Comparison of the effect of twin-block and essix-based modified FMA appliances on dentofacial structures

The aim of this study was to comparatively evaluate the effects of Twin-Block (TB) and Essix-based modified Functional Mandibuler Advancer (EBM-FMA) appliances on the dentofacial structures. Forty-four patients with Class II, division 1malocclusion due to a retrognathic mandible, normal or low-angle growth pattern and peak growth period were divided into three groups. Twenty-nine patients were randomly allocated to one of the two functional appliance treatment groups. Of these, 15 were treated with TB (8 girls, 7 boys; mean age=12.26±0.84) and the remaining 14 were treated with EBM-FMA ( 9 girls, 5 boys; mean age=11.98±0.87). The untreated control group included 5 girls and 10 boys with a mean age of 12.24 ± 0.83years. Both appliances were worn 24 hours/day except eating throughout 12 months. The observation period of the control group was 12 months. Pre-treatment (T0) and post-treatment (T1) cephalograms were used to evaluate skeletal, dental/dentoalveolar and soft tissue changes. Intra-group comparisons were determined with paired samples t-test while inter-group comparisons were determined with one-way ANOVA at p<0.05 level. It was confirmed that both appliances increased sagital growth of the mandible, helped increase the effective mandibular length (TB=0.22 mm per month, EBM-FMA=0.21 mm per month) and had a restricting growth effect on the maxilla compared with control group. The increase in vertical skeletal measurements and proclination of the lower incisors in the EBM-FMA group was less when compared with the TB group. The effects of TB and EBM-FMA appliances on the soft tissue measurements were similar; greater advancement of mandibular soft tissues were observed in both groups. This modified FMA appliance (EBM-FMA) is as effective as TB appliance whether the dentoalveolar effects with the EBM-FMA appliance were more smaller than TB appliance. EBM-FMA appliance can be a possible alternative for patient with increased face height, proclined lower incisors and a Class II division 1 malocclusion due to mandibular deficiency.