Finite element study of controlling factors of anterior intrusion and torque during temporary skeletal anchorage device (TSAD) dependent en masse retraction without posterior appliances: Biocreative hybrid retractor (CH-retractor)

Objectives: To evaluate, using the finite element method (FEM), the factors that allow control of the anterior teeth during en masse retraction with the Biocreative hybrid retractor (CH-retractor) using different sizes of nickel-titanium (NiTi) archwires and various gable bends on the stainless-steel (SS) archwires. Materials and Methods: Using FEM, the anterior archwire section, engaged on the anterior dentition, was modeled in NiTi, and another assembly, the posterior guiding archwire, was modeled in SS. Two dimensions (0.016 3 0.022- and 0.017 3 0.025-inch NiTi) of the anterior archwires and different degrees (08, 158, 308, 458, and 608) of the gable bends on the guiding wire were applied to the CH-retractor on the anterior segment to evaluate torque and intrusion with 100-g retraction force to TSADs. Finite element analysis permitted sophisticated analysis of anterior tooth displacement. Results: With a 08 gable bend all anterior teeth experienced extrusion. The canines showed a larger amount of extrusion than did the central and lateral incisors. With a gable bend of .158, all anterior teeth exhibited intrusion. Bodily movement of the central incisor required a 308~458 gable bend when using anterior segments of 0.016 3 0.022-inch NiTi and 158~308 gable bend with the 0.017 3 0.025-inch NiTi. Conclusions: With the CH-retractor, varying the size of the NiTi archwire and/or varying the amount of gable bend on the SS archwire affects control of the anterior teeth during en masse retraction without a posterior appliance.