LAUSR

BACKGROUND Anterior bite planes are bite-raising appliances used for deep bite correction. However, muscle responses to anterior bite planes of different hardnesses may vary. OBJECTIVES To prospectively evaluate masticatory muscle activity, muscle balance, and maximum bite force (MBF) responses to anterior bite planes fabricated from acrylic resin (ABP) or bi-laminate thermoplastic (TBP) over 6 months in children with a deep bite. METHODS Sixty-six children were randomly assigned to the ABP, TBP, or untreated control groups. Masticatory muscle activity, activity index (AC), and percentage overlapping coefficient (POC) were assessed by surface electromyography; MBF, using a custom-made bite force sensor. Data were collected before, immediately after appliance insertion, and after 2 weeks and 1, 3, and 6 months of treatment. Within- and between-group differences were analyzed using one-way ANOVA/Kruskal-Wallis and Mann Whitney U-tests (α=0.05); Friedman's tests were used to assess within-group differences over time (α=0.08). RESULTS At rest, no dependent variables changed throughout the study. At maximum clenching, masticatory muscle activity immediately dropped significantly but returned to baseline values and was equal to the control group at 1-3 months. The ABP group had significantly lower masseter activity and AC than the TBP group after insertion. Neither POC nor MBF were significantly different within or between groups. CONCLUSION Masticatory muscle activity reduced after anterior bite plane insertion but returned to baseline after 1-3 months. Masseter activity decreased significantly more in the ABP group than TBP group. Neither appliance significantly affected POC or MBF.