Jc 10 /certified fixed orthodontic courses by Indian dental academy

Initial Intrusion of the
Molars in the Treatment of
Anterior Open Bite
Malocclusions in Growing
Patients
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INTRODUCTION
 Openbite can be related to skeletal, dental, and soft tissue
effects and generally contain a combination of these
factors.
Proffit WR. Contemp Orthod. St Louis, Mo: CV Mosby; 1986.
 In open-bite cases of skeletal origin, the factors responsible
for the malocclusion cannot be identified easily.
Proffit WR. Contemp Orthod. St Louis, Mo: CV Mosby; 1986.
Noar JH, Am J Orthod Dentofacial Orthop. 1996.
 Skeletal openbites show more molar and incisor eruption
than dental openbites, and the excessive dentoalveolar
heights increase the severity of the malocclusion.
Cangialosi T. Am J Orthod. 1984
Worms F, Am J Orthod. 1971

 steep mandibular plane, obtuse gonial angle, increased
lower face height, and counterclockwise rotation of the
palatal plane are parameters of skeletal anterior openbites.
 Parameters of dentoalveolar openbites are divergent max.
& man. occlusal planes, mesial inclination of posterior
teeth, and lack of a normal curve of Spee in the lower arch.
 Subtelny JD, Am J Orthod. 1964
Nahoum HI, Am J Orthod. 1972
Fields HW, Am J Orthod Dentofacial Orthop. 1984
Ellis E, Am J Orthod Dentofacial Orthop. 1984
Ellis E, J Oral Maxillofac Surg. 1985
Kim YH. Angle Orthod. 1987; 57:290–321
Dung DJ. Am J Orthod Dentofacial Orthop. 1988
 Treatment of patients with openbite must be performed
early to be successful. Otherwise the opportunity for
growth modification could be lost & surgical correction as
the only possible treatment.

 control of the vertical dimension is considered the
most important factor in the treatment of open bite
malocclusions.
Nahoum HI. Am J Orthod. 1975
Lavergne J. Angle Orthod. 1976
Horn AJ. Am J Orthod Dentofacial Orthop. 1992
English JD. Am J Orthod Dentofacial Orthop. 2001
 Various treatment modalities have been proposed for the
correction of anterior openbites.
Headgear, vertical-pull chincups,
vertical elastics, functional appliances,
posterior bite-blocks, tongue cribs,
transpalatal arches, posterior magnets,
multiloop edgewise archwires, miniplate anchorage,
orthodontic treatment and orthognathic surgery

 The purpose of this study is to present the Molar
Intruder (MI) appliance, which can be used to
intrude molar in the late mixed or early permanent
dentition and to evaluate the treatment effects of
MI.

MATERIALS AND METHODS
 14 patients (8 girls and 6 boys)
 age of 10 years and 7 months (range 9.2 to 12.4 years)
(late mixed or early permanent dentition)
 hyperdivergent phenotype.
(mandibular plane angle greater than 35°)
 anterior openbite (only the molars in occlusion)
 adequate transverse dimension in the maxillary dental
arch.
 Sex and type of malocclusion were not considered in
patient selection.

Appliance construction
 working models were obtained from the patient.
 A construction bite exceeding the freeway space by two
mm was taken using wax rims, and the rim was transferred
to the working models.
 The working models were mounted on a fixator,
 Buccal undercuts where clasps were planned were scraped
(0.5 mm) with a spatula for extra retention.

 Adams clasps (0.7-mm s.s.wire) for the maxillary premolars or
maxillary first molars if only the second molars were to be
intruded.
 Eyelet clasps (0.7 mm s.s. wire) were incorporated to reinforce
the retention of the appliance.
 Molar intrusion spring (0.7-mm s.s. wire)
>Design of the springs was altered if the second molars were erupted
 Acrilization and polishing .

Clinical management
 MI was adjusted in the mouth in a passive state, and then the intrusion
springs were activated.
 Force 1st molar - 110gm
1st & 2nd molar - 180 gm
 Patient was instructed to wear the appliance all day except during
meals.
 Patients were called at three-week intervals to reactivate the springs.
 The average treatment time with the MI was five months. After the
appliance was removed, orthodontic treatments were carried out with
edgewise mechanics

Cephalometric analysis
 17 landmarks and 21 parameters were used in the study.

 Treatment effects were determined by Superimposing the
lateral cephalograms.
1 patient 2

BEFORE
1 PATIENT 2
AFTER

RESULTS

The changes are
 SNB > increased by 1.57°
 ANB > decreased by 1.29°
 Y axis > decreased by 1.36°
 SN/MP angle > decreased by 1.57°
 gonial angle > decreased by 1.50°
 NV-Pog distance > decreased by 1.21 mm.
 anterior face height > decreased by 1.86 mm
 ramus length > increased by 0.46 mm.
 posterior facial height/anterior facial height ratio > increase of 2.25%
 U6-FH distance > decreased by 1.86 mm
 L6-MP distance > decreased by 1.04 mm.
 U1-FH distance > increased by 0.54 mm
 U1/SN angle > increased by 1.46°
 occlusal plane angle > decreased by 2.25°
 overbite > increased by 4.00 mm
 mandibular sulcus contour > decreased by 3.57 mm

DISCUSSION
 Adult skeletal open bite is ideally corrected with a combination of
orthodontics and orthognathic surgerybecause the relapse after
surgery is usually less than that seen with nonsurgical treatment.
Bell WH. J Oral Surg. 1975
Denison TF, Angle Orthod. 1989
 early treatment of hyperdivergent cases with anterior openbites not
only eliminates the risks associated with orthognathic surgery but also
improves a child's self-esteem by improving the appearance.
English JD. Am J Orthod Dentofacial Orthop. 2001
 In this study, The first molars of 8 patients, the second molars of 1
patient , and both the first and second molars of 5 patients were
intruded by the MI appliance.

>In this study, the intrusive force for molars ranged between
110gm and 180 gm, depending on whether only one or two
molars were to be intruded.
>The results showed that the mean maxillary and mandibular
molar intrusion was 1.86 and 1.04 mm. However, when both
the first and second molars were intruded, the average molar
intrusion was reduced by nearly half. It was considered that
180 g of force might be insufficient for intrusion of two
molars.
>Patient compliance problems due to dislodgement were not
observed, but MI may pose dislodgement problems in the
patients with deficient crown length and buccal undercuts.

It is difficult to use the upper springs of the MI with expansion
screws. However, they can be used if precise readjustments are
made during expansion.
 Mandibular incisors were stable after the MI was used, but the
maxillary incisors were extruded an average of 0.54 mm with a
labial tipping of 1.46°. This was attributed to the anterior force
vector of the lower springs.
 Controlling the vertical dimension requires more effort, it is hard
to achieve this goal with high-pull headgear, extraction therapy
or combination of both because of compensatory eruption of
posterior teeth.

 Radiograph showed minimal root resorption in the molars(3 patients).
The resorption rate was minimal.
 The long-term effects of the treatment have not been established.

CONCLUSIONS
 MI is effective in intruding the molars and in reducing the
anterior openbite.
 MI is also effective in selective molar intrusion.
 The intrusive effect of the MI springs almost doubled in the
absence of second molars.
 MI use may be difficult in the patients presenting deficient
crown length.

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