Dimensional Slot Integrity and Precision of Self-Ligating Buccal Tubes

Abstract

Self-ligating brackets, including molar buccal tubes, have gained popularity in recent decades. The primary advantage of using self-ligating systems has been based on the claim that they provide reduced friction and therefore reduced sliding resistance of the arch wire contained within their respective slots.1 This form of reduced friction and sliding resistance has been proposed to require less force and therefore produce more physiologic tooth movements.7-9 Limited scientific evidence is currently available to establish quality control of these products. The purpose of this study is to use Micro Computed Tomography (MicroCT) to analyze self-ligating molar tubes manufactured by different companies. Methods used here provide a novel way for measuring the accuracy and quality of these materials. This study has provided a highly innovative approach that had not been previously accomplished. Forty self-ligating lower left first mandibular molar samples were obtained from four different companies. Five samples from each company were randomly selected and scanned using MicroCT to determine the internal slot lumen of each tube for analysis of precision volumetric measurements. Additionally, qualitative analysis of the lumen of each tube was investigated for the presence of any internal slot defects or imperfections. Results showed that the volumetric slot measurements of all samples were highly statistically significant (P<0.001) and were found to be oversized compared to what is claimed by their respective companies. Qualitative analysis of all samples illustrated varying defects contained within their respective internal slot lumens. Notable defects included notched, beveled and irregular corners, as well as the presence of some bulbous metal projections. Based upon the results obtained in this study, it was determined that the investigated self-ligating buccal tubes, produced by all the companies tested, were oversized and had various internal slot defects. The potential clinical significance of these dimensional inaccuracies may include an increased amount of friction and a lack of torque control during tooth movement.