PubMed · 5228314
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D L Allen. Accurate occlusal bite guards.. https://pubmed.ncbi.nlm.nih.gov/5228314/
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The three states of mammalian being--wakefulness, REM sleep, and NREM sleep--are not mutually exclusive and may occur simultaneously, oscillate rapidly, or appear in dissociated or incomplete form to produce primary sleep parasomnias. Dysfunctions of a wide variety of organ systems may take advantage of the sleeping state to declare themselves, resulting in the secondary sleep parasomnias. Contrary to popular opinion, most of these often bizarre and frightening experiences are not the manifestation of underlying psychological or psychiatric conditions. Formal study in an experienced sleep disorders center usually reveals a diagnosable and treatable condition. Various parasomnias may result in injurious or violent behavior. The forensic science implications are beyond the scope of this article but have been reviewed extensively elsewhere. Continued study of unusual sleep-related events undoubtedly will reveal more fascinating conditions, expanding our knowledge of sleep physiology and strengthening the bonds between clinicians and basic science sleep researchers.
In man, parotid flow has been recorded, using modified Lashley cups, in response to mechanical stimulation of the teeth by repeated chewing and clenching manoeuvres. The rectified and integrated masseter electromyographic activity was used as an indirect measure of the stimulus intensity where necessary. Following the observation that "empty clenching' failed to evoke a parotid salivary response, a series of three experiments 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 explain this observation? (3) What is the threshold for the masticatory-salivary reflex? The results suggest that: (i) empty clenching together with a lateral component of force does not result in a secretion above resting flows; (ii) there is no evidence for the existence of contralateral inhibition of salivary secretion; and (iii) the threshold for the masticatory-salivary reflex is lower than 5% of comfortable chewing forces. We are still unable to offer an explanation for the lack of parotid secretion during empty clenching.