The progression of incipient caries in the pits & fissures of permanent teeth was observed. The subject teeth were 375 cases of [C
0] and 250 cases of [C
1], in 477 primary school children who participated in a fluoride mouth rinsing program (0.05% NaF, once a day, 5 times a week in total). Caries examinations were made every 6 months for 2 years, without X-rays, and each subject was in charge of the same examiner. We found how to judge clinical caries which needs immediate treatment, and other useful information for caries control programs.
The percentage of incipient caries [C
0] which changed into caries [C
1] or [C
2] after 24 months was 51.1% in total, of which 2/3 was caries [C
1]. The percentage of caries [C
0] which disappeared after 6-24 months was about 15%. Besides, no incipient caries [C
0] which progressed to [C
3] could be found in any of the children. The percentage of incipient caries [C
1] which progressed to caries [C
2] after 24 months was 57.4%. There was only one case that progressed to caries [C
3] after 12 months.
Comparing the progression rate, the maintenance rate and the reversion rate, significant differences were recognized between the lower and higher grades. The progression rate of caries [C
0] in the 1st grade group was 69.0% and in the 5th grade group 25.3% after 12 months. It was very high in lower grade groups but low in the higher grade groups. A similar tendency was seen in the progression rate of caries [C
1]. The rate in the 1st grade group was 80.0% and in the 5th grade group 19.4%. On the other hand, the maintenance rate and the reversion rate were high in the higher grade groups. The cases of unchanged or reverted caries occupied about 80% in the 4th and 5th groups. The cumulative progression rate was also studied. Similar differences were recognized between the lower and higher grades. The cumulative progression rate increased most rapidly in the 1st grade group, but more slowly in the higher grade groups.
The concreate methods of caries control to avoid excessive treatment was proposed with fluoride mouth rinsing program. In cases of [C
0], instead of treatment, the preventive action until the next examination was recommended. On the other hand, in cases of [C
1], the treatment or reexamination were recommended. Immediate filling treatment should be given to children in the 1st, 2nd and 3rd grades. For children in the 4th, 5th and 6th grades, the preventive action should be taken without treatment, until the cases of caries [C
1] progress to caries [C
2].
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