title: Morphology and elemental composition of subgingival calculus in two ethnic groups.
abstract: BACKGROUND
  The aim of the present study was to compare the morphology and elemental composition of subgingival calculus between Indo-Pakistani and Caucasian patient groups.
  
  
  METHODS
  Extracted teeth from 14 Indo-Pakistani and 19 Caucasian subjects were collected. Of these, 12 Indo-Pakistani and 10 Caucasian teeth had sufficient subgingival calculus for analysis. Subgingival calculus present on the 22 teeth was classified into six morphological types: 1) crusty/spiny/nodular; 2) ledge/ ring; 3) thin, smooth veneers; 4) finger/fern-like; 5) individual islands/spots; or 6) supramarginal on submarginal. Subgingival calculus was zoned: coronal, mid, and apical. A sample obtained from each zone was subdivided to allow 3 separate analyses: transmission electron microscopic (TEM) x-ray microanalysis for elemental composition, fluoride analysis, and carbonate analysis.
  
  
  RESULTS
  Crusty/spiny/nodular, ledge/ring, and thin, smooth veneers were more 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 were found. No differences within or between the two ethnic groups were found with regard to calcium:phosphate ratios, fluoride, or carbonate content. However, the Indo-Pakistani group showed significantly lower levels of sodium in apical samples than in coronal samples (ANOVA, F1,16 = 5.98, P= 0.03), and significantly lower levels of sodium (ANOVA, F1,12 = 4.75, P= 0.05) and magnesium (ANOVA, F1,12 = 5.16, P= 0.04) in apical samples than in those from Caucasians. After adjusting for smoking, the magnesium results remained significant (ANOVA, F2,11 = 4.64, P= 0.05).
  
  
  CONCLUSIONS
  Subgingival calculus demonstrated differences in morphology between these two ethnic groups and differences in elemental composition, which may influence its overall solubility and contribute to its greater accretion in the Indo-Pakistani subjects.
authors.affiliation: Department of Periodontology, Leeds Dental Institute, UK. a.r.calvert@leeds.ac.uk
authors.forename: E A
authors.initials: EA
authors.lastname: Roberts-Harry
authors.forename: V
authors.initials: V
authors.lastname: Clerehugh
authors.forename: R C
authors.initials: RC
authors.lastname: Shore
authors.forename: J
authors.initials: J
authors.lastname: Kirkham
authors.forename: C
authors.initials: C
authors.lastname: Robinson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002118:Calcium / Q000032:analysis; D003728:Dental Calculus / Q000737:chemistry / Q000208:ethnology* / Q000473:pathology*; D004577:Electron Probe Microanalysis; D004739:England / Q000453:epidemiology; D005260:Female; D005459:Fluorides / Q000032:analysis; D006801:Humans; D007194:India / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D010154:Pakistan / Q000208:ethnology; D010710:Phosphates / Q000032:analysis; D012964:Sodium / Q000032:analysis; D012995:Solubility; D014092:Tooth Root / Q000473:pathology; D044465:White People
chemical_list: D010710:Phosphates; D012964:Sodium; D005459:Fluorides; D002118:Calcium