Backscattered Electron Scanning Electron Microscopy of Early Childhood Caries.

Abstract

IADR London July 2018 Abstract 0459 Backscattered Electron Scanning Electron Microscopy of Early Childhood Caries. A. Boyde1, M. Kaur2 1Biophysics OGD, Queen Mary University of London, London, UK 2M. Kaur, Child Dental Health, Barts and The London School of Medicine and Dentistry, London, UK Objectives: Early childhood caries is a major health problem. We have looked for structural and compositional changes in primary molar decay. Methods: Deciduous molars preserved in 70% ethanol, obtained from anonymised collection. Age at extraction estimated from remaining root lengths in the range 4 to 8 years. Reason for extraction most likely pulpitis, since in every case there was a deep penetrating carious lesion. Further dehydration to 100% ethanol, then xylene, and embedding in PMMA from monomer. Teeth bisected and vertical section surfaces polished flat. Compositional contrast [mostly mineral concentration dependent] imaging using 20kV backscattered electron scanning electron microscopy, uncoated, 50Pa chamber pressure. Fields montaged to cover entire specimen. Higher magnification for detail. One block half stained with iodine vapour to study residual organic matrix and invading microbiota. Results: We have studied disease which must have spread rapidly through dentine. Much destruction of enamel occurred from within, attacking enamel from the enamel dentine junction (EDJ). Even the most demineralised carious dentine frequently showed hyperdense peritubular dentine (PTD): or locally expanded tubules, probably fungal invasion (e.g., Candida spp.): or multiple fine tubes crossing the tubule axis in the collagen fibre direction of the dentine matrix, a hallmark of motile invasive species (e.g. Capnocytophaga spp.), Patches of interglobular dentine (IGD), although normally unmineralised, were sometimes found to be more densely calcified than surrounding carious matrix. In older samples, caries often meets the advancing front of the resorption removing the roots and caries-modified, hyperdense, PTD and intratubular dentine cylinders are ‘left over’ by osteoclasts. Conclusions: Caries involves many microbial species which cannot be identified by morphology alone. However, there are many morphological types of dentine caries. In future, it might be possible to reach some identification with MALDI-TOF mass spectrometry. This is the first report of addition of mineral to IGD in association with remineralisation phenomena in caries.