Evaluation of panoramic images in the assessment of mandibular second molar impaction

To examine the relationship of various mandibular skeletal features determined from assessment of a panoramic image to the impaction of mandibular second molars in children with late mixed to early permanent dentition.

Thirty-six panoramic radiographs were collected from two private orthodontic offices of consecutively screened patients in the late mixed to early permanent dentition. Gonial angle, space ratio, ramus ratio and occlusal plane to posterior ramus ratio were analyzed for any significant relationship with mandibular second molar impaction. Measurements were made on each of the orthopantomograms and compared between the impaction and non-impaction groups.

The overall sample consisted of 36 patients between the ages of 11 to 14 years with a mean age of 12.5 years and included 21 females and 15 males. Eighteen were identified as having impactions and were designated to the IMP group, while eighteen without impactions were designated to the NON group. There was a significant difference in the tooth size to space available ratio between groups with the second molar accounting for 126% of the space available in the IMP group and about 80% of the space available in the NON group (P<0.001). Additionally, a significant difference was found in occlusal plane to posterior ramus angle between the two groups, with the IMP group averaging 73.93º, and the NON group averaging 66.39º (P=0.002).

The mandibular second molars of patients presenting with impactions occupy more of the available space and exhibit a greater occlusal plane to posterior ramus angle. Key words:Impaction, gonial angle, second molar.