Abstract
The purpose of this paper was to elucidate the peripheral control of jaw muscles during jaw movements in children with malocclusion such as anterior cross bite or deep bite. The subjects comprised 7adults with normal anterior interrelation but without any dysfunction of the mandibular movement. Two types of removable bite-blocks, with normal anterior bite and anterior cross bite (anterior overjet -1 mm), were fabricated to perform an anterior tapping and a molar tapping. Electromyograms were recorded from the middle part of the masseter muscle and the posterior part of the temporal muscle.
The masseter muscle activities during tapping movement on wearing the bite-block with anterior cross bite were not much different from those on wearing the normal bite-block. In the temporal muscle activities, however, the response pattern of the periodontal jaw reflex, in which the inhibitory reflex response was induced by anterior tapping but the excitatory reflex was occurred by molar tapping, was more prominently recognized when the bite-block with cross bite was worn than the normal bite-block. The magnitude of the temporal muscle activities was markedly reduced during tapping of the bite-block with cross bite.
The present results were considered to be related to the excess extension of the temporal muscle on wearing the tapping block with cross bite, and it was therefore concluded that the afferent input from the muscle spindle differed from the response pattern of the periodontal jaw reflex.
