Shear bond strength of self-etching bonding systems

Methods: Experiments were carried out by dental students during their regular courses 2008-2011. The dentin bond strength of two self-etching (Optibond-All-in-One, [OBAIO] Kerr; XenoV [XV], Dentsply) and of a three-step etch-and-rinse-system (Optibond FL, [OBFL], Kerr) was tested. 234 (2008), 223 (2009), 209 (2010) and 231 (2011) bovine teeth were ground with a Metaserv grinder/polisher until an adequate dentin surface was exposed. Composite cylinders were fixed with the tested bonding-systems perpendicular to the exposed dentin surfaces. The main differences of the experimental designs were as follows: 2008 bondings were air-dried with bellows, 2009 with high-pressure compressed air and 2010/2011 with low-pressure compressed air. The air pressures were evaluated with an anemometer. Half of the specimens were subjected to thermocycling. Thereafter the specimens were stabilized in gypsum and tested with an universal testing-machine (Zwick). Data were analysed by Wilcoxon tests.

Results: For all 3 systems, a significant difference between preperations with and without thermocycling could be found (all p<0.0001). Significantly larger values were found for preparations without thermocycling. XV showed significantly smaller values as compared to OBAIO (p<0.0001) and OBFL (p<0.0001). Furthermore, OBAIO showed significantly smaller values as compared to OBFL (p<0.0001). The following table shows the percentage of testing failures (specimens broke spontaneously or adhesion was too low to be registered):

Conclusion: This study shows that the shear bond values of the tested bonding-systems depend on the applied technique of air-drying. Furthermore it turned out that the three-step etch-and-rinse-system showed the highest shear bond values and the least testing failures in the hands of unexperienced experimentators independently of the respective air-drying technique.