Disimpacting a buccally impacted canine precisely using frictionless mechanics is a challenge in orthodontics. Various mechanics can be used for aligning an impacted canine and a spring is one of the most versatile methods of accomplishing it. The present study describes a newly designed spring for canine disimpaction using the finite element method (FEM) model. In the present study, the efficiency of the newly designed spring was compared with the T loop. The FEM model of the maxilla was prepared. Harsha's Canine Disimpaction (HCD) spring and T loop with no pre-activation bends were utilized to disimpact the left maxillary canine using a 0.017 x 0.025 inch titanium molybdenum alloy wire. Efficiency of both springs in all dimensions (sagittal, vertical and transverse) was compared. Stress acting on the bone and teeth and number of activations needed for disimpaction were evaluated when the spring was activated by 3 mm. A movement/displacement of 0.8, 0.4 and 0.1 mm was seen in the sagittal (X), transverse (Y) and vertical (Z) planes, respectively, with the HCD spring, and 0.4, 0.1 and 0.1 mm seen in the X, Y and Z planes, respectively, with the T loop. A total of 12-13 and 80 activations were required as per the FEM simulation for disimpaction using the HCD spring and T loop, respectively. Stress concentration in the disto-cervical region was observed during disimpaction with both HCD spring and T loop. Within the constraints and limitations of the present study, it can be concluded that the HCD spring requires lesser activation and brings about greater control of canine disimpaction in all three dimensions when compared to the T loop.
Keywords: finite-element model; loops; maxillary impacted canine; orthodontic tooth movement; rate of tooth movement; spring.
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