The research was conducted on the 160 intact extracted human teeth with one and two roots of the known age and sex. The teeth were disinfected, dried and X-rayed. After that the section of the longitudinal cut through the teeth was performed in order to facilitate monitoring of all tissues and morphological characteristics of the teeth. The age was determined in three ways: Method 1 [G.Bang, E. Ramm, Determination of age in humans from root dentin transparency, Acta Odontol. Scand. 28 (1970) 3-35]--analysis of the translucency of the root dentine, Method 2 [S. Kvaal, T. Solheim, A non-destructive dental method for age estimation, J. Forensic Odonto-stomatol. 12 (1994) 6-11]--analysis of the root and the root canal from the X-ray, Method 3 [G. Johanson, Age determination from human teeth, Odontol. Revy. 22 (1971) 1-126]--analysis of six parameters on each teeth. All data were subject to the correlation and regression analysis which showed the following: all of the three applied methods were in the significant correlation with the real age, and the best of them proved to be Method 3 where the coefficient of correlation was 0.85, p<0.001. The teeth of the maxilla are more convenient for the age determination than the teeth of mandible. They are in the significant strong correlation with the known real age, and in Method 3, the coefficient of correlation is 0.78, p<0.001. Age determination of the teeth with two roots is in significant correlation with the known real age p<0.001 in relation to the determined age on the teeth with one root. The results show that sex too, is in significant correlation with the real age, p<0.001. In practice, the methods used and the results achieved in this research have been enabling the dental age estimation of human remains from mass graves after the 1991 war in Croatia.