Scanning Electron Microscopy Observations of Resin Luting Cement-Dentin Interfaces

Objectives: The purpose of this study was to observe the interfaces between resin luting cement and dentin with scanning electron microscopy (SEM).
Methods: Six self-adhesive luting cements (SALCs), four self-adhesive luting cements with a tooth primer (SALCPs), and six conventional luting cements (CVLCs) were used. Cured resin composite rods were bonded to bovine dentin using the luting materials in different etching modes. Half of the bonded specimens were etched with 6 mol/L of HCl solution and deproteinized by immersion in 6% NaOCl solution. The other half of the specimens were subjected to argon-ion beam etching. The thicknesses of the cement layers were measured using laser scanning microscopy, and morphological features of the interfaces were observed using SEM.
Results: None of the luting materials had cement layer thicknesses over 50 μm. Although all resin cements in etch-&-rinse mode showed a clear hybrid layer, most SALCs had a thinner and more porous hybrid layer than the SALCPs and CVLCs. All SALCPs used with primers and CVLCs showed a thin high-density layer below the primer layer in both etching modes.
Conclusions: The ultrastructure in the vicinity of the resin luting cement–dentin interface depended on materials, etching modes, and primer treatment. In this study, the thickness of the cement layer of all resin cements was within the clinically acceptable range regardless of the etching mode or primer pretreatment. Although SALCs showed no clear thin high-density layers, all CVLCs and SALCPs used with primers showed clear thin high-density layers that may be evidence of a chemical interaction between functional monomers and HAp in the dentin regardless of the etching mode.