Incisal bite

Overbite The overlap of the lower incisors by the upper incisors

in the vertical plane.
Complete overbite An overbite in which the lower incisors contact
either the upper incisors or the palatal mucosa

Incomplete overbite An overbite in which the lower incisors

contact neither the upper incisors nor the palatal mucosa.

Anterior open bite The lower incisors are not overlapped in the
vertical plane by the upper incisors and do not occlude with
them.
Posterior open bite (POB): when the teeth are in occlusion there
is a space between the posterior teeth
 Increase in overbite

 Skeletal factors. It is often stated that a small lower

facial height is associated with a deep overbite.
However, this is not a constant relationship and
occlusal factors must also play a part.
 Occlusal factors:
Where there is no incisor contact due to a large
overjet (Class II Division 1), the lower incisors
will often erupt until they contact the palatal
mucosa and the overbite will be deep.
 Where the overjet is normal and the incisors
are retroclined (Class II Division 2), so that the
inter-incisor angle is increased, the overbite
will also be increased.
 Approaches to the reduction of
overbite
1. Intrusion of the incisors
 Actual intrusion of the incisors is difficult to
achieve. Fixed appliances are necessary and the
mechanics employed pit intrusion of the incisors
against extrusion of the buccal segment teeth; as it is
easier to move the molars occlusally than to intrude
the incisors into bone, the former tends to
predominate. In practice, the effects achieved are
relative intrusion, where the incisors are held still
while vertical growth of the face occurs around them.
2. Eruption of the molars
(relative intrusion)
 Use of a flat anterior bite-plane on an upper
removable appliance to free the occlusion of the
buccal segment teeth will, if worn conscientiously,
limit further occlusal movement of the incisors and
allow the lower molars to erupt, thus reducing the
overbite. This method requires a growing patient to
accommodate the increase in vertical dimension that
results, otherwise the molars will re-intrude under the
forces of occlusion once the appliance is withdrawn.
Relative intrusion
3. Extrusion of the molars
 As mentioned above, the major effect of
attempting intrusion of the incisors is often
extrusion of the molars. This may be
advantageous in Class II division 2 cases as
this type of malocclusion is usually associated
with reduced vertical proportions. Again,
vertical growth is required if the overbite
reduction achieved in this way is to be stable.
Extrusion
There are three possible ways to level a lower arch with an excessive
curve of Spee:
(l) absolute intrusion;
(2) relative intrusion, achieved by preventing eruption of the incisors
while growth provides vertical space into which the posterior teeth
erupt;
(3) extrusion of posterior teeth, which causes the mandible to rotate
down and back in the absence of growth. Note that the difference
between (2) and (3) is whether the mandible rotates downward. This
is determined by whether the ramus grows longer while the tooth
movement is occurring.
4. Proclination of the lower incisors
 Advancement of the lower labial segment anteriorly
will result in a reduction of overbite as the incisors tip
labially. This approach should only be carried out by
the experienced orthodontist. However, in a few cases
where the lower incisors have been trapped behind
the upper labial segment by an increased overbite,
fitting of an upper bite-plane appliance may allow the
lower labial segment to procline spontaneously.
5. Surgery
 In adults with a markedly increased overbite
and those patients where the underlying
skeletal pattern is more markedly Class II, a
combination of orthodontics and surgery is
required.
Sagittal split osteotomy
The reduction of a deep overbite will be stable
only if at the end of treatment the :
 lower incisors occlude with the palatal

surfaces of the upper incisors,

 the inter-incisal angle is within the normal
range,
 and the teeth are in a position of labiolingual
balance.
 AETIOLOGY OF ANTERIOR
OPEN BITE

 Skeletal factors
 Soft tissue factors
 Habits
 Mouth breathing
 Localized failure of development
 1.Skeletal
 Individuals with a tendency to vertical rather than
horizontal facial growth exhibit increased vertical
skeletal proportions. Where the lower facial height is
increased there will be an increased inter-occlusal
distance between the maxilla and mandible. Although
the labial segment teeth appear to be able to
compensate for this to a limited extent by further
eruption, where the inter-occlusal distance exceeds
this compensatory ability an anterior open bite will
result. If the vertical, downwards, and backwards,
pattern of growth continues, the anterior open bite
will become more marked.
 Lower facial height:
The distance from the eyebrow to the base of
the nose should equal the distance from the
base of the nose to the lower most point on the
chin. If the latter distance is increased, the
lower facial height is described as being
increased, and vice versa.
 Frankfort mandibular planes angle (FMPA):
assessment of the FMPA clinically by eye comes with
experience, but the neophyte orthodontist may find it
helpful to assess this angle by placing one hand level
with the Frankfort plane (external auditory meatus to the
lower border of the orbital margin) and the other hand
level with the lower border of the mandible. Then in the
‘mind's eye’ extrapolate the planes and assess where they
would cross. If the angle between these two planes is
around the average of 28°, then the lines would intersect
approximately at the back of the head. If the FMPA is
increased the lines would meet before the back of the
head, and if it is reduced they would cross beyond.
Long vertical growth profiles. A, Class I. B,
Class II Division 1. C, Class III.
 Short vertical growth profiles. A, Class 11
Division 1. B, Class 11 Division 2. C, Class Ill.
This patient has a sever anterior open
bite with contact only on the molars
 2. Soft tissue pattern
 In order to be able to swallow it is necessary to create
an anterior oral seal. In younger children 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 adaptive tongue behavior
(tongue thrust).
Primary atypical tongue behavior (endogenous
tongue thrust)

