Zirconia in Restorative Dentistry: A Review V.M. Mohammed Sagir, 1 Biju P. Babu, 2 Kennet J. Chirayath, 3 Jones Mathias, 4 Renjith Babu 5 Introduction Biomaterials by definition are inorganic compounds that are designed to replace a part or a function of the human body in a safe, reliable, economic, and physiologically and aesthetically acceptable manner (Hench and Ethridge, 1982) [1] . One of the important properties of biomaterials is their so-called biocompatibility [2] . BIOCERAMICS The class of ceramics used for repair and replacement of diseased and damaged parts of musculoskeletal systems are termed bioceramics. In numerous applications, a bioceramic may be in contact with hard tissues at one portion of the surface, such as the root of the tooth implant, and also be in contact with soft tissues, such as the gingival tissues, in the same implant site. The attachment of prosthetic implant materials is also an important application of bioceramics .[3,4] ZIRCONIA Zircon has been known as a gem from ancient times. The name of the metal, zirconium, comes from the Arabic Zargon (golden in colour) which in turn comes from the two Persian words Zar (Gold) and Gun (Colour). Zirconia, the metal dioxide (ZrO2), was identified as such in 1789 by the German chemist Martin Heinrich Klaproth in the reaction product obtained after heating some gems, and was used for a long time blended with rare earth oxides as pigment for ceramics [5] .Zirconia is a bio-inert ceramic material with high mechanical properties and fracture toughness. The R&D on zirconia as a biomaterial was started in the late sixties. The first paper concerning biomedical application of zirconia was published in 1969 by Helmer and Driskell [6] , while the first paper concerning the use of zirconia to manufacture ball IJCDS • AUGUST, 2011 • 2(3) © 2011 Int. Journal of Clinical Dental Science ABOUT THE AUTHORS 1.Dr. V.M. Mohammed Sagir M.D.S., Professor & Head, Royal Dental College, Chalissery, Palakkad Dt. 2.Dr. Biju P. Babu M.D.S., Reader, Royal Dental College, Chalissery, Palakkad Dt. 3.Dr. Kennet J. Chirayath M.D.S., Reader, Royal Dental College, Chalissery, Palakkad Dt. 4.Dr. Jones Mathias M.D.S., Senior Lecturer, Royal Dental College, Chalissery, Palakkad Dt. 5.Dr. Renjith Babu M.D.S., Senior Lecturer, Rajas Dental College, Kavalkinaru, Nagercoil. Corresponding Author: Dr. V.M. Mohammed Sagir Professor and Head Department of Conservative dentistry and Endodontics; Royal Dental College, Iron Hills, Chalissery, Palakkad, Kerala, India - 679536. Abstract The demand for metal free restorations in dental practice has increased mainly due to the strong esthetic demand and concern about metallic hypersensitivity. Zirconia as a bio-material has advantages over other ceramics because of its high mechanical strength and fracture toughness. These advantages are due to the transformation toughening mechanisms operating in their microstructure that can be manifested in components made out of them. The present article showcases the material properties and fabrication of zirconia and highlights on the biological safety and clinical implications. KEYWORDS: Zirconia, Biomaterial, Transformation Toughening, Restorative Dentistry REVIEW 1