Third molar eruption among rural Nigerians.

Times of eruption of third molars were studied in rural Nigerian adolescents--125 males and 133 females. Results of this study showed that the average age for the initial eruption of third molars was 15 years in male subjects and 13 years for female subjects. The incidence of eruption showed a steep rise after the age of 16 years for male subjects and 14 years for female subjects. By the age of 19 years, all third molars had erupted into the oral cavity. The eruption of lower third molars was generally ahead of the upper third molars for all age groups. The results of this study suggest that (1) the timing of third molar eruption is strongly influenced by the availability of mandibular trigone space, (2) the attrition and shrinkage of the dental arch, probably as the result of nonrefined highly fibrous diets, produce larger mandibular trigone spaces, and (3) the early eruption of third molars observed in the present study may be due to the nature of the diet used and the vigorous employment of the masticatory apparatus (from infancy) by the subjects examined.