Oral health of the young has been reported to be associated with the place of residence, due to differences in socio-economic status. The results of studies on the effect of fluoride in drinking water on caries prevalence have been contradictory. The main aim of our study was to investigate the geographical distribution of dental caries prevalence in Finland and analyse possible regional, associated factors. Oral health of 13,564 men born between 1990 and 1992 was screened using a method based on criteria of the World Health Organization for epidemiological studies by 15 calibrated dentists in 20/24 garrisons of the Finnish Defence Forces in 2011. Mean DMFT and DT values in provinces were calculated. Multilevel analysis was applied to the data using generalized linear mixed models and a logit link function. The binary outcome variable was the cariological treatment need (yes/no) and the garrison was treated as random effect. Mean DMFT and DT values varied significantly between provinces in Finland. Increased levels of fluoride in drinking water, Swedish as the main language in the municipality, and living in urban areas were protective factors against cariological treatment need. Dentist density did not affect caries prevalence. The geographical distribution of dental caries further supported estimates of the protective effects of high fluoride levels in drinking water, Swedish as the main language in the municipality, as well as living in urban areas. Effect of fluoride on caries prevalence still exists, and association with the socio-economic status was confirmed.

Oral health of young males has not improved since the previous study among conscripts 15 years ago. Polarization of dental caries still exists. About half of the young male population still has manifested dental caries. Oral health promotion must not be neglected, even in countries with low caries prevalence.

Young men's health behaviour, especially of those with low education, does not promote oral health, which may indicate need for extensive healthcare services in the future. Health promotion should not be neglected.

In this cross-sectional study, association between smoking and dental caries was distinct. The high rate of restorative treatment need among smokers may be explained by their poor health behaviours. Dietary habits of the snuffers seem harmful too, but are compensated by good tooth brushing frequency.