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Dr. Mohammed Alruby
Etiology
and
treatment mechanics
of open bite cases
Prepared by
Dr. Mohammed Alruby

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Dr. Mohammed Alruby
=== airway and craniofacial pattern
=== muscle and craniofacial pattern
=== tongue and anterior open bite
=== thumb sucking
=== failure of eruption
=== trauma stability
=== genetics
Treatment:
Thumb sucking
Tongue thrust
Macroglossia
Airway obstruction
Incisor intrusion
Growing patient
Non growing patient
** bonding to second molars
** esthetics and open bite
** ortho-gnathic correction
1- Airway and craniofacial pattern:

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Dr. Mohammed Alruby
 Nasopharyngeal obstruction contributes to lower position of the tongue and mandible, this
position lead to: increased anterior facial height, steep mandibular plane, large gonial
angel.
Some authors found the relationship between the mouth breathing and the vertical pattern of
facial growth is week relation.
 Some authors found the relationship between the mouth breathing and the vertical pattern
of facial growth is week relation as:
Fields et al: the relationship between the nasopharyngeal obstruction and large face
syndrome is multifactorial.
Shanker et al: conducted that, the children are switched from pattern to other overtime
(nasal, mouth)
Souki et al: reported that, the vertical growth pattern in a group of mouth breather have no
different after tonsillectomy and / or adenoidectomy than in control group of mouth
breathers.
Alves et al: found that the dimension of pharyngeal airway was greater in nasal breather
than in mouth breather by using CBCT.
2- Muscle and its contribution to facial pattern:
= generally, the hyperdivergant patients have weaker mandible muscles and a weaker bite force
than hypodivergant patients.
= the total force exerted by muscle is directly related to its cross sectional area of muscle fibers,
which can be measured by using CT and MRI.
= the difference in size indicate a different loading pattern during function in hyperdivergant and
hypodivergant patients
Muscle orientation:
= The masseter was obliquely oriented in long face subjects and vertically oriented in short face
subjects
= the vertical force component of muscles was 3% and 2% higher in short face subjects than in
long face
= the maximum biting force was 150N in long face subjects and 750N in short face.
= Rowlerson et al 2005 explain why the bite force is lower in long face than others, because
subjects with open bite had higher percentage of type I fibers (slow contracting and fatigue
resistance) in masseter muscle than deep bite subjects.
In deep bite cases had more type II fibers (fast contracting and relatively fatigable)
= Van Spronson 2010, the influence of maximum bite force in determining craniofacial
morphology is controversial, because electro-myographic studies shown that maximum bite force
is produced for only 6 minutes/day so the effect of muscle force is negligible or small.
NB: hyperdivergant growth pattern, which under a strong genetic influences, might result in a
dentofacial morphology with week musculature. These environmental interactions on the
genetically determined craniofacial structures could possibly determine the final expression of
long face morphology.
3- Tongue and anterior open bite:
= various habits such as: tongue thrust, finger sucking, and anatomic condition as: macroglossia,
have been reported as a causative factor for anterior open bite development

