Abstract
Introduction: The present study was designed to clarify whether the bilateral cooperation in the human periodontal-masseteric reflex (PMR) differs between central incisors and canines. Methods: Surface array electrodes were placed on the bilateral masseter muscles to simultaneously record the firing activities of single motor units from both sides in seven healthy adults. During light clenching, mechanical stimulation was applied to the right maxillary central incisor and canine to evoke the PMR. Unitary activity was plotted with respect to the background activity and firing frequency. The slope of the regression line (sRL) and the correlation coefficient (CC) between the central incisor and canine and the lateral differences between these values were compared. Results: There were significant differences in the sRL and CC, as well as lateral differences, between the central incisor- and canine-driven PMR. Discussion: These results suggest that the PMR differs depending on both the tooth position and laterality.
Highlights
Jaw movement during mastication exhibits a rhythmic pattern controlled by a central mechanism (Delcomyn, 1980; Morquette et al, 2012)
Subjects were excluded from this study if they had any acute or chronic injury or systemic disease, such as acute pain, that could interfere with the outcome; chronic pain, clinical pathology, or previous surgery related to the masticatory system; or if they complained of symptoms of temporomandibular disorders before the test
From the seven subjects, 32 pairs of motor units (MU) were recorded from the right and left masseter muscles that responded to mechanical stimulation
Summary
Jaw movement during mastication exhibits a rhythmic pattern controlled by a central mechanism (Delcomyn, 1980; Morquette et al, 2012). Experiments on animals have established the existence of a pattern generator for mastication (Dellow and Lund, 1971), there is evidence that masticatory forces are precisely controlled by peripheral feedback and that these forces change from bite to bite depending on the consistency of the bolus (Lund, 1991; Thexton, 1992; Türker, 2002) and the required task (Farella et al, 2009). Afferent information regarding forces acting on the teeth is important for the sensorimotor regulation of mastication (reviewed in Lund, 1991; see Türker et al, 2007). The force-encoding properties of periodontal afferents that supply anterior teeth have been described in several animal species (Hannam, 1982; Linden, 1990). While some studies have been performed in humans, they only targeted the incisors
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