. Cochrane review, by Oliveira , 2007 showed that there is weak

evidence that the interventions FR-4 with lip-seal training and palatal crib associated with high-

pull chin cup are able to correct anterior open bite. Given that the trials included have potential

bias, these results must be viewed with caution.

6. Teuscher activator

7. BIS

8. MIS

9. Concorde appliance

10. Van Beek appliance

11. Twin block appliance modifications including:

TB with high-pull headgear inserted in the flying spring can be utilized to correct the

anteroposterior discrepancy while controlling the vertical dimension. Park 2001

Thick Twin block appliance: The ramps measure 5 mm to 8 mm in thickness in the premolar

region. This impinges on the patient's freeway space, which, in turn, results in increased masseter

tension. This tension not only restricts vertical descent of the maxillary posterior teeth, but also

produces a relative intrusion of the posterior aspect of the maxilla in growing patients." This

phenomenon, which is called the bite-block effect, provides excellent vertical control. Although

long-term studies documenting the results of this treatment are not yet available, the early results

are promising.  Clark 2010

TB with occlusal stopper

Avoid trimming the appliance

5. Extraoral Traction

1. Vertical pull chin-cup therapy has been used to limit excessive vertical growth and has been

shown to close AOBs when combined with premolar extractions and fixed appliances as well as

palatal crib

2. High-pull headgear applied to the maxillary molar teeth worn for 14 hours per day has been

used to inhibit eruption of the posterior teeth and hence limit vertical growth. Many strategies

available including:

High pull headgear to a maxillary splint.

High pull headgear to buccal splint.

Headgear can be applied directly to the upper molar bands of a fixed appliance .

Cochrane review, by Oliveira , 2007 showed that there is weak evidence that the interventions

FR-4 with lip-seal training and palatal crib associated with high-pull chin cup are able to correct

anterior open bite. Given that the trials included have potential bias, these results must be viewed

with caution.

6. Fixed Appliances

Anterior open bites can be closed using fixed appliances with

A. Extraction of terminal molars

B. Bracket set up (more gingival at anterior teeth, reduced canine tipping)

C. Wire bending to allow incisor extrusion

D. Tongue timer which act as a tongue thrust breaker

E. Vertical intermaxillary elastics to extrude the anterior teeth. Use of anterior elastics may be

successful in patients in whom a digit sucking habit has artificially inhibited eruption, but should

not be used if the etiology is primarily skeletal.

F. Segmental arch mechanics using 17*17 elgioalloy to extrude the incisor similar to Rickets

mechanics.

G. Kim mechanics

Also, it has been noted that one of the features of a skeletal

anterior open bite is mesial tipping of the molars, resulting

in rotation of the occlusal plane (Kim, 1987).

Therefore, by uprighting the molars the anterior open bite

can be closed. This can be achieved using multi-loop

archwires or curved nickel– titanium wires, creating an

increased curve of Spee in the maxillary arch and a reduced curve of Spee in the mandibular arch

combined with anterior elastics.

To help upright and distalize the buccal dentition again, loss of the terminal molar is

recommended.

Using a multiloop edgewise archwire appliance in conjunction with heavy anterior elastics has

been shown to achieve molar intrusion and simultaneous incisor extrusion in the closure of

anterior open bites.

This is usually achieved using multiloop edgewise archwires made from 0.016 x 0.022 stainless

steel archwires. Kim recommends an 0.018” slot and standard edgewise brackets for reasons that

are obscure.

Use of the technique with an 0.022” straight-wire appliance system has produced no problems.

The archwires are an ideal shape with five L-lopps on each side starting from between the lateral

incisors and canine and working distally until between 6s and 7s.

The vertical dimensions of the loops should be 2-3 mm and the horizontal dimensions 5 mm

except in the molar region where it is increased to 8 mm. Tip backs of 3-5º are placed on each

loop.

This effectively produces a curve of Spee in the upper arch and a reverse curve of Spee in the

lower arch.

These are counteracted by placing 3/16” heavy elastics vertically between the most anterior

loops in the maxilla and mandible.

This transfers all the active force in the archwire to the posterior segments thus intruding and

uprighting the posterior buccal segments.

When the terminal molars are out of contact and no further reduction of the anterior open bite

occurs; at this stage, flat 0.016” x 0.022” archwires are placed to upright the molars while

continuing the anterior elastics.

H. Modified Kim mechanics

For some years clinicians have used reverse curve nickel-titanium archwires instead of multiloop

wires and they seem to work well. Enacar et al (1996) and (Harradine and Birnie, 2000).

