Age estimation is one of the most important procedures for human identification. Cameriere et al. proposed a method for age estimation based on the analysis of the pulp/tooth ratio by using dental x-rays, based on the apposition of secondary dentine. The objective of this study was to develop linear regression models for age estimation, by means of the pulp/tooth ratio of mandibular canines and premolars using orthopantomographies (OPGs) in a Chilean population of adults of known age and sex. We analyzed 162 digital OPGs (67 men and 95 women) through ImageJ software, in order to measure these areas. By means of regression analysis, the possible interactions between age, sex and pulp / tooth ratio were studied. This relationship decreased regularly with age and ranged from 0.03 to 0.6 for premolars and 0.04 to 0.6 for canines, respectively. The best model of age estimation was for the relation of the lower left canine, obtaining a coefficient of determination of R2=8.7 %. The mean absolute error, with a confidence interval of 95 %, ranged between 5.6 and 5.72 years. The ANCOVA analysis showed no significant differences between men and women for age estimation, as well as for both sides of the oral cavity. According to the results, the pulp/tooth ratio is a reliable methodology for estimating age in adults. However, the results showed that, in actual cases, it is necessary to use additional estimation methods since, at least in the sample analyzed, the adjustment indicated by coefficients of determination showed uncertainty in age estimation produced by the linear regression models.