CAD/CAM全瓷冠边缘适合性的评价

目的：研究采用计算机辅助设计及制作系统（Kavo Everest）制作的氧化锆全瓷冠的边缘适合性。方法：选取1颗无龋的离体前磨牙行牙体预备,双重印模法取模,翻制20个相同尺寸的超硬石膏代型,将代型随机分为2组,分别制作10个金属烤瓷冠和10个Kavo Everest氧化锆全瓷冠。然后采用双色硅橡胶印模法复制间隙模型,应用光学显微镜采集间隙图像及使用AutoCAD2006软件对其厚度进行测量。结果：利用失蜡铸造法制作的金属烤瓷冠的垂直边缘间隙（69.6±29.7）μm,水平边缘间隙（56.1±20.8）μm,绝对边缘间隙（91.1±28.8）μm;利用CAD/CAM制作的氧化锆全瓷冠的垂直边缘间隙（51.4±19.9）μm,水平边缘间隙（41.1±16.8）μm,绝对边缘间隙（66.2±21.9）μm。两种系统制作的冠的水平边缘间隙、垂直边缘间隙、绝对边缘间隙均具有显著性差异（P〈0.05）。结论：利用Kavo Everest系统制作的全瓷冠具有良好的边缘适合性。     

Effect of Two Self-Adhesive Cements on Marginal Adaptation and Strength of Esthetic Ceramic CAD/CAM Molar Crowns

Purpose: This study evaluated the effects of adhesive cements on marginal adaptation and fracture resistance of ceramic molar crowns. Materials and Methods: Seventy‐five extracted maxillary molars were selected. The occlusal morphology of 15 molars (control) was scanned and transferred to the crowns in the test groups by CAD/CAM. Sixty molars received full‐coverage crown preparations with 6‐degree axial taper, 1.0‐mm shoulder, and 2.0‐mm occlusal reduction. They were assigned to four groups, and pulpal pressure was simulated. The 15 crowns in each test group were seated with resin‐based self‐adhesive cements, Rely‐X (RX) and Multilink (MS), one multistep bonded adhesive luting composite resin, Variolink (VL), and glass‐ionomer cement, Ketac Cem (KC). Test and control molars were subjected to thermal and mechanical fatigue stress (TMS: 12,000 × 5°C to 50°C; 2.4 million × 49 N) for 18 days in a masticator. Marginal adaptation [“continuous margin%” (CM%)] of the crowns was determined by scanning electron microscopy (200×). Finally, molars were occlusally loaded until fracture in a testing machine, and fracture load (N) was recorded. Marginal adaptation and strength data were statistically analyzed. Results: TMS significantly (p < 0.001) reduced CM% in all groups. After TMS, CM% at the cement‐dentin interface was significantly (p < 0.001) higher for RX than for all other cements. At the crown‐cement interface both self‐adhesive cements MS and RX had significantly better CM% than VL (p < 0.05) and KC (p < 0.001). Fracture resistance of natural untreated molars was significantly (p < 0.001) higher than that of experimental crowns. Fracture resistance of RX cemented crowns was significantly (p < 0.05) higher than that of other crowns. Occlusal morphology significantly influenced fracture resistance (p < 0.05). Conclusions: Self‐adhesive cement RX offers a valid alternative to multistep resin‐based luting composite with respect to marginal adaptation to dentin and fracture resistance. The latter is also influenced by occlusal morphology, necessitating careful monitoring of occlusal contacts.     

CAD/CAM瓷嵌体的适合性研究

应用体视显微镜观测新型的ＣＥＲＥＣⅡ型机制作的瓷嵌体与离体人牙粘接前后的适合性。结果表明：粘接前，洞型与嵌体轴壁间隙，龈壁间隙，Ｈｅ面平均间隙５８．５μｍ；粘接后，平均边缘浮升量，粘接剂厚度在轴壁，龈壁，Ｈｅ面平均厚度８０μｍ。提示：ＣＥＲＥＣⅡ型机制作的瓷嵌体具有良好的适合性，可以满足临床的应用。     

287件 CAD/CAM二氧化锆全瓷修复体3年临床疗效观察

目的：探讨 CAD／CAM氧化锆全瓷修复体的临床疗效及失败原因。方法：对206例患者、287件 CAD／CAM氧化锆全瓷修复体进行3年前瞻性随访研究,按照美国加州牙科协会（CDA）制定的标准,通过 Kaplan-Meier 生存分析、Log-Rank 检验及卡方检验,统计累积生存率,分析修复体类型、修复牙位、基牙桩核与否等因素对全瓷修复体生存率的影响。结果：观察期内CAD／CAM二氧化锆修复体有5件发生瓷崩裂,4件出现明显牙龈炎症,3件基牙发生根尖周炎;修复体3年累积生存率为95．7％。其中单冠、联冠、固定桥的3年累积生存率分别为96．3％、93．6％、95．7％（P ＞0．05）,前牙组与后牙组的3年累积生存率分别为94．5％、96．3％（P ＞0．05）,基牙桩核组与非桩核组3年累积生存率分别为95．0％、96．1％（P ＞0．05）。结论：CAD／CAM二氧化锆修复体3年累积生存率较高,修复体类型、修复牙位及基牙桩核与否对其生存率影响均无显著性差异;瓷崩裂是最常见的失败原因。     

