BBB seminar: Bruce Matthews

Bruce Matthews
Department of Physiology and Pharmacology, University of Bristol, UK

Dentine forms the bulk of our teeth and surrounds a highly vascular, densely-innervated core, the dental pulp. Pulp is innervated by Aβ, Aδ, and C-fibres. In the crown, the dentine is covered by non-vital enamel. It is an avascular tissue, 2-3 mm thick, that is penetrated by tubules, c. 1 µm in diameter, that radiate from the pulp. At the pulpal end of each tubule is an odontoblast cell that has a process that extends into the tubule for approximately one third of its length. Non-myelinated nerve terminals accompany these processes about 100 µm into some tubules. The outer ends of the tubules contain no vital material. Human dentine is sensitive throughout its thickness, and particularly just below the enamel, to a wide range of different forms of stimulus that all cause pain. These include hot, cold, osmotic and mechanical stimuli, changes in hydrostatic pressure, and drying. Experiments in experimental animals indicate that there are two main classes of afferent nerve in teeth: one that responds to movement of the contents of the dentinal tubules and another that is sensitive to hot and chemical stimuli. Responses to cold stimuli appear to excite receptors by causing movement of the tubule contents. But recent human experiments indicate that more specific cold receptors are present. Other evidence indicates that intradental afferents express TRPM8, TRPA1, ASIC3, and P2X₃ ion channels. It has been suggested that the odontoblast, as well as being responsible for forming the dentine, may function as a sensory receptor but there is no conclusive evidence for functional connections between these cells and nerves.

Chair: Karin Johanne Heyeraas <karin.heyeraas@biomed.uib.no>, Department of Biomedicine