Principles of crystal phase formation in Ivoclar Vivadent glass-ceramics for dental restorations

This article describes the main principles that are involved in the development of glass-ceramics for restorative dental products. These principles include the controlled nucleation and crystallization of crystal phases in glass-ceramics. The aim of these liquid-to-solid state reactions is to produce glass-ceramics with different crystal phases, such as lithium disilicate, which feature special microstructures and crystal phase contents in order to influence the properties of the resulting material. Two fundamentally different nucleation and crystallization mechanisms have been identified in this respect: firstly, internal nucleation and crystallization by heterogeneous, amorphous or nano-crystalline phases to precipitate, e.g. lithium disilicate (Li2Si2O5) and secondly, surface nucleation and crystallization by means of controlled surface activation to precipitate, e.g. leucite (KAlSi2O6). The authors show methods for developing also glass-ceramics of fluorapatite type (Ca5(PO4)3F) and glass-ceramics with high ZrO2 content. The use of the principles mentioned allows Ivoclar Vivadent AG to develop glass-ceramics with e.g. high mechanical strength, chemical durability and good optical properties, which are suitable for use in restorative dentistry. Metal-free and metal-supported dental restorations such as crowns, inlays, veneers and bridges are presented as examples of typical applications.