Patterns of Jaw Reflexes Induced by Incisal and Molar Pressure Stimulation in Relation to Background Levels of Jaw-Clenching Force in Humans.

Abstract

Patterns of jaw reflexes induced by periodontal stimulation were examined in ten adults. Surface electromyograms (EMGs) from the masseter and anterior temporal muscles were recorded when pressure stimulation was applied to either an incisor or a molar. Reflex responses to periodontal pressure stimulation varied, depending on the background levels of jaw-clenching force that preceded stimulation (background clenching force, BCF). At low BCF, excitatory reflexes were elicited from the jaw-closing muscles and jaw-clenching force. However, the magnitude of excitatory reflexes varied with the location of the stimulated tooth along the dentition. While excitatory reflexes were induced equally in the masseter and temporal muscles during incisal stimulation, stronger excitatory reflexes were induced in the temporal muscle than in the masseter muscle during molar stimulation. At high BCF, inhibitory reflexes in the jaw-closing muscles and jaw-clenching force were elicited in eight subjects (group A) during periodontal stimulation. However, excitatory reflexes in the muscles and force were elicited in the remaining two subjects (group B). In the subjects of group A, stronger inhibitory reflexes were elicited in the temporal muscle than in the masseter muscle, and jaw-clenching force also decreased during both incisal and molar stimulation. In the subjects of group B, the magnitude of excitatory reflexes decreased with increases in BCF.

Comparison of the Physiological Properties of Human Periodontal-Masseteric Reflex Evoked by Incisor and Canine Stimulation

“…It has been shown that the change from an excitatory reflex to an inhibitory reflex is related to the size of MUs, BGA, or the direction and strength of the mechanical stimulation applied to the teeth (Trulsson and Johansson, 1996; Türker et al, 1997; Yang and Türker, 2001; Brinkworth and Türker, 2005). When axial pressure stimulation was applied to the maxillary molar, an inhibitory reflex occurred in the masseter muscle when the occlusal force was large, while an excitatory reflex was easily evoked when the occlusal force was small (Yamamura et al, 1993). Sowman and Türker (2008) found that the RR of incisor-driven PMR is negatively correlated with the amount of pre-load applied to the incisor.…”

Periodontal mechanoreceptor input reduces synchronous discharge of voluntarily activated masseter motor units in man

“…Since this type of PMR stimulation is known to elicit an excitatory effect on the masseter motoneurons (Yamamura et al, 1993;Taguchii et al, 1995), the effectiveness of other excitatory inputs must have decreased during the PMR stimulation.…”

“…As tonic stimulation of PMRs induces excitatory effects on the jaw-closer motoneurons (Yamamura et al, 1993;Taguchii et al, 1995), the PMR input to the motoneurons should contribute significantly to their discharge during a voluntary biting task (Morimoto and Nagashima, 1989).…”

A multiparametric analysis of occlusal and periodontal jaw reflex characteristics in young adults with normal occlusion

“…Periodontal jaw-reflex recordings were carried out by a slight modification of the method described by Yamamura et al (1993). An impression of the maxillary *Yoshida Co., Tokyo, Japan.…”

“…In fact, reflex responses to pressure stimuli applied to the periodontium or PDL varies according to the levels of background jaw-clenching force (BCF) prior to stimulation: an excitatory reflex occurs when the BCF is low whereas an inhibitory reflex is elicited hy a high BCF (Yamamura et al 1993). Therefore, measuring the periodontal jaw reflex by a force sensor embedded ivithin a bile block would offer means for a chairside evaluation of a novel occlusal parameter useful in oral rehabilitation.…”