1. After symptoms and occlusal scores were obtained by an indexed protocol, EMG of masseter (Ma), anterior and posterior temporalis (Ta and Tp) and anterior digatricus (Di) of both sides were recorded in 24 TMD symptomatic (group S) and 20 asymptomatic subjects (group N), and analyzed for following parameters : 1) integrated activities of rest position (RP-IEMG), ICP (ICP-IEMG) and 70% MVC (70% MVC-IEMG), and their shifts over time 3) durations of SP and its latency (SPD and SPL) 4) Asymmetric index (AI) of the above parameters. Results indicated that 1) Compared with group N,RP-IEMG of Ta and ICP-IEMGs of Ma and Ta were significantly larger and smaller respectively, and the ratios of 70% MVC-IEMG to biteforce (BF) in jaw elevators were significantly greater in group S.2) MPF shifts over time were significantly more rapid in group S.3) SPDs were were highly longer in group S.4) Als of SPD and SPL showed significantly larger values in group S.5) Symptoms of jaw movements negatively asso
ciated with ICP-IEMG and 70% MVC-IEMG.6) Muscle symptoms positively associated with SPD for Ma, and TMJ pains and sounds had positive and negative tendencies in relation to SPD respectively. 7) The associations between occlusion and EMG were relatively weak and disorganized.
2. To investigate the relationship between musticatory muscle activities and TMD symptoms, TMD subjects were selected from the students of Kagoshima University Dental School, and were classified into 2 groups with (group M) or without (group NM) muscular problems. Normal subjects were also selected for control (group N). Masseter muscle activities and daily life pattern were examined by means of the portable 24-hour electromyography in each subjects, and were divided in 4 periods, as the eating, the studying, the sleeping, and the others. In TMD subjects, compared with group N,the numbers of bursts and the integrated activities of masseter muscle were smaller in the eating period, conversely were larger in other 3 periods. In the periods except the eating, the integrated activities in group M were larger than these in group NM.
3. The oral behavior patterns, such as clenching, grinding and unilateral mastication, are thought to aftect TMD because of hyper-and unilaterally imbalanced activities in masticatory muscles. To investigate the oral behavior patterns, muscle activities of the masseter and the anterior temporalis were examined by means of the portable 24-hour electromyography analysing system in both TMD patients and normal subjects. In the eating period, the low frequency and the short duration of muscle activities were seen in TMD patients compared with normal subjects. In the sleeping and the ordinary periods, opposite tendency was observed.