ENCODING OF TOOTH LOADS BY HUMAN PERIODONTAL AFFERENTS AND THEIR ROLEIN JAW MOTOR CONTROL

Microneurography has been used to analyze the functional properties of human periodontal mechanoreceptors. Signals were recorded from single afferents in the inferior alveolar nerve while controlled forces were applied to the teeth. We have found that all periodontal afferents ad apt slowly to maintained loads. Most afferents are tuned broadly to di rection of force application, and about half respond to forces applied to teeth adjacent to the one to which the afferent distributes. Popul ations of periodontal afferents, nevertheless, reliably encode informa tion about both the teeth stimulated and the direction of forces appli ed to the individual teeth. Information about the magnitude of steady forces is made available in the mean firing-rate response of periodont al afferents. Most afferents exhibit a marked ''hyperbolic'' relations hip between the static discharge rate and the force amplitude; the hig hest sensitivity to changes in static force is observed at forces belo w 1 N. Similarly, the dynamic sensitivity is highest at low forces. Th ese afferents efficiently encode food contact during biting and contin uously discharge while food is held between the incisors. Subjects spo ntaneously exert low contact forces matched to the sensitivity charact eristics of these periodontal afferents when holding food substances b etween the incisors. If periodontal afferent information is not availa ble, the control of the hold forces is severely impaired. Moreover, si nce only a few afferents encode information about the rapid and strong force increase employed to bite through food, we conclude that subjec ts rely on signals from periodontal afferents to regulate the jaw musc les primarily when they first contact, manipulate and hold food substa nces between the teeth. A potential role for periodontal afferents in the spatio-intensive control of jaw actions is discussed. Copyright (C ) 1996 Elsevier Science Ltd