Biomechanics of open bite

BIOMECHANICS OF OPEN BITE
CORRECTION
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CONTENTS
• What is an open bite ?
• Evolution of open bite
• Classification of open bite.
• Various treatment modalities.
• Biomechanics of treatment modalities.
1. Biomechanics of open bite correction before growth completion
2. Biomechanics of open bite correction after growth completion
Conclusion.

Biomechanics of treatment
modalities.
1. Biomechanics of open bite correction before growth completion
biomechanics of – a) habit breaking appliance
b) functional appliances
- activator
- bionator
- FR-4
- twin block
c) orthopedic appliance
2. Biomechanics of open bite correction after growth completion
biomechanics of - a) fixed appliance mechanotherapy for open
bitecorrection
b) surgical management for open bite correction

WHAT IS AN OPEN BITE ?

OPEN BITE
The Glossary of Orthodontic Terms
defines open bite as a developmental or
acquired malocclusion whereby no vertical
overlap exists between maxillary and
mandibular anterior or posterior teeth.

Evolution of open bite

• Open bite develops as result of the interaction of many
etiologic factors.
• In young children, digit habits and pacifiers are the
most common etiologic agents.
• In the mixed dentition years other than the normal
transitional open bite, some openbites are probably
attributable to lingering habits, where others are clearly
skeletal in nature.

In the adolescent and the adult, it is difficult to
assign singular causation. The influence of the
tongue,lip, and airway on the development of
malocclusion remains to be substantiated.
Variations in growth intensity, the function of the
soft tissues and the jaw musculature, and the
individual dentoalveolar development influence
the evolution of open bite problems.

SKELETAL FACTORS IN THE DEVELOPMENT OF AN
OPEN BITE TYPE:
1. The combination of
 excessive development
of the upper mid-face
heights (cranial base to
molars)
 a lack of development of
posterior facial heights
(S-Go) results in the
downward and backward
rotation of the mandible.

2. The posterior half of the
palate is tipped
downward, carrying the
molars further
downward. This gives
rise to a large
palatomandibular
plane angle.

3. Because of the short ramus and the lower
palate, the pharyngeal space is constricted. In
order to breathe, these persons keep their
tongues forward. Further enhanced by the
dental open-bite, there is a tongue-thrusting
tendencies.

4. When enlarged tonsils are
present, the tongue is further
confined anteriorly. As the
narrow palatal vault reduces
the necessary space, there is
a tendency towards tongue
protrusion. This, in turn, may
be a factor in the creation of
bi-dental protrusion

CLASSIFICATION
1. Dento Alveolar Open Bite.
2. Skeletal Open Bite.

Dento Alveolar Open Bite
 The extent of the
dentoalveolar open bite
depends on the extent
of the eruption of the
teeth.
Eg: Supraocclusion of the
molars and
infraocclusion of the
incisors can be primary
etiologic factors.

3. In vertical growth
patterns the
dentoalveolar
symptoms include a
protrusion in the upper
anterior teeth with
lingual inclination of
the lower incisors.

4. In horizontal growth
patterns, tongue posture
and thrust may cause
proclination of both
upper and lower incisors.

5. A lateral open bite may be considered
dentoalveolar in combination with infra-occlusion
of molar teeth.

Skeletal Open-Bite

Skeletal Open Bite.
1. Skeletal Class I Open Bite
2. Skeletal Class II Open Bite
3. Skeletal Class III Open Bite

Positional Deviations
Acc to Sassouni…
1. The four bony
planes of the face
are steep to each
other, bringing the
center 0 close to
the profile.
diagram

2. The anterior arc,
therefore follows the
convexity of the
profile.

3. The posterior vertical
chain of muscles is
arcuate, and the
masseter muscle is
posterior to the buccal
teeth, thus creating a
mesial component of
forces responsible for
the dental protrusion.

4. The cranial base angle and the gonial angle
are obtuse.

Dimensional Deviations
1. The total posterior facial
height (S-Go) tends to
be half the size of the
anterior total facial
height (N-Me).

2. The Lower Anterior
Facial Height exceeds
the Upper Anterior
Facial Height.

3 The facial breadths
tend to be narrow,
giving a long, ovoid
appearance in the
frontal view.

5.The ramus is short
with an antegonial
notch at its lower
border.
6. The mandibular
symphysis is narrow
antero posteriorly
and long vertically.

