Analyses of the caries decline and incidence among Norwegian adolescents 1985-2000

Since most studies of caries decline are descriptive time-trend analyses, the purpose of this article was to identify factors statistically associated with the caries decline among Norwegian adolescents after 1985. The DMFT scores for the age groups 12 and 18 years reported annually by 19 counties were analysed. The average caries-free proportions of 18-year-olds increased from 2% to 15% between 1985 and 2000, while the DMFT declined by 49%; 10.2 +/- 0.75 to 5.2 +/- 0.78. The decline for the 12-year-olds was 53%. The mean DT at the dentinal level remained at about 0.8 for 12-year-olds and 1.5 for 18-year-olds throughout the observation period. There was no significant difference in DMFT increment from age 12 to 18 between the birth cohorts 1973 (3.8 +/- 0.46) and 1982 (3.0 +/- 0.52) when controlling for counties. The variables migration and children per dentist were significantly associated with the DMFT decline in multivariate analyses. The caries decline for 18-year-olds was significantly steeper before than after 1990. The decline among the 18-year-olds may be attributed to fluoride and more restrictive criteria for placement of fillings in teenagers in the 1980s and fewer filled teeth before the age of 12 years in the 1990s.