Morphology and elemental composition of subgingival calculus in two ethnicgroups

Background: The aim of the present study was to compare the morphology and elemental composition of subgingival calculus between Indo-Pakistani and Ca ucasian patient groups. Methods: Extracted teeth from 14 Indo-Pakistani and 19 Caucasian subjects w ere collected. Of these, 12 Indo-Pakistani and 10 Caucasian teeth had suffi cient subgingival calculus for analysis. Subgingival calculus present on th e 22 teeth was classified into six morphological types: 1) crusty/spiny/nod ular; 2) ledge/ring; 3) thin, smooth veneers; 4) finger/fern-like; 5) indiv idual islands/spots; or 6) supramarginal on submarginal. Subgingival calcul us was zoned: coronal, mid, and apical. A sample obtained from each zone wa s subdivided to allow 3 separate analyses: transmission electron microscopi c (TEM) x-ray microanalysis for elemental composition, fluoride analysis, a nd carbonate analysis. Results: Crusty/spiny/nodular, ledge/ring, and thin, smooth veneers were mo re commonly found in the Indo-Pakistani group; individual islands were more prevalent in the Caucasian subjects. Supramarginal on submarginal calculus was found only in the Indo-Pakistani group. No finger/fern-like deposits w ere found. No differences within or between the two ethnic groups were foun d with regard to calcium:phosphate ratios, fluoride, or carbonate content. However, the Indo-Pakistani group showed significantly lower levels of sodi um in apical samples than in coronal samples (ANOVA, F-1,F-16 = 5.98, P = 0 .03), and significantly lower levels of sodium (ANOVA, F-1,F-12 = 4.75, P = 0.05) and magnesium (ANOVA, F-1,F-12 = 5.16, P = 0.04) in apical samples t han in those from Caucasians. After adjusting for smoking, the magnesium re sults remained significant (ANOVA, F-2,F-11 = 4.64, P = 0.05). Conclusions: Subgingival calculus demonstrated differences in morphology be tween these two ethnic groups and differences in elemental composition, whi ch may influence its overall solubility and contribute to its greater accre tion in the Indo-Pakistani subjects.