 Rarely there is an inborn atypical pattern of

neuromuscular activity by which the tongue tip
retains a more infantile position, and comes
forwards to contact the lips during swallowing
(an endogenous tongue thrust). This can
produce both an increase in overjet and a
reduction in overbite.
 3. Habits
 The effects of a habit depend upon its frequency,
duration and intensity. The persistence of pernicious
habit can lead to the malocclusion acquiring a skeletal
component .If a persistent digit-sucking habit
continues into the mixed and permanent dentitions,
this can result in an anterior open bite due to
restriction of development of the incisors by the
finger or thumb.
 Characteristically, 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.
 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 over development 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.
 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.
 Features of dental anterior open
bites
 Intraoral features:
 1. Open bite limited to the anterior segment, often
asymmetrical.
 2. Proclined maxillary and/or mandibular incisors.
 3. Spacing between maxillary and/or mandibular anteriors.
 4. Narrow maxillary arch is a possibility.
 5. "Fish mouth" appearance.
Extraoral features:
 No unusual features.
 Features of skeletal anterior open
bites
 Extraoral features:
 1. Long face due to increased lower anterior face height.
 2. Incompetent lips.

 3. An increased Frankfort mandibular plane angle.

 4. An increased gonial angle.

 5. Marked antigonial notch.

 6. A short mandible is a possibility.

 7. Maxillary base may be more inferiorly placed (vertical

maxillary excess).
 8. The angle formed by the mandibular and maxillary

planes is also increased.

 Features of skeletal anterior open
bites
 Intraoral features:

 1. Mild crowding with upright incisors.

 2. Gingival hypertrophy.
 3. Maxillary, occlusal and palatal planes tilt
upwards.
 4. Mandibular occlusal plane canted downwards.
 MANAGEMENT OF
ANTERIOR OPEN BITE
 Management of an anterior open bite due purely to
a digit-sucking habit can be straightforward, but
where the skeletal pattern, growth, and/or soft
tissue environment are unfavorable, correction
without resort to orthognathic surgery may not be
possible.
 In the mixed dentition, a digit-sucking habit that has
resulted in an anterior open bite should be gently
discouraged. If a child is keen to stop, a removable
appliance can be fitted to act as a reminder. However, if
the child derives support from his habit, forcing him to
wear an appliance to discourage it is unlikely to be
successful.
 Although a number of barbaric designs have been
described (involving wire projections for example), a
simple plate with a long labial bow for anterior retention
will usually suffice if a habit-breaker is indicated.
 After fitting, the acrylic behind the upper incisors should
be trimmed to allow any spontaneous alignment.
 A period of observation may be helpful in the
management of patients with an anterior open bite
which is not associated with a digit-sucking habit.
In some cases an anterior open bite may reduce
spontaneously, possibly because of maturation of
the soft tissues and improved lip competence, or
favourable growth.
 Approaches to the management
of anterior 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
This approach can be considered in the
following situations (particularly if the AOB does not
present a problem to the patient):
 mild cases;

 where the soft tissue environment is not favorable,

for example where the lips are markedly
incompetent and/or an endogenous tongue thrust is
suspected;
 in more marked malocclusions where the patient is

not motivated towards surgery.

 Orthodontic correction of the
anterior open bite
 If growth and the soft tissue environment are
favorable, 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.

 Extrusion of the incisors to close an anterior open bite
is inadvisable, as the condition will relapse once the
appliances are removed. Rather,
 treatment should aim to try and intrude the molars, or
at least control their vertical development.
 Intrusion of the molars can be attempted with high-
pull headgear and/or by using buccal capping on a
removable appliance.
 A chin cup with a vertical pull head cap may
be used for the correction of anterior open
bites in the pre-adolescent age group.
 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. In order to achieve true growth
modification it is necessary to apply an intrusive
force to the maxilla for at least 14–16 hours per day
during the pubertal growth spurt, continuing until
growth is complete.
 Surgery

 This option can be considered once growth is

complete 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.