Glasses based on feldspar are extremely biocompatible. 2 Glasses in dental ceramics derive principally from a group of mined minerals called feldspar and are based on silica (silicon oxide) and alumina (aluminum oxide), hence feldspathic porcelains belong to a family called aluminosilicate glasses. The blocks are then dried over several days before sintering. A plasticized ceramic mixture is pressed and extruded through a nozzle to give its form. 1).įeldspathic ceramics are obtained by simply mixing powder and water. The two first sub-categories will be treated in the same paragraph because of their similar characteristics including their different microstructure ( Fig. Zirconium oxide and lithium silicate reinforcedĭirect CAD/CAM compatible polycristalline ceramics: Therefore, an adjusted classification can be developed from Li & all most adapted to direct CAD/CAM: Recently, zirconia, under certain conditions, can also be machined chairside to realize monolithic restorations. Today, predominantly glassy and particle-filled glasses represent almost all machinable ceramics for direct CAD/CAM. Based on their microstructure, dental ceramics fall within three basic classes 11, 12, 13, 14, 15, 16: Many classifications of ceramics were proposed and used. Inside the glassy matrix, the nature of filler would prevent the development of micro-fractures. Mechanical properties decrease with the fragile glass phase but increase with the filler content. 10 This glassy matrix permits the diffusion of light for translucency in depth. The higher the glass rate is, the greater the importance of translucency is, which will work best to imitate the properties of enamel and dentin. The glassy matrix defines the aesthetic properties of the ceramic. 10, 12 They improve mechanical properties (fillers) or stabilize polycrystalline structure (doping). It is either particles (crystal or glassy high melting point) or modified atoms, called “doping” for polycrystalline ceramic. Kelly proposes to consider ceramic as a “composite”, meaning a composition of two or more distinct entities 10, 11 formed from a matrix (glass or polycrystalline) in which are incorporated additive elements called fillers in various quantity. The objective of this article is to classify chairside CAD/CAM materials and to define their characteristics and indications. Practitioners may encounter problems choosing the right material for the clinical situation among this large range of material and the related commercial communication. Blocks are available in different size, shade, and translucence and can require a post milling treatment, which would be different according to the type of material. Nowadays, manufacturers propose more than 20 blocks for a chairside use. Metal blocks are also available, but their existence and their use are today almost anecdotal. Currently, manufacturers try to combine the advantages of these two families of materials by providing a ceramic network infiltrated with resin polymers. 6, 7 The next step was to increase the mechanical properties of these resins with the incorporation of ceramic particles. This is the resin class, much less mechanically resistant but which has the property of deforming before fracture, unlike ceramics. The idea to propose softer materials less susceptible to brittle fracture was also developed. A post-milling crystallization will be necessary to access the final shade and mechanical strength. To maintain rapid milling, some of them are offered at a pre-crystallized stage. Therefore, reinforced ceramic has been developed. 2 Then, the desire to extend the indications of CAD/CAM restorations (onlays, crowns) has driven the practitioner to work with more mechanically resistant materials. Feldspathic ceramics were well adapted for small occlusal inlays (CEREC I). Initially, materials had to be mechanically strong but also easily machinable. 3, 4 The current systems offer a three-dimensional (3-D) design program and can fabricate inlays, onlays, veneers, crowns, as well as three unit bridges and custom lithium disilicate implant abutments.
Cad cam dentistry software#
Systems have evolved through a series of software and hardware. 2 Since the 80's, different systems have been developed, such as known CEREC. The first chairside CAD/CAM 1 produced inlay was made in 1985 using a ceramic block comprising fine grain feldspathic ceramic (Vita Mark I, Vita Zahnfabrik).