Changes in Ultrastructure and Properties of Bracket Slots After Orthodontic Treatment With Bicuspid Extraction

This study examined the effects of an orthodontic treatment using a bicuspid extraction on the surface roughness and mechanical properties of stainless steel (SS) brackets adjacent to the extraction space. Four experimental groups were employed; groups 1 and 2 used the Archist (R) SS brackets before and after the extraction treatment, respectively, and groups 3 and 4 used the Victory (R) SS brackets before and after the extraction treatment, respectively. The slot surfaces of the bracket were scanned in air at a resolution of 512 x 512 pixels with a scan speed of 0.8 line/s. The viscoelasticity of the bracket slot was determined from the force-distance curves of atomic force microscopy. The orthodontic treatment with bicuspid extraction led to a significant increase (p<0.0001) in surface roughness in both groups. In particular, the Archist (R) SS brackets showed more changes than the Victory (R) SS brackets (p<0.0005). However, there was no significant difference in properties of the Victory (R) and Archist (R) brackets between before and after treatment. This suggests that the orthodontic treatment with bicuspid extraction is more responsible for the changes in surface roughness than the properties of the brackets. SCANNING 33: 25-32, 2011. (c) 2011 Wiley Periodicals, Inc.