Hall technique crowns and children's masseter muscle activity: A surface electromyography pilot study

Background: Hall technique crowns (HTCs) alter the occlusion temporarily, potentially affecting jaw muscles, particularly the masseter – the primary jaw-closing muscle. Aim: To assess masseter muscle activity (MMA) in children treated with a unilateral HTC. Design: In 12 children treated with a single HTC, bilateral MMA was recorded with surface electromyography (sEMG) for ten cycles of Rest Position (RP) and Maximum Voluntary Clenching (MVC) over 20 seconds immediately pre-HTC cementation (P_base), immediately post-HTC cementation (P_immed), at 2 weeks post-HTC cementation (P_2w) and at 6 weeks post-HTC cementation (P_6w). t test, ANOVA and post hoc statistics were used (P <.05). Results: As expected, MMA was low at rest and increased during maximal jaw clenching (P <.0001). MMA (mean ± SD) increased significantly (P <.001) between RP and MVC at: P_base [from 1.60 μV·s (±0.96) to 5.40(±2.30)]; P_immed [1.57(±1.15) to 3.75(±1.87)]; P_2w [1.39(±0.54) to 5.54(±1.45)] and finally P_6w [1.46(±0.56) to 6.45(±2.56)]. Rest MMA at P_base, P_immed, P_2w and P_6w remained unchanged (P =.18) whereas P_base clench MMA reduced by a third at P_immed (P <.001), returned to and exceeded baseline levels at P_2w (P =.822) and P_6w (P <.001), respectively. Conclusions: This pilot study showed that Hall technique crowns may affect masseter muscle activity in children. Clench MMA was reduced immediately post-treatment but returned to and later exceeded baseline levels at 2 and 6 weeks, respectively. Rest MMA remained unchanged.