correlation between third molar size axial angulation, developmental stage and its relative position with possibility of mandibular second molar impaction in prospective possible impaction for lower second molars

ABSTRACT

Simultaneous formation of third molar crown with second molar eruption may possibly cause to second molar impaction due to third molar bud intervention. A tooth impaction leads to numerous clinical problems for the patient and the present study assessed the effect of third molar size, axis angulation, developmental stage and its bud position with possibility of mandibular second molar impaction in patients with doubtful impaction of lower second molars. In this descriptive-analytical study, 5420 records of 10-12 years old patients underwent orthodontic treatments in Tehran and Shahid Beheshti Dental Schools and private clinics were assessed and 38 patients [26 females and 12 males] were selected with possible impaction of lower second molars forming case group. 38 control patients with no prospective possibility for impaction of second molars were selected from the same centers and matched with the cases. The third molar axis angulation towards second molar, first molar and mandible base, mesiodistal width of wisdom teeth relative to second molar, Nolla developmental stage and third molar bud position regarding second molars were calculated and analyzed by student t, chi-square and mann-whitney U tests in both groups. The mean value of third molar angulation towards second molar, first molar and mandibular base were 24.16, 49.26 and 54.42 degrees in case group and 14.42, 39.39 and 45.0 degrees in control group respectively with significant differences [P<0.001 in three variables]. The mean mesiodistal width of third molar relative to second molar was 0.9903 in case Group and 0.9695 in control Group with no significant differences. Nolla developmental stage and marginal ridge of third molar bud towards second molar showed no definite effect on second molar impaction. The results suggest third molar angulation towards second molar, first molar and mandibular jaw base to be significantly higher in patients with possible mandibular second molar impaction than those without prospective possibility for second molar impaction. Although, no significant differences in mesiodistal width of third molar relative to second molars, developmental stage and marginal ridge of third molar bud regarding second molar were observed between the two groups