The influence of cutaneous tissue afferents on masticatory pain-pressure thresholds.

Pain-pressure thresholds are routinely used in orofacial pain research to record tenderness in masticatory muscles. This method is employed to stimulate deep tissue afferents, which are thought to be at least partially responsible for pain in temporomandibular disorders. Like other psychophysical measurements, however, this technique must stimulate cutaneous tissues before stimulating deeper tissues. This study examined 39 asymptomatic volunteers to quantify the effect of cutaneous sensory afferents on pain-pressure thresholds. In a randomized, double-blind fashion, pain-pressure thresholds were recorded at four facial sites before and after subjects received intradermal local anesthetic or a dry needle stick. Pain-pressure thresholds were significantly elevated after local anesthetic (P < .0001), suggesting that cutaneous tissues contribute significantly to the pain-pressure threshold. The authors discuss potentially important roles of cutaneous tissues in the assessment of deeper tissues and offer two theories of how the skin may be an important link in the assessment of temporomandibular disorders.