Background and Aim: Functional appliances refer to a variety of removable or fixed appliances designed to alter the mandibular position both sagitally and vertically, resulting in orthodontic and orthopedic changes. Despite the long history of functional appliances, there is still much controversy related to their effectiveness and mode of action. The aim of this study was to evaluate dental and skeletal effects of Fa II in patients with class II malocclusion due to mandibular deficiency.

Materials and Methods: In this before-after clinical trial, 35 patients with class II div I malocclusion were selected. These samples were under treatment with Fa II appliance for 11 months. The range of age of females was 10-13 years and males 11-14 years. Combination analysis was used to determine skeletal and dental effects. Paired t-test was used to compare the differences of mean value pre and post treatment. P<0.05 was considered as the level of significance.

Results: There was significant difference between pre and post treatment in respect to posterior and anterior facial height, eruption of upper and lower posterior teeth, eruption of upper anterior teeth, mandibular body length, ANB angle, IMPA and 1 to SN. No significant difference was observed between pre and post treatment regarding facial growth.

Conclusion: Treatment with Fa II functional appliance leads to significant alterations in dental and skeletal elements of craniofacial complex and improvement of dental and jaws relationship.