The study was designed to investigate the accuracy and precision of the development of the third mandibular molar, determined on panoramic x-rays, as an indicator of chronological age - a method which is used in Sweden to estimate chronological age in certain young foreign individuals with uncertain birth records. Accuracy test: The mean difference between the estimated and true chronological age was determined in a sample of 372 14.5-24.5-year-old subjects. The data were arranged in subgroups according to sex and age. The accuracy test showed a systematic underestimation of age, increasing with age in both sexes. The 95 per cent confidence interval of the difference between estimated and true chronological age was large, about +/- 4.5 years in girls and +/- 2.8 years in boys. The association between dental age and chronological age, expressed in correlation coefficients, was poor. Precision test: The intra-examiner error was low but the 95 per cent confidence interval of the difference was large, +/- 0.8 years. The dental development of the third mandibular molar should not be used for estimation of chronological age in individual subjects, due to its very low accuracy.
