The purpose of this study was to investigate the effects of phosphoric acid on tensile bond strength of composite resin to Er: YAG laser (The KaVo K. E. Y Laser® 1242)-irradiated enamel.
Twenty-one extracted human incisors were used. Flat enamel surfaces were prepared and irradiated with an Er: YAG laser at 4Hz and 200mJ, with water colling. The teeth were divided into 3 groups--Group 1: no acid etch./Single Bond and Z100/3M (nSB); Group 2: acid etch for 15sec. Single bond and Z100 (SB); Group 3: acid etch for 60sec./Single Bond and Z100 (60SB). The restoratives were applied in a plastic mold with a bond diameter of 2.4mm. Tensile bond strengths were determined after storage in a moisture box at 37°C for 24hours (n=7). The surfaces of specimens were observed by SEM.
The results (MPa±SD) were as follows: nSB 4.2±1.7; SB 7.5±2.7; 605B 9.1±3.2. A one-way ANOVA revealed significant differences of bond strength values by the surface treatment methods (p<0.05). From the results of tensile bond strengths, it can be concluded that the application of phosphoric acid improved the tensile bond strength of composite resin to the Er: YAG laser-irradiated enamel. SEM observation showed that some enamel influence by Er: YAG laser irradiation remained, even if it was etched with 35% phosphoric acid.
