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Sensory differences between crown and root dentin in human teeth.

Earlier ultrastructural investigations of human teeth have revealed differences in the innervation between crown and root dentin. In the present investigation, an intradental comparison of human teeth was made to estimate the sensitivity to different stimuli applied to two cavities, one in the buccal cusp and the other half-way between the cervix and the apex of the tooth. It was found that the pain produced by the different stimuli in the cuspal cavity was described as "sharp" or shooting, while the same stimuli applied to the root cavity provoked "dull" pain, often of a longer duration. Gentle stimuli, such as dry absorbent paper, only produced pain in the cuspal cavities. Ultrastructural examination revealed no nervous elements in the vicinity of the ground surface of the tested cavities in the crown or in the root. Odontoblastic cells including nuclei, were a common finding in the dentinal tubules of both the roots and the cusps, indicating aspiration of these cells. In some cases, in the cuspal areas, accompanying nerve-fibres had also been aspirated. The conclusion of the present investigation is that there are differences in sensibility between crown and root dentin. These differences are observed in both intensity and modality, supporting earlier findings of morphological discrepancies in the innervation of the coronal and root dentin.