Incidence and progression of approximal carious lesions among school children in Western Australia

Background. An understanding of carious lesion behaviour is important in timing and frequency of radiographic examinations. The aim of this study was to examine the occurrence and behaviour of approximal enamel lesions in permanent teeth among children in Western Australia and test the effect of easily measured factors on the rate of lesion progression. Methods: Bitewing radiographs of children enrolled with the School Dental Service in Western Australia were scored for the occurrence and progression of enamel caries using established criteria. Time to lesion occurrence was estimated by the use of the Kaplan-Meier analysis, bivariate tests of survival functions were undertaken using the log rank test and the influence of the measured factors were tested using the multivariate Cox proportional hazard model. Results: The median time to occurrence of enamel caries was 6.1 months; median time to dentine caries was 77.7 months. Multivariate analysis shows gender (hazard ratio, male 0.65), baseline permanent tooth caries experience (hazard ratio 1.15) and time at risk since eruption (hazard ratio 0.88) were important factors in the initiation of enamel caries while time since eruption (hazard ratio 0.87), clinician's rating of risk (hazard ratio, moderate risk 2.78, high risk 5.00) and residence in fluoridated area (hazard ratio, fluoridate 0.44) were all statistically significant for enamel caries progression. Conclusions: Time to occurrence of enamel lesions in approximal surfaces is relatively rapid while progression into dentine is relatively slow. Clinicians were able to assign the risk of lesion progression in a child. Residence in a fluoridated area has a marked retarding effect on enamel lesion progression but not on initiation of enamel lesions. These factors may be useful in developing a schedule for timing and frequency of radiographic examinations among children in Western Australia.