A comparitive evaluation of the shear bond strength of Er:YAG laser ablation on enamel at 3 different power outputs with that of onventional acid etching technique - An invitro study

Abstract

The aim of this study is to determine whether bonding of stainless steel orthodontic brackets to tooth enamel prepared by laser etching would result in a similar bonding capability as those prepared by acid etching using 37 % phosphoric acid; and also to compare the shear bond strength.Eighty four samples were prepared for the study. The 4 groups were Group 1- The enamel was etched with 37 % phosphoric acid, Group 2- Er: YAG laser etching was done at 1W power output, Group 3- Er: YAG laser etching was done at 2W power output and Group 4- Er:YAG laser etching was done at 3W power output. All groups have 20 teeth for shear bond strength testing and one tooth for SEM evaluation. Shear bond strength testing was performed on all teeth using Instron universal testing machine.Analysis of the variance indicated a significant difference (P < 0.005) among the groups. Maximum shear bond strength was shown by laser etching at 2 W to the tooth surface for 15 seconds in compared to conventional acid etching. In this study the highest shear bond strength was found in the 2-W laser etched group (16.09±0.42) MPa, followed by the 1-W laser etched group (12.62± 0.35) MPa, 3-W laser etched group( 12.01±0.31) MPa and acid etched group.(6.42±0.32)MPa.The results showed that at that laser etching at 2 W to the tooth surface for 15 seconds had statistically significant higher shear bond strength in comparison to conventional 37% phosphoric acid technique. The use of increasing the laser power output more than 2 W did not significantly increase the bond strength. The shear bond strength of all the three Laser etched groups was clinically acceptable. Enamel etching with Er: YAG Laser (2W for 15 seconds) produced maximum bond strength than acid etching and could be a viable alternative method.