Abstract
The aim of this study was to determine the variation in buffer capacity in dental plaque from different areas of the dentition that may be related to the caries status of associated tooth surfaces. Twoday or four-day plaque samples were collected from 8 different sites from each of 15 adult subjects living in Hokkaido; the upper-anterior-buccal(UAB) and lingual(UAL), upper-posterior-buccal(UPB)and lingual(UPL), lower-anterior-buccal(LAB) and lingual(LAL), lower-posterior-buccal (LPB) and lingual (LPL). Wet plaque samples were weighed and 25 mM KCl was added to give a final concentration of 10 mg/ml. The samples were dispersed with a sonication and vortex mixing. A small stir bar was added to the suspension. A micro pH electrode was then placed and the pH was determined. The suspension was then titrated with 10 mM-HCl to pH 3.0. Titration curves were expressed by the 3rd order polynomial (y: pH, x: volume of acid). Statistical analyses among 8 different sites were carried out using the ANOVA and Scheffe test. Statistical analyses among 2-day plaque and 4-day plaque were carried out using the Mann-Whitney U test. The highest pH without acid (initial pH) in 2-day plaque was LAL (7.28±0.36 SD) and the lowest was LPB (653±0.29 SD) with statistical significances (p<0.0001), and the highest pH in 4-day plaque was LAL (7.14±0.30SD) and the lowest was UAB (6.33±0.53 SD) and LPB (6.33±0.41 SD) with statistical significances (p<0.0001). Significant differences were seen in the volume of acid added from pH 6.0 to 5.5, as well as from pH 5.5to 3.0 in both 2-day and 4-day plaque. Plaque associated with the LAL, which is very prone to saliva and less prone to caries, had significantly the highest volume of acid added in the 2-day plaque (pH 6.0-55: 36.16±9.47 SE nmolH+/mg plaque, p<0.05, pH 5.5-3.0: 439.69±55.61 SE nmolH+/mg plaque, p<0.0001), as well as in the 4-day plaque (pH 6.0-5.5: 29.44±4.05 SE nmolH+/mg plaque, p<0.01, pH 55-3.0: 318.33±50.36 SE nmolH+/mg plaque, p<0.001). Compared to the 2-day and 4-day plaque samples, significant differences were seen in the volume of acid added in each. The 2day plaque showed higher than the 4-day plaque in UPB, UPL and LPB(from pH 5.5 to 3.0: p < 0.05).
These facts indicated that mature plaque would show more cariogenecity than immature plaque. These results suggested that site-specific plaque buffer capacity may reflect the differences in exposure to saliva, resulting in differences in local cariostatic challenge.
