Evaluation of the frictional resistance between different bracket types, archwires and ligation materials: An in-vitro study

In orthodontic treatment, brackets need to slide along the archwire to allow for alignment of the teeth. The lesser the friction between the bracket and the archwire, the easier it is to align the teeth and the lighter the forces required to make such movements. In recent years, patients’ esthetic demands have driven the field of orthodontics to find alternatives to conventional stainless steel bracket systems. While ceramic brackets meet the esthetic demands, their inferior frictional characteristics have always been an issue for orthodontists.The present in-vitro research study evaluates and compares the frictional resistance between various types of brackets, archwire materials and ligation methods. The purpose of the study was to equate the frictional resistance among 12 different groups using the universal testing machine, so as to recognize the factors involved in the in-vitro appraisal of resistance to sliding (RS) and inferring their clinical implications. In this study, 120 pre-adjusted edgewise upper central incisor brackets with MBT 0.022″ slot were used, which included 40 standard metal brackets, 40 ceramic brackets, 20 self-ligating metal brackets and 20 self-ligating ceramic brackets. 0.019″ x 0.025″ SS (stainless steel) archwires, esthetic archwires, Teflon-coated ligatures and conventional elastic modules to ligate the archwire to the brackets except in self-ligating brackets, were used. The average frictional resistance of Group A10 was the minimum succeeded by A9, A12, A4, A11, A8, A3, A7, A2, A6, A1 and A5. In the comparison of the mean frictional resistance of 12 different groups, the ANOVA test showed noticeably different frictional resistance amongst the groups (F=745.80, P< 0.001). Self-ligating metal bracket combinations with different archwires showed a significantly smaller magnitude of friction than self-ligating ceramic, metal and ceramic bracket combinations. Teflon-coated ligature combinations possess less friction in comparison with conventional elastomeric module combinations.