AN IMMUNOHISTOCHEMICAL STUDY OF THE PULPAL NERVE SUPPLY IN PRIMARY HUMAN TEETH - EVIDENCE FOR THE INNERVATION OF DECIDUOUS DENTIN

The innervation of pulp and dentine was studied in fully formed human deciduous teeth using antibodies to calcitonin gene related peptide (C GRP). Freshly extracted healthy teeth were divided, fixed, demineralis ed, cryosectioned and treated with antibodies to human CGRP which was then labelled with horseradish peroxidase. Bundles of nerve fibres pas sed from the apex of the root to the coronal region where a subodontob last plexus was formed. In the cervical half of the root some nerve fi bres branched away from the main bundles to supply both the odontoblas t layer and the dentine. Branches from the coronal subodontoblast plex us also reached the odontoblast layer and the dentine. Most of the ner ve fibres terminated in the odontoblast layer. In some areas a margina l plexus of nerves was observed between the odontoblasts and the prede ntine; intratubular nerve fibres arose either from this plexus or dire ctly from the pulp. The dentine of the crown was more densely innervat ed than that of the root. In the crown the cervical one third had the most densely innervated dentine followed by the pulp horn and the midd le third. The most densely innervated areas occurred in regions where the marginal plexus was present. Although many tubules contained a sin gle nerve filament more complex patterns of termination were also obse rved. The maximum penetration of a nerve fibre into the dentine was 12 5 mu m. The pattern of the deciduous innervation shows some similariti es to the permanent dentition but among the differences is the high de nsity of dentinal innervation in the cervical region. The latter point correlates with the clinical impression of greater sensitivity experi enced by patients during invasive procedures performed without anaesth etic in the cervical area.