The aim of this study was to review the medical charts of patients asking for extraction of impacted mandibular third molars at the clinic of the Faculty of Dentistry (Finis Terrae University, Chile) in the period January 2009–May 2010.

117 panoramic X-ray (218 impacted mandibular third molars) were classified according to age (15–20 years and 20–25 years) and gender.

The impacted mandibular third molars 4.8 and 3.8 were distributed according to the Pell and Gregory classification; the latter allows grouping the relationship of impacted tooth to anterior border of the ramus (Class 1, 2, 3) and the relationship of impacted tooth to oclusal plane and second molar (A, B, C position)

Using statistical software Systat v 13, χ ² for data collection, we found that the presence of impacted mandibular third molars was 49% in male and 58% in female patients; the mean age was 18 years (15.3%). Classifying the teeth according to PR analysis, we found 4.8 (right mandibular third molar) IIC position 22.2% p < 0.05 ( p = 0.000) and 3.8 (left mandibular third molar) position IIC 24.5% p < 0.05 ( p = 0.000).

The PR analysis allowed us to conclude that the IIC vertical is the most prevalent position associated with impacted mandibular third molars; moreover, for the quirurgical extraction osteotomy and odontosection is required. A larger sample is needed for further studies.

Conflict of interest: None declared.