cosmetic dentistry_ beauty & science International Edition

I review _ ceramics _Abstract The plethora of ceramic systems available today for all types of indirect restorations can be con- fusing and overwhelming for the clinician. Having a better understanding of them is important. In this article,theauthorsuseclassificationsystemsbased onmicrostructuralcomponentsofceramicsandthe processing techniques to help illustrate the various properties. _Introduction Many different types of ceramic systems have been introduced in recent years for all types of indirect restorations, from very conservative non- preparation veneers, to multi-unit posterior fixed partialdenturesandeverythinginbetween.Under- standing all the different nuances of materials and material processing systems is overwhelming and can be confusing. This article will cover what types of ceramics are available based on a classification of the microstructural components of the ceramic. A second, simpler classification system based on how the ceramics are processed will give the main guidelines for their use. The term “ceramic” derives from the Greek “keramos”, which means “a potter or a pottery”. This word is related to a Sanskrit term meaning “burned earth”, since the basic components were claysfromtheearthheatedtoformpottery.Ceram- ics are non-metallic, inorganic materials. Ceramics refertonumerousmaterials,includingmetaloxides, borides, carbides, nitrides and complex mixtures of these materials.1 The structure of these materials is crystalline, displaying a regular periodic arrange- ment of the component atoms, and may exhibit ionic or covalent bonding. Although ceramics can be very strong, they are also extremely brittle and 26 I cosmeticdentistry 1_2014 Fig. 1_A scanning electron micrograph of the microstructure of a glass veneer porcelain. Figs. 2a & b_An anterior porcelain veneer restoration. Fig. 3_A scanning electron micrograph of the microstructure of a feldspathic veneer porcelain. Acid etching removes the glass and reveals the leucite glass. Fig. 4_A metal–ceramic restoration. (Ceramics performed by Yi-Wing Chang.) Fig. 5_A scanning electron micrograph of the microstructure of a pressable ceramic. Leucite crystals reinforce the glass. Ceramics overview: Classificationbymicrostructure and processing methods Authors_ Profs. Edward A. McLaren & Russell Giordano, USA Fig. 2a Fig. 2bFig. 1 Fig. 4 Fig. 5Fig. 3 CDE0114_26-34_McLaren 11.06.14 14:06 Seite 1