Comparison of shear bond strength of orthodontic metal brackets recylced using different methods: An in-vitro study

Abstract

The aim of this study was to compare the effect of recycling orthodontic metal brackets by sandblasting with aluminum oxide particles of different sizes and by laser blow method after first and second rebonding /recycling. 120 human premolars extracted for orthodontic purpose were randomly divided into four groups. 40 MBT prescription Orthodontic metallic brackets were bonded on the buccal surface of the samples. Brackets were recycled by sandblasting with 3 different particles size and laser. Debonding of all brackets was performed using a universal testing machine and shear bond strength was determined. Brackets were examined under Field emission scanning electron microscope from each group at each level to compare the surface characteristic of new and rebonded brackets. Data were analyzed with paired test, ANOVA, and post hoc tests.The shear bond strength of group I (sandblasted with 25µm alumina) was significantly higher at the end of 1st recycling compared to group II(50 µm) and III(100 µm) but it was comparable to group IV(laser) at the end of 1st recycling. Group IV showed clinically significant higher shear bond strength compared to group II and III after 1st and 2nd recycling. The shear bond strength for group II and III (sandblasted with 50 and 110µm alumina) was significantly much lower after 2nd recycling as compared to new i.e., Control (p value<0.001⁎⁎⁎).25µm alumina sandblasting and Er-YAG laser blow method obtained better results after three successive recycling. Overall sandblasting emerged as the best method to recycle the orthodontic brackets.