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Aust Dent J. 2012 Sep;57(3):319-24. doi: 10.1111/j.1834-7819.2012.01704.x. Epub 2012 Jun 24.

Relationship between composite fracture toughness and bond strengths to enamel and dentine.

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Melbourne Dental School, The University of Melbourne, Victoria, Australia.



This study aimed to evaluate the association between the fracture toughness of two nanofilled-hybrid resin composites (Clearfil Majesty Esthetic [CME], Kuraray Medical, Japan; Estelite Σ [ES], Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self-etching primer system (Clearfil SE Bond [CSE]; Kuraray).


Twenty-four permanent human molars were sectioned into enamel and dentine specimens and finished with 600-grit silicon carbide paper, bonded with CSE and either CME or ES, for μ-shear bond strength (μSBS) and μ-tensile bond strength (μTBS). The specimens were tested until failure at a cross-head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using independent samples t-tests. Eight single-notched bar-shaped specimens, 30 mm × 5.2 mm × 2.2 mm, were prepared for each resin composite and fracture toughness measured using four-point bending at a cross-head speed of 0.5 mm/min. Results were analysed using independent samples t-tests.


For μSBS and μTBS, there was no significant difference between the resin composites for enamel or dentine. The fracture toughness of CME was significantly higher than that of ES.


For both enamel and dentine, resin composite fracture toughness affected neither μTBS nor μSBS to enamel or dentine.

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