Changing time trend in caries prevalence in Norwegian children and adolescents

The purpose of the present study was to determine whether or not the decline in caries prevalence had continued among Norwegian 5-, 12- and 18-yr-olds from 1985 to 1991. The analysis was carried out at national, county and dental district level based on the annual census reports from public dental officers. Caries decline continued at national level. Some counties exhibited increases from 1 year to the next, more so in the last 3 years than in the first 3 years of observation, but not consistently. There was stronger evidence for a leveling out or reversal of caries trend at district than at county level. Reversal affected more 5- than 15-yr-olds and more 12- than 18-yr-olds. The chief dental officers in districts reporting a reversal of trend in caries prevalence and in comparison districts showing continued caries decline were interviewed by telephone concerning factors which might explain the observed caries trend. The interviews revealed no obvious explanation why caries prevalence increased in some dental districts while it continued to decline in others. It is concluded that a reversal in caries trend has occurred in some Norwegian dental districts between 1985 and 1991 and that there is a need for a more detailed study of the situation.