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Dr. Mohammed Alruby
= tongue size or function ply important role for developed anterior open bite, unfortunately,
macroglossia is difficult to diagnose because there is no simple method is valuable to measure the
volume of tongue, but there is some indication for macroglossia as:
1- Flaring of anterior teeth
2- Indentation on the lateral border of the tongue
3- Lateral extension of tongue on to the occlusal surface of lower teeth
= some researches claim that tongue thrusting appears to be a compensatory or adaptive behavior
to the altered craniofacial skeleton.
Stages of tongue swallowing:
1- Stage 1: loss of contact of dorsal tongue with the soft palate
2- Stage 2: Passage of bolus head a cross the posterior inferior margin of the ramus of the
mandible (pharyngeal stage)
3- Stage 3: passage the bolus head through the opening of esophagus. Stage 2 and 3 is
involuntary
The posture of the tipoff tongue was more anterior during all stages in open bite subjects than
control one to maintain oral seal.
= in open bite subjects the anterior part of the dorsum is lowered and its middle part is elevated.
= during swallowing the rear part of the tongue has minimal or no movement and marked
movement occur in the anterior and middle part of the tongue.
4- Thumb sucking:
= another environmental factors that associated with the anterior open bite.
= figure sucking and hyperdivergant face pattern are significant risk factors not only for
development but also for increased the severity of open bite.
5- Problem related to failure of eruption;
= ankylosis of primary teeth
= failure of eruptive mechanism (primary failure)
= secondary failure due to cyst.
= ankylosis permanent teeth: do not respond to orthodontic treatment
6- Trauma:
= skeletal trauma involving the condyle cause sever anterior open bite.
= arrested condylar growth or ankylosis of condyle result in altered vertical growth of the
mandible
= trauma to dentition, particularly the incisors, can result in localized anterior open bite if
the damaged tooth become ankylosed before the patient’s finishes growing.
7- Genetics:
Postures and morphology of the tongue
Skeletal growth pattern of jaws especially mandible
Vertical relationship of jaws bases.
Treatment strategies
1- Treatment of thumb sucking or figure sucking:
- Use tongue crib to prevent or stop this habit
- Series of loops that are sit closely to the anterior part of the palate and attach to upper
molar bands, these loops act as a mechanical obstruction for the habit

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Dr. Mohammed Alruby
2- Treatment of tongue thrust:
= use tongue crib and after crib placement the tip of the tongue was positioned posteriorly
during all stages of deglutition. Taslan et al 2010 report decrease in tongue pressure from 21
gm to 13 gm/cm and from 216gm to 143gm after 10 to 13 gm tongue crib therapy.
= other devices as myofunctional appliances is more effective in treating tongue thrust as:
activator, bionator, twin block, and Frankel functional regulator.
3- Treatment of macroglossia:
= by surgical resection to reduce the tongue volume, followed by the procedures to
correct the open bite.
= reduce tongue volume is better for stability after correction.
4- Treatment of airway obstruction:
Through adenoid and tonsils removal, allergy treatment, that allow establishment of normal
growth pattern. Some cases must be followed by using functional devices to stop the habit of
mouth breathing.
5- Correction of open bite by incisor extrusion:
Extrusion of upper and lower incisors to correction anterior open bite, for cases with normal
skeletal pattern or vertical dysplasia and deficient incisors display at rest or when smile.
Patient with vertical maxillary excess and treated by incisor extrusion may lead to excessive
display of incisors and gingival tissue and also there is some problems with long term stability.
1-Extrusion arches: is indicated for
1- Spontaneous correction of anterior open bite does not occur after tongue crib therapy
2- When constant extrusive force is desired in anterior teeth with minimal posterior side effect
3- Non-compliant patients who will not wear anterior vertical elastics
The extrusion arch is a couple of force system that produce single extrusive force and at the same
time tip forward moment and intrusion in posterior segment. To prevent the tip forward moment
we can added:
1- Buccal stiff sectional wire for molars and premolars
2- Force of extrusion keep light
3- Add vertical elastics for posterior segment
2-vertical elastics:
= indicated in patients with anterior open bite in which the occlusal planes diverge anteriorly
= vertical elastics between upper and lower incisors lead to reduce the open bite.
3-Multiloop edge wise arch wire: MEAW
= for sever open bite cases by using 16x16 stst wire
= most of reduction is achieved by extrusion of anterior teeth with negligible molar intrusion.
4-implant:
= some cases are ideally to close the bite by intruding the posterior teeth through implant that
allow pure intrusive force.
= titanium mini-implant in the buccal cortical bone in the apical region of 1st
and 2nd
molars
produce 3 to 5mm molar intrusion.
6- Treatment in growing patients:
= the prevalence of open bite is two to three times higher in children than in adults
= spontaneous correction of malocclusion occurs in more than two third of patients during mixed
dentition period

