Three dimensional analysis of tooth movement using different types of maxillary molar distalization appliances

Abstract

Objective: The purpose of this study was to compare the three dimensional changes of tooth movement using four different types of maxillary molar distalization appliances; pendulum appliance (PD), mini-implant supported pendulum appliance (MPD), stainless steel open coil spring (SP) and mini-implant supported stainless steel open coil spring (MSP). Methods: These experiments were performed using the Calorific machine? which can simulate dynamic tooth movement. Computed tomography (CT) images of the experimental model were taken before and after tooth movement in 1 mm thicknesses and reconstructed into a three dimensional model using V-works 4.0 (TM). These reconstructed images were superimposed using Rapidform 2004 (TM) and the direction and amount of tooth movement were measured. Results: The mean reciprocal anchor loss ratio at the first premolar was 17 - 19% for the PD and SP groups. The appliances using mini-implants (MPD or MSP) resulted in less anchorage loss (7 - 8%). On application of a pendulum appliance or MPD, distalization was obtained by tipping rather than by bodily movement. Furthermore, the maxillary second molar tipped distally and bucally. But on application of MSP, distalization was achieved almost by bodily movement. Conclusions: Regarding tooth movement patterns during molar distalization, stainless steel open coil spring with indirect skeletal anchorage was relatively superior to other methods. (Korean J Orthod 2008;38(6):376-387)