SEMG activity of jaw-closing muscles during biting with different unilateral occlusal supports

P>The aim of this study was to test the hypothesis that experimental and reversible changes of occlusion affect the levels of surface electromyographic (SEMG) activity in the anterior temporalis and masseter areas during unilateral maximal voluntary biting (MVB) in centric and eccentric position. Changes were achieved by letting 21 healthy subjects bite with and without a cotton roll between the teeth. The placement alternated between sides and between premolar and molar areas. The SEMG activity level was lower when biting in eccentric position without than with a cotton roll between teeth (P < 0 center dot 043). It was always lower with premolar than with molar support when biting with a cotton roll (P < 0 center dot 013). In the anterior temporalis areas, the SEMG activity was always lower on the balancing than on the working side (P < 0 center dot 001). Such a difference was also found in the masseter areas but only during molar-supported centric biting (P = 0 center dot 024). No differences were found when comparing the SEMG levels in masseter areas between centric and eccentric biting (P > 0 center dot 05). In the anterior temporalis area, the balancing side SEMG activity was lower in eccentric than in centric but only in molar-supported biting (P = 0 center dot 026). These results support that the masseter and anterior temporalis muscles have different roles in keeping the mandible in balance during unilateral supported MVB. Changes in occlusal stability achieved by biting with versus without a cotton roll were found to affect the SEMG activity levels.