Correlative analysis of cement-dentin interfaces using an interfacial fracture toughness and micro-tensile bond strength approach

- Bond strength of composite cements to dentin was evaluated both by iFT and μTBS.
- μTBS appeared more discriminative than iFT for bonding effectiveness of cements to dentin.
- Correlation between iFT and μTBS was moderate and not significant.
- The etch-and-rinse and 'universal' self-etch composite cements performed best in both tests.

ObjectivesTo determine the interfacial fracture toughness (iFT) and micro-tensile strength (μTBS) of composite cements bonded to dentin.MethodsFifty feldspar ceramic blocks (Vita Mark II, Vita Zahnfabrik) were luted onto dentin using two self-adhesive (G-CEM LinkAce, GC; SpeedCEM, Ivoclar Vivadent), two self-etch (Multilink Primer & Multilink Automix, Ivoclar Vivadent; Scotchbond Universal & RelyX Ultimate, 3 M ESPE), and one etch-and-rinse (Excite F DSC & Variolink II, Ivoclar Vivadent) composite cement (n = 10). After 48 h in 100% relative humidity at 37 °C, one half of each tooth was sectioned in sticks with a chevron notch at the cement-dentin interface and tested in a 4-point bending test setup (iFT). The remaining half of the tooth was sectioned in micro-specimens and stressed in tension until failure (μTBS). The mode of failure was determined with a stereomicroscope at 50× magnification. Data were submitted to Weibull analysis and Pearson's correlation (α = 0.05).ResultsAt 10% probability of failure, no significant differences could be found using iFT, while the etch-and-rinse composite cement Variolink II presented a significantly higher μTBS at this level. At 63.2% probability of failure, the self-adhesive composite cement G-CEM LinkAce revealed a significantly lower μTBS and iFT, and the self-etch cement Multilink Automix also revealed a significantly lower μTBS than all other cements. The correlation found between iFT and μTBS was moderate and not significant (r2 = 0.618, p = 0.11).SignificanceOverall, the etch-and-rinse and 'universal' self-etch composite cements performed best. The micro-tensile bond strength and interfacial fracture toughness tests did not correlate well.

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