Resin Bond Strengths to High-Repetition Er:YAG Laser-Irradiated Dentin

Objectives:This study investigated the influence of the condition (output energy levels and pulse repetition rate) of Er:YAG laser on bond strength between resin and lased dentin. Methods:Bovine teeth were cut at the cervix and the exposed coronal surfaces were prepared to flat dentin surfaces with SiC abraded paper. The dentin surfaces were then irradiated by Er:YAG laser uniformly with X-Y table (PMG615, shift speed 1mm/sec) at ‡@100mJ/pulse-10pps, ‡A50mJ/pulse-20pps, and ‡B33mJ/pulse-30pps. The lased surfaces were pre-conditioned with a combined solution of 10% citric acid and 3% ferric chloride for 15 seconds, rinsed with water and sufficiently dried. The conditioned surfaces were bonded the PMMA square rods with 4-META/MMA-TBB resin. The bonded samples were trimmed to obtain the mini-dumbbell-shaped bonded specimens and tensile bond strength (TBS) of those were measured after the storage in 37°C water for 24 hours. As a control, the TBS to non-lased dentin surfaces were also tested. After the TBS testing, the fracture mode was analyzed under the SEM. Results:The TBS of control was 22.9+/-5.7 MPa and was higher than the other three lased groups. The higher energy levels and the lower repetition rate, the higher TBS was obtained in the lased groups (‡@17.9+/-3.3MPa, ‡A11.4+/-4.4MPa and ‡B9.9+/-3.7MPa). The SEM observation in the lased groups showed the failures within- and/or top of the resin-impregnated lased dentin (RILD) were partially shown. Conclusion:These results showed the low mechanical properties of RILD and it may be due to the low-bond strength between the resin and Er:YAG-lased dentin.