comparative study of the shear bond strength of flowable composite in permanent teeth treated with conventional bur and contact or non-contact er:yag laser

introduction :the aim of this study was to evaluate and compare the in vitro effect of the erbium-doped yttrium aluminum garnet (er:yag) laser with different radiation distances and high-speed rotary treatment on the shear bond strength of flowable composite to enamel of human permanent posterior teeth . methods : freshly extracted human molar teeth with no caries or other surface defects were used in this study (n=45). the teeth were randomly divided into 3 groups. group 1: treated with non-contact er:yag laser and etched with er:yag laser, group 2: treated with contact er:yag laser and etched with er:yag laser, group 3 (control): treated with diamond fissure bur and etched with acid phosphoric 37 % . then the adhesive was applied on the surafces of the teeth and polymerized using a curing light appliance. resin cylinders were fabricated from flowable composite. shear bond strength was tested at a crosshead speed of 0.5 mm/min. results: the amount of shear bond strength (sbs) in the 3 treatment groups was not the same (p<0.05).the group in which enamel surfaces were treated with diamond fissure bur and etched with acid (conrtol group) had the highest mean shear bond strength (19.92±4.76) and the group in which the enamel surfaces were treated with contact er:yag laser and etched with er:yag laser had the lowest mean shear bond strength (10.89±2.89). mann-whitney test with adjusted p-value detected significant difference in shear bond strength between the control group and the other 2 groups (p < 0.05). conclusion: it was concluded that both contact and non-contact er:yag laser treatment reduced shear bond strength of flowable resin composite to enamel in comparison with conventional treatment with high speed rotary. different er:yag laser distance irradiations did not influence the shear bond strength of flowable composite to enamel.