The concept of computer-aided design/computer aided manufacturing(CAD/CAM) was first mentioned decades ago in the field of dentistry.The technology to make dental restorations has found wide application recently and developed rapidly in prosthodontics and oral implantology,for it could save patients’ time and manpower,have precision on prostheses’ edging,etc.Until now there are several commercial CAD/CAM systems on market.With the use of CAD/CAM technology in dentistry,it has broken the traditional pattern of making dentures manually.Meanwhile,it brings opportunity for material science.The machinable/milled materials in dentistry should have not only excellent biocompatibility,but also machining and physical properties.Both of them are important.Nowadays,a great number of blocks are made from feldspar ceramics,glass-ceramics,alumina oxide,zirconium oxide,titanium,composite materials,wax and so on.Lots of researchers have had their focus on metal-free materials,because it can make the restorations look more natural and not show the inside metal color.However,strength like feldspar ceramics has its own disadvantages.It has strict indications,otherwise the restoration may fail.The technique called In-Ceram has been used long time ago.It also has long clinical experience and excellent long-term prognosis.People have explored this technique in CAD/CAM restorations.Studies have manifested that it can be utilized this way.At first,alumina was milled with pores;then,glass was infiltrated to the milled material.After zirconia had its success used in orthopedics,it became more and more popular to investigate whether this stuff was suitable in dentistry or not.Luckily,it has been proved adaptable for making single crown in posterior area,fixed partial dentures,in particular,and milling it using CAM equipment,due to the partially sintered block’s hardness like chalk.Several milled polymer materials are made for temporary crowns or bridges.In recent years,because of the phenomenon about microleakage of the direct fillin
