Evaluation and Comparison of Moment-to-Force Ratio of a New “PRP Loop” with that of Opus Loop and L Loop- A Finite Element Method Study

Abstract

Introduction: Extraction space closure is the foremost challenging procedure in the field of orthodontics which needs a robust understanding of biomechanics. There are two commonly used methods of space closure, one which involves friction, also called sliding mechanics, and the other is frictionless. The advantages of frictionless mechanics are there is no force loss due to friction and low anchorage taxing. The preferred method for the retraction of teeth is loop mechanics and which ensures controlled tooth movement. Aim: To evaluate and compare the Moment-to-Force (M/F) ratio of PRP loop with that of Opus loop and L loop by Finite Element Method (FEM). Materials and Methods: An in-vitro study was conducted by using FEM analysis in DMIHER University with technical assistance from the Department of Mechanical Engineering VNIT Nagpur. Computer models of Loops design were prepared on Analysis of Systems (ANSYS) version 10 (V10) software. Opus loop, L loop and Platelet-Rich Plasma (PRP) loop were modelled as SOLID 64 beam elements. Different pre-activation bends were given to the models in α and β nodes of the loop. Statistical analysis was done with Statistical Package for Social Sciences (SPSS) version 27.0 software to compare the mean of all three loops. Results: Total 36 FEM models were studied. PRP loop showed greater M/F ratio than Opus and L loop with 15ºα and 25ºβ pre-activation bends in both 0.017×0.025 and 0.019×0.025-inch Titanium Molybdenum Alloy (TMA) wire i.e., 9.09 and 9.12, respectively. On comparison of M/F ratio of PRP loop, Opus loop and L loop prepared with 0.017×0.025 and 0.019×0.025 TMA wire, at 15ºα and 25ºβ pre-activation bend in 0.019×0.025 TMA, PRP loop showed highest M/F ratio of 9.12 as compared to 0.017×0.025 TMA wire. Conclusion: The study concluded that PRP loop is an efficient retraction loop with ideal moment force ratio for translatory movement of tooth. PRP loops had highest M/F ratio than Opus loop and L loop, indicating that PRP can be used for translatory movement of tooth in wires of different materials. Therefore, for proper utilisation of PRP loop, it must be prepared with either 0.017×0.025 inch TMA or 0.019×0.025 inch TMA wire.

Keywords

• finite element analysis
• friction mechanics
• loop mechanics
• retraction force