The effect of normal occlusal forces on fluid movement through human dentine in vitro.

Receptors inside human incisors appear to respond to stress (comparable to pressure as opposed to force) on the crown. This ability may be used to limit the stress applied to teeth or to discriminate between the hardness of objects clenched between upper and lower teeth. Here the hypothesis that these receptors are activated by fluid squeezed out of dentinal tubules when the loaded tooth is stressed was tested. Vertically compressing the crowns of extracted human teeth with loads of from 20 to 120 N, similar to those used in other studies and during natural chewing, did indeed displace fluid into the pulp. The fluid was displaced away from the crown immediately after the tooth had been loaded and moved back into the crown when the load was removed. The volume ranged from 3.5 to 22.2x10(3) pl, similar to that known to stimulate single pulpal nerve fibres. Thus, normal chewing forces could displace sufficient fluid out of dentine to excite putative mechanoreceptors somewhere inside the dentine/pulp complex.