Open bite/ dental crown & bridge courses

OPEN BITE
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INTRODUCTION
• Open bite is a malocclusion that occurs in
the vertical plane, characterized by lack of
vertical overlap between the maxillary and
mandibular dentition. Open bite can occur
in the anterior and the posterior region
and are called anterior open bite and
posterior open bite respectively

Definitions
I. Open bite is defined as a condition where
a space exists between the occlusal or
incisal surfaces of the maxillary and
mandibular teeth in the buccal or anterior
segments when the mandible is brought
into a habitual or centric occlusion
(Graber).

II. According to Moyers, there are 2
definitions of open bite.
• The first defines open bite as the absence
of vertical incisal overlap.
• The second defines open bite as the
absence of an occlusal stop.
• Open bite is the failure of a tooth or teeth
to meet antagonists in the opposite arch
or the occlusal planes

• III. Proffit defined Over Bite as the vertical
overlap of the incisors. Normally the lower
incisor edges contact the lingual surface
of the upper incisors at or above the
cingulum (i.e. 1-2 mm overbite). In open
bite, there is no vertical overlap and the
vertical separation is measured.

CLASSIFICATION
I. According to location Open bite divided into:-
• Anterior open bite
• Posterior open bite
II. According to Moyers:
• Simple open bite:
• When the cephalometric analyses reveal no
abnormal measures and the sole problem is the failure of
some teeth to meet the line of occlusion.
• Complex or skeletal open bite:
• When the cephalometric analyses reveal
disharmonies in the skeletal components of the anterior
face height.

Etiology of Open Bite
Multifactorial:
• Disturbances in the eruption of teeth and
alveolar growth. E.g. Ankylosed primary molars.
• Mechanical interference with eruption and
alveolar growth. E.g. Finger sucking, foreign
body in mouth (Pins, pencil)
• Vertical skeletal dysplasia which may be
genetically determined.

. Mouth breathing :
could cause different head, jaw and tongue
position which would effect the jaw growth and
tooth positions.
• Different postures seen in mouth breathing:
– Lowering the mandible
– Positioning the tongue downward and forward
– Tipping back of the head.

• The type of Open Bite associated with
mouth breathing is called ‘Skeletal Open
Bite or adenoid facies.
Characterized by
– Excessive eruption of posterior teeth
– Tendency towards Maxillary constriction
– Excessive overjet
– Anterior open bite

• Tongue thrust:
Tongue thrust itself is not responsible for anterior open
bite
• Tongue thrust is a adaptive feature of anterior open
bite
• Tongue thrust is of 2 types
– Simple tongue thrust swallow
- Complex tongue thrust swallow

• Simple tongue thrust- The teeth are in occlusion, the lips
tightly closed, tongue held against palate behind the
anterior teeth.
• Complex tongue thrust- Associated with chronic maso
respiratory distress, mouth breathing, tonsillitis or
pharyngitis.
Root of the tongue may enchroach on the enlarged facial
pillars. To avoid this enchroachment, the mandilble reflex
drops separating the teeth providing more room for the
tongue to thrust forward during swallowing to a more
comfortable position

• Thumb sucking can cause
– Flarred and spaced maxillary incisors
– Anterior open bite
– A narrow upper arch
Anterior open bite associated with thumb
sucking arise by
- interferences with normal eruption of incisors
and excessive eruption of posterior teeth.

• When the thumb or finger is placed between the
anterior teeth , the mandible must be positioned
downward to accommodate it.
The thumb impedes incisor eruption. The
separation of jaw alters the vertical equilibrium
on the posterior teeth. There is over or supra
eruption of posterior teeth.
1mm of elongation posteriorly causes 2mm of
bite opening.

•Rotation of the jaws

• Lip sucking and lip biting.
• Foreign bodies: Pipes, pen, pencil.
• Trauma or pathology of condyle.

Clinical Considerations
• Various forms of anterior open bite may be
observed depending on the severity of the
malocclusion
1. Cases with an overjet combined with an open
bite of less than 1mm can be designated as
Pseudo Open Bite problem.
2. Simple open bite exists in cases in which more
than 1mm of space may be observed between
the incisors but posterior teeth are in occlusion.

