Microtensile bond strength testing and failure analysis of hybrid and flowable composites.
OBJECTIVE
Few studies have been performed on the cohesive tensile strength of flowable resin composites and hybrids, or on the coupling strength of flowables to hybrid composites. Thus, the purpose of this study was to measure interfacial microtensile bond strengths between hybrid resin composite and flowable resin composite/compomer.


METHODS
A polyvinyl siloxane mold was used to fabricate specimens for 9 groups, each consisting of 15 rectangular beams (2 x 2 x 20 mm). Flowable and hybrid resin composites and their paired couplings with each manufacturer's product line were tested. Materials include Heliomolarflow, Revolution, and Dyractflow as representative flowable resin composites and compomer. Heliomolar HB, Prodigy, and Esthet X were selected as representive hybrid resin composites. Resin specimens were cured for a total of 80 s and immersed in water for 7 days. A microspecimen former was used to trim rectangular specimens into specimens with a circular cross section (diameter = 1.0 mm) with a 2 mm gauge length. Specimens were subjected to tensile forces in a passive-gripping space mounted on a Vitrodyne machine.


RESULTS
The results are expressed in MPa. Kruskal-Wallis one-way ANOVA on ranks demonstrated significant differences in microtensile bond strength among groups (p < 0.001).


CONCLUSIONS
The cohesive tensile strength of resin composites were material dependent. Flowable and hybrid composites from the same manufacturer have comparable cohesive tensile strengths. The coupling strength of flowable/hybrid combinations were comparable to cohesive strength of the hybrid composites with the exception of Esthet X/Dyractflow, where the coupling was stronger than the cohesive strength of either resin composite alone.
Jones
Cindy T
CT
Department of Oral Rehabilitation, School of Dentistry, Medical College of Georgia, Augusta, Georgia 30912-1260, USA.
Chan
Daniel C N
DC
Pashley
David
D
de Goes
Mario Fernando
MF
Nelson
Steven K
SK
D000180:Acrylic Resins / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D004548:Elasticity; D019544:Equipment Failure Analysis; D008422:Materials Testing / Q000379:methods; D011140:Polyurethanes / Q000737:chemistry*; D013718:Tensile Strength
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C513708:Heliomolar; D011140:Polyurethanes; C111840:flowable hybrid composite