cosmetic dentistry_ beauty & science

_Abstract All imaginable types of materials and tech- niques, from very conservative ceramic restora- tions to very complex restorations of either metal or high-strength crystalline ceramics veneered with porcelain, have been introduced and tried over the years, with varying levels of success. Un- fortunately, there is considerable misinformation, and a general lack of published rational treatment planningguidelines,aboutwhentousetheceram- icsavailableindentistry.Thisarticleprovidesread- ers with a systematic process for treatment plan- ning with ceramic materials. Specific guidelines are outlined for the appropriate clinical conditions for using the various ceramic materials available. _Introduction Many types of ceramic materials and process- ing techniques have been introduced throughout the years. As early as 1903, Charles Land patented all-ceramic restorations, using fired porcelains for inlays, onlays and crowns.1 Insufficient under- standing of material requirements for survival in the oral environment, poor ceramic processing techniques, and the inability of adhesive cemen- tation led to early catastrophic failure. Since then, all imaginable varieties of materials and tech- niques, from very conservative ceramic restora- tions to very complex porcelain veneered of either metal or high-strength crystalline ceramics, have been introduced and tried with varying levels of success.2 The authors have previously published two detailed descriptions of, or classification sys- tems for, ceramics used in dentistry, one based on the microstructure of the material and the second on the way in which the material is processed.3 There is considerable misinformation and a general lack of rational treatment planning guide- lines published regarding the use of different ce- ramics in dentistry. The literature is replete with various accounts of clinical success and failures of all types of dental treatments. Sadowsky4 pub- lished a review of the literature covering treat- ment considerations using aesthetic materials, for example whether to use amalgam or composite and the success rates of different treatments. No recent literature could be found presenting a thorough discussion of when to use the various ceramics,forexamplewhenfeldspathicporcelains should be used, when either pressed or machined glass-ceramics are appropriate, when different types of glass-ceramics should be employed, whenahigh-strengthall-ceramiccrownsystemof either alumina or zirconia is ideal, and when metal ceramics are suitable. This article provides a systematic stepwise process for treatment planning with ceramic materials and presents specific guidelines for the appropriate clinical conditions for applications of the various systems. 06 I I review _ ceramics cosmeticdentistry 2_2013 Fig. 1_Image of prepared tooth: Significant dentine is exposed along the proposed length, flexure and tensile stress risk is at least medium, and the restoration thickness would be at least 0.9 mm. This was noted in the chart. Fig. 2_Image demonstrating excessive enamel crazing, leakage, and staining. Flexure, tensile, and shear sheer risk would be medium to high. The substrate would depend on preparation. Fig. 3_Image demonstrating deep overbite in which shear and tensile stresses would be at least medium. Bonded porcelain would require maintenance of enamel and an occlusal strategy to reduce leverage on the teeth. Ceramics: Rationale for material selection Authors_Prof. Edward A. McLaren & Yair Y. Whiteman, USA Fig. 1 Fig. 2 Fig. 3