Color in Zirconia‐Based Restorations and Related Factors: A Literature Review

Zirconia ceramic is a popular trend in esthetic and restorative dentistry. Computer‐aided design/computer‐aided manufacturing (CAD/CAM) systems have been well developed to fabricate zirconia frameworks and restorations with acceptable mechanical properties. Zirconia ceramics have excellent optical characteristics; however, achieving optimal esthetic outcomes with zirconia‐based restorations is still challenging due to multiple effective factors on the final color. These factors are different layers of a zirconia‐based restoration and its underlying structures including: dental substrate, cement, zirconia coping, veneering ceramic, and glaze. Moreover, the laboratory procedure of these restorations’ fabrication is another effective factor on the resultant color. Unpredictable esthetic results may be obtained without estimation of the role of each factor and its effect on the final color. This review discussed the color aspect of zirconia‐based restorations according to these factors and based on the literature. In the past decade, investigators have been concerned with the shade reproduction with zirconia‐based restorations; however, there are no sufficient clinical guidelines on how to reproduce the appearance of natural teeth with these restorations. Zirconia‐based restorations have presented a new chance for accomplishing optimum esthetics. Nonetheless further investigations are needed on these restorations to establish clinical guidelines on esthetics.     

烤瓷修复体的选色统计

目的 通过对比色记录的统计分析,比较Vita比色板与宁波地区人群牙冠颜色的适应性及分布频率,并提出临床比色要点。方法 随机收集我院烤瓷科1290例烤瓷修复患者的原始记录,对患者的性别、修复体的位置及选色结果进行分析,并作统计学处理。结果 比色板4种色调中以选A色凋为最多,占总数的77.44％。4种色调选色与性别的关系,经统计处理,A、B、C、D色调间男女无显著差异。但A色调内男女选择有非常显著差异。结论 宁波地区人们牙冠颜色主体在红棕色区（A色调）,并分布在VITA比色板小颜色较亮部分,男性较女性选色略深。     

Microtensile Bond Strength and Impact Energy of Fracture of CAD-Veneered Zirconia Restorations

Purpose: With state-of-the-art CAD/CAM technology, the fabrication of large and complex zirconia frameworks is just a click away. On the other hand, veneering of the frameworks is still operator-dependent. The aim of this work was to evaluate CAD veneering of zirconia restorations in terms of zirconia veneer bond strength and impact energy of fracture in a step towards complete automation of the fabrication process.
Materials and Methods: A new CAD/CAM system was used to fabricate a resin replica of the esthetic ceramic required to veneer a zirconia framework. The replica was seated on the zirconia framework and further processed using press-on technology. The bond strength between zirconia and the CAD veneer was evaluated using microtensile bond strength test. The impact energy of fracture of the specimens was also investigated. Manually layered zirconia specimens served as a control (α= 0.05).
Results: There was no significant difference in the microtensile bond strength between zirconia and either of the used veneers (39 MPa). Even though the impact energy of fracture of the CAD-veneered and manually layered specimens was almost identical (0.13 J), the former demonstrated a cohesive fracture of the veneer, while the latter failed by delamination of the veneer ceramic.
Conclusion: CAD veneering is a reliable method for veneering zirconia restorations.     

Complete Arch Monolithic Zirconia Prosthesis Supported By Cobalt Chromium Metal Bar: A Clinical Report

Complete arch fixed implant supported prosthesis made of monolithic zirconia is a popular treatment option with minimal complications, as documented in the literature over a 5‐year period. One of the limitations of this material is its inability to be used when the span between adjacent implants is excessively long. A potential solution to mitigate this problem is to support the zirconia prosthesis with a metal substructure, which intrinsically has higher tensile strength. This clinical report describes the successful use of this prosthetic design in a male patient with bruxism and history of multiple implant failures in the maxilla. This resulted in a large anterior‐posterior span between the anterior implants in the maxillary lateral incisor region and the distal implants in the pterygoid region. This article also describes the use of a split file digital workflow to scan the prototype prosthesis and then digitally design and mill the screw‐retained cobalt chromium bar, as well as the overlaying of zirconia prosthesis which was retained by separate screws. This novel approach offers promise for management of the atrophic maxilla where implants with remote anchorage are used resulting in broader distribution of implants.     

氧化锆和玻璃陶瓷颜色及半透明度稳定性的体外研究

目的:研究紫外线老化对氧化锆和玻璃陶瓷的颜色及半透明度的影响.方法:制备高透氧化锆、低透氧化锆、高透玻璃陶瓷、低透玻璃陶瓷试件各12个、共48个,试件厚度(1.60±0.02)mm,利用600目金刚砂纸磨光.试件经紫外灯(波长253.7 nm,功率250 w/m2)照射0 h、12 h和24 h后,利用光谱辐射度计分别...     

粘接材料对渗透铝瓷全瓷修复体颜色的影响

目的 探讨不同粘接材料对渗透铝瓷全瓷修复体颜色的影响。方法 制作12个A2色直径12.5 mm、底层厚度0.5 mm的GI－Ⅱ渗透铝瓷试件,在其上烧结A2色1.0 mm厚的 Vitadur α饰面瓷完成渗透铝全瓷试件,并制作12个直径12.5 mm、厚2 mm的铸造Ni-Cr合金背景试件。将全瓷试件和背景试件分别用树脂粘接剂、玻璃离子粘固粉、磷酸锌粘固粉粘接,根据粘接材料的不同分为3组,每组4个。用JY9800型白度色度计测量各组粘接前、后的L*、a*、b*颜色参数。结果 粘接材料对全瓷修复体的最终颜色有一定的影响,其中树脂对修复体的颜色影响最小,磷酸锌粘固粉的影响最大,其粘接前后的色差可肉眼分辨。结论 全瓷修复体的粘接推荐使用树脂粘接剂,以减小粘接材料对全瓷修复体最终颜色的影响。     

Marginal Accuracy of Monolithic and Veneered Zirconia Crowns Fabricated by Conventional and Digital Workflows

Purpose

To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered).

Materials and Methods

A prepared maxillary first molar was used for the study. Four workflow combinations were evaluated: (1) intraoral scanning and monolithic zirconia (IOS-M), (2) intraoral scanning and veneered zirconia (IOS-V), (3) conventional impression and monolithic zirconia (IMP-M), and (4) conventional impression and veneered zirconia (IMP-V). All of the specimens had similar designs. The veneered groups had a buccal cutback for esthetic veneer application. A total of 10 crowns were produced in each workflow. The vertical and horizontal marginal accuracies were measured with a traveling microscope. Depending on the normality of the data, one-way analysis of variance test or Kruskal-Wallis test were applied to evaluate the differences among the groups (α = 0.05).

Results

The most superior vertical marginal accuracy was observed for IOS-V (mean = 22.5 μm; SD = 6.7 μm), followed by IMP-V (mean = 23.9 μm; SD = 7.8 μm), IOS-M (mean = 28.7 μm; SD = 10.3 μm), and IMP-M (mean = 39.8 μm; SD = 22.0 μm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9 μm; SD = 4.3 μm) followed by IMP-M (mean = 21.3 μm; SD = 5.7 μm), IMP-V (mean = 19.2 μm; SD = 5.3 μm) and IOS-V (mean = 17.6 μm; SD = 5.7 μm) (p < 0.001).

Conclusions

Monolithic zirconia crowns fabricated digitally had superior marginal accuracy than monolithic zirconia crowns fabricated conventionally. Esthetic buccal veneering of predominantly monolithic zirconia copings improved the vertical and horizontal marginal accuracies.