Influence of third molars in mandibular fractures. Part 1: mandibular angle-a meta-analysis.

The aim of this systematic review was to investigate the influence of the presence and position of mandibular third molars on angle fractures. An electronic search was conducted in the PubMed, Scopus, Web of Science, Cochrane Library, and VHL databases, through January 2016. The eligibility criteria included observational studies. The search strategy resulted in 704 articles. Following the selection process, 35 studies were included in the systematic review and 28 in the meta-analysis. Twenty studies presented a score of ≤6 stars in the Newcastle-Ottawa scale assessment, indicating a risk of bias in the analysis. The presence of a mandibular third molar increases the chance of an angle fracture (case-control and cross-sectional studies: odds ratio (OR) 3.83, 95% confidence interval (CI) 3.02-4.85, I2=83.1%; case-control studies: OR 3.27, 95% CI 2.57-4.16, I2=81.3%). The third molar positions most favourable to angle fracture according to the Pell and Gregory classification are class B (OR 1.44, 95% CI 1.06-1.96, I2=87.2%) and class II (OR 1.67, 95% CI 1.36-2.04, I2=72.4%). Class A (OR 0.60, 95% CI 0.45-0.81, I2=87.1%) and class I (OR 0.51, 95% CI 0.37-0.71, I2=89.4%) act as protective factors for angle fracture. The results suggest that the presence of the third molar increases the chance of angle fracture by 3.27 times and that the most favourable positions of the third molar for angle fracture are classes B and II, whilst classes A and I act as protective factors.