The Effects of the Placement of Prefabricated Metal Crowns Utilizing the Hall Technique on Masseter Muscle Activity: A Surface Electromyography Study in Children
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Hall technique crowns, used to restore non-pulpal carious primary molars, change the occlusal apparatus temporarily, of which the masseters muscles are part of. Surface-electromyography (sEMG) is used to assess masseter muscle activity (MMA). The aim of this study is to assess the effect of Hall technique crowns on MMA in children by measuring sEMG. Bilateral MMA was recorded (mean integrated sEMG expressed in μV.s) for ten cycles of Rest Position (RP) and Maximum Voluntary Clenching (MVC) over 20 seconds immediately-pre (P₁) and immediately-post (P₂) cementing a single HTC in 12 healthy children with caries. Further post op results at two weeks (P₃) and six weeks (P₄) results were obtained for 9 and 7 out of the 12 children respectively. T-test, ANOVA and post hoc statistical analyses were used. Significance was set at (p<0.05). Bilateral MMA was low at rest and increased during clenching in children. MMA increased significantly (p<0.001) between RP and MVC at P₁ from 1.85(+0.96) to 5.49(+2.30) μV.s; at P₂ from 1.77(+1.15) to 3.75(+1.81); at P₃ from 1.39(+0.54) to 5.54(+1.45) and finally at P₄ from 1.46(+0.56) to 6.6(+2.56). While there were no significant differences between all RP-MMA readings at P₁, P₂, P₃ & P₄ (p=0.18), the MVC-MMA readings differed significantly (p<0.001) as MVC-MMA at P₁ (baseline) reduced by a third at P₂, returning to (p=0.822) and increasing above (p<0.001) MVC-MMA baseline levels at P₃ and P₄ respectively. Children’s masseter muscle clenching activity, as measured by sEMG, reduced immediately after cementing a single HTPMC. The activity returned to, and later exceeded, baseline levels at two and six weeks respectively. HTPMCs had minimal effect on masseter muscle rest activity.