Influence of occlusal contact on cervical muscle activity during submaximal clenching

The aim of this study was to clarify the relationship between changes in the occlusal contact area and cervical muscle activity. A decreases in the occlusal contact area using bite planes (stage 1: full contact bite plane, stage 2: bilateral molar removed from contact, and stage 3: bilateral molar and premolar removed from contact) was experimentally simulated in seven subjects (aged 23-25 years) with normal dentition, and muscle activity of the sternocleidomastoid muscle (SCM) and trapezius muscle (TRM) during 50 and 10% of maximum voluntary contraction (MVC) was measured by surface electromyography. The SCM activity during 50% MVC was stage 1: 31.2 +/- 9.4 muV and stage 3: 35.3 +/- 12.3 muV. The TRM activity during 50% MVC was stage 1: 15.2 +/- 0.7 muV and stage 3: 18.3 +/- 2.9 muV. At the 50% MVC, stage 3 showed significant differences in comparison with stage 1 (P < 0.05, ANOVA). These findings suggested that the sternocleidomastoid and TRM play roles in the exertion of occlusal force, and decreases in the occlusal contact area influence the amount of SCM and TRM activity.