Extraction vs nonextraction orthodontic treatment: A systematic review and meta-analysis

Objectives: To compare four first premolar extraction and non-extraction treatment effects on intraarch width, profile, treatment duration, occlusal outcomes, smile aesthetics and stability.

Materials and Methods: Electronic search of literature to June 2nd, 2023 was conducted, using health science databases with additional search of grey literature, unpublished material and hand searching, for studies reporting non-surgical patients with fixed appliances regarding sixteen sub outcomes. Data extraction utilized customized forms, quality assessed with ROBINS-I and Cochrane RoB 2. GRADE assessed certainty of evidence.

Results: Thirty (29 RS, 1 RCT) studies were included. Random effect meta-analysis (95%CI) demonstrated maxillary (MD -2.03mm;[-2.97, -1.09];P<0.0001) and mandibular inter-first molar width decrease (MD -2.00mm;[-2.71, -1.30];P<0.00001) with four first premolar extraction. Mandibular intercanine width increase (MD 0.68mm;[0.36, 0.99];P<0.0001) and shorter treatment duration (MD 0.36years;[0.10, 0.62];P=0.007) in non-extraction group. Narrative synthesis included three and five studies for upper and lower lips-E plane, respectively. For ABO-OGS and maxillary/mandibular anterior alignment (Little’s Irregularity Index) each included two studies with inconclusive evidence. No eligible studies for UK PAR score. Class I subgroup/sensitivity analyses favoured same results. Prediction interval indicated no significant difference for all outcomes.

Conclusions: Four first premolar extraction results in maxillary and mandibular inter-first molar width decrease and retraction of upper/lower lips. Non-extraction treatment results in mandibular intercanine width increase and shorter treatment duration. No significant difference between the two groups regarding maxillary intercanine width, US PAR score and posttreatment smile aesthetics. Further high-quality focused research recommended.