Forensic age determination has become increasingly important over the past few years. Dental age estimation is frequently used as a part of this process due to the technique simplicity and reliability. This process is done taking into account pre-established values that, often, concern the population of the undocumented person. In this manner, population parameters are needed. In this paper, the authors present data concerning the third molar eruption in a Portuguese population: The minimum age for alveolar emergence of third molars ranged from 6.6 to 11.3 in females and 7.4 to 8.3 in males, for gingival emergence was 11.1 to 15.1 for females and 8.3 to 14.4 in males and for complete emergence was 15.9 to 19.4 in females and 13.4 for males. Complete emergence was found to be a useful marker for diagnosing age inferior 16 years, both in males and females, with 99.2% and 99.3% of correct predictions, respectively. These findings point out that it is possible to estimate the age of investigated persons based on alveolar, gingival and complete emergence of the third molars in the occlusal plane.