Hooks are provided by using crimpable hooks.

7. Molar intrusion using skeletal anchorage

Like Dental implants, mini-plates, mini-screws , ankylosed teeth (Cousely 2008 use TPA with

two palatal TAD for posterior teeth intrusion, while Etilita et al 2012 use TPA with two buccal

TAD). Park et al (2008).

This technique showed that the pd is improved as the crestal bone is moved more coronal and

thus improving the crown root ratio. Byani 2012

The following points should be considered:

consider the skeletal relationship including the vertical, transverse, and anterior-posterior

relations. For example, a skeletal class 2 open bite with a long anterior facial height can be

treated successfully by the intrusion of the posterior teeth as this would produce a closing

counterclockwise rotation of the mandible with a shortening of the anterior facial height and a

correction of the open bite. Sugawara et al (2002) reported that during intrusion of the molars

with a skeletal anchorage system, the anterior lower facial height, mandibular plane angle, and

ANB difference reduced significantly, whereas the overbite and Wits appraisal increased

significantly. Hence, the intrusion of the molars is best suited to skeletal open bite patients who

show long face types with class 1 or mild class 2 skeletal patterns whereas in class 3 open bites,

the class 3 malocclusion would get worse as the anterior open bite closed

Incisor exposure at rest and smile are important objectives to consider before treatment. Patients

who do not show sufficient incisor exposure should not be treated by molar intrusion, making the

more conventional method of incisor extrusion a more suitable option for open bite correction

Periodontal condition should be carefully considered.

For patients with a dual occlusal plane, segmental intrusion of the posterior buccal segments is

indicated. However, during the active intrusion phase, careful monitoring of the first, second,

and third order relationship of the intruded molars should be monitored.

This can be achieved by

a. placing miniscrews on both the buccal and palatal,

b. using a transpalatal bar or a splint

c. An alternative design of splint

8. Repelling magnets (Kiliaridis, 1990)

Kalra, Burstone and Nanda (1989) have suggested that magnets may be beneficial in treating anterior open bites by:

• intruding upper and lower posterior teeth so as to allow mandibular autorotation

• distracting the condyle downwards and forwards to allow compensatory condylar growth which

would again favour mandibular autorotation

9. Orthognathic Surgery

Where there is an obvious step in the occlusal plane, two piece maxilla

No step, one piece maxilla.

Subapical osteotomy of the anterior (Kole technique) or posterior segment (Schuchart

technique)depend on the etiology

Recently Bisase 2009 recommend anticlockwise rotation of BSSO with rigid fixtion.

10. Adjunctive procedure

Glossectomies. Their effectiveness in closing anterior or posterior open bite problems has not

been substantiated (Proffit, 1990).

Surgical procedures to improve the patency of the airway

Occlusal equilibration (Janson 2008)

Corticotomy assisted molar intrusion (Akay 2009)

Stability of AOB

1. In general: AOBs treatment is stable in approximately 80% of treated cases with slightly better

with surgical treatment than non-surgical (5% differences).(Huang, 2002). Lopez-Gavito 1985

showed that 1/3 is lost.

2. Extraction: There is also evidence of greater stability of open bite correction when orthodontic

treatment is undertaken with extractions (Janson et al., 2006).

3. Extrusion or intrusion: In treatment resulting in molars intrusion, the rate of relapse ranges

from 17 to 30%: whilst in treatments with incisor extrusion, relapse may be even greater,

reaching sometimes 40% of treated cases. (Suguwara 2011)

Causes of relapse

Continued unfavorable posterior mandibular growth rotation

Unfavorable tongue position

Continued habit

Excessive extrusion of incisors

Relapse after surgery

Management of relapse

Overcorrection is recommended to compensate for any relapse.

Using headgear attached to a URA with a high pull direction of force untile growth cessed.

Retainer with passive bite blocks, which supposedly place intrusive forces on the posterior

teeth, could be used &should be continued until facial growth has almost ceased and this is often

well into late teens.

Some recommend lip and tongue muscle exercises once a day, which was supervised once a

week by a speech and language therapist

Daytime wraparound retention with modified contour,

in which the wire is engaged in the CEJ to counteract the

intrusion relapse of anterior teeth, usually this is used at

day time while at night a different appliance is used but

with tongue crib.

PFR can be used as removable retainer with posterior bite

plane. If the tongue play a role in the open bite then holes

or spur in the palate can help to minimize the relapse.

