Abstract
We have been studying the site-specificity of dental plaque cariogenecity that may be related to the caries status of associated tooth surfaces. The aim of this study was to clarify the two different sites of acid production in dental plaque by determining the plaque pH curves following sucrose exposure. Two-day plaque samples were collected from the upper-anterior-buccal (UAB) and the lower-anteriorlingual (LAL) in each of the 9 adult subjects. Wet plaque samples were transferred to plastic sticks and immediately put into pre-weighed plastic tubes. The samples were weighed and 0.85% KCl solution (1 mg wet plaque/100μl)was added. A stir bar was then added to the p1astic tubes. A micro pH electrode was then inserted and the pH was determined. After 5 minutes,10% sucrose (1 mg wet plaque/30μl) was added, plaque pH was then measured at 60 different time points (1-60 min), and the plaque pH curves were recorded. After plotting the curves, the area under each curve (AUC) was calculated. Mean pH values were reported as the log of the mean hydrogen ion activity (i. e.,10-pH), and all statistical comparisons were made based on the hydrogen ion activities. Statistical analyses between 2 different sites were carried out using the Mann-Whitney U test.
The results were as follows.
1. The initial pH (without acid) of plaque in the LAL (mean±S. D.: 7.18±0.36)was significantly higher than in the UAB (6.09±0.37) (p<0.01).
2. The AUC of plaque in the UAB (mean±S. D.: 9,01±6.84(mmol/L⋅min))was significantly larger than the LAL(0,52±0.64(mmoVL⋅min))(p<0.01).
In conclusion, the site-specific acid production, which may reflect the differences in exposure to saliva, plaque in the UAB is more cariogenic than in the LAL.
