Abstract
An in vitro pH cycling system was used to investigate the reaction patterns of human enamel and root dentine samples. Both proximal surfaces of 10 premolars from 10-year-olds and 10 from 50-year-old subjects were analyzed by lesion depth and mineral distribution pattem measurements by microradiography. Each 24-hour pH cycling regimens of demineralization and remineralization were done in the order of dem./rem./dem./rem. and dem. for a total of 5 days. There was no change of lesion depth between mesial and distal proximal surfaces in any subject, and the deepest lesion depth in root dentine from 50-year-old subjects was approximately 150μm. Compared with the root dentine of 10-year-old subjects this value was statistically significant (p<0.01), although there was no statistically significant difference in lesion depth of the enamel. Mineral distribution pattem of enamel samples from both groups of subjects mainly showed subsurface lesions with one thick surface layer. Appearance of the lamination type of leions was restricted to 4 enamel samples from 10-year-old subjects. In root dentine samples from both subjects, remineralization was confirmed in cement and dentine simultaneously. Hyper-remineralized cement was found in the 3 cases of 10-year-old subjects and in 2 cases of 50-year-old subjects. Mineral distribution of the hyper-re-mineralized layer on top of the lesion ranged from 60%/vol to 70%/vol. In the current investigation, a tendency toward forming subsurface lesions with a rather thick enamel surface was seen if demineralization were followed by remineralization at similar time period. Considering thot remineralized enamel and root dentine are more resistant to cariogenic challenges, this finding was also clinically important.
