The use of zirconia, that is, zirconium dioxide (ZrO2), as a biomaterial in biomedicine started in the early 1980s. Since then, a growing number of laboratory and clinical studies has been conducted on this special ceramics to assess its unique characteristics. Moreover, zirconia has manifested its extraordinary advantages when used in dental clinical practice since the late 1990s, such as its prominent biocompatibility, satisfactory esthetical performance, and outstanding biomechanical properties. With the development of fabrication methods and more extensive knowledge of this material, zirconia has been employed in more and more dental restorations. Examples are single-crown and root canal posts to long-span fixed dentures and, recently, its use as a subgingival implant material. We discuss among others also alumina (Al2O3) as a biomaterial, zirconium metal, and tissue reactions to zirconia.