STUDIES ON THE PREVENTION OF DENTAL CARIES WITH STANNOUS FLUORIDE

Abstract

This study was the result of three successive experiments that started from 1959, 1960 and 1962. Only first grade children of the primary schools in Tokyo and Yokohama city were used for the experiment.Experiment 1959: -The children who had lower first permanent molars free from carious lesions were selected from 16 schools. These children totalling 1.221 were divided into three groups, i. e., 2% NaF group, 4% SnF2 group and the control group independently in Tokyo and Yokohama area. All children were recieved dental prophylaxis and the children of experimental group were applied with respective fluoride solution for three minutes according to Knutson's method. The control group was similarly treated with distilled water. The treatment of all groups were carried out four times within one month.After two years, the 23 per cent (Tokyo) reduction and the 33 per cent (Yokohama) reduction were shown in children who were treated with 2% NaF as compared with the control group being evaluated by DMFT. In 4% SnF2 group, there were 20 per cent reduction in Yokohama, area, but no reduction in Tokyo area. These reduction were considered statistically significant at 1% level by Chi-square test.Experiment 1960: -The children totalling 994 were selected from 24 schools similarly as in 1959, and were divided into four groups that were 2% NaF, 2% SnF2, 8% SnF2 and the control group. All children were recieved dental prophylaxis and topical application of respective fluoride solution or distilled water (in the control group) according to Muhler's method. Two per cent NaF group and 2% SnF2 group were recieved four treatment during one month, but the control group and 8% SnF2 group were recieved a single treatment.After two years, the reduction of new carious teeth in 2% NaF group were indicated as 39 per cent (Tokyo) and 23 per cent (Yokohama) when compared with the control group. Per cent reduction of the SnF2 group versus the control group were indicated as follows, 2% SnF2 group was 16 per cent (Tokyo) and 6 per cent (Yokohama); 8% SnF2 group was 27 per cent (Tokyo) and 15 per cent (Yokohama). Two per cent NaF group in Tokyo and Yokohama and 8% SnF2 group in Tokyo were considered to show the significant reduction, but in other groups it was not significant (at 1% level).Experiment 1962: -The children in a school totalling 132 in Yokohama city were divided into two groups. The experimental group were recieved a single application of 2% NaF solution followed by a single application of 8% SnF2 solution on all the teeth after the dental prophylaxis. The latter treatment was applied in the following seven days. The other group served as the control without treatment.After one year, 57 per cent reduction (a significant difference at 10% level) was shown in this group evaluated by DMFT incidence, but after two years, there was indicated only 13 per cent reduction which was not statistically significant.In Yokohama city the children of six schools totalling 819 were divided into two groups. The experimental group was recieved a single application of 8% SnF2 solution on all the teeth after the dental prophylaxis, and control group was not treated. After one year, the 4 per cent or 7 per cent reduction was shown according to the DMFT incidence per capita or the DMFT percentage. After two years, there was no reduction being evaluated by DMFT incidence. These reduction were not considered to be significant.One of the reasons of apparently lower percentage reduction in SnF2 group might be attributed to the pigmentation on the fissures and pits after the stannous fluoride treatment, which were wrogly diagnosed as carious lesions and filled by the dentists in practice. To support this assumption, the filling teeth ratio in the SnF2 group was actually increased.