Shear Bond Strength to Primary Enamel: Influence of Er: YAG Laser Irradiation Distance

Purpose: The purpose of this study was to evaluate in vitro the influence of Er: YAG laser irradiation distance on the shear bond strength of an adhesive restorative system to primary enamel. Methods: Fifty buccal surfaces of extracted human canines were ground and divided into 5 groups (N=10). The control group was etched with 35% phosphoric acid (CA). In the lased groups, the enamel surface treatment was performed with the Er: YAG laser (80mJ/2Hz) by varying the irradiation distance (12, 14, 16, and 17 mm), followed by acid etching. An adhesive agent (Single Bond) was applied on the bonding sites, and resinous cylinders (Filtek Z250) were prepared. Shear bond strength tests were performed in a universal testing machine (0.5 mm/minute). Failure mode was assessed using a X40 magnification stereomicroscope. Data were submitted to statistical analysis by analysis of variance. Results: The means in MPa were: (1) CA=18.76 (+/- 6.68); (2) 12 mm=12.73 (+/- 5.46); (3) 14 mm=15.9 (+/- 6.81); (4) 16 mm=20.1 (+/- 6.94); and (5) 17 mm= 15.15 (+/- 6.81). There was no statistically significant difference (P<. 05) among the tested groups. Conclusion: The different Er: YAG laser distance irradiations did not influence the adhesive resistance of the resinous system to enamel, even when compared with the control group (acid etching solely).