Correlation of clinical pain symptoms with histopathological changes of the dental pulp: a review.

Pulpalgia is strong and often throbbing and it can start and stop spontaneously. When evoked, pain in pulpitis outlasts the stimulus. The pain is difficult to localise and often radiates to other parts of the face. But the pain symptoms vary. There are cases of severe pulpitis progressing to abscess formation and even necrosis without any symptoms (silent pulpitis). In some cases slight pulpal inflammatory changes will cause severe pain. It seems that correlation between clinical symptoms and histopathological condition of the pulp is not clear. Pulpal inflammatory changes may cause hypersensitivity of the intradental nerves. Vasodilation, increased vascular permeability and extravasation will cause increased intrapulpal pressure. This could spontaneously activate the pulpal nerves. The increased pressure will selectively activate the C-fibres while blocking the A-fibres which are more vulnerable to hypoxia. This would explain the change in pain symptoms during progress of pulpitis to dull type of pain. Some of the inflammatory mediators can excite the pulpal nerves while others even have an analgesic effect. Some of the exogenous compounds (bacterial metabolites and substances released during the breakdown of dentine) induce nerve activity in the pulp while others have a depressing effect. The net effect will probably depend on the relative proportions and concentrations of these substances in the pulp. This would also explain the variability of pain symptoms in pulpitis. Also the condition of dentine with blocked or patent dentinal tubules is important. If the substances with depressive effect are predominantly in greater proportions and concentrations, and if the dentinal tubules are blocked, this could be the case of "silent pulpitis".