Masticatory exercise as an adjunctive treatment for hyperdivergent patients.
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OBJECTIVE: This retrospective study was designed to evaluate the morphologic effects of masticatory muscle exercise as an adjunctive therapy for hyperdivergent patients treated with fixed orthodontic appliances. MATERIALS AND METHODS: Three samples of 50 subjects were selected, including one sample treated with orthodontics combined with exercise, one sample treated with orthodontics only, and an untreated control sample. Subjects were matched on the basis of age, sex, mandibular plane angle (MPA), treatment duration, and treatment rendered. Patients in the treated exercise sample were instructed to clench their teeth together as hard as possible for 15 seconds and to repeat this process at least four times for a total of one minute; this one-minute exercise was to be performed as often as possible throughout the day. Morphologic data was derived from pre- and posttreatment lateral cephalograms. RESULTS: Exercise with orthodontics produced significant (P < .05) increases in overbite compared to orthodontics alone. However, changes in vertical facial morphology were not significantly different between the two treated samples. Relative to untreated controls, both treated samples showed significantly greater increases in the MPA (S-N to Go-Me), Y-axis, and the lower to total facial height ratio; the treated samples also showed significantly less true forward mandibular rotation than the untreated controls. CONCLUSION: Short-term clenching exercises performed daily are insufficient as an adjunct to traditional orthodontic treatment for correcting or controlling the vertical dimension.