The purpose of this study is to evaluate the OABC classification, which is divided into 4 classes by the location of dental caries at the dental health examination in infants aged 18 months in Japan, regarding the predictability of caries development in future.
The subjects, 309 infants initially aged 18/19 months, were dentally examined for 22 months, and the relationship between caries increment over the study period and the OABC classes at the age of 18/19 or 24/25 months was analyzed statistically. The following results were obtained.
1) No sex difference in caries prevalence was found. The mean dmft of combined sex groups at the age of 18/19 months, 24/25 months and 40/41 months was 0.54, 2.41 and 9.40, respectively, and the mean dmfs of the same age groups was 0.90, 4.11 and 17.81, respectively, in ascending order.
2) The mean dmft increment over a 22-month period in infants that belonged to each class at 18/19 months of age expanded in the order B, O
1, C, O
2 and A, and the mean dmfs increment over the same period increased in the order O
1, O
2, B, A and C. Therefore, the number of dmf surfaces was more useful than the number of dmf teeth in the comparison of carious increment between the OABC classes.
The three classes of A, B and C at the age of 18/19 months were not enough to evaluate the prediction of caries development for 22 months, because the differences among the caries increments of these classes were small and not statistically significant.
3) The dmfs increment over a 16-month period in infants that belonged to each class at 24/25 months of age increased in the order O
1, O
2, A, B and C, and there were significant differences between every two classes except O
1 and O
2.
Consequently, it seems that the OABC classification is more suitable for 24-month-old infants than for 18-month-old infants.
4) The caries increments over a 22-month period among the infants in 6 new subdivisions (Table 8) in the class 0 at the age of 18/19 months were compared.
The infants with preclinical caries such as white spots had significantly more caries increment than others, so it was thought that the infants with preclinical caries should be differentiated from other subjects. Furthermore, since there were significant differences between D
1 and D
2, and D
1 and D
3 in the infants without preclinical caries, it was supposed that the boundary of debris scores between O
1 and O
2 should be changed to the lower one.
5) A new classification containing 3 divisions, i. e., D
1P·OI), D
2/3P·OII), and D
1/2/3P+ (OIII), in the infants belonging to the class 0 at the age of 18/19 months was proposed. When the mean caries increments over 6 or 22 months periods in these classes were compared, there were statistically significant differences between every two classes except between OI and OII in dmfs increment over 6 months. Therefore, it was suggested that the new classification for 18/19 month-infants was useful and that class of infants with preclinical caries (OIII) was equivalent to class A from the study of individual caries susceptibility over 22 months.
6) When this newly proposed classification was applied to infants at the age of 24/25 months, there was statistically significant difference between OI and OIII in the mean dmfs increment over 16 months, so that this classification seemed to be also suitable for 24-month-old infants.
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