Objective: To compare the effects of two treatment modalities for correction of Class II malocclusion in late growing patients: one-phase fixed orthodontic treatment using Class II intermaxillary elastics versus two-phase treatment with Twin-block appliance (TB) followed by fixed appliance.
Material and Methods: The pretreatment and posttreatment lateral cephalograms of 20 females with skeletal Class II due to mandibular deficiency, treated with either one-phase of fixed appliance using Class II intermaxillary elastics (10 patients, mean age 12.55+0.88), or two-phase of TB appliance followed by second phase of fixed appliance (10 patients, mean age 11.57+1.03) were retrieved from the archive of the Orthodontic Department. Cephalometric analysis was carried, and the results were statistically analyzed and compared.
Results: The two-phase treatment group showed significant mandibular growth represented by significant increase in the SNB angle (1.91+0.72) and the mandibular length (Co-Gn=3.66+2.04). There was significant reduction in the ANB angle (-1.91+0.49) and minor decrease in the SNA angle (-0.44+0.26). No statistically significant skeletal changes were observed in the one-phase treatment group. The mandibular incisors were more proclined and only significantly intruded in the one-phase treatment group. Both the upper and lower lips moved forward which was more statistically significant in the two-phase treatment group. The angle of convexity was only statistically improved in the two-phase treatment group.
Conclusion: Satisfactory treatment outcomes were achieved by the two treatment modalities. However, the two-phase treatment was able to produce significant skeletal changes represented by increased mandibular growth, with less mandibular incisors proclination, together with better soft tissue profile.