Statement of problem
A new CAD/CAM material, called Resin Nano Ceramic (RNC) is not a resin or composite and also not a pure ceramic. It is formulated using silica and zirconia nanomer fillers by weight of 80% which provide excellent strength, fracture and wear resistance properties. At present, the studies on bond strength and surface treatment of new RNC materials are difficult to find.
Purpose
The aims of this study were to evaluate the influence of different surface treatment methods on the bond strength of resin cement to RNC using microtensile bond strength (μTBS) test and to analyse the change of the surface by micromorphologic testing methods.
Materials and methods
RNC onlays (Lava™ Ultimate, 3M ESPE, Saint Paul, MN, USA) (n=30) were treated using air abrasion with and without universal adhesive or HF etching followed by universal adhesive with and without silane coupling agent or tribological silica coating with and without universal adhesive and divided into 6 groups. Onlays were luted with a resin cement to dentin surfaces. μTBS test was performed and evaluated by one-way ANOVA and Tukey HSD. Nano scratch test, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy were used for micromorphologic analysis. The roughness and elemental proportion were evaluated by Kruskal-Wallis test and Mann-Whitney U test.
Results
Tribological silica coating showed the highest roughness, followed by air abrasion and HF etching. After HF etching, the RNC surface presented decrease of oxygen, silicon and zirconium ratio with increase of carbon ratio. Air abrasion with universal adhesive showed the highest bond strength followed by tribological silica coating with universal adhesive. HF etching with universal adhesive showed the lowest bond strength .
Conclusion
Air abrasion and tribological silica coating showed the highest resin bond strength to RNC and roughness. Application of universal adhesive to RNC surface resulted in increase the resin bond strength. In spite of using universal adhesive, HF etching showed lower bond strength and insufficient surface roughness.