Does Appliance Design Affect Treatment Outcomes of Class II Division 1 Malocclusion? A Two-Center Retrospective Study.

Objectives: The purpose of this retrospective study was to compare the pre- and post-treatment values of patients treated with monoblock and twin-block appliances with the values of the skeletal Class I individuals.

Material and methods: The initial lateral cephalometric radiographs of the pubertal untreated skeletal class I patients and cephalometric radiographs of 60 (30 monoblock, 30 twin-block) patients before and after the functional treatment were included in the study. Skeletal, dental, and soft tissue measurements were performed by a single researcher using Dolphin Imaging software version 11.95 (Dolphin Imaging, Chatsworth, CA, USA). Paired t-test was used for statistical evaluation and P < 0.05 was considered statistically significant.

Results: In both monoblock and twin-block groups, there was a statistically significant increase in the measurements of the lower jaw and the vertical direction values (sella nasion B point (SNB), pogonion nasion perpendicular, Y-axis, sella nasion-gonion gnathion, palatal-mandibular angle, anterior facial height, mandibular length P < 0.05); however, in the Twin-block group, the lower jaw was found to be displaced more forward (change for twin-block; SNB = 2.35, Wits appraisal = -4.77). The most measurements of the twin-block treated group were similar to the control group.

Conclusions: Both functional appliances have been identified to be useful in achieving treatment targets; however, with twin-block, results closer to ideal values are obtained.