the effect of laser irradiation on shear bond strength of gi to dentin after cpp-acp treatment

background dentin sensitivity is one of the most important problems in dentistry. enamel loss due to root exposure is serious issue and common exposure is one of the reasons for dentin hypersensitivity. there are different methods for solving this problem. one of the most conservative and least expensive methods is use of casein phosphopeptide-amorphous calcium phosphate (cpp-acp) paste. objectives the aim of this study was to evaluate shear bond strength of gic to dentin, with or without laser, cpp-acp paste and polyacrylic acid treatments. materials and methods fifty sound human third molars were bisected in a mesiodistal direction using a diamond disk. using 400, 600 and 800 grit silicon carbide paper, dentin surfaces were exposed. the teeth were divided into five groups. in groups a, b, d and h, cpp-acp (gc tooth mousse itabashi-ku, tokyo, japan) was applied for one hour the first day and repeated at the same time of day for a total of five days. in groups b, c, d and e, the specimens were subjected to laser for 10 seconds using er, cr: ysgg laser. in groups b, c, h and g, specimens were treated with 10% polyacrylic acid for 20 seconds. a plastic tube containing gi was positioned over the tooth. samples were loaded in shear bond using a universal testing machine (zwick/roell, germany), at a 0.5 mm/minute crosshead speed. results despite the failing of groups a and d, group analysis showed that there were no significant differences between the groups. the predominant type of fracture in all groups was adhesive. conclusions application of cpp-acp, without preconditioning with polyacrylic acid, can decrease shear bond strength. laser irradiation has no effect on shear bond strength of gic to dentin in this condition.