Extraction of premolars in orthodontic treatment does not negatively affect upper airway volume and minimum cross-sectional area: a systematic review with meta-analysis

Background Extraction of premolars is usually prescribed for the orthodontic treatment of cases with inadequate space within the dental arch or when anterior teeth retraction is indicated; however, it has been advocated that this treatment approach could negatively influence the airways. Objective To identify and critically appraise studies of premolar extractions during orthodontic treatment on upper airway dimensions. Search methods: Electronic unrestricted searches in nine databases until October 2024. Selection criteria: Clinical studies on humans comparing comprehensive orthodontic treatment with versus without the extraction of premolars using cone-beam computed tomography to assess upper airway volume or minimum cross-sectional area (minCSA). Data collection and analysis: After duplicate study selection, data extraction, and risk-of-bias assessment according to Cochrane, random-effects meta-analyses of Mean Differences (MD) with their 95% confidence intervals (CI) were performed, followed by subgroup/meta-regression analyses and assessment of the quality of evidence. Results Twelve papers corresponding to 11 unique retrospective non-randomized studies were included, covering 891 patients (35.8% male; 20.0 years-old on average). No statistically significant differences in the effect of orthodontic treatment on the volume of the nasopharynx, palatopharynx, glossopharynx, oropharynx or oral cavity were seen between patients treated with versus without premolar extractions (P > .05). Similarly, no significant differences were seen between extraction and non-extraction patients in terms of minCSA of the nasopharynx, palatopharynx, or glossopharynx (P > .05). On the contrary, patients treated with premolar extractions showed increased minCSA of the oropharynx compared to those treated without premolar extractions (4 studies; MD = 23.00 mm2; 95% CI = 10.74–35.26 mm2; P = .009). No significant effects from patient age, sex, or equivalence of the extraction/non-extraction groups were found, while the strength of evidence was moderate in all cases due to the inclusion of non-randomized studies with high risk of bias. Conclusions Limited evidence of moderate strength indicates that, on average, premolar extractions during comprehensive orthodontic treatment have little to no effect on the volume and minCSA of the airways. Registration CRD42024621355