Associate Professor, Department of Restorative Science and Prosthodontics, The Ohio State University College of Dentistry, Columbus, Ohio.
Assistant Professor, Imam Abdulrahman Bin Faisal University, College of Dentistry, Department of Substitutive Dental Sciences, Dammam, Saudi Arabia.
J Prosthet Dent. 2018 Jul;120(1):71-78. doi: 10.1016/j.prosdent.2017.11.003. Epub 2018 Feb 6.
Veneering with porcelain may adversely affect the marginal fit of long-span computer-aided design and computer-aided manufacturing (CAD-CAM) implant-supported fixed prostheses. Moreover, data regarding the precision of fit of CAD-CAM-fabricated implant-supported complete zirconia fixed dental prostheses (FDPs) before and after porcelain layering are limited.
The purpose of this in vitro study was to evaluate the effect of porcelain layering on the marginal fit of CAD-CAM-fabricated complete-arch implant-supported, screw-retained FDPs with presintered zirconia frameworks compared with titanium.
An autopolymerizing acrylic resin-fixed complete denture framework prototype was fabricated on an edentulous typodont master model (all-on-4 concept; Nobel Biocare) with 2 straight in the anterior and 2 distally tilted internal-hexagon dental implants in the posterior with multiunit abutments bilaterally in canine and first molar locations. A 3-dimensional (3D) laser scanner (S600 ARTI; Zirkonzahn) was used to digitize the prototype and the master model by using scan bodies to generate a virtual 3D CAD framework. Five presintered zirconia (ICE Zirkon Translucent - 95H16; Zirkonzahn) and 5 titanium (Titan 5 - 95H14; Zirkonzahn) frameworks were fabricated using the CAM milling unit (M1 Wet Heavy Metal Milling Unit; Zirkonzahn).The 1-screw test was applied by fixing the frameworks at the location of the maxillary left first molar abutment, and an industrial computed tomography (CT) scanner (XT H 225 - Basic Configuration; Nikon) was used to scan the framework-model complex to evaluate the passive fit of the frameworks on the master model. The scanned data were transported in standard tessellation language (STL) from Volume Graphics analysis software to PolyWorks analysis software by using the maximum-fit algorithm to fit scanned planes in order to mimic the mating surfaces in the best way. 3D virtual assessment of the marginal fit was performed at the abutment-framework interface at the maxillary right canine (gap 3) and right first molar (gap 4) abutments without prosthetic screws. The facial or buccal aspects of the teeth on frameworks were layered with corresponding porcelain (Initial Dental Ceramic System; GC) and CT-scanned again using the same protocol. Marginal fit measurements were made for 4 groups: titanium (Ti) (control), porcelain-layered titanium (Ti-P) (control), zirconia (Zir), and porcelain-layered zirconia (Zir-P). 3D discrepancy mean values were computed and calculated, and the results were analyzed with a repeated measures 3-way ANOVA using the maximum likelihood estimation method and Bonferroni adjustments for selected pairwise comparison t-tests (α=.05).
The 3D fit was measured at gap 3 and gap 4. Statistically significant differences in mean 3D discrepancies were observed between Zir-P (175 μm) and Zir (89 μm) and between Zir-P and Ti-P (71 μm) (P<.001).
Porcelain layering had a significant effect on the marginal fit of CAD-CAM-fabricated complete-arch implant-supported, screw-retained FDPs with partially sintered zirconia frameworks. 3D marginal discrepancy mean values for all groups were within clinically acceptable limits (<120 μm), except for the layered zirconia framework.
瓷贴面可能会对长跨度计算机辅助设计和计算机辅助制造（CAD-CAM）种植体支持的固定修复体的边缘拟合产生不利影响。此外，关于 CAD-CAM 制造的种植体支持全锆固定义齿修复体（FDP）在分层瓷之前和之后的拟合精度的数据有限。
本体外研究的目的是评估在 CAD-CAM 制造的全弓种植体支持、螺丝固位 FDP 上分层瓷对边缘拟合的影响，这些 FDP 具有预烧结氧化锆框架，与钛相比。
在前牙有 2 个直的和后牙有 2 个远中倾斜的内部六方种植体的无牙颌模型（诺贝尔生物医学公司的 All-on-4 概念）的模型上制作了自聚合丙烯酸树脂固定全口义齿框架原型，双侧犬牙和第一磨牙位置有多个单元基台。使用三维（3D）激光扫描仪（S600 ARTI；Zirkonzahn）通过扫描体对原型和模型进行数字化，以生成虚拟的 3D CAD 框架。使用 CAM 铣床单元（M1 湿重金属铣床单元；Zirkonzahn）制造了 5 个预烧结氧化锆（ICE Zirkon 半透明-95H16；Zirkonzahn）和 5 个钛（Titan 5-95H14；Zirkonzahn）框架。通过将框架固定在上颌左侧第一磨牙基台的位置来应用单螺钉测试，并使用工业计算机断层扫描（CT）扫描仪（XT H 225-基本配置；尼康）扫描框架-模型复合物，以评估框架在模型上的被动拟合。使用 PolyWorks 分析软件将扫描数据从 Volume Graphics 分析软件以标准曲面语言（STL）传输，使用最大拟合算法拟合扫描平面，以最佳方式模拟配合表面。在无修复螺丝的上颌右侧犬牙（间隙 3）和右侧第一磨牙（间隙 4）基牙的牙冠-框架界面进行 3D 虚拟边缘拟合评估。在框架的牙齿的颊面或唇面用相应的瓷（初始牙科陶瓷系统；GC）分层，并再次使用相同的协议进行 CT 扫描。对 4 组进行了边缘拟合测量：钛（Ti）（对照）、分层钛（Ti-P）（对照）、氧化锆（Zir）和分层氧化锆（Zir-P）。计算并计算了 3D 差异的平均值，并使用最大似然估计法和 Bonferroni 调整进行重复测量 3 向方差分析，对选定的配对比较 t 检验进行了分析（α=.05）。
在间隙 3 和间隙 4 处测量了 3D 拟合。在 Zir-P（175μm）和 Zir（89μm）以及 Zir-P 和 Ti-P（71μm）之间观察到 3D 差异均值的统计学显著差异（P<.001）。
瓷贴面对部分烧结氧化锆框架 CAD-CAM 制造的全弓种植体支持、螺丝固位 FDP 的边缘拟合有显著影响。所有组的 3D 边缘差异均值均在临床可接受范围内（<120μm），除了分层氧化锆框架。
