The Comparison of Shear Bond Strength of Brackets Adhered to Enamel Pretreated with Three Methods of CO2, Er, Cr:YSGG Lasers with Acid Phosphoric

The purpose of this study was to evaluate the effect of CO2 and Er, Cr:YSGG Hydrokinetic lasers on enamel conditioning for bonding of brackets in comparison with acid etching technique. Ninety intact freshly preserved extracted premolars were chosen and divided into three groups (30 each). Then the teeth in acid etch group were conditioned with acid etching technique with 37% phosphoric acid and in CO2 group were conditioned with setting 3W (pps 150 mj) using CO2 laser and in laser ErCr YSGG group were conditioned with setting 3W (pps 150 mj) using ErCr YSGG Hidrokiase laser. Then 3M brackets were bonded to teeth by 3M light cure composite in each group. For determination of bonding strength the samples were exposed to cutting force of 1 mm velocity per minute with universal testing machine. Descriptive and t test were used for comparison between groups with P<0.05 level of significance. The mean values of bonding strengths to MP were as follows: for acid etching technique 11.3, laser CO2 technique 8.8, laser ErCr YSGG Hidrokinetic technique 9.5. The highest value of bonding strength, although statistically insignificant, was in acid etch group. The results of this study showed that use of laser conditioning enamel surface treatment produced less bonding strength in comparison with acid etching, but its difference was not significant. Moreover, the high SD (Variations- standard deviation) seen in both laser groups compared with acid etch group, makes questionable the reliability and predictability of laser-etching method. Further studies on clinical application of laser are still needed.