Can area delimitation and tube type impact microshear bond strength of adhesives to dental substrates?

Background he need of delimiting the bonding area on microshear bond strength (µSBS) test remains an unclear issue. In addition, there are different types of tube to perform the resin composite cylinders on µSBS test. The aim of this study was to evaluate the influence of the adhesive area delimitation and type of tube used to build up specimens for µSBS testing of adhesive systems, to enamel and dentin.  Methods 120 bovine incisors were ground to achieve flat buccal enamel (n=60) and dentin (n=60) surfaces. Specimens of each substrate were randomly allocated into 6 groups (n=10) according to the adhesive system-a two-step self-etch (Clearfil SE Bond) and a universal adhesive (Scotchbond Universal Adhesive) applied in the self-etch and etch-and-rinse modes– and type of tube used to build up the specimens: starch and polyethylene. 4 resin composite cylinders (Filtek Z250) were made on each surface; in 2 of them the area delimitation was performed. The specimens were subjected to µSBS test after 24 h of water storage at 37°C. Data were submitted to three-way ANOVA and Tukey’s post hoc tests (α=0.05). Results The delimitation of the adhesive area did not influence on the bond strength to dentin (p=0.349) nor to enamel (p=0.158). The type of tube differently affected the ranking of adhesives in both substrates. Conclusions The delimitation of the adhesive area does not influence on the µSBS to enamel and dentin, irrespective of the tube type used to build up the resin composite specimens. The tube type’s impact on the bond strength depends on the dental substrate and adhesive system.