The effect of Winter’s red line, angle of impaction, and radio-morphometric indices on surgical difficulty of impacted mandibular third molar: a prospective observational study

Introduction
The most common oral and maxillofacial surgical procedure is the surgical extraction of impacted third molar in the mandible. Predicting third molar difficulty depends on various clinical, anatomical, and radiographic variables. OBJECTIVES: The purpose of this study was to correlate the Winter’s red line, angle of impaction, and bone density (gonial and antegonial indices) with surgical difficulty.

Material and methods
This prospective observational study included 55 patients, who had undergone surgery for removing impacted lower third molars under local anesthetic. Independent (predictor) variables were pre-operative measurement of Winter’s red line in millimeters, angle of impaction in degrees, and bone density evaluated with two radio-morphic indices, i.e., gonial and antegonial, both measured in millimeters. Dependent (outcome) variables included surgical difficulty determined by surgical technique and operation time.

Results
Regarding the red line and angle of impaction, there was a strong positive correlation between them with duration of surgery. With respect to density indices, there was a weak correlation between gonial and ante­gonial indices with duration of surgery. All variables were associated with an increased difficulty determined by surgical technique.

Conclusions
The Winter’s red line and angle of impaction have a strong influence on determining the difficulty of impacted mandibular third molar’s surgery, while the gonial and antegonial indices are not clinically relevant to determine the surgical difficulty.