Effects of Two-Phase Treatment with Functional Appliances Followed by Extraction versus One-Phase Treatment with Extraction in Class II Growing Patients: A Case–Control Study

Objectives: Fixed appliance treatment with premolar extraction is often required after functional appliance treatment to relieve crowding and improve facial aesthetics in the Asian population. This study compared the treatment efficacy of two approaches for treating Class II division 1 malocclusion: functional appliance followed by fixed appliance treatment with extraction (two-phase) and fixed appliance treatment with extraction (one-phase). Methods: Growing skeletal Class II patients with an overjet of ≥6 mm treated with two- or one-phase orthodontics were included. The two groups consisted of 29 patients (mean age = 12.55) and 30 patients (mean age = 12.72), respectively. Pre- and post-treatment cephalograms were analysed and skeletal, dental, and soft tissue characteristics were compared using independent t-tests. Treatment changes were compared within and between groups using paired and independent t-tests, respectively. Stepwise discriminant analysis was performed to identify the variables that best predicted pre-treatment group allocations. Results: At baseline, there were no significant between-group differences in age, gender, cervical vertebral maturation, or overjet. The two-phase group had greater Class II skeletal discrepancies (ANB angle and Wits appraisal). During treatment, the two-phase group showed greater improvements in intermaxillary relationship and facial convexity compared with the one-phase group (p < 0.01). Following treatment, the two-phase group had a greater L1/APog distance (p < 0.05). Facial convexity and Wits appraisal were identified as parameters significantly influencing the clinicians’ decision to use a one- or two-phase approach. Conclusions: In patients requiring premolar extraction, two-phase (vs. one-phase) treatment produced greater improvements in the intermaxillary relationship and facial convexity.