2014 Volume 57 Issue 4 Pages 313-324
Purpose: It was reported that low-energy laser ablation of dentin, which causes little pain, significantly reduced the resin bond because the superficial layer of lased dentin was mechanically weakened due to the formation of structural defects and a heat-denatured layer. It was also reported that the bonding performance of the resin-modified glass-ionomer cement (RMGI) to lased dentin was relatively stable compared to the bonding resin regardless of the power output. In this study, to develop a new dentin bonding system suitable for Er: YAG-lased dentin, the bonding performance of RMGI to dentin irradiated at various output powers was evaluated and compared with that of the bonding resin.
Methods: Flat dentin surfaces from freshly-extracted bovine teeth were prepared and irradiated with Er: YAG (Erwin Adverl) laser at low power (50 mJ/1 pps, low-irradiation), medium power (150 mJ/1 pps, medium-irradiation), and low power followed by medium power (finishing-irradiation). These lased dentin and non-lased dentin were subjected to the following bonding procedures prior to the placement of the composite (Clearfil AP-X): G-Bond Plus (G group), Self-Conditioner/Fuji Lining Bond LC (FLB group), and Self-Conditioner/Fuji Lining LC (FL group). The micro-tensile bond strengths (μTBSs) and fractomorphology were evaluated (Dunnet’s multiple comparison and Fisher’s PLSD, p=0.05), and cross-sectional observation of the interface was conducted under SEM.
Results: For the G group, the μTBSs to the lased dentin at any output power were significantly lower than those to the non-irradiated dentin (p<0.05). Most of the specimens demonstrated adhesive failure or mixed failure (dentin and bonding resin) and some cracks from the denatured layer in the lased dentin to the bonding resin. However, both the FLB and FL groups exhibited approximately the same μTBSs to the lased dentin of the medium- and finishing-irradiation, while those to the lased dentin of low-irradiation were relatively low in comparison with those to non-irradiated dentin (p<0.05). Mixed failure (RMGI and dentin) or cohesive failure in RMGI occurred, and good adaptation between the RMGI and lased dentin along with microcrack formation within RMGI was observed characteristically in both groups.
Conclusion: The present findings revealed that RMGI might reduce strain concentration at the adhesive interface and exhibited relatively stable bonding performance to the laser-irradiated dentin, demonstrating the efficacy of RMGI as a possible dentin bonding system for Er: YAG-lased dentin.
