Närhi M
Department of Physiology, University of Kuopio, Finland.
Dent Clin North Am. 1990 Jul;34(3):439-48.
Irritation of human teeth can evoke pain sensations of varying qualities depending on the type and intensity of the stimuli used. For example, drilling or air drying of dentin typically induces sharp, piercing pain, while intense heating of the tooth can cause dull, aching pain sensation. The dental pulp is richly innervated by both myelinated (A-fibers, mostly A delta-type) and unmyelinated (C-fibers) axons. A-fibers seem to be responsible for the sensitivity of dentin. They respond to stimuli that induce sharp pain in human teeth, for example, drilling of dentin and drying of dentin with air blasts. C-fibers are activated only when the stimuli used reach the pulp proper. They respond to intense heating. In human teeth, dull pain is induced at a temperature level corresponding to the heat thresholds of intradental C-fibers. The other functional characteristics of C-fibers indicate that they may play a role in the mediation of the dull pain connected with pulpal inflammation. Accordingly, activation of intradental nerve fibers of A- and C-type may contribute to the varying qualities of pain sensations induced by stimulation of human teeth.
根据所使用刺激的类型和强度，对人类牙齿的刺激会引发不同性质的疼痛感。例如，对牙本质进行钻孔或吹干通常会引发尖锐、刺痛感，而对牙齿进行强烈加热会导致钝痛、酸痛感。牙髓由有髓鞘（A纤维，主要是Aδ型）和无髓鞘（C纤维）轴突丰富地支配。A纤维似乎负责牙本质的敏感性。它们对在人类牙齿中引发尖锐疼痛的刺激做出反应，例如，对牙本质进行钻孔和用气枪吹干牙本质。只有当所使用的刺激到达牙髓本身时，C纤维才会被激活。它们对强烈加热做出反应。在人类牙齿中，在与牙髓内C纤维的热阈值相对应的温度水平下会引发钝痛。C纤维的其他功能特征表明它们可能在与牙髓炎症相关的钝痛的介导中起作用。因此，A类和C类牙髓内神经纤维的激活可能导致人类牙齿刺激所引发的不同性质的疼痛感。
