Upper Incisor Changes Due to Modifying the Point of Application of Forces during Space Closure in MBT Technique

Statement of Problem: A recent technique (MBT) has been introduced for easy and efficient orthodontic treatment by means of straight wire fixed appliances. Although this technique has many advantages, in space closure stage causes up righting problem in upper incisors, which should be adjusted by applying additional torque in anterior region. The purpose of this clinical trial was to determine whether there is a significant difference in final incisor inclination (torque) of two groups one treated with MBT technique and the other by changing the point of application of the closing force (in anterior region). Twelve patients (8 girls, 4 boys) with Cl I malocclusion and crowding, whom were candidate for first premolars extraction, were selected. For space closure, 6 anterior teeth (canine to canine) in upper and lower jaws ligated and the applied force was from the hooks on canines to hooks on the first molars. After space closure the results compared with the results of a previous study which treatment plan was according to original MBT technique (anterior hooks soldered to arch wire). Forces applied randomly among quadrants by NiTi coil spring (American Orthodontics Co.) or active tie backs with elastic modules (Dentaurum Co.) The results showed a statistically significant difference between final torques of two techniques (P=0.0001). Also, the rate of space closure with NiTi coils was significantly greater than active tie back (P=0.0001). Anchorage loss in two groups compared and the results indicated significantly lower anchorage loss in NiTi coil spring group (P=0.035).