• There is a lack of chin mental protuberance
development.
• According to the Sheldonian somatotyping, the
open-bite type rates high in ecto-morphs.
• The palatal vault is high and narrow.

SKELETAL CLASS II OPEN BITE
1. In this type, in some instances,
the rotation of the mandible may
be purely positional. Often this is
due to a downward and
backward rotation of the
mandible.
2. This rotation is associated with
excessive extrusion of the
molars. If these interferences
were removed, the mandible
could be permitted to rotate in a
closing direction, improving
the Class II and the open-bite
patterns simultaneously.

SKELETAL CLASS III OPEN BITE
1. This combination
consists primarily of an
open-bite with a palatal
deficiency or a large
mandible.

Among the facial deformities, these have
probably the worst prognosis in terms of
dentofacial orthopedics.
If correction of this open-bite is attempted by
rotating the mandible in a closing direction, the
protrusion of the chin is increased.

On the other hand, the reduction of the
mandibular protrusion is attempted by rotating
the mandible downward and backward, the
open-bite is increased.

VARIOUS TREATMENT
MODALITIES
OF
OPEN BITE

1. Habit therapy:
2. Appliance therapy:
3. Surgical management:

BIOMECHANICS OF HABIT
BREAKING APPLIANCE

TREATMENT IN THE DECIDUOUS DENTITION
1. Control of abnormal habits and elimination of
dysfunction should be given top priority in the
deciduous dentition.
2. The anterior open bite improves as soon as
the habit is stopped.
3. Treatment with screening appliances is
indicated in such open- bite cases.

Screening Appliance
1. Screening appliances intercept and eliminate
all abnormal perioral muscle function in
acquired malocclusions resulting from abnormal
habits, mouth breathing, and nasal blockage.
2. Open bite created by finger sucking and
retained visceral deglutition-pattern, tongue
function can be helped with vestibular screens.

Mixed Dentition-treatment

Tongue Crib
1. A removal or fixed appliance can inhibit tongue
thrust.
2. The crib used with a removable appliance for an
anterior open bite consists of a palatal plate
with a horseshoe-shaped wire crib.
3. The crib is placed in the area of local tongue
dysfunction and resultant malocclusion.

NORMAL OCCLUSION

ANTERIOR TONGUE THRUST

TONGUE CRIB

5. The acrylic also can be
interposed between the
teeth, covering the
occlusal surfaces of the
upper molars, to prevent
eruption of these teeth
and enhance anchorage
of the plate, which is
especially beneficial in
open-bite problems.

The bite-block here can be 3 to 4 mm, which is
usually beyond the postural vertical dimension
in open-bite patients.
In such cases a stretch reflex is elicited from
the closing muscles that enhances the
depressing action on the buccal segments and
helps close the anterior open bite.

BIOMECHANICS OF FUNCTIONAL
APPLIANCE IN OPEN BITE
CORRECTION

Activator
1. The bite is opened 4 to 5 mm to develop a
sufficient elastic depressing force and load the
molar that are in premature contact.
2. Properly constructed activators that follow this
principle can influence the vertical growth
pattern in these cases.

To “close the V” between
upper and lower dental
arches by depressing
the posterior maxillary
segments with the
activator in a manner
analogous to that of
orthognathic surgery

Bionator
1. Used to inhibit abnormal posture and function of
the tongue.
2. The construction bite is as low as possible, but
a slight opening allows the interposition of
posterior acrylic bite blocks for the posterior
teeth, to prevent their extrusion.
3. To inhibit tongue movements, the acrylic
portion of the lower lingual part extends into the
upper incisor region as a lingual shield. Closing
the anterior space without touching the upper
teeth.

4. The palatal bar has the
same configuration as
the standard bionator,
with the goal of moving
the tongue into a more
posterior or caudal
position.

5. The labial bow differs
from the standard
appliance, that the wire
runs approximately
between the incisal
edges of the upper and
lower incisors.

