Metal-ceramic restorations can not fully simulate the translucency of the natural teeth due to the inclusion of metal coping or frameworks which is totally light opacity in nature. Their higher light reflectance than the natural ones results in chalky shade especially in the gingival and middle portion of the crown, which makes the restorations look artificial. Simulation of the color depth of the restoration is difficult because of fewer layers of porcelain and tooth for light reflectance, as well as absence of light transmittance in the areas of metal substrate. Since all-ceramic materials have quite similar optical properties as the natural tooth structure and can eliminate the problems associated with the metal substrate of metal-ceramic restorations, as erosion, biocompatibility and light obstruction, various all-ceramic systems are prevailing the market nowadays. Basically they can be divided into four categories which are heat-pressed glass ceramic, glass-infiltrated ceramics, densely-sintered aluminum oxide polycrystalline, and partially stabilized tetragonal zirconium oxide polycrystalline. Different material has its specific mechanical properties and clinical indications. To insure optimum long-term clinical results, critical factors, such as requirement on strength and toughness, translucency of natural teeth to be replaced, color masking capability of the material, precision of different systems and costs of the restorations, should be taken into comprehensive consideration during clinical selection of all-ceramic material for specific patients. The purpose of this article is to provide some basic knowledge on characteristics of different all-ceramic materials and some critical points on their clinical application.
