Bonding of contemporary glass ionomer cements to dentin

Objective: The objective of this study was to investigate the microtensile bond strength (μTBS) of contemporary glass ionomer cements (GIC) to sound coronal dentin. Methods: Three specimen teeth were prepared for each material tested: Fuji IX GP (GC), ChemFlex (Dentsply) and Ketac-Molar Aplicap (ESPE). GIC buildups were made according to the manufacturers’ instructions. After being stored at 37°C, 100% humidity for 24 h, the teeth were vertically sectioned into 1×1 mm beams for μTBS evaluation. Representative fractured beams were prepared for scanning (SEM) and transmission electron microscopic (TEM) examination. Results: Results of the μTBS test were: Fuji IX GP (12.4±8.6 MPa), ChemFlex (15.0±9.3 MPa) and Ketac-Molar Aplicap (11.4±7.7 MPa). One-way ANOVA and a multiple comparison test showed that ChemFlex had a statistically higher μTBS (p<0.05). SEM fractographic analysis showed that the predominant failure modes were interfacial and mixed failures. The GIC side of the fractured beams revealed dehydration cracks, a high level of porosity, and voids with an eggshell-like crust. TEM analysis of the demineralized dentin sides of the fractured beams revealed the presence of an intermediate layer along the GIC–dentin interface. This zone was present on the fractured dentin surface in the case of interfacial failure, and beneath GIC remnants in specimens that exhibited a mixed failure mode. Significance: The findings suggest that the bonding of GIC to dentin is not weak and that the μTBS values probably represent the weak yield strengths of GICs under tension.