Reflex control of the jaw muscles by stimuli from receptors in the periodontal membrane.

In the opinion of a number of investigators, the only function of the mechano-receptors in the periodontal membrane is to inhibit closure of the jaws via a reflex pathway when a predetermined pressure on the teeth has been exceeded. In our opinion, the receptor system in the periodontal membrane may also play a role in a complex regulatory system which controls the movements of the lower jaw during chewing. In order to test this hypothesis a study was made of the changes occurring in the contraction pattern of three masticatory muscles of the cat, when the cuspids in the upper jaw were displaced in various directions. In all the experimental animals used, electromyographic changes in the three muscles investigated, could be recorded as a result of displacement of the cuspids. The results obtained suggest, at least in the case of the temporal and pterygoid muscles, that there are specific reflexogenic zones in the periodontal membrane, These results support the previously suggested hypothesis that a number of the pressure-sensitive receptors in the periodontal membrane play a role in a regulatory system which controls the movements of the lower jaw--as during chewing--by exerting a reflex influence on the degree of contraction of the masticatory muscles. In the discussion this hypothesis is worked out in more detail and the extent to which the results fit the chewing pattern of the cat is examined. In the conclusion, the author asks whether the finding of a regulatory system in the cat may also be applied to man.