Prevalence of impacted third molars in dental students.

To study the prevalence of third molar impaction in dental students, the radiographs of 113 female and 144 male students in the age groups 20-39 years were investigated. Half of the individuals had all four third molars, whereas 10% of the individuals lacked all third molars. A radiologic definition of impaction, which is illustrated, is suggested. One or more impacted third molars were found in 33% of the individuals. The difference between the sexes regarding impacted third molars was not significant. Calculated by number of teeth, one fourth of all third molars were impacted and were then mostly in a vertical or mesioangular position. The frequency of impacted third molars was higher in the lower jaw compared to the upper jaw.