Studies of dental root surface caries. 2: The role of cementum in root surface caries

Artificial caries lesions were produced in roots of teeth using an acetate buffer system, when the layer of cementum was either normal in thickness, e xcessively thickened by hypercementosis, or had been removed completely. Th e rates of lesion progression were measured in each case using polarized li ght microscopy to measure lesion depth. Analysis of calcium (Ca) and phosph orus (P) loss during the demineralizing process was carried out. The remova l of cementum was found to significantly increase the initial rate of penet ration of the lesion into the root, although this rate progressively reduce d to a level consistent with that found in normal roots after seven days of demineralization. The overall depth remained consistently greater than tha t observed in normal roots, or when lesions were produced entirely within h yperplastic cementum. Chemical analysis also showed removal of cementum res ulted in an initial doubling of the Ca and P lost from the root surface. Prior direct exposure of segments of normal roots to the oral environment w as found not to significantly alter the rate of artificial lesion progressi on, in comparison with that in the originally protected segment of the root surface. It was concluded that an intact cementum layer has the intrinsic ability to protect the underlying dentine of exposed tooth roots against acidic demin eralization and that prior exposure to the oral environment does not signif icantly alter this ability.