The impact of extraction vs. non-extraction orthodontic treatment on the angulation of third molars on panoramic radiographs: a systematic review and meta-analysis

Background The angulation of third molars is a critical factor influencing the likelihood of impaction. Orthodontic premolar extractions have been hypothesized to affect the eruption path of developing third molars by modifying available space and mesial drift patterns. Objective This systematic review and meta-analysis aimed to assess whether premolar extraction during orthodontic treatment alters the angulation of developing third molars compared to non-extraction protocols. Eligibility criteria Observational studies comparing angular measurements of third molars between extraction and non-extraction orthodontic treatments were included. Studies without a control group or adequate cephalometric data were excluded. Information sources A comprehensive literature search was conducted across two electronic databases (MEDLINE, Scopus) up to November 2024, following PRISMA 2020 guidelines. Risk of bias and synthesis of results Risk of bias was evaluated independently by two reviewers using the ROBINS-I tool. A random-effects meta-analysis was conducted, and the certainty of the evidence was assessed using the GRADE approach. Results Nine studies (865 participants) were included. For mandibular third molars, extraction was significantly associated with improved angulation (SMD = − 0.37; 95% CI: − 0.59 to − 0.15; p = 0.004). Significant differences were found in M3L/M2L (MD = − 1.31; 95% CI: − 1.76 to − 0.85; p = 0.003) and M3L/PP (MD = − 4.85; 95% CI: − 8.50 to − 1.21; p = 0.02). No statistically significant difference was observed in the M3L/MP angle. In the maxilla, only the M3U–PP angle showed a significant change (MD = − 5.79; 95% CI: − 11.53 to − 0.04; p = 0.049). Meta-regression revealed no association with age, sex, or premolar type. Certainty of evidence ranged from low to moderate.