REACTIVITY OF YOUNG AND OLD HUMAN ENAMEL TO DEMINERALIZATION

The aim of this study was to determine the susceptibility of newly eru pted and old permanent teeth to artificial, caries-like attacks. Two g roups of caries-free teeth were used. Group 1 consisted of 38 teeth ex tracted for orthodontic reasons (9-12-yr-old children); group 2, of 40 teeth extracted for periodontal reasons (45-65-yr-old patients). Afte r thorough cleaning, a test window was isolated on the incisal two-thi rds of the buccal surface. After demineralization with 6% HEC gel at p H 4.9 for 8 days, longitudinal ground sections were prepared for imbib ition studies in polarized light and for secondary ion mass spectromet ry (SIMS). In the young teeth, the lesions appeared to be uniform in t heir extension in the enamel, whereas the old teeth showed less marked and thinner surface zones and greater depth of the positively birefri ngent body of the lesion. Polarized light microscopy and SIMS data sup port the hypothesis that there are different enamel pathways in the in itiation of the natural carious process.