Microleakage of Self-Etch Adhesive System in Class V Cavities Prepared by Using Er:YAG Laser with Different Pulse Modes. 
In vitro studies evaluated cementum surface morphology and microleakage of three different energy density parameters of Erbium: Yttrium Aluminum Garnet (Er:YAG) laser compared with diamond bur preparation on class V cavities with self-etch adhesive system and composite resin restoration.  Standard class V cavities were prepared at cervical area below the cementoenamel junction (CEJ) in 80 extracted premolars, by using a diamond bur on the buccal surface.  All teeth were randomly allocated into four groups: Group 1, diamond bur; Group 2, Er:YAG 50 mJ/15 Hz, 3.77 J/cm(2); Group 3, Er:YAG 75 mJ/15 Hz, 5.65 J/cm(2); and Group 4, Er:YAG 100 mJ/15 Hz, 7.53 J/cm(2).  Five cavities from each group were evaluated by scanning electron microscopy (SEM).  The 15 remaining cavities from each group were restored with self-etch adhesive and nano-hybrid composite.  After thermocycling, all sample teeth were immersed in 0.2% methylene blue dye and sectioned buccolingually.  Statistics were analyzed using the one way ANOVA and Mann-Whitney U tests with Bonferroni correction.  The morphology showed micro-irregularities in the cementum surface of the laser group with the absence of a smear layer.  The microstructure characteristics were increased surface roughness followed by increasing laser energy transmission.  The Er:YAG laser groups were statistically significant, with less microleakage than the diamond bur group (p<0.05).  There was statistically significant difference between the occlusal and gingival microleakage in all the groups (p<0.05).  When the laser groups were compared, the lowest microleakage was achieved with energy density at 3.77 J/cm(2) on the occlusal and gingival cementum margin, which showed less microleakage than at energy densities of 5.65 and 7.53 J/cm(2) with Er:YAG laser.  These observations indicate that the micro-irregularities of the cementum surface could facilitate the formation of a hybridization zone with a self-etch adhesive system.  Therefore, the microleakage of Er:YAG laser irradiation was significantly decreased compared with diamond bur cavities.