Analysis of the effects of some surface preparation methods on the bond strength of orthodontic attachments to amalgam surface

Abstract

This in-vitro research was aimed to examine the shear bond strength of metal brackets to silver amalgam using various surface preparation techniques to determine the best method to achieve appropriate bond strength between bracket and amalgam surface. Ninety amalgam blocks were divided into six groups and randomly assigned to one of the following conditioning groups (n=15): group 1 (control): etching with 37 phosphoric acid for 20 seconds, group 2: sand blasting with aluminum oxide (Al2O3), group 3: CO2 laser, group 4: CO2 laser plus sand blast, group 5: Er:YAG laser and group 6:Er:YAG laser plus sandblast. All Bond II was used in all groups and brackets were bonded with Transbond XT. After thermocycling, all samples were tested for shear bond strength by a universal testing machine. Data were analyzed by SPSS-22 software using Kruskal-Wallis and Mann-Whitney tests. The significance level was set at p <= 0.05.The results showed the mean shear bond strength was significantly higher in all five experimental groups than in control group (p <= 0.05). Shear bond strength was significantly higher in CO2 + sandblasting group than in sandblast group, but it was not significantly higher than Er:YAG,Er:YAG + sandblast and CO2 groups. Moreover, the results indicated a significantly higher shear bond strength in Er:YAG group than in sandblast group (p <= 0.05). Preparation by CO2 + sandblast (with mean shear bond strength of 6.3 Mpa) showed a higher shear bond strength than other methods, so it is considered an acceptable preparation method.