The aim of this study was to determine the variation in mineral ion contents (Ca, P, F) in dental plaque from different areas of the dentition in order to help explain the site-specificity of caries formation.4-day plaque samples were collected from 8 different sites of 15 male subjects living in Hokkaido (average age 25.2 yr. ) upper-anterior-buccal (UAB) and lingual (UAL), upper-posterior-buccal (UPB) and lingual (UPL), lower-anterior-buceal (LAB) and lingual (LAL), lower-posterior-buccal (LPB) and lingual (LPL). Plaque samples were weighed, freeze-dried, and subjected to acid extraction, using a mixed-acid digestion procedure that was described by Margolis and Moreno (1992). The acid extracts were analyzed for Ca using atomic absorption, P using colorimetry and F using the F ion electrode.
For the plaque wet and dry weights, the highest site was the UPB(mean±S. D.: 17.96±8.75mg wet weight,3.26±1.36 mg dry weight) whereas the lowest site was the UAL(2.62±259 mg wet weight,0.71±0.51 mg dry weight). However the water content of plaque samples were similar at all sites (around 80%), with the possible exception of the UAL site.
Statistical differences were seen in the Ca and P tested using two-way ANOVA (p<0.0001), and in F (p<0.05). Plaque associated with the LAL, which is very prone to saliva and less prone to caries, had significantly highest levels of Ca and P using Scheffe's test. It was concluded that sitespecific plaque mineral contents may reflect the differences in exposure to saliva, resulting in differences in local cariostatic challenge.