Abstract
Clinical application of a leaf gauge which can be used to locate the deviated mandible in centric relation are reported. However, a rationale for the treatment of abnormal muscles activities by the use of the leaf gauge is still unclear.
The aim of this study was to investigate a rationale for the physiological effects based on the biomechanical factors of deprogramming of abnormal masticatory muscle activity after created abnormalities due to experimental occlusal interference.
The detail method is following our former reports (Mushimoto et al, Yaegashi, 1994) . Six volunteer student were selected as subjects with normal occlusion without any symptomatic CMD. Subsequent recorded EMGs from bilateral masseter, anterior and posterior temporal muscles during brief maximal clench before and after insertion of a leaf gauge were analyzed. At the same time, Condylar Position Index applying X-ray Shuller and propotional ratio elongation of the masticatory muscles during insertion of the leaf gauge either 4mm or 16mm thick were also analyzed.
It was found that the reduced muscles activities were recovered by application of a leaf gauge, condylar position translated to anteriously and the masticatory muscles were elongated during the insertion of a leaf gauge.
In conclusion, it might be assumed that the positive feedback via the higher central from the elongated masticatory muscles activate the inhibited masticatory muscles.
