抄録
Surface electromyogram was utilized as one of the diagonostic methods for patients with craniomandibular disorders to investigate masticatory muscle contraction. We attempted to determine normal ranges of asymmetry and activity indices, proposed by Naeije M.et al., in masseter and temporal muscles during intercuspation at the clenching levels of 10%and 50% maximum voluntary contraction (MVC).
Normal ranges were calculated with the parametric statistics on the asymmetry index in 88 males and 75 females (mean 22.7 yr.), and on the activity index at each side in 47 males and 39 females (mean 22.5 yr.).
Significant differences of asymmetry indices were found between sexes, between muscles and between clenching levels (p>0.05).Normal range of asymmetry index at 10% and 50% MVC was respectively:-51.57 to 64.69 and -39.19 to 34.07 for the masseter muscle and -56.42 to 71.51 and-32.99 to 29.65 for the temporal muscle in males;-35.79 to 58.83 and-27.82 to 29.71 for the masseter muscle and -30.90 to 51.97 and -20.12 to 26.01 for the temporal muscle in females. Positive value indicated right side prevalence.
No difference of the activity index was found between right and left sides.Normal range of activity index at 10%and 50%MVC was respectively:-94.22 to 35.85 and -38.84 to 44.13 in males;-81.98 to 6.19 and -49.49 to 27.36 in females (the negative value indicated dominance of the temporal muscle).
