Abstract
The purpose of this study was to evaluate the acidogenicity of lactose from the pH curve after lactose exposure on a pH-electrode covered with plaque, and to find out the difference between the acidogenicity in children's and in adults' plaque. To analyse statistically the pH-curves, plaque-pH was monitored 5 to 10 times on 3children and 3 adult volunteers respectively, and then 4 parameters (minimum pH value, returning time to pH 6, initial acid production activity and the area between the pH-curve and pH 6 level) were evaluated.
Furthermore, the plaques accumulated on hydrogen-ion sensitive filed effect transistor (pH-ISEFT) and enamel were analysed bacteriologically.
The following conclusions were obatined.
1)Data obtained from the four parameters indicate that acid production from lactose was lower than that from sucrose, but not statistically significant, except for acid production obtained from initital acid production activity. Also, except for initial acid production activity, three parameters showed considerable difference among subjects.
2)Acidogenicity (especially in minimum pH value and initial acid production activity)increased with age in plaque over six days (2-,4- and 6-days), and a marked increment of acidogenicity was shown between 2-days and 4-days.
3)With increasing lactose concetration (1,5 and 10%) acidogenicity (in minimum pH value and the area between the pH-curve and pH 6 level) increased, but initial acid production activity did not change.
4)Acid production in children's plaque following the application of lactose or sucrose did not differ from that in adults' in minimum pH value and initial acid production activity. However, the returning time to pH 6 was shorter and the area between the pH-curve and pH 6 level in children was smaller than that in adults.
5)There was no difference in bacterial composition between 4-day-old plaque accumulated on pH-ISFET and on enamel.
