APPROXIMAL PLAQUE PH FOLLOWING TOPICAL APPLICATIONS OF STANDARD BUFFERS IN-VIVO

In this study, the null hypothesis was tested that topical application of standard buffer solutions, pH 7.00 and pH 4.01, to 4-day-old plaqu e deposits accumulated in situ causes the plaque to attain the pH valu es of the buffer solutions applied. Following a 4-day abstention from all oral hygiene procedures, the plaque pH of four interdental sites i n each of 5 volunteers was measured at resting state and following top ical applications of buffers pH 7 and pH 4. Later the same day plaque pH was measured following rinses with the buffers. Topical application of buffer pH 7 caused a plaque pH increase from a mean value of 6.40 to 6.59 within 30 s, while buffer pH 4 caused plaque pH to drop to a m ean value of 5.11. Rinsing with buffers caused plaque pH to increase t o 6.50 (buffer pH 7) and to drop to 4.99 (buffer pH 4). Statistical an alysis of the results led to rejection of the null hypothesis. The res ults thus indicated that the validity of the in situ approach of calib ration of plaque-covered indwelling electrodes may be questioned.