6. The labial part of the bow is placed at the height
of correct lip closure thus stimulating, the lips to
achieve a competent seal and relationship.
The vertical strain on the lips tends to
encourage the extrusive movement of the
incisors, after eliminating the adverse tongue
pressures.

FRANKLE IV
The working principle of
the FR in establishing the
mandibular forward
rotation with the
posterior edges of the
buccal shields as a
rotational center.
Anteriorly, the mandible is
raised by the force of the
anterior vertical muscle
chain being strengthened
by lip seal exercises.

1. Normally, anterior open bite problems show
protracted tongue posture with incompetence of
lips. The tongue tooth contact replaces the lip
seal during deglutition to create negative
atmospheric pressure.
2. FR IV along with lip exercises cause lip contact,
reducing tongue protrusion and cause the
tongue to move back into its normally raised
position in proximity with palate, during
deglutition. www.indiandentalacademy.com

TWIN BLOCK
• Maintain occlusal contact
to intrude the posterior
teeth

PITFALLS
• Do not allow the second
molars to over erupt
• Extend occlusal cover or
occlusal rests distally to
second molars.

• Do not trim the upper
block in open bite cases.
• This will allow the lower
molars to erupt and again
popping the bite open.

BIOMECHANICS OF HEAD GEAR

Centers of resistance in
midfacial complex.
1. Alveolar process.
2. Maxilla.

Direction of force passes
behind both alveolar
and skeletal centers of
resistance, producing
clockwise rotation of
maxilla and maxillary
dentition.

between alveolar and
skeletal centers of
clockwise rotation of
maxilla and
counterclockwise rotation
of maxillary dentition.

above both alveolar and
skeletal centers of
counterclockwise rotation
of maxilla and maxillary
dentition.

Lloyd E Pearson
Describes seven different procedures for
treatment of open bite with backward rotating
mandible

OCCIPITAL HEADGEAR WITH CHIN
CUP

1. In the mixed dentition open-bite patient we could
intrude the upper first permanent molars and then
remove the remaining deciduous teeth, permitting
open-bite closure.
2. occipital headgear with a transpalatal arch to control
the inclination of the molars as they are intruded.
3. After the molars have been intruded perhaps 3 mm the
deciduous teeth are removed, the mandible is hinged
closed, and the anterior open-bite is closed.

4. The lower molars will often tend to extrude in
this type of situation. Unless mechanics are
designed to control their eruption.
5. An addition of a vertical pull-chin cup to the
occipital headgear and transpalatal arch would
intrude the upper molars, while preventing the
eruption of the lower molars.
6. As the open bite closes the mandible hinges
upward, reducing the height of the lower face.

Extraction of first premolars and use a vertical pull-chin cup

1. Extraction of first premolars and use a vertical
pull-chin cup with (16 ounces of forces)
2. This can close the mandibular plane angle,
reduce the lower facial height and close anterior
open bites.
3. Approximately 40
of closure of the mandibular
plane angle was found in his study.

possible mechanisms of action at work
a) maxillary sutures are pressure sensitive and
some intrusion of the maxilla could occur.
b) The posterior teeth tend to move forward
mesially.
c) A retardation of eruption of the posterior
teeth.

Mandibular bite- block therapy

1. Mandibular bite- block therapy, augmented with
vertical pull-chin cup therapy, can produce a
favorable holding of the vertical height
throughout the growth period,
intrusion of posterior teeth,
The hinging of the mandibular plane in a
counterclockwise direction and
closure of anterior open bites.

MANDIBULAR BITE BLOCK THERAPY WITH VERTICAL PULL CHIN CUP
THERAPY

AFTER CORRECTION

Magnetic bite blocks.

1. Magnetic bite blocks.
2. Although we get rapid results, two difficulties
arise with bite blocks
a. Extreme mouth opening which is difficult to tolerate the
appliance by the patient.
b. lateral movement of the mandible, that can cause
some temporomandibualr joint strain.

MAGNETIC BITE BLOCKS

vertical reduction genioplasty.

1. One advantage, is that it does not involve the
temporomandibular joints,
2. It can be done after non-surgical treatment as
an adjunct to bring the chin up and forward, to
improve facial balance, and to achieve
competency

The Extrusion Arch

1. The extrusion arch is a term coined to describe
the reverse action of already existing and well
established intrusion arch.
2. Wire used is
 16 x 22 SS or 17 X25 TMA with 900
offset bend at the
molars.

