Comparative Evaluation of Twin Block and Forsus Fatigue Resistant Device in the Management of Class II Malocclusion: A Systematic Review.

Class II malocclusion due to mandibular retrusion is commonly managed with functional appliances, yet the comparative effectiveness of removable and fixed modalities remains uncertain. This systematic review evaluated the skeletal, dentoalveolar, soft-tissue, and airway effects of the Twin Block (TB) appliance and the Forsus Fatigue Resistant Device (FFRD) in the correction of Class II malocclusion. Electronic searching and manual screening identified nine eligible comparative clinical studies for qualitative synthesis. The included studies comprised predominantly nonrandomized designs and together represented 377 participants, with 188 treated using FFRD and 189 using TB. Across the included evidence, both appliances were effective in correcting Class II malocclusion and improving overjet, overbite, and molar relationships. However, the pattern of correction differed between the appliances. TB consistently demonstrated a greater skeletal contribution, with more favorable mandibular advancement, increased mandibular length, and greater improvement in sagittal jaw relationship. In contrast, FFRD treatment relied more on dentoalveolar compensation, particularly proclination of the mandibular incisors. Soft-tissue outcomes, though limited, showed esthetic improvement with both appliances. Airway-related findings were reported in only a few studies and suggested a possible advantage of TB in improving pharyngeal dimensions, although results were not fully consistent across studies. Overall, the available evidence suggests that while both appliances are clinically effective, TB provides a stronger skeletal effect, whereas FFRD achieves correction predominantly through dental adaptation. Further well-designed prospective trials are required to strengthen the comparative evidence base.