Ch12 openbite

Anterior open bite and posterior open bite

-Orthodontics-By Cezar Edward

Definitions

• Anterior open bite (AOB): there is no

vertical overlap of the incisors

when the buccal segment teeth are in

occlusion .

More common POB

• Posterior open bite (POB): when the

teeth are in occlusion there

is a space between the posterior teeth.

Anterior open bite - Aetiology

• inherited and environmental factors

Skeletal + Soft tissues + Habits + Localized failure of development.

In many cases the aetiology is multifactorial.

1 Skeletal pattern• The individuals who have vertically facial growth more than

horizontally the lower facial height is increased interocclusal distance will increased (interocclusal=btw Max & mand) some compensatory effects will occur ; some overeruption BUT if it is large it will result in OPENBITE

Lateral cephalometric radiograph of a

patient with a marked

Class II division 1 malocclusion on a Class

II skeletal pattern with

increased vertical skeletal proportions.

Note the thin dento-alveolar

processes.

Patient with increased vertical skeletal

proportions and an anterior open bite.

2 Soft tissue pattern

• Dr Mudar Kamal said that : -there are 2 schools :-

1st school says that tongue (when the pt swallow) will cause ant. Openbite … But 2nd school says that the pt had openbite and during swallowing he uses his tongue to achieve an ant. Oral seal …

Dr. M Kamal said that 2nd school is better

patients with an anterior open bite due to a digit-sucking habit the lips are

often incompetent and a proportion will achieve an anterior seal by positioning

their tongue forward between the anterior teeth during swallowing. Individuals

with increased vertical skeletal proportions have an increased likelihood

of incompetent lips and may continue to achieve an anterior

oral seal in this manner even when the soft tissues have matured.

3 Habits

-The effects of a habit depend upon its duration and intensity.

-the anterior open bite produced is asymmetrical (unless

the patient sucks two fingers) and it is often associated with a posterior crossbite. Constriction of the upper arch is believed to be caused by cheek pressure and a low tongue position.

After a sucking habit stops the open bite tends to resolve ,

although this may take several months. During this period the tongue

may come forward during swallowing to achieve an anterior seal. In a

small proportion of cases where the habit has continued until growth is

complete the open bite may persist.

4 Localized failure of development

• This is seen in patients with a cleft of the lip and alveolus , although rarely it may occur for no apparent reason.

5 Mouth breathing

-It has been suggested that the open-mouth posture adopted by individuals who habitually mouth breathe, either due to nasal obstruction or habit, results in overdevelopment of the buccal segment teeth. This leads to an increase in the height of the lower third of the face and consequently a greater incidence of anterior open bite.

-On balance, it would appear that mouth breathing per se does not

play a significant role in the development of anterior open bite in most

patients.

Management of anterior open bite

• Removal the causes :- by habit breaking appliances “fixed or removable “

• Headgear & myofunctional appliance

• Fixed ortho. Treatment.

• surgery

Approaches to the management ofanterior open bite

• There are three possible approaches to management.

• 1-Acceptance of the anterior open bite

• 2-Orthodontic correction of the anterior open bite

• 3-surgery

Acceptance of the anterior open bite

• ( particularly if the AOB does not present a problem to the patient)

• mild cases

• where the soft tissue environment is not favourable, for example

where the lips are markedly incompetent and/or an endogenous

tongue thrust is suspected

• more marked malocclusions where the patient is not motivated

towards surgery

Orthodontic correction of the anterior open biteIf growth and the soft tissue environment are favourable, an orthodontic solution to the anterior open bite can be considered. A careful assessment should be carried out, including the anteroposterior and vertical skeletal pattern, the feasibility of the tooth movements required, and post-treatment stability.

Methods of intruding the molars

• High-pull headgear

• Fixed appliance mechanics

• Buccal capping on a

removable/functional appliance

• Repelling magnets

• Temporary anchorage devices (TADs)

cases

• In the milder malocclusions the use of high-pull headgear during conventional treatment may suffice.

• In cases with a more marked anterior open bite associated with a Class II skeletal pattern, a removable appliance or a functional appliance incorporating buccal blocks and high pull headgear can be used to try to restrain vertical maxillary growth.

A patient wearing a maxillaryintrusion splint and high-pull headgear. Theface-bow of the headgear slots into tubesembedded in the acrylic of the occlusalcapping, which extends to cover all themaxillary teeth.

#

In cases with bimaxillary crowding and proclination, relief of crowding

and retraction and alignment of the incisors can result in reduction

of an open bite. Stability of this correction is more likely if the lips were

incompetent prior to treatment but become competent following retroclination of the incisors.

Surgery

This option can be considered once growth has slowed to adult levels

for severe problems with a skeletal aetiology and/or where dental compensation

will not give an aesthetic or stable result. In some patients

an anterior open bite is associated with a ‘gummy’ smile which can

be difficult to reduce by orthodontics alone necessitating a surgical

approach.

Management of patients with increasedvertical skeletal proportions and reducedoverbite

• Space closure appears to occur more readily in patients with in -

creased vertical skeletal proportions.

• Avoid extruding the molars as this will result in an increase of the

lower facial height. If headgear is required, a direction of pull above

the occlusal plane is necessary, i.e. high-pull headgear. Cervical-pull

headgear is contraindicated.

• If overbite reduction is required, this should be achieved by intrusion

of the incisors rather than extrusion of the molars. For this reason

anterior bite-planes should be avoided.

• Avoid upper arch expansion. When the upper arch is expanded

the upper molars are tilted buccally which results in the palatal

cusps being tipped downwards ,If arch expansion

is required, this is best achieved using a fixed appliance so that

buccal root torque can be used to limit downward tipping of the

palatal cusps.

• Avoid Class II or Class III intermaxillary traction as this may extrude

the molars.

(a) Intra-oral view of a van Beek appliance; (b) extra-oral view showing

the high-pull headgear; (c) lateral cephalometric radiograph of the

patient prior to treatment; (d) lateral cephalometric radiograph of the

same patient 1 year later.

Posterior open bite• aetiology is less well understood.

In some cases an increase in the vertical

skeletal proportions is a factor, although this is more commonly

associated with an anterior open bite which also extends posteriorly. A

lateral open bite is occasionally seen in association with early extraction

of first permanent molars , possibly occurring as a result of

lateral tongue spread.

eruption disturbances.

Affected teeth may erupt and then cease to keep pace with vertical

development becoming relatively submerged or may fail to erupt at all

Although these teeth are not

ankylosed they do not

respond normally to orthodontic

force and indeed usually

become ankylosed if traction is

applied. Extraction is the only

treatment alternative.

More rarely, posterior open bite is seen in association with unilateral

condylar hyperplasia, which also results in facial asymmetry. If this

problem is suspected, a bone scan will be required. If the scan indicates excessive cell division in the condylar head region, a condylectomy alone, or in combination with surgery to correct the resultant deformity, may be required.

Thank u