Abstract
The purpose of this study was to develop the removable plaque-pH measuring device for children and adults with complete dentition, and then to evaluate the morphological changes of plaque formation on the pH-ISFET by SEM.
1) The plaque-pH measuring device and the effect of the sucrose application on changes in the plaque-pH value.
The hydrogen-ion sensitive field effect transistor electrode (pH-ISFET) placed on the enamel was mounted into casted box-like case (10×7×2 mm). Two lead wires connected to the electrode were pluged into the device, and fixed by a guttapercha plate. This device was attached by an orthodontic sheath (ST-lock; Sankin Industry) to the buccal surface of the upper first molar of the child (9 y. )or adult (29 y. ). The subjects were asked neither to brush the electrode area nor change their eating habits. The pH value of 4-day-old plaque was recorded after the application of 10% sucrose solution to the plaque. The plaque-pH of the subjects reached the minimum pH value of approximately 4.1 within 10 minutes.
2) Figures of the plaque revealed by SEM.
The pH measuring device consisting of both pH-ISFET and the enamel was removed and examined by SEM using critical point drying at 2,4 and 6 days. It was found that the surface of the electrode was completely covered with the plaque which is similar to that on the adjacent enamel. Coccal organisms were dominant in 2-day-old plaque, and then were overcome by filamentous organisms with the lapse of time.
