title: Kinematics of the tooth tapping movement.
abstract: Electrical activity in the masseter muscles and tooth contact vibrations were recorded simultaneously from subjects tapping their teeth slowly into maximal intercuspidation and again with maximal frequency. High speed cinephotography was also used with four of the ten subjects. Three main parts could be distinguished on the obtained graphical representation of the tooth tapping movement: tooth contact phase (TCP), opening phase (OP) and closing phase (CP). Tapping frequency was increased by decreasing the jaw opening degree and the durations of TCP, OP and CP. The jaw velocity immediately before tooth contact, which may be of significance for the reflex response, was however not increased. The average jaw speed was nevertheless increased from 10 to 15 cm/s since the turning from OP to CP was more abrupt in high than in low frequency tapping. The duration of electrical activity after tooth contact was significantly shorter at tapping with high than with low frequency. The teeth maintained contact without detectable rebound between each open-close cycle. The OP started about 100 ms after the cessation of electrical activity both at low and high tapping frequency. The time between end of electrical activity and the start of a new OP was supposed to be dependent upon the relaxation time of the masseter muscles.
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003766:Dental Occlusion; D003768:Dental Occlusion, Centric; D004576:Electromyography / Q000295:instrumentation; D005260:Female; D006801:Humans; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology*; D009040:Motion Pictures; D009068:Movement; D010474:Percussion; D013997:Time Factors; D014070:Tooth / Q000033:anatomy & histology; D014732:Vibration