A quantitative AFM analysis of nano-scale surface roughness in various orthodontic brackets

In orthodontics, the surface roughnesses of orthodontic archwire and brackets affect the effectiveness of arch-guided tooth movement, corrosion behavior, and the aesthetics of orthodontic components. Atomic force microscopy (AFM) measurements were used to provide quantitative information on the surface roughness of the orthodontic material. In this study, the changes in surface roughness of various orthodontic bracket slots before and after sliding movement of archwire in vitro and in vivo were observed through the utilization of AFM. Firstly, we characterized the surface of four types of brackets slots as follows: conventional stainless steel (Succes®), conventional ceramic (Perfect®), self-ligating stainless steel (Damon®) and self-ligating ceramic (Clippy-C®) brackets. Succes® and Damon® brackets showed relatively smooth surfaces, while Perfect® had the roughest surface among the four types of brackets used. Secondly, after in vitro sliding test with beta titanium wire in two conventional brackets (Succes® and Perfect®), there were significant increases in only stainless steel bracket, Succes®. Thirdly, after clinical orthodontic treatment for a maximum of 2 years, the self-ligating stainless steel bracket, Damon®, showed a significant increase in surface roughness. But self-ligating ceramic brackets, Clippy-C®, represented less significant changes in roughness parameters than self-ligating stainless steel ones. Based on the results of the AFM measurements, it is suggested that the self-ligating ceramic bracket has great possibility to exhibit less friction and better biocompatibility than the other tested brackets. This implies that these bracket slots will aid in the effectiveness of arch-guided tooth movement.