Cephalometric Evaluation of the Effects of Twin Block Appliance in Class II Division 1 Malocclusion

Objectives: 1. To assess the mean change in skeletal, dento-alveolar and soft tissues of Class II division 1 malocclusion patients on lateral cephalogram from baseline (T0) to 1 year (T1) following twin block appliance (TBA) therapy
2. To compare the effects of TBA on skeletal, dental, soft tissues in patients with different cervical vertebrae maturation stages (CS2, CS3, CS4)
Methods: After taking an informed consent, pre and post- treatment lateral cephalogram of 53 patients of aged 9-16 years were obtained. They presented with Class II division 1 malocclusion and required treatment with TBA. The appliance wear was monitored and those who did not wear it for >12 hours/day were excluded. Several lines and angles were drawn on lateral cephalogram to evaluate the skeletal, dental and soft tissue variables. Overjet was measured on the dental casts and skeletal maturity stage was assessed by Baccetti method. The pre and post-treatment variables were compared by Paired t-test. One-way ANOVA was used to compare the difference in cephalometric variables between the three cervical verterbral maturation groups (p=≤ 0.05).
Results: There was significant improvement in skeletal relationship of underlying jaws (ANB=p<0.001), increase in the vertical jaw relationship (GoGn-SN=p<0.013), increase in mandibular unit length and body (Co-Gn, Go-Gn=p<0.001). There was significant reduction in upper incisor inclination whereas lower incisor incisors inclination increased (p<0.001). There was significant retraction of upper lip (p<0.01), increase in nasolabial (p<0.02) and Z-angle and decrease in H-angle (p<0.001). The pre and post treatment changes were significantly different for variables SNB, ANB, Co-Gn, Overjet, UI-SN between the three cervical vertebral maturation groups(p<0.05).
Conclusions: Twin block appliance results in improvement in skeletal relationship of the underlying jaws, overall increase in mandibular unit length and mandibular body, decrease the inclination of upper incisors, increase the inclination of lower incisors and improve overall facial profile. More skeletal effects were observed when appliance is given in CS-3 and CS-4 stage as compared to CS-2