Dentoalveolar changes following extraction of mandibular primary second molars in patients with congenitally missing second premolars-a longitudinal randomized controlled trial.

BACKGROUND: Early management of congenitally missing mandibular second premolars may influence craniofacial growth, yet the long-term effects of extracting the primary second molars remain unclear. OBJECTIVES: To evaluate the skeletal and dental effects of extracting mandibular primary second molars in patients with congenitally missing mandibular second premolars and to compare with historical control data. TRIAL DESIGN: Prospective, randomized longitudinal split-mouth trial. MATERIALS AND METHODS: This longitudinal study is based on 40 patients (aged 9-12 years) with bilateral agenesis of mandibular second premolars, who were randomly assigned to either extraction or hemisection of the primary second molar. Randomization to determine the side and order of extraction or hemisection was performed using an online tool, with allocation concealment ensured by sequentially numbered, opaque, sealed envelopes prepared in advance by the author responsible for treatment assignment, who was not involved in patient care. The present study examines the overall treatment effect, regardless of the method applied in the split-mouth design. Cephalometric analyses were performed at baseline (T1) and after 4 years (T2). Dental casts were evaluated at T2 to measure residual space. A control group of 29 untreated individuals with normal occlusion was included for comparison. All measurements were conducted by an independent examiner blinded to the treatment assignment. RESULTS: In the extraction group both the maxilla and the mandible exhibited forward growth (P < .05), while only minor changes were detected in the control group. Extraction caused significant retroclination of the lower incisors by 4.5° (P < .01) and retrusion by 1.8 mm (P < .01), leading to an increased overjet of 1.2 mm (P < .05) and overbite of 1.5 mm (P < .05). Compared with controls, dental changes were significantly greater in the extraction group (P < .05). Residual space after extraction showed no significant correlation with cephalometric changes. CONCLUSION: Extraction of mandibular primary second molars in cases of agenesis induces favourable dental changes without detrimental skeletal effects. This approach may be a viable option in selected patients, although caution is recommended for those with deep bite tendencies. TRIAL REGISTRATION: The trial was registered with https://www.researchweb.org/, registration number: 967125.