Trends in reasons for tooth extractions in Norway from 1968 to 1998

The aims of this study were (i) to determine the reasons for extraction of permanent teeth in Norway in 1998 and (ii) to describe changes in reasons f or extraction in time-trend and quasi-longitudinal perspectives over 30 yea rs based on three cross-sectional studies. The 1998 data were obtained from questionnaires distributed to a national random sample of 1,500 dentists, of whom 1,008 responded (67%). A total of 1,495 teeth were extracted for 1, 164 patients (age 10-92 years) during a period of 2 weeks. Caries accounted for 40% of the extractions and periodontal diseases for 24%. Caries was th e primary reason in patients 10-45 years old, while periodontal diseases do minated among adults >45 years old. In a time-trend perspective, among pati ents greater than or equal to 21 years, a significant decrease in the propo rtion of extractions because of caries was observed between 1968 and 1988, while non-significant changes were found between 1988 and 1998. Extractions because of periodontal disease accounted for about 26% in all surveys. Fol lowed longitudinally, the three cohorts born 1923-32, 1933-42, 1943-52 show ed a decrease in the proportion of extractions due to caries, and an increa se in the proportion of periodontal extractions during the period, more so between 1968 and 1988 than between 1988 and 1998. The three cohorts showed a variable trend of change, which may indicate that period and age effects do not necessarily operate in the same direction.