Innervation of root dentine in human premolars

Based on autoradiographic studies it is generally held that the mammalian root dentine is only sparsely innervated. Previous electron microscopic studies on human teeth did not reveal nerve fibres beyond radicular predentine. It is the purpose of this communication to provide ultrastructural evidence for the presence of nerve fibres in apical root dentine of human premolars. Two healthy mandibular second premolars, removed due to orthodontic reasons, which formed part of a previous study, were utilized for this investigation. Root discs of about 0.6 mm thickness were removed at about 2 mm cervical to the root apex and processed for light and electron microscopy. Transmission electron microscopic examination revealed numerous nerve fibres along the pulp-predentine border and in patches of predentine. Distinct nerve fibres were observed in the inner mineralized portion of the radicular dentine. The axons existed in close association to the odontoblastic processes, but no synaptic contacts or junctional complexes could be observed.