Insightful Understanding of the Role of the Mechanical Properties in Defining the Reliability of All-Ceramic Dental Restorations: A Review

Since the last two decades, restorative dentistry has been witnessing an increased acceptance of the use of the well-known all-ceramic materials for the fabrication of single dental restorations, such as inlays, onlays, crowns, anterior and posterior fixed partial dentures (PFPDs). These restorations certainly offer the potential for better biocompatibility coupled with superior aesthetic qualities, especially when compared with the conventional prostheses made from porcelain that is fused with metal ceramic restorations. However, brittleness and extreme sensitivity of all-ceramic materials to micro-like defects or cracks that are inherently present, or may grow, in their microstructure during different laboratory fabrication steps, during necessary clinical adjustments, or from post-placement chewing activity, remain major shortcomings of these dental restorations. In fact, many researchers are of the opinion that the improved mechanical properties can significantly improve the lifetime of all-ceramic restorations and result in enhanced reliability. Therefore, efforts of researchers, as well as manufacturers, have been directed towards the improvement of the mechanical properties in order to overcome such limitations. This article reviews the characterization of the most important mechanical properties that can delineate the behavior of all-ceramic dental materials upon loading. These include fracture mechanics, the brittle nature of ceramics, the relationship between microstructural features and fracture behavior, sources of cracks and flaws that may initiate a fracture and the effect of different fabrication procedures and/or clinical adjustments on the mechanical behavior of dental ceramics are also reviewed and discussed.

Clinical Application of CAD/CAM Customized Zirconia Abutment in Maxillary Anterior Region

[Objectives]To explore the difference between the CAD/CAM customized zirconia abutment and the finished titanium abutment in the maxillary anterior region.[Methods]A total of 60 implants were selected from 60 patients who had undergone maxillary single anterior implant implantation in the Department of Oral and Maxillofacial Surgery,Affiliated Hospital of Qingdao University from July 2017 to July 2018.They were randomly divided into an observation group and a control group(30 patients/group).The observation group used CAD/CAM customized zirconia abutment and all-ceramic crown,while the control group used finished titanium abutment and all-ceramic crown.Twelve months after the crown restoration,mechanical complications,pink esthetic(another spelling of aesthetic)score(PES)and white esthetic score(WES),and patient satisfaction were used as clinical observation indicators to evaluate the restoration effect.[Results]For 12 months after crown restoration,the implant survival rate of the two groups of patients was 100%,and there was no abutment breakage,loosening,falling off,or screw loosening and breakage.The PES and WES of the observation group were significantly higher than those of the control group(P<0.05).The patient satisfaction of the observation group was significantly higher than those of the control group(P<0.05).[Conclusions]CAD/CAM customized zirconia abutment implant restoration in the maxillary anterior region can obtain good esthetic restoration effect in a short term,and has good clinical application effect.