3. Complex open bite exists in those case in which open
bite extends from premolar or deciduous molars of one
side to that of the other.
4. The compound or infantile open bite is completely
open including the molars.
5. The iotrogenic open bite is the result of orthodontic
therapy which produces atypical configurations
because of appliance manipulation or adaptive
neuromuscular response.

• In mixed dentition period various therapeutic measure may cause
open bite.
1. Open activator with high construction bite can cause tongue thrust
and resultant open bite during intrusion of posterior teeth. Posterior
open bite can be caused in deciduous molar area.
2. In expansion treatment- Buccal segment are tipped buccaly with
elongation of lingual cusps. This creates prematurity and effectively
opens the bite.
3. In distalization of maxillar first molar with extraoral force the molars
are often tipped down and back, elongating the mesial cusps. This
creates a molar fulcrum that opens the bite.

Cephalometric criteria
• A proper cephalometric analysis enables a
classification of Malocclusion.
In vertical growth pattern:
Dentoalveolar symptom
– Protrusion of upper anterior teeth.
– Lingual inclination of lower incisors.
Horizontal growth pattern:
- Tongue thrust and posture may cause
proclination of upper and lower incisors

• Lateral open bite can be considered
dentoalveolar in combination with infra
occlusion of molars.
Causes
– Cheek bite, lateral tongue thrust

• Skeletal open bite
– Excessive anterior facial height
– Short posterior face height
– Mandibular base is usually narrow
– Presence of antegonial notching.
– Symphysis in usually narrow and long
– Ramus is short
- Growth pattern is vertical

• Features of Anterior Open Bite:
– Open bite limited to anterior segment, often
asymmetrical
– Proclined maxillary or mandibular incisors
– Spacing between maxillary and mandibular
anteriors.
– Narrow maxilar arch.
– ‘Fish mouth’ appearance.

• Features of Skeletal Open Bite:
Extra oral features:
– Long face due to increased LAFH
– Incompetent lips
– An increased mandibular plane angle
– An increased gonial angle
– Marked antigonial notch
– A short mandible is a possibility
– Maxillary base may be more inferiorly placed

• Intra oral features
– Mild crowding
– Gingival hypertrophy
– Maxillary occlusal and palatal plate tilt
upwards.
– Mandibular occlusal plane canted downwards

• Posterior Open Bite:
Causes:
1. Mechanical interference with eruption: Either before or
after tooth emerges from alveolar bone. Mechanical
interference may be
– Ankylosis of tooth to the alveolar bone(Trauma)
E.g.Trauma, supernumerary teeth, non resorbing
deciduous roots.
After the tooth emerges from the alveolar bone,
– Pressure from the soft tissues (Cheek,finger,tongue)
can be obstacle to eruption.

2. Failure of the eruptive mechanism of
tooth so that expected amount of
eruption does not occur.

TREATMENT OF OPEN BITE:
Therapy depends on localization and
etiology of M.O. Habit control and
elimination of abnormal perioral muscle
function are causal therapeutic
approaches to dentoalveolar open bite.

Appliance used to remove the etiology of Anterior Open Bite

• Treatment in Decidious Dentition:
– Many instances open bite improves as the habit is
stopped
– Screening appliance can be used
• Screening appliance intercept and eliminate all
abnormal perioral muscle function in acquired
MO resulting from abnormal habit. mouth
breathing, nasal blockage.
• Self correction of M.O is frequently possible

• Another level of intervention is reminder therapy.
1. Bitter medicine may be placed on adhesive type
which is wrapped around the thumb.
2. Reward system can be implemented. Reward
for not engaging into the habit.
3. Elastic bandage loosely wrapped around the
elbow prevents the arm from flexing and fingers
being sucked.

