A LIGHT-MICROSCOPIC AND ULTRASTRUCTURAL EXAMINATION OF CALCIFIED DENTAL-TISSUES OF HORSES .3. DENTIN

Ultrastructural examinations of equine dentine found that dentinal tub ules extended from the amelodentinal junction towards the pulp forming primary curvatures, The number of dentinal tubules/unit area and thei r diameters increased significantly from the amelodentinal junction to wards the pulp cavities, particularly in regular secondary dentine, bu t irregular secondary (tertiary) dentine contained no dentinal tubules . Dentinal tubules contained odontoblast processes that appeared to ex tend as far as the amelodentinal junction, but due to iatrogenic loss during specimen preparation, odontoblasts were seldom found in regular secondary dentine. In primary dentine, the dentinal tubules were surr ounded by large amounts of peritubular dentine that increased in diame ter from the amelodentinal junction towards the junction of primary an d secondary dentine. The site of the dentinal tubule within the peritu bular dentine varied at different dentinal sites. Peritubular dentine was present in primary dentine only and was surrounded by a thin layer of intertubular dentine. When acid etched, peritubular dentine gave d entine a honeycomb appearance adjacent to the junction of primary and secondary dentine.