Résumé
A cross sectional sample composed of one hundred panoramic radiographs for 100 healthy Egyptian subjects of both sexes with mean age of 19 +/- 2.3 years, aiming to assess the root-crown ratios of mature permanent teeth and calculating the normal mean values of these ratios and their variations by arch, sex and ethnic group. Two thousand and eight hundred teeth were measured on panoramic radiographs films, the mean root-crown ratios didn't differed significantly between the repeated measurements [p>0.05]. Results of this study showed that there are no significant differences between root-crown ratios of right and left teeth for both males and females groups, there are a high coefficient of correlations of the root-crown ratio for the teeth in the same arch. Finally, the root-crown ratios of upper posterior teeth for males were significantly higher than females. The root-crown ratio could be used as a reference to help in orthodontic diagnosis, treatment planning and prognosis