Effect of viscosity of dual-cure luting resin composite core materials on bond strength to fiber posts with various surface treatments

Background/purposeThe objective of this study was to evaluate the viscosity of two dual-cure resin composite core materials and their bond strength to fiber posts treated with various surface treatments.Materials and methodsViscosity at 60–90 seconds after mixing two resin composite core materials, Clearfil DC Core (DC) and Build-It FR (BI), was tested by a rheometer. Eighteen fiber posts (FibreKor) were divided into three groups according to the following post surface treatments: (1) no surface treatment; (2) application of silane coupling agent (Silane); and (3) application of silane followed by Bond-1 adhesive resin (Silane + Bond-1). Treated posts were cemented into artificial post spaces using DC or BI. After 24-hour storage, each specimen was serially sliced into 12 beams for a microtensile bond strength test. The data were divided into upper, middle, and bottom regions, and statistically analyzed (α = 0.05). Failure modes were observed using a scanning electron microscope.ResultsThe viscosity of BI at 60 seconds after mixing was lower than that of DC. Bond strengths were found to be affected by luting resin composites, surface treatment, and region. For DC, bond strength was significantly improved in the group of Silane + Bond-1 (P < 0.05). For BI, application of Silane significantly improved bond strength (P < 0.05), but application of Silane + Bond-1 had no advantageous effect on it.ConclusionBond strengths between luting resin composites and fiber posts were affected by post surface treatments, depending on the resin composite used. Application of a low-viscosity adhesive resin to the post surface seemed to be beneficial for a high-viscosity luting resin composite.