Fixed Modified Nance-Hyrake appliance to train the tongue

Difficulty associated with the treatment of AOB, Burford 2003 Sandler 2011

1. Tendency to vertical growth rotation which worsens the class 2 and makes the use of

functional appliance challenging

2. Most of the orthodontic treatment are extrusive which make the treatment worse

3. Quick loss of the extraction space for two reasons: the masticatory muscles restrict the

posterior mandibular teeth more than their maxillary counterparts; and the thin cortices and

trabecular bone of the maxilla provide less resistance to movement than the thick cortices and

more dense trabeculae of the mandible

4. Poor soft tissue compliance that make stability poor

Posterior open bite

Caused by

1. Failure of eruption

2. Tongue interfere with eruption

3. Trauma and Ankylosis

4. Hemimandibualr hyperplasia when the vertical compensation is not sufficient

Treatment

1. Habit breaker posteriorly

2. Composite build up

3. Orthodontic extrusion by FA or TAD

4. Segemental dentoalveolar osteotomy

5. Segemental maxillary or mandibular surgery

Summary of the evidences

Definition: Dental AOB: It is present when there is no incisor contact and no vertical overlap of

the lower incisors by the uppers (Houston, 1996).

Incidence: In U children is 4% at age 9 years, falling to 2% by the early teenagers (O’Brien,

1993).

Type of growth of the mandible: Nielsen et al 1991

True rotation, matrix rotation & apparent total rotation as described by Bjork 1969

Bjork's structural signs help to predict type of growth rotation , (Bjork, 1969)

PFH:AFH ratio (Jarabak ratio) Jarabak, 1972, 58 high angle case, reduced OB

UAFH-LAFH ratio: Nahoum (1975) believed that patients with a dental open bite and a UAFH-

LAFH ratio of less than 65% (normally they are equal) are considered to be poor risks for

conventional orthodontic treatment alone.

Increased dentoalveolar height in molar region and reduced dentoalveolar height in incisor

region due to strong muscle allowing molar eruption. (Neilsen, 1991).

Dung and Smith (1988).

Overbite depth indicator (ODI) Kim in 1974

Skeletal factors: Mainly genetically in origin. Vertical growth pattern more genetically correlated

than horizontal one; if you had the long face in one generation then chances are that you would

have a long face in the next generation. (Hunter 1968)

Soft tissue factors : Muscle of mastication: Hunt 1997 & Benington 1999 showed large muscle

fibres in deep bite and small size muscle fibres in AOB

Chronic nasal obstruction (Solow & Tallgren 1976)

Adenoids (Aronson, 1979).

Digit Sucking Habits: The incidence of digit sucking is around 30% at 1 year of age, reducing to

12% at 9 years and 2% by 12 years. Most persistent suckers are female (Brenchely, 1992).

The severity of the malocclusion depends on the age of the patient, the intensity, frequency and

duration of the habit. Larsson, 1987

Prevention of digit-sucking sucking habits, BOS guidelines 2000

Myofunctional Therapy : Muscle exercise described by Laurie Park 2007

The functional regulator appliance (FR IV) Cochrane review, by Oliveira , 2007 showed that

there is weak evidence that the interventions FR-4 with lip-seal training and palatal crib

associated with high-pull chin cup are able to correct anterior open bite. Given that the trials

included have potential bias, these results must be viewed with caution.

TB with high-pull headgear inserted in the flying spring can be utilized to correct the

anteroposterior discrepancy while controlling the vertical dimension. Park 2001

Thick Twin block appliance: This phenomenon, which is called the bite-block effect, provides

excellent vertical control. Although long-term studies documenting the results of this treatment

are not yet available, the early results are promising. Clark 2010

Kim mechanics, (Kim, 1987).

Modified Kim mechanics, for some years clinicians have used reverse curve nickel-titanium

arch-wires instead of multiloope wires and they seem to work well (Harradine and Birnie, 2000).

Molar intrusion using skeletal anchorage: Like Dental implants, mini-plates, mini-screws ,

ankylosed teeth (Cousely 2008 use TPA with two palatal TAD for posterior teeth intrusion,

while Etilita et al 2012 use TPA with two buccal TAD)

In general: AOBs tend to relapse in approximately 20% of treated cases.(Huang, 2002)

Extraction: There is also evidence of greater stability of open bite correction when orthodontic

treatment is undertaken with extractions (Janson et al., 2006).

Extrusion or intrusion: In treatment resulting in molars intrusion, the rate of relapse ranges from

17 to 30%: whilst in treatments with incisor extrusion, relapse may be even greater, reaching

some-times 40% of treated cases. (Suguwara 2011)