| Research Abstract |
To establish imaging diagnostic criteria of masticatory muscle tendon-aponeurosis hyperplasia(HyTAM): 1) the tendon and aponeurosis of the masseter were analyzed involving normal subjects(control group) and HyTAM patients(HyTAM group) employing CT, and then 2) muscle activity levels during mandibular movement, occlusion, and maximum voluntary clenching were analyzed. 1) The human tendon and aponeurosis in the masseter were classified into the following 4 types based on the findings of CT image analysis : Type I, a single thin tendon was present at the anterior margin of the masseter ; type II, a single, tendon continuous from the zygomatic process to the mandibular masseter ridge was present at the anterior margin of the masseter ; type III, multiple tendons continuous from the zygomatic process to the mandibular masseter ridge were present in the masseter ; and type IV, others. Types I, II, III, and IV were noted on 163, 14, 19, and 4 sides of the masseter in the control group, respectively, and 0, 1, 31, and 2 sides in the HyTAM group, respectively. 2) Regarding mandibular movement, the maximum mouth opening was significantly smaller in the HyTAM than in the control group, but no significant differences were noted in the amount of anterior or lateral movement. The occlusal force of maximum clenching was significantly greater in the HyTAM than in the control group. The muscle activity levels of the temporal and masseter muscles while maximum clenching were significantly greater in the HyTAM than in the control group, but no significant difference was noted in the temporal-to-masseter muscle activity level ratio. It was suggested that the analyzing of the tendon and aponeurosis of the masseter and masticatory muscle activity levels during mandibular movement, occlusion, and maximum voluntary clenching were useful.
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