Muscle Exercise Effects on the Early Treatment of Skeletal Open Bite Malocclusions

Objective: This prospective study evaluates the treatment effects of light masticatory muscle exercises for mixed dentition skeletal open bite patients. Methods: Thirty-one patients (mean age 9.3 ± 1.3 years) were selected for early orthodontic treatment with a bonded palatal expander. After palatal expansion, the bonded expander was sealed and remained in place for 3 months. Upon removal of the bonded palatal expander, a transpalatal arch with an acrylic button 3 mm off the palate, a lower lingual arch, and a high-pull headgear were placed for approximately one year of additional treatment. Patients were randomly assigned to either an exercise or non-exercise group. Patients in the exercise group clenched on a soft bite wafer for one minute, five times per day. Cephalometric data was obtained from pre- and post treatment lateral cephalograms. Lateral cephalograms from a retrospective control group were matched by age, sex and mandibular plane angle. Results: High-pull headgear therapy alone had an intrusive effect on the maxillary molars and increased overbite. Exercise in combination with high-pull headgear produced significant reductions in the ANB and gonial angle and mandibular antorotation by an average of 2.2° . Conclusions: Treatment results suggest that clenching exercises helped control the vertical dimension and its effects on facial morphology may help to reduce aberrant vertical growth patterns.