Dental impression

A dental impression is a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (or cast) can be formed. They are made by using a container which is designed to roughly fit over the dental arches ("trays"). Impression materials are designed to be liquid or semi-solid when first mixed and placed in the tray, and then quickly set to a solid (usually a few minutes depending upon the material), leaving an imprint of the structures in the mouth. Impressions, and the study models which are cast from them, are used in several areas of dentistry including prosthodontics (such as making dentures, inlays and plastic casts), orthodontics, restorative dentistry (e.g. to make impressions of teeth which have been prepared to receive indirect extracoronal restorations such as crowns or bridges), maxillofacial prosthetics (prosthetic rehabilitation of intra-oral and extra-oral defects due to trauma, congenital defects, and surgical resection of tumors) restorative, diagnosis and oral and maxillofacial surgery for both intra oral and or extra-oral aims (e.g. dental implants).