• Treatment of Open Bite in mixed dentition:
3 types of Open Bite MO can be differentiated
1. Dentoalveolar Open Bite
- In the early mixed dentition – Screening therapy indicatod
- In the late mixed dentition – Screening therapy unsuccessful
- In such cases fixed appliance treatment is done but long post
treatment retention required.
Swallowing exercise may also bring about reinforcement of mature
deglutation pattern for the tongue during both treatment and
retention.

• Skeletal Open Bite:
Depends on 2 factors:
1.Severity of Malocclusion
2.Possibility of dentoalveolar compensation
Growth pattern is almost vertical
Inclination of maxillary base is decisive in
treatment planning
• Rotation of jaw base
• Divergent- Prognosis is poor
• Maxillary Base
• - Tipped downward and forward- Functional
therapy successful

• Functitonal therapy includes
Activator
FR4
Bionator

- Bionators are used to close open bite
- Prevents tongue inserting into the space
- Maxillary parts of acrylic joined anteriorly unlike
standard bionator
- Anterior part not in contact with the teeth or
alveolar bone
- Small white blocks used for stabilization has
indentations on the surface
- Bite blocks prevent the posterior teeth from
errupting
- Anterior teeth are allowed to erupt freely

open bite activator

- Used in the treatment of dentoalvealor
open bite
- Eruption of posterior teeth is prevented
- Elongation of anterior teeth encouraged
- Acrylic is not ground away from occlusial
surface of posterior teeth
- Anterior teeth allowed to erupt freely

3. Combined Open Bite:
Because of dual nature of etiology
combined treatment approach is needed.
– Elimination of abnormal perioral muscle
– Improvement of skeletal relatioship

• Treatment of Open Bite in the mixed and
early permanent dentition:
– Headgear
• Functional appliance with bite blocks

• Treatment in Permanent dentition
– Fixed appliance therapy with screening
appliance
– Box elastics
– Repelling magnets placed in the posterior bite
plates
– Anterior attractive and posterior repelling
mode to achieve normal over bite

Surgical correction:
Long face problem
– Treated by intrusion of maxilla. This allows
mandible to rotate around the condyle,
thereby reducing the mandibular plain angle
and shortening the face

Surgical approach involves
Le fort 1 down fracture of the maxilla with
superior reposition of the maxilla after
removal of the bone from the lateral walls
of the nose, sinus and nasal septum.
Results are quite stable.

• In mandible,
Inferior border osteotomy of the mandible
to reduce vertical height of the chin.
Usually a combination of maxillary
intrusion and repositioning of the chin is
done.

• Management of Open Bite in M.B.T techniques
• Early management of Open Bite
– Finger and thumb appliance which provide a barrier
can be used to correct minor problem
– Palatal expansions in narrow maxilla- Helps in
providing space for eruption, ritroclination of incisors.
– Help to open the airway and encourage nasal
breathing and provides more room for tongue.
- Palatal bars and lingual arches- Reduce the
vertical eruption of molars.

– Posterior bite planes on the upper or lower posterior
teeth.
– High pull facebow and chin caps- Limit the vertical
eruption of molars.
– Removal of deciduous canines and sometimes
premolar in case with significant crowding/protection-
Allows eruption and retroclination of incisors.
– Myofunctional therapy benefits in severe cases
– Adenoids and tonsils if contributing factors- should be
removed.

Management of Open Bite during full
orthodontics treatment:
While non extraction treatment is generally
preferred in orthodontics, some Open Bite
cases may benefit from extractions.
Primarily to allow for eruption and
retroclination of incisors.

• Some possibilities are
1. If upper or lower arches show crowding ,
protrusion then upper or lower bicuspid
extraction.
2. Lower arch does not require extraction for
lower incisors retraction and molars are more
than 3-4mm class II – Extraction of only upper
bicuspids considered for retraction and
retroclination of incisors.

3. During bracket placement in open bite, upper
and lower anterior brackets can be placed
0.5mm more gingivally- Helps to achieve bite
closure as treatment proceeds
4. If class II or class III elastics are required-
Should be attached posteriorly to premolar
rather than molar. They minimize extrusive
effect on the back of the arches

Open bite/ dental crown & bridge courses

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