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Introduction: The main reason for seeking orthodontic treatment for Class II malocclusions is aesthetic improvement. Growth modification treatment procedures offer better results for a patient with significant potential growth. Aim: The aim of this cephalometric clinical study was to distinguish skeletal and dental corrections on skeletal class II division I growing subjects with Twin Block therapy (TB) and the changes were assessed using SO-analysis by Pancherz. Materials and Methods: Strict diagnostic protocol viz. growing individuals with horizontal growth pattern, skeletal class II due to retrognathic mandible with positive VTO, bilateral class II molar relation, minimal crowding in either arch or overjet more than 5mm was used. Out of 28 selected cases,17 patients received TB therapy and 11 patients were maintained as control group. Standard removable TB appliances with lower incisor capping were delivered to treatment group. The horizontal advancement was about 8mm and 2-3mm vertical opening between the upper and lower central incisors were maintained for all the cases. The mean time interval between the initial (T1)and post treatment (T2) cephalograms of Twin-Block group was 11 month,with a range of 8 month to 13 month. In the control group, the mean time interval between the first (C1)and second (C2) cephalometric films was 12 month,with a range of 10 month to 14 month. T1and T2 cephalograms were traced and S-O analysis was used to segregate dental and skeletal effects. Statistical Analysis: SPSS software was used for statistical analysis. Results: Skeletal Changes: In this study, the mean movement of maxilla was 0.67mm which represents significant restriction of forward maxillary growth in contrast to control groups. Dental Changes: In this study the maxillary molars appear to move distally with a mean value of 0.13mm. Comparing this to the movement of maxillary jaw base itself, maxillary distal movement of molar is less. But still it contributes to Class II correction. Conclusion: The overjet reduction and molar relation correction are more skeletal in nature.