Influence of Er:YAG laser on cavity preparation and surface treatment in microleakage of composite resin restorations.

OBJECTIVE: The purpose of this study was to assess microleakage on class V cavities prepared by Er:YAG laser with varying surface treatment. BACKGROUND DATA: There has been little reported research on microleakage at cavities prepared and treated with Er:YAG laser. METHODS: Fifty preparations using Er:YAG laser or a highspeed handpiece were developed. The surface treatment was performed as follows: Er:YAG laser (group 1); 35% phosphoric acid (group 2); laser + acid (group 3); finishing with low-speed + laser + acid (group 4); conventional preparation developed with a high-speed handpiece + acid (group 5--control). The samples were restored with Single Bond/Z250, thermocycled, isolated, and immersed in a 50% AgNO(3) solution. The restorations were sectioned, and the microleakage was measured in milimeters using a specific computer software. Data were analyzed employing ANOVAand Tukey test. RESULTS: Statistical analysis showed that group 5 (G5) obtained the lowest results of microleakage (22.05%), and it was statistically similar (p > 0.05) to G1 (37.7%) and different (p < 0.05) from the other groups (G2 = 50.4%; G3 = 43%; G4 = 44.2%). The occlusal margins (22.62%) demonstrated less microleakage (p < 0.05) than the cervical margins (56.32%). CONCLUSION: The use of Er:YAG laser for cavity preparation and surface treatment negatively influenced the marginal sealing of composite resin restorations.

Influence of pulse frequency Er:YAG laser on the tensile bond strength of a composite to dentin.

PURPOSE: To evaluate the influence of different pulse frequencies of Er:YAG laser on the tensile bond strength of a composite to dentin. METHODS: The dentin surface treatment was performed by Er:YAG laser at 1, 2, 3 and 4Hz pulse frequencies and 80 mJ, for 20 seconds, followed by etching. The control group was etched by phosphoric acid solely. The Single Bond/Z250 system was used. The specimens were subjected to tensile strength tests in a testing machine (0.5mm/minute) after water storage (37 degrees C/24 hours). RESULTS: The averages in MPa were: 1Hz: 13.45 (+/- 5.31); 2Hz: 9.54 (+/- 2.13); 3Hz: 7.29 (+/- 1.26); 4Hz: 7.41 (+/- 2.44) and control group: 16.95 (+/- 2.57). The Kruskal-Wallis test revealed statistically significant difference. The increased frequency of the Er:YAG laser decreased the composite bond strength.