Purpose: To investigate the effects of nanozirconia fillers conditioned with 10-methacryloyloxydecyl dihydrogen phosphate (MDP) with or without zirconium hydroxide precoating on bending strength, Vickers hardness, and translucence of dental resin composites. Methods: We obtained nanozirconia fillers coated with different concentrations of Zr(OH) 4 using wet-chemical synthesis. We analyzed coating quality by observing electron-diffraction patterns using transmission electron microscopy. We conditioned zirconia fillers, with or without prior Zr(OH) 4-coating, using MDP-containing primers and evaluated the formation of chemical bonds using nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). We then performed three-point bending-strength tests, Weibull analysis, Vickers hardness, and translucence-parameter analysis with or without addition of different concentrations of zirconia using untreated zirconia fillers as controls. Results: We achieved desirable Zr(OH) 4 coating using 5 mmol/L zirconium chloride. NMR and XPS analysis detected stronger Zr-O-P peaks on MDP-conditioned zirconia fillers with prior Zr(OH) 4-coating compared with MDP-conditioned fillers alone, suggesting that MDP bonding with zirconia was enhanced by zirconium hydroxide. Our three-point bending-strength tests revealed that increasing levels of untreated zirconia fillers decreased the three-point bending strength of the resin composites, while MDP-conditioned zirconia fillers with or without prior Zr(OH) 4 coating improved three-point bending strengths. Adding 5 wt% and 7.5 wt% MDP-conditioned zirconia fillers with prior Zr(OH) 4 coating achieved the highest three-point bending strength. Furthermore, addition of zirconia fillers decreased the translucence of silica-based resin composites. Conclusion: MDP conditioning with prior Zr(OH) 4 coating is recommended for treating nanozirconia fillers of resin composites.

PURPOSEThe aim was to study the masking ability of high-translucency monolithic zirconia and provide guidance in selecting resin luting cements in order to mask discolored substrates.MATERIALS AND METHODS160 high-translucency zirconia specimens were divided into 32 groups depending on their thickness and shades. Using five shades of try-in paste, the specimens were luted onto the sub strates (Co-Cr, precious-metal, opaque porcelain-sintered Co-Cr, opaque porcelain-sintered precious-metal, and 5M3-shade zirconia). All CIELAB color parameters were measured and statistically analyzed.RESULTSZirconia shade and thickness and try-in paste shade affected CIELAB color parameters (P=.000) in different substrates groups, and there were interactions among these factors (P=.000). All five try-in paste shades can be chosen to achieve ΔE values of zirconia with 1.2 – 1.5 mm for masking dark-tooth-like 5M3-shade and zirconia with 1.5 mm for masking precious-metal groups < 2.6. Only suitable try-in paste shades were used, can ΔE values that less than 2.6 be achieved when applied translucent monolithic zirconia with 0.7–1.0 mm for masking dark-tooth-like 5M3-shade and zirconia with 0.7 – 1.2 mm for masking precious-metal groups.CONCLUSIONChoosing suitable resin cement shades is necessary for high-translucency monolithic zirconia to achieve ideal masking ability (ΔE < 2.6) on the dark-tooth.

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