1 Associate professor, Director of Orthodontic surgery fellowship, Shahid Beheshti University, Tehran, Iran

2 Associate professor, Orthodontic department, Islamic Azad University, Tehran, Iran

3 Professor, Heal of Orthodontic department, Shahid Beheshti University, Tehran, Iran



Aim: The main goal of this study was to compare the effects of a differently designed functional appliance (R-appliance) with a bionator treated group in Class II Division I (C1 II Div I) cases.
Materials and Methods: 22 patients (12 girls, 10 boys) treated with R-Appliance were selected as experimental group. Control group consisted of 22 patients (11 boys, 11 girls) treated with a bionator. All of the patients had a C1 II Div I malocclusion due to mandibular deficiency. Lateral cephalograms were analyzed at the beginning (T1, T 1) and the end of the study (T 2, T 2).
Results: Paired T-test showed that SNB significantly increased in both groups. The same test revealed that IMPA was reduced in the R-appliances treated group by 4.5°±3.5° (P<0.001) but it was increased by 1.9°±3.9° (P<0.03) in the bionator group. Analysis utilizing T-test showed that the inter group difference of IMPA was statistically significant (P<0.01). SNA showed an increase of 0.1°±1.6° (P<0.9) in the R-appliance treated group; while, it was decreased for 0.4°±0.9° (P<0.1) in the bionator treated group.
Conclusions: Both groups were successful in advancement of mandible; however, the R-appliance achieved this result without retroclination of the lower incisors.