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Dr. Mohammed Alruby
= various methods have been used to manage hyperdivergant facial pattern in growing patients
as:
a- Headgear:
=Occipital and vertical pull headgear have an intrusive force on the maxillary molars
=Avoid using of cervical pull headgear in patients with hyperdivergant facial pattern
because molar extrusion can occur, leading to clockwise rotation of mandible.
b- Posterior bite block;
= passive acrylic bite blocks are functional appliances that open the mandible beyond inter-
occlusal distances by 3—4mm and maintain the pressure applied by masticatory force on
posterior teeth
= spring loaded bite block and magnetic bite block (active occlusal corrector) provide
continuous vertical force on the occlusal surfaces of posterior teeth within neuro-muscular
system
c- Vertical pull chin cup:
= vertical pull chin cups (VPCCs) used in conjunction with fixed appliances, or posterior
bite blocks, or removable appliances.
= the magnitude of force is 400gm/side, worn for 12h/ day, direction of force is 3cm from the
outer canthus of eye
d- Masticatory muscle exercise:
= clinching exercise increase the contractile forces on the elevator muscle of the mandible.
= significant reduction of anterior facial height, gonial angel, and counter clockwise rotation
of the mandible have been reported.
Common method: = chewing exercise on hard gum
= clinching exercise on soft bite block
For minimum of 45 to 150 minutes/day for 10 to 12 months of exercise is necessary to produce
significant results changes in dentofacial complex.
e- Trans-palatal arch:
= Harness: the force generated by tongue musculature on palatal arch during swallowing
can prevent the vertical development of the maxillary molars
= Chiba et al 2003: during deglutition, the mean tongue pressure exerted 37 to 709gm/cm
= when the loop of the palatal bar was 6mm from the roof of the palate, increase the level
of pressure.
7- Treatment of non-growing patients:
= some cases with vertical maxillary excess and excessive vertical dimensions can be treated by
using TADs to intrude molars to correct the vertical dimension without need for surgery.
= the major advantages of molar intrusion with TADs is the favorable skeletal changes that
enhance the patients dento-facial esthetics
= the suggested force magnitude for molar intrusion is about 50 to 200gm per tooth
For En-mass intrusion of molars and premolars, the force was approximately 200 to 400gm
= rate of intrusion for single maxillary molars is 0.75mm/month
= -- -- -- -- en mass of posterior segment 0.5mm/month
= time of intrusion of molars 5 to 7 months for: 2----4mm
= during intrusion of upper posterior segment, the lower lingual arch was used with 16 x22 stst
arch wire to prevent the compensatory eruptive response in lower arch
Results out come after intrusion:
1- Forward rotation of the mandible

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Dr. Mohammed Alruby
2- Increase chin projection
3- Decrease lower anterior facial height
4- Decrease in mandibular plane angel
8- Ortho-gnathic surgery:
= a segmental Le fort I osteotomy is routinely performed to reduce the vertical maxillary excess in
patients with two maxillary occlusal plane and transverse deficiency that allow superior
positioning and expansion of maxilla
= three degree of forward autorotation of the mandible was achieved when the maxilla was
impacted 1.3mm posteriorly and 3mm anteriorly, this autorotation leads to:
- Decrease the anterior facial height
- Decrease the mandibular plane angel
- Minor forward of pogonion
= in addition to Le fort I osteotomy, mandibular surgery may be performed to correct any
associated mandibular deformity
9- Extraction for open bite closure:
There is different pattern of extraction to correct anterior open bite as;
- Extraction of 2nd
molars
- Extraction of 1st
molars
- Extraction of 2nd
premolars
- Extraction of 1st
premolars
This extraction pattern allows extrude of anterior segment and move the posterior segment
anteriorly (wedge effect)
a- 2nd
molars extraction:
One of the practical options in patient who have anterior open bite (divergent occlusal plane)
Not need any space closure during treatment
b- 1st
molars extraction:
= This extraction pattern slightly reduced the vertical skeletal relationship but most of patients the
2nd
molars replace the 1st
molars and anterior open bite not resolved.
= as the molars is protracted into the extraction space, extrusion of the distal aspect usually occurs
due to poor mechanics, so there is maintain or increase the anterior open bite
c- Premolars extraction:
= most common method used for anterior open bite associated with crowding or over jet
= extrusion of anterior teeth is more effective treatment rather than wedge effect
= this method works well in case when divergence of occlusal plane is started anteriorly from 1st
or 2nd
premolars.
NB: open bite in mixed dentition:
1-Dento-facial type:
In early mixed: use of tongue crib or oral screen to
stop the habit
In late mixed: use multi-bracket appliance with long
time retention.
2-Skeletal type:
The treatment depends on the severity of malocclusion
and the possibilities of dento alveolar compensation

