Pulpal inflammation alters the physiological properties of intradental nerves in the adjacent teeth

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Stimulation of the tooth crown induces vasodilation in the tooth pulp. This vasodilation seems to be mediated by the release of neuropeptides from the terminals of activated fine caliber afferent fibers. It has been suggested that the vasodilator response in the pulp spread as an axon reflex along the peripheral nerve branches when the tooth pulp is stimulated. On the other hand, branched dental nerves supplying the pulps of multiple teeth have been identified by electrophysiological and anatomical studies.The aims of this study were to investigate whether pulpal blood flow changes and intradental nerve activity can be induced by stimulation of an adjacent tooth to confirm the existence of branched afferents innervating both tooth pulps.Mustard oil or mechanical stimulation was applied to maxillary second premolar tooth pulps and pulpal blood flow and/or intradental nerve activity in the ipsilateral canine tooth were recorded in the cat. Mustard oil application to the second premolar p … More ulp significantly increased blood flow in the canine tooth. Sectioning of the infraorbital nerve and its branches on the experimental side did not affect this pulpal blood flow increase. The paraperiosteal injection of lidocaine without vasoconstrictor significantly inhibited the canine pulpal blood flow increase induced by mustard oil application to the second premolar pulp. Sporadic firing or sometimes bursts of action potentials in the canine pulp nerves were recorded during and/or after the mustard oil application to the second premolar pulp in some cases. Single pulp nerve units firing in synchrony with the mechanical stimulation of the second premolar pulp were recorded in some canines, which substantiated the existence of branched afferents innervating both teeth. These findings suggest that stimulation of the second premolar pulp may induce axon reflex-related vasodilation and intradental nerve firing in the canine pulp via branched afferent fibres innervating both the second premolar and canine teeth. Less