Influence of the volume of composite and photoactivation method on push-out bond strength and Knoop hardness of a resin composite.
OBJECTIVE
The aim of this paper was to evaluate the influence of modulated photoactivation methods and volume of composite on Knoop hardness (KHN) and push-out bond strength (PBS) of Filtek Z350 to root dentin.


METHODS
Three volumes (small, medium and large) of composite were bulk inserted in cavities prepared in 90 premolars. The specimens were photoactivated with continuous light, pulse-delay, or soft-start methods and submitted to PBS and KHN tests. The failure pattern was evaluated in stereomicroscope after the bond strength test. The data were submitted to two-way ANOVA and Tukey's test (P<0.05).


RESULTS
Modulated photoactivation methods showed a higher PBS than continuous method (P<0.05). Medium volume of composite showed higher PBS than small and large volumes when photoactivated with continuous method (P<0.05). Pulse-delay significantly increased KHN for medium and large volumes in comparison to continuous method (P<0.05). Medium volume of composite showed KHN significantly higher than small and large volumes (P<0.05).


CONCLUSIONS
The volume of composite influenced the PBS and KHN of resin composites. Pulse-delay showed the highest bond strength to dentin, as well KHN similar to the conventional method. The analysis of the failure pattern showed predominance of adhesive failure.
Department of Restorative Dentistry, Dental Materials Division, Piracicaba Dental SchoolUniversity of Campinas, Brazil. amerbc@fop.unicamp.br
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Correr
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Costa
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Correr-Sobrinho
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Guiraldo
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Sinhoreti
D003188:Composite Resins; D001840:Dental Bonding; D003799:Dental Stress Analysis; D006245:Hardness Tests; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing
D003188:Composite Resins