Reflex responses induced by tooth unloading

The reflex response of the masseter muscle to the rapid unloading of a sing le maxillary incisor tooth was studied. Unloading of a static force of 2 N in the horizontal direction resulted in a short-latency excitation, inhibit ion, and long-latency excitation of masseter muscle activity occurring at l atencies of approximately 13, 20, and 40 ms, respectively, with a correspon ding change in bite force occurring slightly later in each case. Following the blocking of periodontal input by the injection of local anesthetic arou nd the stimulated tooth, inhibitory responses were abolished. Therefore, it is concluded that the observed masseteric inhibition was caused by the unl oading of periodontal mechanoreceptors and thus that these receptors may co ntribute to the jaw unloading reflex.