Närhi M, Kontturi-Närhi V, Hirvonen T, Ngassapa D
Department of Physiology, University of Kuopio, Finland.
Proc Finn Dent Soc. 1992;88 Suppl 1:15-22.
In hypersensitive teeth pain is typically induced by cold and hot fluids or foods brought to contact with the sensitive dentin or by osmotic and mechanical stimuli. The results of animal experiments indicate that intradental A-type nerve fibres are responsible for the sensitivity of dentin. They are most probably activated by the hydrodynamic mechanism. Thus, their activation is to a great extent dependent on the condition of dentin with either open or blocked dentinal tubules. Blocking of the tubules effectively prevents the nerve activation. Correspondingly, in human experiments, the condition of the dentinal tubules greatly affects dentin sensitivity. In clinical studies significantly more open tubules are found in sensitive compared to non-sensitive areas. However, hypersensitivity may sometimes persist despite of effective blocking of the tubules. This may indicate that some other mechanisms may operate in the nerve activation instead of, or in addition to the hydrodynamic one. Inflammation may sensitize the nerve endings to such an extent that smaller fluid shifts would be sufficient for nerve activation or, for example, thermal stimulation may activate the nerves by a direct effect. On the other hand, spontaneously occurring changes in the exposed dentin, which in many cases seem to block the tubules may reduce the responses to hydrodynamic stimulation and, thus, have an opposite effect on dentin sensitivity. The results of animal experiments indicate that functional changes of this kind may occur. These results also indicate that real dentin hypersensitivity can develop as a result of inflammation induced sensitization of the nerves in the pulp-dentin border in teeth with open dentinal tubules.(ABSTRACT TRUNCATED AT 250 WORDS)
在牙齿敏感症中，疼痛通常由与敏感牙本质接触的冷热流体或食物诱发，或由渗透和机械刺激引起。动物实验结果表明，牙髓内的 A 型神经纤维负责牙本质的敏感性。它们很可能是通过流体动力机制被激活的。因此，它们的激活在很大程度上取决于牙本质的状态，即牙本质小管是开放还是堵塞。堵塞小管可有效防止神经激活。相应地，在人体实验中，牙本质小管的状态极大地影响牙本质敏感性。临床研究发现，与非敏感区域相比，敏感区域有更多开放的小管。然而，尽管有效地堵塞了小管，牙齿敏感症有时仍会持续。这可能表明，在神经激活过程中，可能存在其他机制替代流体动力机制，或与之并存。炎症可能会使神经末梢敏感化，以至于较小的液体流动就足以激活神经，或者例如热刺激可能通过直接作用激活神经。另一方面，暴露牙本质中自发出现的变化，在许多情况下似乎会堵塞小管，这可能会降低对流体动力刺激的反应，从而对牙本质敏感性产生相反的影响。动物实验结果表明可能会发生这种功能变化。这些结果还表明，真正的牙本质敏感症可能是由于牙本质小管开放的牙齿中，牙髓 - 牙本质交界处的神经因炎症而致敏所致。（摘要截选至 250 字）