Intraoral Digital Impression Technique: A Review

With the techniques of computer‐aided design and computer‐aided manufacturing (CAD/CAM) being applied in the field of prosthodontics, a concept of intraoral digital impressions was put forward in the early 1980s. It has drawn comprehensive attention from dentists and has been used for dental prosthesis fabrication in a number of cases. This new digital impression technique is expected to bring about absolute digitization to the mode of prosthodontics. A few published articles have indicated that dental prostheses fabricated from intraoral digital impressions have exhibited remarkable advantages over those from conventional impressions in several respects. The present review discusses intraoral digital impression techniques in terms of the following aspects: (1) categories and principles of intraoral digital impression devices currently available; (2) operating characteristics of the devices; and (3) comparison of the manipulation, accuracy, and repeatability between intraoral digital impression and conventional impression.     

The Effects of Adhesive Type and Thickness on Stress Distribution in Molars Restored with All‐Ceramic Crowns

Purpose: This study investigated the effects of luting cement type and thickness on the stress distribution within all‐ceramic crowns using finite element analysis. Materials and Methods: An all‐ceramic crown restoration of the mandibular right first molar was prepared according to standard dental processes and scanned using micro‐computed tomography. Eight 3D FE models were then developed that accounted for two adhesive systems, each with cement thickness of 60 μm, 90 μm, 120 μm, and 150 μm. The models were subjected to four loading conditions, and stresses in the veneer and core layers were evaluated. Results: The stress distribution and maximum stresses in the veneer, core, and cement are presented in corresponding loading conditions. The cement with higher elastic modulus resulted in lower tensile stresses in the veneer and core layers, and the shear strength of the cement was critical to the intactness of the all‐ceramic crown. Conclusion: The cement thickness acts as a cushion between the crown and dentin substrate. Although there is an optimal thickness (approximately 90 μm) that can reduce the stress level in ceramic crowns, cement thickness is not very important to stresses in the core or veneer in most cases when compared to the influence of loading conditions or cement moduli.     

CAD/CAM系统中牙颌数据库的建立

目的：建立CAD／CAM系统中标准牙冠及牙列的三维数据库。方法：利用探针式扫描仪扫描全牙列28颗标准牙冠模型,处理数据,重建各牙冠的三维图形,并结合国人牙冠平均值进行校正。结果：扫描仪所测数据处理、校正后,重建了国人28颗标准牙冠的数据库以及标准牙尖交错He全牙列。结论：单个标准牙牙冠以及标准牙尖交错He全牙列数据精确可靠,为CAD／CAM系统的开发打下基础。     

数字化口腔修复（7）--CAD／CAM镜像模式的应用（附病例报告）

目的：观察CEREC?椅旁计算机辅助设计和制作（computer aided design／computer aided manufacturing, CAD／CAM）镜像模式全瓷冠修复上颌前牙的临床疗效。方法：临床病例为1颗上前牙牙体缺损的患者,经过完善的根管治疗后,采用CAD前牙镜像模式全瓷冠修复,按照改良的USPHS标准分别进行6个月和1年的临床疗效评价。结果：各个复查阶段结果表明：修复体无脱落,折断、劈裂等不良现象。临床指标均达到A级指标。结论：CAD／CAM镜像修复前牙牙体缺损是一种可行,效果良好的修复方法。     

CerecⅡ型CAD/CAM全瓷冠的初步临床研究

目的　探讨由SiemensCerecⅡ型CAD/CAM系统加工陶瓷内冠 ,经玻璃渗透和烤瓷工艺制成前磨牙全瓷冠与镍铬合金烤瓷冠的临床效果。方法　分别制作 6个全瓷冠和 6个镍铬合金烤瓷冠 ,比较修复体颜色、形态、基牙龋患率、边缘密合度、边缘着色、修复体折断情况、菌斑指数 (PI)和牙龈指数 (GI) ,随访 6个月至 1年。结果　CerecⅡ型CAD/CAM全瓷冠与金属烤瓷冠在外形基牙龋患率 ,修复体边缘密合度及折断情况 ,无统计学差异。全瓷冠在颜色 ,菌斑指数 (PI)和牙龈指数 (GI)方面优于镍铬合金烤瓷冠 (P <0 .0 1)。结论　与镍铬合金烤瓷冠相比 ,CerecⅡCAD/CAM全瓷冠颜色美观 ,近期修复效果良好 ,值得临床推广应用。     

间接印模法对CAD/CAM全瓷底层冠适合性影响

目的 研究间接法采集印模对CAD／CAM全瓷底层冠适合性的影响，为临床应用提供依据。方法 制备下颌第一前磨牙制备体10件，其中5件翻制石膏工作模型。通过Cerec 2 CAD/CAM系统摄像装置分别对制备体和模型采集印模，采用自制的MC切削陶瓷加工制作全瓷底层冠，粘结于制备体上。用体视显微镜测试适合性。结果 间接法采集印模制作的全瓷底层冠的适合性，与直接法相比无显著性差异（P＞0.05)，说明间接法采集印模对CAD／CAM全瓷底层冠的适合性无明显影响。结论 临床上用Cerec2 CAD/CAM制作全瓷底层冠时可应用间接法采集印模。