Objectives Radiographic evaluation of the third molar maturation is used to estimate dental age, especially in adolescence. This study aimed to assess the application of three age estimation methods (Cameriere's third molar maturity index (I-3M), Demirjian's maturation stages, and The London Atlas) to determine whether an individual is 18 years or older (adult) or younger than 18 years (minor). Materials and methods The dental age was estimated using the I-3M, Demirjian's maturation stages, and The London Atlas methods on panoramic radiograms of a total of 500 Turkish individuals aged 14-22 years. A logistic model was derived with an individual's adult or minor status as the dependent variable, and each method and sex as predictive variables. The adult status was determined using dental age estimation methods and the performance of these methods in differentiating adults from minors was evaluated. The three methods were compared case-wise for their accuracy in predicting adult status. Results Logistic regression analysis showed that sex and each estimation method were statistically significant in discriminating adults and minors (p < 0.05). In the case-wise comparison for estimate adulthood, both Demirjian's stages and I-3M methods tended to perform better than the London Atlas method, with this trend reaching statistical significance (p < 0.05). Conclusions Cameriere's I-3M and Demirjian's development stages are useful methods for adult age assessment in the tested population.