Lee Culp, CDT and Edward A. McLaren, DDS, MDC
Abstract: As dentistry continues to evolve, new technologies and materials are continually being offered to the dental profession. Throughout the years restorative trends and techniques have come and gone. Some material developments have transformed the face of esthetic dentistry, while other initial concepts have already phased out and disappeared. Today, all-ceramic restorations continue to grow in the area of restorative dentistry,from pressed-ceramic techniques and materials to the growing use of zirconia,and new materials that can be created from CAD/CAM technology. This article will explore new uses for the all-ceramic material known as lithium disilicate, and the use of a digital format to design and process this material in new and exciting ways. An overview of the material as well as unique clinical procedures will be presented.
Embracing proven alternative solutions and transforming traditional methods can be challenging to dental restorative teams facing increasing patient demands while being tasked to deliver high-strength restorative options without compromising esthetic outcomes. Traditionally, dental professionals have used a high-strength core material made of either a cast-metal framework or an oxide-based ceramic (such as zirconia or alumina). This approach has two disadvantages.
Compared with glass-ceramic materials, the substructure material has high value and increased opacity but may not be esthetically pleasing.1 This is especially an issue in conservative tooth preparation when the core material will be close to the restoration’s exterior surface.
The other problem is that although the high-strength material has great mechanical properties, the layering ceramic with which it is veneered exhibits a much lower flexural strength and fracture toughness.2,3 The zirconia core (with a 900 MPa to 1000 MPa flexural strength) is less than half of the cross-sectional width of a restoration; it must be completed with a veneering material with a flexural strength in the range of 80 MPa to 110
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MPa range (depending on delivery method).4 The veneering material tends to chip or fracture during function. Also, such restorations depend significantly on the ability to create a strong bond interface between the dissimilar materials of oxide-ceramic and silica-based glass-ceramic, a bond that is not difficult to create.5 However, the quality of the bond interface can vary substantially because of cleanliness of the bond surface, furnace calibration, user experience, and other issues.
