3-DIMENSIONAL EFFECTS IN RETRACTION APPLIANCE DESIGN

The clinical importance of the three-dimensional effects of the force systems supplied by appliance designs used for retraction has long bee n appreciated. However, quantification of these force systems is not a s well known. In this work, a numerical method is used to provide quan titative insight into three-dimensional effects for typical appliance designs. One problem that occurs clinically is the axial rotation of a single rooted tooth as a result of the forces being applied by the re traction device on the tooth's buccal surface. An out-of-plane preacti vated bend can be used to counteract this rotation. The proposed numer ical method can accurately determine the force systems resulting from this out-of-plane preactivation as well as the in-plane force systems. It is shown that the out-of-plane effects are independent of the in-p lane behaviour so that the usual forces and moment to force ratios are maintained.