Abstract
The present study was performed to confirm the usefulness of four parameters for the reevaluation of the Stephan curve after giving three subjects three types of foods. The four parameters were (1) minimum pH, (2) the time required to reach the minimum pH, (3) the time required to return to the fasting pH, and (4) the area between the Stephan curve and the fasting pH level (pH changed area). The experimental design was set up using a table of orthogonal arrays (L9 (34)).
Dental plaque pH was determined in vivo by using a glass microelectrode with a Beckman pH meter before and after eating.
The following results were obtained.
1) In general, all subjects showed a classical “ Stephan curve ”. Dental plaque pH fell (within 25min.) after eating and gradually returned to the fasting pH.
2) Dental plaque pH fell greatly after drinking orange juice or eating chocolate, but the pH did not fall after eating potato chips.
The Stephan curve produced by orange juice was different from that of chocolate. The former showed a rapid pH fall and a quick return, whereas the latter showed a slow fall and a slow return to the fasting pH.
3) The Stephan curves showed considerable difference among three subjects. One of the subjects showed a great change after eating, but the others showed only a slight change.
4) The differences between foodstuffs and between individuals had more effect on the Stephan curve than the differences between the time of pH measurement.
5) It was concluded that the four parameters were useful for the quantitative analysis of the Stephan curve.
