Cl V LASER Prepared Composite Restorations- Etching Time and Microleakage

LASERs are used to prepare cavities, however the effect that this has on leakage of the restoration is unclear.

Objective: To evaluate the effects of different etching times on microleakage of class V composite restorations prepared by bur and Er.Cr: YSGG laser.

Methods: Class V cavities prepared on both buccal and lingual surface 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 under the magnification (20X). 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. Additional 6 samples were prepared without filling and studied under SEM for the surface configurations. Data were analyzed with Kruskal-Wallis and Wilcoxon test (P<0.05).

Results: There was no significant difference in leakage of the three groups at the occlusal or gingival margin by Kruskal-Wallis. Comparing the paired laser prepared and bur prepared cavities by Wilcoxon sign ranked test revealed also no significant difference. Gingival margins of the cavities demonstrated greater dye penetration in all groups and was statistically significant in group 2 in both laser (p=0.0129) and bur (p= 0.0346) prepared cavities and also in group 3 bur prepared (p=0.03).

SEM study showed no smear layer but melted and recrystallized enamel and dentin have been observed.

Conclusion: within the limits of this study we concluded occlusal margins provide better marginal sealing than gingival margins regardless of laser or bur preparation. Statistically no significant difference has been observed in both laser and bur prepared cavities.