Effect of Etching-Time on Microleakage of Resin-Composite-Restorations After Conventional and Er:YAG-Laser-Preparation

Objectives: The aim of this study was to evaluate the effect of different etching times on microleakage of class V composite restorations prepared by conventional bur and Er,Cr:YSGG laser.
Methods: Class V cavities prepared on both buccal and lingual surfaces of 30 human molars by bur or Er,Cr:YSGG laser (Waterlase MD, Biolase) with 3.5W, 20 Hz , 60% air, 80% water. Samples were divided into 3 groups: 10s, 20s, and 40s etching time (37% H₃PO₄) and filled with composite (Z250, 3M ESPE). Samples were thermocycled [500 cycles (5-65°C)], stained with basic fuschin (0.5%, 72 h, 37°C), sectioned longitudinally, and evaluated at 20X magnification. The dye penetration at occlusal and gingival margins was evaluated according to ISO standards on a 0 (no dye penetration) to 3 (dye penetration into the pulpal floor) scales. Data were analyzed statistically using Kruskal-Wallis and Wilcoxon test (P<0.05).

Results: There was no statistical significant difference in microleakage among the three test groups at either the occlusal or gingival margins. Comparing laser prepared and bur prepared cavities, no statistical significant difference was detected. Gingival margins of the cavities demonstrated greater dye penetration in all groups, and it was statistically significant in group 2 (cavities etched for 20s) for both laser (p=0.0129) and bur (p= 0.0346) prepared cavities, furthermore group 3 (cavities etched for 40s) bur prepared was statically significant (p=0.03).

Conclusions: Occlusal margins provide better marginal sealing than gingival margins, regardless of the method of cavity preparation.