Mode Of Action
AT THE MOLAR:-
1. A second order couple is generated at the molar with
crown tipping mesially and root tipping distally.
2. The equilibrium is achieved because the anterior end of
the wire extrudes the incisors and posterior end
intrudes the molars.
3. Relatively very minimal buccal flaring of the molar is
seen.

MODE OF ACTION AT MOLAR

PROXIMAL VEIW

• AT THE INCISORS:-
• Extrusion can involve single teeth or group of teeth.
• When a group of teeth are to be extruded ,a
segment of heavy arch wire may be used in the
brackets of the anterior teeth, and the teeth are
extruded as if they were one big tooth.
• Whether the extrusion arch is tied segmentally or to
continuous arch wire or placed directly into the
brackets the effect is the same

Low transpalatal arch
1. It is considered that the
transpalatal bar
interferes with the
normal vertical descent
of the upper molars, and
therefore retards
maxillary vertical
alveolar development.

2. It is believed that, tongue
pressure against the
transpalatal arch during
swallowing, especially
when the transpalatal
arch is placed low in the
palate, will inhibit
maxillary alveolar
vertical growth.

Low Mandibular Lip Bumper
1. Cetlin and Hoeve advocated the use of a lip
bumper for the development of the lower dental
arch.
2. They suggested that if the lip bumper were
adjusted low, the cheek and lip mucosa would
rest above the appliance, and this will inhibit
vertical mandibular molar dentoalveolar
development.

3. But there is no further explanation or evidence
that a lower lip bumper can be used to prevent
eruption of the mandibular molar teeth.

Wedge Principle Coupled With The
Extraction Of Teeth
Two major approaches of applying the wedge
principle by extraction of teeth to control the
vertical dimensions.
1.Loss of posterior anchorage so that the anchor
teeth move mesially and are located farther
anteriorly in the arch in an area of greater vertical
dimension.
2. Extraction of first or second molars in both
arches to decrease the posterior dentoalveolar
height.

Garlington and Logan found that enucleation of
mandibular second premolars is beneficial,
 To control the vertical dimension.
 Increased in forward rotation of the mandible.
 Significant decrease in lower anterior face height.
 The criteria selection :-
a. Minimal lower arch discrepancy (6 to 10mm).
b. A mandibular plane angle greater than 380.
c. A hyperdivergent skeletal pattern.
d. Increased lower anterior facial height.

 Pearson stated that after the extraction of
premolar teeth, there is some mesial drift of the
posterior teeth (out of the wedge) and this
permits the mandible to hinge closed.

High Angle Begg Cases
1. In high angle begg cases we avoid class II
elastics to avoid open bite and accentuation of
present class II .
2. We give mild class I elastics in such cases.

Bracket Position
1. The placement point for incisor brackets may
vary in cases of infraocclusion.
2. In cases of open bite, placing anterior brackets
I mm more towards the gingival side.

Triangle Elastics
1. Triangle elastics aid in the improvement of
class I cuspid intercuspation and increasing the
overbite relationship anteriorly by closing open
bites in the range of 0.5 to 1.5 mm.
2. They extend from the upper cuspid to the
lower cuspid and first bicuspid teeth.

Anterior Vertical Elastics
 Class II orientation.
 Class III orientation

Avoid Intermaxillary Elastics
1. Intermaxillary elastics from the posterior teeth
have a vertical force vector which extrudes
these teeth and can further open the posterior
vertical dimension.
2. Class II elastics from 6 - 6 should not be
utilized until these teeth are well anchored in
buccal cortical bone .

How To Use Class II Or Class III Elastics
1. If class II or III elastics are required, they
should be attached posteriorly to premolars
rather than molars.
2. These ‘short elastics minimize the extrusive
effect on the back of the arch

ACTIVE VERTICAL CORRECTOR
1. AVC is a simple
removable or fixed
orthodontic appliance
that intrudes the
posterior teeth of both
the maxilla and
mandible by reciprocal
forces.