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Dr. Mohammed Alruby
In moderate cases; functional appliances with extra-
oral forces and extraction of teeth can solved all
problems
In severe cases: extraction of four premolars in some
cases and other cases impaction of buccal segment with
surgery
3- Combined type: treat the peri-oral abnormal function of
muscles and improve the skeletal relationship
NB: open bite in deciduous dentition:
Control the abnormal habits and eliminate
dysfunction
Habits: thumb sucking, tongue thrust, mouth
breather: -------- tongue crib and oral screen
Dysfunction: long face syndrome: ------- use chin
cup to redirect the growth.
Bonding 2nd
molars:
= bonding of 2nd
molars in patients with open bite increased the open bite because normally 2nd
molars in upper arch is more gingivally than upper 1st
molars and more occlusally in lower arch
(curve of spee)
= when straight wire is placed causing upper 7 and lower 6 to supra-erupt that lead to tipping in
occlusal plane which lead to downward and backward movement that aggravate open bite cases,
So: if alignment of 2nd
molar is needed, care must be taken to engage the 2nd
molar passively.
Esthetics and open bite:
= there are 3 major esthetic factors that must be considered when planning the correction of an
open bite cases; incisors display, occlusal planes, inter-labial gap
= functional occlusal plane in patient with anterior open bite and divergent occlusal plane is a
limiting factor to determine the amount of correction that can be done by orthodontics.
= the incisors must be erupting until level of positive over bite, if the amount of incisors display at
rest and curing is reduced, extrusion of upper incisors is maintained until an acceptable level of
display is achieved
= in some cases, correction of the remaining amount of over bite can be achieved by extruding of
lower incisors, but this extrusion will accentuate the lower curve of spee
= patient with long face with excessive gingival display and anterior open bite, the counter clock
wise of mandibular plane is recommended.
= inter-labial gap increased in severe cases of open bite (skeletal) and can be resolved by:
1- Retracting of upper and lower incisors that followed by change in lip response
2- Reduce the posterior facial height (molars intrusion) before take any decision for any of the
above must ensure the length of the lips is normal or not.
Stability and retention:
= the etiology of hyper-divergent face is multifactorial so the stability of treatment in growing and
non-growing patients depend on the clinician’s ability to address the cause of this malocclusion.
= Little et al 1985 follow 10 years of patients with anterior open bite and treated orthodontically:
- 85% of treated case has 3mm relapse

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Dr. Mohammed Alruby
- 74% of treated case had stable results.
= the introduction of TADs has enabled orthodontist to intrude the maxillary and mandibular
molars, correct the open bite non-surgical with stable results. But there are several studies that
report percentage of relapse after treatment by TADs in cases of open bite anterior:
1- Lee and Park 2008 reported 10.35% relapse for intruded molars and 18% relapse for
anterior open bite after 18 months
2- Sugawar et al 2002 reported 30% relapse after molars intrusion (12 months)
= major relapse of intrusion occurs in 1st
year after treatment.
= in deciduous and mixed dentition: functional appliances are useful or posterior teeth loaded with
acrylic to prevent over eruption.
= in permanent dentition; Hawely retainer with inter-occlusal cover the posterior teeth to prevent
relapse by over eruption of buccal segment, some authors advised used of bonded lingual retainer
in lower segment.
= positioners are suggested used during retention phase, the elasticity of positioner between the
molars applies an intrusive force through daily chewing exercises
= some authors advise masticatory muscle exercises involving chewing gum or soft bite wafer
during retention might in retaining the obtained results.
Ortho-gnathic treatment of open bite cases;
= skeletal open bite is usually having excessive facial height due to vertical excess. Surgical
approach is by maxillary intrusion at posterior area and the mandible respond by rotate upward
and forward to reduce mandibular plane angel.
= in cases with long distance from incisal edge to the base of chin can be corrected by:
- Orthodontic intrusion of incisors
- Anterior segment surgery
- Genioplasty of chin