Finite element analysis of stresses on adjacent teeth during the traction of palatally impacted canines.

OBJECTIVE: To evaluate stresses on maxillary teeth during alignment of a palatally impacted canine (PIC) under different loading conditions with forces applied in vertical and buccal directions. MATERIALS AND METHODS: A three-dimensional finite element model of the maxilla was developed from a cone beam computed tomographic scan of a patient with a left PIC. Traction was simulated under different setups: (1) palatal spring extending from a transpalatal bar (TPB) anchored on the first molars (M1) and alternatively combined with different archwires (0.016 x 0.022-inch; 0.018 x 0.025-inch) with and without engaging second molars and (2) a buccal force against 0.018-inch, 0.016 x 0.022-inch, and 0.018 x 0.025-inch archwires with and without engaging the left lateral incisor (I2). RESULTS: Without fixed appliances, stresses were assumed by M1; with fixed appliances, stresses were distributed on all teeth, decreasing mesially toward the midline. Direct buccal pull exerted most stress on neighboring I2 (19-20% with different wire sizes) and first premolar (12-17%), decreasing distally, along a similar pattern with different archwire sizes. When I2 was bypassed, stresses on adjacent teeth increased only by 3-6%. Higher stresses occurred with the lighter round wire. CONCLUSIONS: This first research on stresses on adjacent teeth during PIC traction provided needed quantitative data on the pattern of stress generation, suggesting the following clinical implications: use of distal-vertical pull from posterior anchorage (TPB) as initial movement and when using a buccal force, bypassing the lateral incisor and using heavier wires that would minimize side effects.