Active vertical corrector

3. By effective intrusion of posterior teeth, the mandible is
allowed to rotate in upward and forward directions.
4. The uniqueness of this appliance is that, it corrects
anterior open bite problems by actually reducing
anterior facial height.
5. Problems formerly thought to require orthognathic
surgery, can now be treated successfully with AVC.

Method of Action :-
1. Force system -- generated by repelling
magnets,
2. AVC is considered superior to a static bite block
appliance energized only by the intermittent
force from the muscles of mastication.
3. The constant force system of the AVC results in
greater rapidity of tooth movement.

Multiloop Edgewise Arch Wire
1. Multiloop Edgewise Arch Wire was developed
by Kim to achieve these goals :-
A, Correcting the inclination of the occlusal planes.
B, Aligning the maxillary incisors relative to the lip
line.
C, Uprighting the axial inclinations of the posterior
teeth.

1. The MEAW contains horizontal and vertical
loops fabricated from a 16 x 22 ss wire in an L -
shape fashion
2. The vertical loops act as a break between the
teeth, lowers the load deflection rate and
provides horizontal control.
3. The horizontal loops further reduces the load
deflection rate and provides vertical control.

4. Typical tip back bends of 3-5degrees are given
on each tooth.
5. Elastics are placed between the loops that lie
mesial to opposing cuspids.
6. Recommended elastic size is 3/16 inch heavy,
with a force approximately 50 gms when the
jaw is closed.

 KIMS technique was later modified by AYHAN
ENACAR et.al, using 16 x 22 reverse curve
NiTi arch wires with heavy intermaxillary
elastics applied in the canine region

Skeletal Anchorage System
1. Skeletal anchorage system was developed for
tooth movements.
2. SAS consists of titanium miniplates, that are
temporarily implanted in the maxilla or the
mandible as an immobile anchorage.
3. These miniplates are fixed at the buccal
cortical bone around the apical regions of the
lower first and second molars on both the
sides.

4. Elastic threads are used as a source of
orthodontic force to reduce excessive molar
height.
5. The lower molars were intruded about 3 to 5
mm, and open-bite was significantly improved
with little if any extrusion of the lower incisors,
with counter clockwise rotation of the occlusal
plane .

 SAS is an effective adjunctive biomechanical
procedure for correction of skeletal open-bite
malocclusion with out unfavorable side-effect.

Conclusion
Surgical management:

• One method of surgical correction is to extract
second and/or third molars if they are the only
source of centric contacts.
• Glossectomies have been used to correct open
bite problems associated with abnormal tongue
habits. Their effectiveness in closing anterior or
posterior open bite problems has not been
substantiated.

• Surgical procedures to improve the patency of
the airway must be undertaken with caution.
Documenting the amount and location of the
obstruction is a prerequisite.
• In many cases, a more conservative medical
approach may serve the same purpose when
the obstruction is related to allergies

• This is especially important because it is recognized that
a reduction in tonsilar and adenoid tissue occurs near
adolescence, and other children appear to "outgrow"
certain allergies.
• Severe skeletal open bites in patients who are not
growing are often treated by combined orthodontic-
surgical approach.
• Superior repositioning of the maxilla, via total or
segmental maxillary osteotomies, is indicated in skeletal
open bite patients with excess vertical maxillary growth.

• Maxillary impaction allows forward and upward
rotation of the mandible, therefore decreasing
the lower face height and eliminating anterior
open bite.
• This upward and forward autorotation often
makes mandibular reduction or reduction
genioplasty necessary as well.
• Superior repositioning of the maxilla is one of
the most stable orthognathic surgical
procedures.

conclusion
The treatment of open bite remains a challenge
to the clinician, and careful diagnosis and timely
intervention will improve the success of treating
this malocclusion.

REFERENCES
1. Subtelny, J. D.: Open-bite: Diagnosis and
treatment, Am.J.orthod. 42; 337, 1964.
2. Hellman, M.: Open bite, Am J. orthodont. 17:
421, 1931.
3. Robert J Issacson, Closing anterior open bite
:the extrusion arch. Seminars in orthodontics.
7.34 – 41 .2001
4. Vertical Control with a Headgear- Activator
CombinationCLAUDE CHABRE, DCD, DSO
JCO 1990 OCT 618 - 624

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Biomechanics of open bite

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