Estimation of two dental caries indices based on Japanese primary school children's caries experiences in one or two specific teeth.

Abstract

This is an attempt to estimate, from dental caries experience in specific kinds of permanent teeth, the indices (DMF rate, DMFT index) which are widely employed in epidemiological studies. In this study, the estimation was based on the records of the 1981 school dental examinations conducted on 3rd graders (8-9 yr.) and 6th graders (11-12 yr.) at 143 primary schools in Japan. The estimation models used were multiple regression models and the optimum model was determined mainly by AIC and coefficient of determination.Results were: 1. The DMF rate had high correlation with the LFM (lower first molars) DMF rate in both the 3rd and the 6th graders, and the DMF rate could be estimated well with this particular kind of tooth. 2. As regards the DMFT index, the model with the combination of the UFM (upper first molars) DMFT and the LFM DMFT might have been adopted in the 3rd graders. In the 6th graders, the model with the combination of the UFM DMFT and the UCI (upper central incisors) DMFT was adopted. Both models with the combination of these two kinds of teeth provide more persuasive explanation than does any of several other partial recording methods previously proposed.The fitness of the determined model of the DMF rate would be enhanced by incorporating into the variable the kinds of teeth having the frequency distribution of caries experience most similar to that of the DMF rate, that is, the kind of tooth which is most susceptible to dental caries, using the‘individual’as the unit. In the case of the DMFT index, the fitness would be enhanced by incorporating into the variable the teeth in which caries prevalence increases greatly at that particular age of the subjects, using the‘tooth’as the unit.On this hypothesis, even in the case of junior and senior high school students or adults, the DMF rate can be estimated well with the caries prevalence of lower first molars. And in estimating the DMFT index at that age, it is supposed that there is a need for not only using the combination of the UFM DMFT and the LFM DMFT or the UCI DMFT, but also for adding the second molars DMFT as one of the variables.