Objectives: Translucency combined with high strength is a major advantage of zirconia restorations. Also the possibility to shade zirconia turned out to be an important feature for frameworks but particularly for full contour indications. Aim of this study is to characterize the translucency of colored and uncolored zirconia materials -all claimed to be highly translucent- by their contrast ratio (CR) respectively opacity.
Methods: Fully sintered zirconia sample disks (thickness 1mm, diameter 14mm) were prepared according to manufacturer's instructions. N=5 for each group. Surfaces on both sides were finally polished with 3µm diamond suspension. Uncolored group: LP: Lava Plus zirconia (3M ESPE), HT: Crystal HT (Dental Laboratory Milling Supplies), WZ: Zenotec Bridge Translucent (Wieland), ZH: Translucent ICE (Zirkonzahn). Colored group: Zirconia materials as above with the following shading liquids: LPA3: Lava Plus A3 (3M ESPE), HTA3: Prettau A3 (Zirkonzahn), WZA3: Zr A3 (Wieland), ZHA3: Color Liquid A3 (Zirkonzahn). CR was recorded on a photospectrometer Color i7 (X-Rite Corp.). D65 lamp. Measuring mode: Remission contrast ratio. Aperture: 10mm. Specula: excluded. UV irradiation: on.
Results: CR of uncolored zirconia materials (Fig.1): LP 69.0% [0.4], HT 70.3% [1.9], WZ 70.0% [0.9], ZH 74.4% [1.3]. CR of ZH is significantly lower compared to the others. CR of colored materials (Fig. 2): LPA3 76.8% [0.2], HTA3 79.7% [1.14], WZA3 83.2% [0.2], ZHA3 88.0% [1.3]. CR values of all colored groups are significantly different to each other.
Conclusion: Within the uncolored zirconia materials differences in their translucency can be detected; as a trend between LP, HT and WZ, significantly between ZH and all others. However, since zirconia commonly is used in its colored form the detected significant differences between all colored materials are of particular relevance. So, this study gives a valuable guideline to the practitioner to select a colored zirconia material with a translucency of his choice.
Keywords: Ceramics, Color, Prostheses and Prosthodontics
See more of: Dental Materials 3: Ceramic-based Materials and Cements