Relationship between Occlusal Contacts and Masticatory and Sternocleidomastoid Muscle Activity

Objectives: The aim of the present study was to clarify the relationship between the number of occlusal contacts in the intercuspal position and masticatory and sternocleidomastoid muscle activity during maximum voluntary teeth clenching in healthy young subjects.

Methods: This study included 20 healthy subjects (7 women and 13 men). They had natural dentition and bilateral molar support. The electromyographic (EMG) potential of the masseter, temporalis, anterior belly of the digastric and sternocleidomastoid muscles were recording during: 1. a 3-second maximum voluntary clenching (MVC) on cotton rolls positioned on the posterior teeth (standardized recording): and 2. a 3-second MVC in the intercuspal position. EMG potentials recorded in the intercuspal position were standardized as a percentage of the mean potentials of the standardized recording, and the EMG muscle activity was calculated. The number of occlusal contacts in the intercuspal position was assessed using 12 μm thick shim stocks. Ten subjects with less than 7 occlusal contacts (few contacts) and 10 with at least 9 occlusal contacts (multiple contacts) were selected and grouped accordingly. Individual muscular activities were compared using the Mann-Whitney U test.

Results: The MVC recorded in the masseter, temporalis, and sternocleidomastoid muscles in the “multiple contacts” group was significantly greater than that recorded in the “few contacts” group (P< 0.05).

Conclusions: Thus, we can conclude that the number of occlusal contacts in the intercuspal position is significantly related to the masticatory and sternocleidomastoid muscle activity in healthy young adults.