Effect of CO(2), Nd:YAG and Er:YAG Lasers on Microtensile Bond Strength of Composite to Bleached-Enamel

BACKGROUND: Tooth restoration immediately after bleaching is challenging due to the potential problems in achieving adequate bond strength. OBJECTIVE: The aim of this study was to evaluate the effect of surface treatment with ER:YAG, ND:YAG, CO(2) lasers and 10% sodium ascorbate solution on immediate microtensile bond strength of composite resin to recently bleached enamel. MATERIALS & METHODS: Ninety sound molar teeth were randomly divided into three main groups (n:30) : NB (without bleaching), HB (bleached with 38% carbamide peroxide) and OB (bleached with Heydent bleaching gel assisted by diode laser). Each group was divided into five subgroups (n:6) : Si (without surface treatment), Er (Er:YAG laser), CO(2) (CO(2) laser), Nd (Nd:YAG laser) and As (Immersion in 10% sodium ascorbate solution). The bonding system was then applied and composite build-ups were constructed. The teeth were sectioned by low speed saw to obtain enamel- resin sticks and submitted to microtensile bond testing. Statistical analyses were done using two- way ANOVA, Tukey and Tamhane tests. RESULTS: µTBS of bleached teeth irradiated with ND:YAG laser was not significantly different from NB-Nd group. Microtensile bond strength of OB-Er group was higher than NB-Er and HB-Er groups. The mean µTBS of HB-CO(2) group was higher than NB-CO(2) group; the average µTBS of HB-As and OB-As groups was also higher than NB-As group. CONCLUSION: Use of Nd:YAG, CO(2) lasers and 10% sodium ascorbate solution could improve the bond strength in home-bleached specimens. Application of ND:YAG laser on nonbleached specimens and Er:YAG laser on office-bleached specimens led to the highest µTBS in comparison to other surface treatments in each main group.