Impaction status of third molars in Jordanian students.

The status of third molars was studied radiographically in 108 male and 124 female Jordanian students (mean age, 20.4 years). The results showed that 9.1% of third molars were congenitally missing. Approximately 73% of the subjects had all four third molars, 12% had three third molars and 11% had two third molars. Only 1.7% had agenesis of all third molars. Third molar agenesis showed predilection for the maxilla over the mandible. There was no significant sexual dimorphism in the agenesis of third molars. Impaction of third molars was found in one third of the subjects with predilection (5.2%) to the maxilla. The proportion of impaction in males was 17.4% and in females 16.2%. Angular position of mandibular third molars revealed that half of the teeth were mesially tilted (average angle 20 degrees +/- 13 [SD] and 41% were in vertical position. A highly significant correlation (r = 0.79, p < 0.001) in the inclination angles was observed between the right and left side of the mandible. The level of eruption of third molars showed 58% of the teeth were fully erupted to occlusal plane, whereas 26% were embedded below the cervical line of adjacent second molar (level C). Males showed a significantly higher frequency (p < 0.001) of level C eruption than females. Results indicated that 11.6% of the subjects or 8.4% of the third molars had incomplete root formation, of which two thirds to one thirds root completion was at a ratio of 4.3:1. The clinical significance of these results is discussed.