A masseteric excitatory reflex response preceding the silent period which appears following tapping movement of the jaw, was investigated in order to evaluate its origin. In the pre-anaesthetic state, the latency of response did not change with the intensity of tapping. However, its amplitude increased depending on the intensity of tapping. The response did not disappear even after the anaesthesia. After the anaesthesia the lighter the intensity of tapping was, the longer the latency of the response, coming up to that of the jaw-jerk reflex. The pre-anaesthetic response had an intricate wave form comparing with the post-anaesthetic one. From the above findings it was concluded that the response must be a complex one in nature originating in the muscle spindle of jaw closing muscles and in a certain receptor of the structures surrounding the tooth.

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PubMed1981

The role in masseter muscle activities of functionally elicited periodontal afferents from abutment teeth under overdentures.

Five overdenture wearers with a small number of remaining natural teeth were selected to evaluate the effect of the afferent input from periodontal mechanoreceptors on masseter activity in man. As a control, a full denture wearer was included. The subjects were instructed to chew a piece of gum, and/or tap their teeth. Surface EmG from the bilateral masseter muscles were recorded and analysed. When functional pressure was applied, during chewing, to the abutment teeth as well as to mucosa through the denture base, masseter activities were encouraged. Following application of anaesthesia to the periodontal membrane of the abutments, masseter activities were reduced. The duration of the silent period (SP) appearing in the EMG burst following tooth tapping was significantly increased with root support compared to mucosal support only. With topical anaesthesia of the periodontal tissues, SP duration decreased significantly. In conclusion, it has become apparent that the pressure sensibility of abutment teeth bearing functional pressure under an overdenture base is capable of facilitating masseter activity, as one of the sources of oral sensory input during mastication.

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PubMed1980

The delay time of tooth vibration signal recorded at facial skin surface.

The onset of a tooth vibration signal with a mini acceleration pickup attached to the skin on the forehead was delayed by 0.1788 ms on average after the actual tooth impact. When the signal was recorded at the zygomatic arch, the delay time was 0.1008 ms on average, which was significantly shorter than that obtained from the forehead (P less than 0.001). The difference due to a transposition of the vibrated tooth was also smaller (0.025 less than P less than 0.05) and had almost no effect on the intensities of the tooth flipping force. The delay time was even more prolonged when a poor frequency specification pickup and/or low pass filter were applied.

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PubMedDate not supplied

Functional significance of pressure sensation conveyed by removable partial dentures.

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