DENTOALVEOLAR AND SKELETAL EFFECTS FOLLOWING TREATMENT OF SKELETAL CLASS II MALOCCLUSION WITH TWIN BLOCK APPLIANCE IN HYPERDIVERGENT AND NORMOVERGENT PATIENTS

Abstract

Background: Skeletal Class II malocclusion, often due to mandibular retrusion, is a prevalent orthodontic condition in growing children. Functional appliances such as the Twin Block are widely used for orthopedic correction, yet treatment response varies based on vertical growth patterns. Evaluating the skeletal and dentoalveolar effects of Twin Block therapy in different facial divergence types is essential for individualized treatment planning and optimizing clinical outcomes.

Objective: To evaluate and compare the dentoalveolar and skeletal effects of Twin Block therapy in normodivergent and hyperdivergent patients diagnosed with skeletal Class II malocclusion.

Methods: A quasi-experimental study was conducted at Margalla Institute of Health Sciences, Rawalpindi, over one year. Seventy-three patients aged 10–14 years with CVMI stages 3 or 4, SNB <78°, and permanent dentition up to first molars were selected through consecutive non-probability sampling. Pre- and post-treatment lateral cephalograms were evaluated for sagittal skeletal (SNA, SNB, ANB, Go-Gn), vertical skeletal (MMA, PFH/AFH), and dentoalveolar (U1-SN, L1-MP, U1-L1) parameters. Data were analyzed using SPSS v26, applying paired and independent sample t-tests with significance set at p ≤ 0.05.

Results: Significant post-treatment improvements were found in SNB (0.9° ± 0.4, p=0.01), ANB (−1.3° ± 0.6, p=0.001), and Go-Gn (1.6 mm ± 0.8, p=0.02). Mandibular plane angle decreased by 0.8° ± 0.6 (p=0.03). Normodivergent patients exhibited superior sagittal improvements in ΔSNB (1.1° ± 0.4) and ΔANB (−1.5° ± 0.5) compared to hyperdivergent patients (p<0.05). Significant dentoalveolar changes included increased L1-MP (2.7° ± 1.3, p=0.001) and decreased U1-L1 (−2.3° ± 1.8, p=0.01), while vertical alveolar height changes were not statistically significant.

Conclusion: Twin Block therapy effectively corrects skeletal Class II malocclusion in growing patients, especially those with normodivergent profiles. However, associated dentoalveolar compensations necessitate careful treatment planning.