Abstract
The remineralization of root surfaces was investigated microradiographically in vitro using thin sections of root samples with or without cementum. Samples with cementum and with exposed dentin were prepared from extracted human premolars. They were demineralized in a 0.1M lactic acid gel (pH=5) for 2 w and sectioned to the thickness of about 100 μm. The sections were subsequently coated with nail varnish except for the demineralized surfaces and were remineralized in 20 mM Hepes (pH=7) with 1ppm F^- containing 1.5mM Ca^<2+> and 0.9 mM phosphate for 8 days. During the remineralization period, the sections were microradiographed repeatedly at days 0, 1, 2, 4, and 8 under wet conditions. After demineralization (day 0), the lesion depth values l_d and the mineral loss values ΔZ were roughly the same, 108 μm and 2,660 vol% ・ μm, respectively, indicating no difference between the samples with and without cementum. If we consider remineralization the subsurface mineral loss values ΔZ' (vol% ・ μm) were not different significantly between samples with and without cementum up to day 8. In contrast, the width of hyper-remineralization layer l_a (μm) and the mineral accumulation value ΔZa (vol% ・ μm) indicated that the hyper-remineralization occurs more rapidly and in large amounts in dentine compared with the samples with cementum present. Correspondingly, the maximum level of mineral V_<max> was significantly higher (p<0.05) in the dentine samples (74 vol%) than in the samples with cementum (38 vol%) at day 2. In contrast, the subsurface lesion width l' (μm) in the cementum covered samples was lower by 12 % (day 4) and by 26 % (day 8) with respect to the dentine samples, respectively. The results suggest that demineralization in root surfaces is most likely independent of the cementum layer, while (hyper-) remineralization process is strongly influenced by absence and presence of cementum.
