Evaluation of Effects and Effectiveness of Various α and β Angulations for Three Different Loop Made of Stainless Steel Arch Wires - A FEM Study

Comparing the Efficiency of a Newly Designed Spring With the T Loop for Buccal Canine Disimpaction: A Finite Element Study

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.

Comparative assessment of the efficacy of closed helical loop and T-loop for space closure in lingual orthodontics-a finite element study

BACKGROUND

Retraction in lingual orthodontics has biomechanical differences when compared to labial orthodontics, which is not yet established. Thus, we have intended to compare the biomechanical characteristics of closed helical loop and T-loop on 1 mm activation with 30° of compensatory curvatures during retraction in lingual orthodontics.

METHODS

STb lingual brackets were indirectly bonded to maxillary typhodont model that was scanned to obtain FEM model. Closed helical loop (2 × 7 mm) and T-loop (6 × 2 × 7 mm) of 0.016″ × 0.016″ TMA wire were modeled without preactivation bends. Preactivation bends at 30° were given in the software. Boundary conditions were set. The force (F) and moment (M) of both the loops were determined on 1 mm activation, using ANSYS software. M/F ratio was also calculated for both the loops.

RESULTS

T-loop exerted less force, thus increased M/F ratio as compared to closed helical loop on 1 mm activation.

CONCLUSIONS

When torque has to be preserved in the anterior segment during retraction in lingual orthodontics, T-loop can be preferred over closed helical loop.