THE EFFECTS OF UNILATERAL AND BILATERAL CHEWING, EMPTY CLENCHING AND SIMULATED BRUXISM, ON THE MASTICATORY-PAROTID SALIVARY REFLEX IN MAN

In man, parotid flow has been recorded, using modified Lashley cups, i n response to mechanical stimulation of the teeth by repealed chewing and clenching manoeuvres. The rectified and integrated masseter electr omyographic activity was used as an indirect measure of the stimulus i ntensity where necessary. Following the observation that 'empty clench ing' failed to evoke a parotid salivary response, a series of three ex periments has been undertaken to address the following questions. (1) Is a lateral component of force required to evoke a flow during empty clenching? (2) Does contralateral inhibition of salivary secretion exp lain this observation? (3) What is the threshold for the masticatory-s alivary reflex? The results suggest that. (i) empty clenching together with a lateral component of force does not result in a secretion abov e resting flows; (ii) there is no evidence for the existence of contra lateral inhibition of salivary secretion; and (iii) the threshold for the masticatory-salivary reflex is lower than 5 % of comfortable chewi ng forces. We are still unable to offer an explanation for the lack of parotid secretion during empty clenching.