VARIABLES RELATED TO MASSETER MUSCLE FUNCTION - A MAXIMUM R(2) IMPROVEMENT ANALYSIS

A multiple linear regression analysis, with stepwise maximum R2 improv ement technique by forward selection and pair switching, was used to s elect the occlusal, morphologic, and histologic variables which explai ned most of the variation in bite force and electric masseter muscle a ctivity. The variables comprised tooth contact and facial morphology t ogether with thickness and fiber characteristics of the masseter muscl e. The study included 13 healthy women, 21-28 yr of age, with a minimu m of 24 teeth and no serious malocclusion. Significant exploratory mod els (R2: 0.55-0.85) were shown concerning bite force, and electromyogr aphic amplitude during resting posture, maximal voluntary contraction (ICP), and unilateral chewing, as well as contraction time (chewing si de). Muscle thickness and molar contact had a significant, positive ef fect on the level of forceful muscle contraction. The explorative mode l both demonstrated explicable relations, and offered better insight i nto interrelations than did univariate analysis.