prostheses (mainly dentures) are sometimes considered a form of indirect dental restoration, as they are made to replace missing teeth. There are numerous types of precision attachments (also known as combined restorations) to aid removable prosthetic attachment to teeth, including magnets, clips, hooks, and implants which may themselves be seen as a form of dental restoration. The CEREC method is a chairside CAD/CAM restorative procedure. An optical impression of the prepared tooth is taken using a camera. Next, the specific software takes the digital picture and converts it into a 3D virtual model on the computer screen. A ceramic block that matches the tooth shade is placed in the milling machine. An all-ceramic, tooth-colored restoration is finished and ready to bond in place. Another fabrication method is to import STL and native dental CAD files into CAD/CAM software products that guide the user through the manufacturing process. The software can select the tools, machining sequences and cutting conditions optimized for particular types of materials, such as titanium and zirconium, and for particular prostheses, such as copings and bridges. In some cases, the intricate nature of some implants requires the use of 5-axis machining methods to reach every part of the job. Cavity classifications Greene Vardiman Black classification: G.V. Black classified the cavities depending on their site: Class I Caries affecting pit and fissure, on occlusal, buccal, and lingual surfaces of molars and premolars, and palatal of maxillary incisors. Class II Caries affecting proximal surfaces of molars and premolars. Class III Caries affecting proximal surfaces of centrals, laterals, and cuspids. Class IV Caries affecting proximal including incisal edges of anterior teeth. Class V Caries affecting gingival 1/3 of facial or lingual surfaces of anterior or posterior teeth. Class VI Caries affecting cusp tips of molars, premolars, and cuspids. Graham J. Mount's classification: Mount classified cavities depending on their site and size. The proposed classification was designed to simplify the identification of lesions and to define their complexity as they enlarge. Site: Pit/Fissure: 1 Contact area: 2 Cervical: 3 Size: Minimal: 1 Moderate: 2 Enlarged: 3 Extensive: 4 Materials used Alloys The following casting alloys are mostly used for making crowns, bridges and dentures. Titanium, usually commercially pure but sometimes a 90% alloy, is used as the anchor for dental implants as it is biocompatible and can integrate into bone. Precious metallic alloys gold (high purity: 99.7%) gold alloys (with high gold