Osteoclastic Resorption of Enamel in Third Molars.

Abstract

IADR London July 2018 Abstract 2810 Osteoclastic Resorption of Enamel in Third Molars. A. Boyde and G.R. Davis Biophysics OGD, Queen Mary University of London, London, UK Objectives: The most cervical enamel in deciduous teeth is normally resorbed during the latter stages of tooth shedding and the resorbed surface may be repaired by attachment cementum. With the notable exception of the Equidae, occlusal surface enamel is not normally subject to organised osteoclastic attack in mammalian teeth. In human teeth, occlusal enamel may be attacked in the case of ankylosed deciduous teeth which fail to shed, and in permanent teeth which are retained within the jaws for protracted periods. There are several reports in the clinical literature of atypical radiolucencies in human third molars which have arisen by external resorption extending from the occlusal surface. The present study aims to shed further light on this topic using 3D microscopic imaging. Methods: We studied apparently sound human third molars, collected with informed patient consent, fixed and stored in 70% ethanol with no records of the identity of the individuals, or clinical histories. They were subjected to high contrast resolution x-ray microtomographic (XMT) study. Using the XMT knowledge, teeth were sectioned and the cut surfaces polished.. After water jet washing, they were studied, uncoated, in a Zeiss EVOMA10 SEM using 20kV backscattered electrons, and 50Pa chamber pressure. Results: XMT and SEM showed empty intracoronal resorption cavities close to the occlusal EDJ, with no discolouration of the adjacent dentine or enamel. These excavations were at the end of long tunnels connecting to the fissure system of the occlusal surface. The detail of resorbed surfaces of both enamel and dentine bear the characteristic osteoclastic imprint. Resorption pits were also present on external coronal surfaces, and, unexpectedly, surface overlapping projections were also frequently found. Conclusions: We conclude that the intra-coronal cavities arise by osteoclastic excavation starting at the enamel surface in a pre-eruptive period extended by delayed eruption caused by impaction.