Glass-ceramics dental applications

To date, glass-ceramics have been used clinically for only limited applications. These include material for filling bony defects along the lines of a bone graft (Pavek et al., 1994), reconstruction of the ossicular bones (Hughes, 1987), spine reconstruction (Yamamuro and Shimizu, 1994), and dental reconstruction (Kudo et al., 1990 Yukna et al., 2001). 

Dicor. Tradename. A castable, machineable glass-ceramic based on mica (tetra-silicic fluormica) with up to 7% added Zr02 to improve chemical durability and translucency for dental applications. (P.J. Adair, Dentsply International and Corning Glass. U.S. Pat, 4431420 1984)... 

The unique feature of DICOR dental restorations include the close match to natural teeth in both hardness and appearance. The glass-ceramic may be accurately cast using a lost-wax technique and conventional dental laboratory investment molds. The high strength and low thermal conductivity of the material provide advantages over conventional metal-ceramic systems. The application of DICOR glass-ceramics as a biomaterial in dentistry is discussed in Section 4.4.2.2. 

In the development of biocompatible and bioactive glass-ceramics for medical uses, two different types of materials must be addressed that differ in their application environment and preferred properties materials for use in implantology (medical prostheses) and materials used in restorative dentistry (dental prostheses). For reasons of clarity, the difference between the two different groups of biomaterials must be addressed at this stage. The first... 

The situation with regard to glass-ceramics for restorative dental applications is different. These materials must also fulfill the standards for biomaterial use, such as compatibility with the oral environment. Bioactivity on the surface of the dental restoration, however, must not occur. More importantly, the surface properties of the glass-ceramics, such as shade, translucency, toughness, and wear, must correspond to those of natural teeth. Even higher standards are placed on the chemical durability of the material compared with that of natural teeth, since cavities should not occur in the new glass-ceramics. 

These desired applications determine the main requirements to be fiilfilled in the development of glass-ceramics for dental applications. The main objective is to produce a new biomaterial, the properties of which correspond to those of natural teeth. The most important properties are mechanical properties, biochemical compatibility with the oral environment, and a degree of translucency, shade, opalescence, and fluorescence similar to that of natural teeth. An abrasion resistance similar to that of natural teeth must also be achieved. The new biomaterial must demonstrate higher chemical durability than natural teeth, to prevent it from being susceptible to decay. 

Two types of DICOR glass-ceramics are produced for dental applications. The first type is a castable glass-ceramic with which dental restorations are fabricated in the dental laboratory. The second type is a machinable glass-ceramic with which dental restorations are machined using CAD/CAM technology in the dental clinic. 

The success of the IPS EMPRESS glass-ceramic as a dental restorative has been proven in comprehensive clinical tests and successful application worldwide since 1991. 

Selected examples in Section 4.4.2.6.B are used to describe the processes that are suitable to achieve optimal joining of the different materials. In addition, measuring methods for evaluating the results were carried out. These glass-ceramic-metal composites for dental applications demonstrate that a multicomponent glass-ceramic and metals can be used for a variety of applications in medical and technical fields. 

The most important properties of the dentin and incisal materials are shown in Table 4-19. The coefficient of linear thermal expansion plays an important role in the optimal joining of ious types of apatite-leucite glass-ceramics and the Zr02-rich opaquer, which are applied to the different metals. Therefore, CTE of the opaquer has been included as a comparative value in Table 4-19. A comparison of CTE of glass-ceramics and of the opaquer with that of metals clearly shows that the application of the glass-ceramic to the metal framework systematically builds up compressive strain. As a result, the finished dental product demonstrates surface tension and a controlled increase in strength, ensuring retention on the substructure. 

In terms of quantity, the incisal and dentin materials comprise the largest part of the apatite-leucite glass-ceramics of the IPS d.SIGN system. Their microstructure and properties are described in Section 2.4.6. The main applications of these glass-ceramics include dental crowns and multi-unit bridges. 

Figure 4-52 Application of opal glass and opal glass-ceramic (E1-E5) in restorative dentistry (dental crown), a) scheme, b) clinical situation.

The main indication of glass-ceramic restorations by the CEREC system was the preparation of inlays and veneers crowns also were prepared. The ProCAD glass-ceramic is characterized by an improved mechanical strength and allows the application for dental posterior and anterior crowns, inlays, and onlays. ProCAD is produced by Ivoclar Vivadent AG (Liechtenstein). 

In recent yeors, there has been an increasing interest in glass-ceramic applications where optical properties are key. A parallel but unrelated trend involves the use of glass-ceramics as dental and surgical prostheses. In the optical area, the most significant properties are in the near infrared range in combination with excellent transparency. Efficient broadband luminescence in crystallites is the basis of applications such as tunable lasers and optical amplifiers, both of which can be made in both bulk and fiber form as glass-ceramics. 

BUrke H., Durschang B., Meinhardt J., and Muller G., "Nucleation and Crystal Growth Kinetics in the Zr02-Strengthened Mica Glass-Ceramic for Dental Application," Glastech Ber. Glass Set. Technol, 73 [Cl] 270-77 (1971). 

Frank M., Schweiger M., Rheinberger V., and Holand W., "High-Strength Translucent Sintered Glass-Ceramic for Dental Application," Glastech Ber. Glass Sci. TechnoL, 71C, 345-48 (1998). 

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