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Changes in prevalence of approximal caries in 17-year-olds and related restorative treatment strategies over a 6-year period.

Two cohorts of 17-yr-olds treated in a municipal child dental service in 1978-79 and 1984-85 had bitewing radiographs taken at the examination before the last course of treatment in the service. All radiographs were read by one examiner, who did not know to which cohort the individual belonged. The subsequent treatment was recorded from the treatment records by another examiner, who was unaware of the results of the radiographic examination. According to radiographic scores, the proportion of decayed or filled (DFS) approximal surfaces had decreased from 23.2% to 17.4% during the period (difference: 25%). The proportion of unfilled surfaces which were decayed (DS) had remained almost constant, while 9.6% of the surfaces were filled (FS) in 1978-79 compared to 3.1% in 1984-85 (difference: 68%). Thus, in spite of a 25% decrease in total caries experience (DFS), a reduction of 68% would be claimed if fillings (FS) were interpreted as expression of disease prevalence. The risk of an approximal surface being filled decreased to about one fifth from 1978-79 to 1984-85, and the risk of being filled was nearly three times as high for approximal surfaces of children who already had approximal fillings at the time of examination. Thus, both the year of examination and the subject's previously received treatment seemed to influence the treatment strategy of the dentist.