Quantification of Enamel Periodicity in Indians

Objectives: Cross-striations in enamel have been reported to correspond to daily crystal deposition by ameloblasts during enamel formation. The current study aims to quantify the enamel periodicity in teeth from Indian individuals.
Methods: Ten extracted teeth, collected from individuals of Indian origin, were sectioned into 100±20 µm thin sections using a hard-tissue microtome and subsequently polished to remove the “cut-marks” formed due to the sectioning protocol. The sections were then characterized using polarized light microscopy (PLM) at 10X and 50X magnifications. The number of cross-striations were manually counted between two Retzius lines in each enamel section by a single investigator at three different sites. The counts of the cross-striations were then analysed using one-sample Wilcoxon Signed Rank test, comparing with the reported median count of 7. Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction were used to investigate the difference in the number of cross-striations in Indians, Singaporean Chinese and Heilongjiang Chinese subjects (unpublished data in our lab).
Results: A significant difference was demonstrated in the number of cross-striations (Median=6.16) in Indians with respect to the value 7 (p<0.05). Moreover, a significant difference was found in the number of cross-striations between Indians and Singaporean Chinese (p<0.05), but not with Heilongjiang Chinese subjects (p>0.05).
Conclusions: Enamel periodicity may not be solely determined by race. Environmental and/or other external factors may play a more important role than ethnic variations. Further research may be warranted to validate the results of the study.