The eruption pattern of third molar amongst 1071 rural Nigerians (523 males and 548 females) aged 11-21 years was assessed. The earliest age at which the third molar erupted for males and females was 14 and 13 years respectively with females significantly ahead of males (P<O.Ol). A full compliment of erupted third molars was recorded at age 14 years in 1.1 per cent of the population. However, the mean age for the eruption of 1, 2, or 3 and all third molars were 16.58 and 17.50 years respectively. Whilst third molar-eruption was significantly earlier in the mandible, no right-left side differences were found. Problems often associated with the erupting third molars are likely to be seen earlier in young rural Nigerians than in the western countries.
The third molar has been the most widely discussed tooth in the literature. Apart from being the last tooth to erupt into the oral cavity, it exhibits the greatest variation in the human dentition. Developmental absence occurs in 13-15 per cent of individuals, making these teeth the most frequently missing of the permanent series'-3. The incidence of impaction of the lower third molar ranges from 9 to 24 per cent74i. It has also been questioned recently, whether the erupting third molar has any role in the late adolescent crowding of incisors in the mandibular arch'
Against this background, it is important to accurately determine the times of eruption of third molars in order to assist in oral health planning, diagnosis, prevention and providing therapeutic measures' 9-1'. A number of studies have attempted to determine the eruption times of third molars in various Rantanen" reported that lower third molars erupt at age 19 years in Finnish males whilst the upper third molars emerge 1 year later. In females however, both upper and lower third molars erupted at age 20 years. Furthermore, radiographic assessment of Finnish conscripts showed that 58 per cent with mean age of 20.3 years had unerupted third molarsIh. Similarly, H u n P reported a median of 20.5 years for the emergence of maxillary third molars in a group of high school pupils in Boston, USA. However, the universally accepted eruption times of third molar into the oral cavity varies from 17 to 21 years"'.