"Evaluation of Treatment Effects of Two Different Fixed Functional Appliances in Patients With Class II Div 1 Malocclusion Using CBCT- A Randomized Controlled Clinical Study"

Class II malocclusion is one of the most frequent problems in orthodontics ,as it affects one third of patients seeking orthodontic treatment. McNamara reported mandibular retrusion as the most common characteristic of Class II malocclusion rather than maxillary prognathism. Functional orthopaedic appliances are widely used to treat Class II malocclusion in growing patients .Contrary to removable appliances, fixed devices do not require patient collaboration and can be worn in association with multibracket therepy, so that class II malocclusion can be corrected in a single phase treatment.

.Most popular flexible devices are the Jasper Jumper, Eureka spring, and the Forsus device (FRD)Forsus Fatigue Resistant Device [FRD]is a three piece (L pin module) or two-piece (EZ2 module) system, composed of a telescoping spring that attaches at upper first molar and a push rod linked to lower archwire, distal to either the canine or first premolar bracket. The FRD spring and rod create an equal and opposite force to maxillary and mandibular dentition.1The clinical application of the FRD was described by Vogt in 2006.PowerScope is one of the latest innovation in Class II correction developed by Dr. Andy Hayes. Inventors claims the following advantages of powerscope over other functional appliances. It is delivered as a one-size-fits-all appliance pre-assembled with attachment nuts for quick and easy chairside application .

The appliance is a wire-to-wire installation with attachments placed mesial to the first molar in the maxillary arch and distal to the canine of the mandibular arch. Internal NiTi spring mechanism delivers 260 gms of force for continous activation during treatment.

The dental, skeletal and soft tissue short-term effects of comprehensive fixed appliance treatment combined with ForsusTM in ClassII patients have been evaluated previously. However no previous study compared the posttreatment effects of PowerScope2TM and ForsusTM.The purpose of this controlled clinical study is to evaluate the treatment and posttreatment effects induced by PowerScope2 in growing patients with ClassII malocclusion and to compare it with Forsus(FRD) on CBCT.

The majority of the studies examined the changes of the upper airway through lateral cephalometric radiography. This method limited the accuracy of airway measurement since the two-dimensional (2D) images only allowed an anteroposterior dimension measurement in sagittal plane, and failed to provide a full-scaled view of the upper airway. Therefore, 3D evaluation of the upper airway in growing patients during fixed functional appliance treatment needs to be established .Cone beam computed tomography (CBCT) is an acceptable technique for 3D volumetric depiction and morphological evaluation of the upper airway using a lower-radiation method with a greater spatial resolution . It allows 3D registration of pre- and post-treatment data through identification of specific structures in the cranial base. Therefore, the changes of the upper airway before and after mandibular advancement can be precisely evaluated. As the patients involved in our research were underage, their normal development may affect on the upper airway morphology during the treatment period. Thus, an untreated control group is needed. In the present study, the control group was selected from records of patients with the same diagnosis who just began orthodontic treatment, and matches well with the post-treatment patients of fixed functional appliance group through age, sex and development condition strategy, so that effects of fixed functional appliance on the upper airway morphology can be evaluated.