OBJECTIVESThis study investigated the incidence of caries in infants and explored the risk factors related to noteworthy variations between urban and rural areas.

METHODSSubjects were 232 infants (111 males and 121 females) aged 1.6 and 3 years born in "N" town between the fiscal years of 1997 and 2001. Infants aged 1.6 and 3 years had 99.6 and 100% participation in health checkups, respectively. Of the total, 148 and 84 infants were living in the urban and rural areas, respectively, of "N" town.

RESULTSCaries incidence and the average number of carious teeth (decayed/missing/filled teeth, dmft) for infants aged 1.6 years were significantly higher in the rural area than in the urban area, indicating that environmental factors that predispose infants to develop dental caries exist in the rural area. In addition, logistic regression analysis for infants in each of the two areas revealed that risk factors of the child-care environment, for example living with grandparents and brushing by parents, stood in marked contrast with each other. Moreover, the odds ratio of the risk factor dozing off while drinking showed a marked difference between the areas, although this risk factor was common in both areas.

CONCLUSIONSThe results of this study indicated that several factors of the child-care environment, for example the daytime caring person, are related with caries development. Scientific elucidation of the risk factors that give rise to high prevalence of caries in specific regions and access to the whole picture of the disease mechanism may have great potential to lead to the development of effective countermeasures and to contribute to the reduction of dental caries in preschool children.