Materials and methods. Standard Class V cavities were prepared on buccal surfaces of 96 sound bovine teeth. The samples were randomly divided into 4 groups based on the disinfection method: Group 1: Nd:YAG laser Group 2: Diode laser Group 3: photodynamic therapy and Group 4: the control. Self-etch bonding agent (Clearfil SE Bond) was applied and all the cavities were restored with composite resin (Z100). After thermocycling and immersing in 0.5% basic fuchsin, the samples were prepared for microleakage evaluation under a stereomicroscope. Data was analyzed with Kruskal-Wallis and Wilcoxon signed-rank tests at P< 0.05. 

Results. There were no significant differences in the microleakage of occlusal and gingival margins between the study groups (P >0.05). There were no significant differences in microleakage between the occlusal and gingival margins in the Nd:YAG laser group (P >0.05). In the other groups, microleakage at gingival margins was significantly higher than that at the occlusal margins (P< 0.05). 

Conclusion. Nd:YAG and Diode lasers and photodynamic therapy can be used to disinfect cavity preparations before composite resin restorations.