Tecnica De Estratificacion

Departments Digital Dentistry
Dental Impressions Using 3D Digital Scanners: Virtual Becomes Reality

by Nathan S. Birnbaum, DDS; Heidi B. Aaronson, DMD Abstract The technologies that have made the use of three-dimensional (3D) digital scanners an integral part of many industries for decades have been improved and refined for application to dentistry. Since the introduction of the first dentalimpressioning digital scanner in the 1980s, development engineers at a number of companies have enhanced the technologies and created in-office scanners that are increasingly user-friendly and able to produce precisely fitting dental restorations. These systems are capable of capturing 3D virtual images of tooth preparations, from which restorations may be fabricated directly (ie, CAD/CAM systems)or fabricated indirectly (ie, dedicated impression scanning systems for the creation of accurate master models). The use of these products is increasing rapidly around the world and presents a paradigm shift in the way in which dental impressions are made. Several of the leading 3D dental digital scanning systems are presented and discussed in this article. The Concept of Impression Making Themost critical step in the process of fabricating precisely fitting fixed or removable dental prostheses is the capture of an accurate impression of prepared or unprepared teeth, dental implants, edentulous ridges, or intraoral landmarks or defects. Unless a wax or resin pattern is made directly on the teeth, on the edentulous ridges, or in the defects, which is a time-consuming and generallyimpractical effort, the dentist or auxiliary must achieve an exact duplication of the site so that a laboratory technician, usually at a remote location, can create the restoration on a precise replica of the target site. Traditionally, the paradigm for transferring the necessary information from the patient’s oral cavity to the technician’s laboratory bench has been to obtain an accurate negative of thetarget site, from which the technician is able to fabricate an accurate gypsum positive duplicating the original intraoral situation. The advent of highly innovative and accurate impressioning systems based on new technologies has created a paradigm shift in the concept for impression making. These systems are poised to revolutionize the way in which dental professionals already are and willcontinue making impressions for indirect restorative dentistry. From Bites to Bytes: A Brief History of Impressioning in Dentistry Impression making for restorative dentistry is a relatively recent concept in the millennia-old history of restorative dentistry. The earliest physical proof or record of prosthetic treatment to replace missing teeth goes back to Etruscan times, approximately 700 bc inwhich teeth were carved from ivory and bone and affixed to adjacent teeth with gold wires. It was not until 1856, when Dr. Charles Stent perfected an impression material for use in the fabrication of the device that bears his name for the correction of oral deformities, that documentation exists of the use of an impression material other than beeswax or plaster of Paris, which had inherent problems,respectively, of distortion or difficulty of use, for creating an oral prosthesis.1 The first use of an elastomeric material for capturing impressions of tooth preparations, as well as other oral and dental conditions, was not until 1937, when Sears introduced agar as an impression material for crown preparations.2 In the mere 71 years that elastic impression materials have been in use, numerousformulations have been developed, all of which have exhibited particular shortcomings in the goal of obtaining precise reproduction of the oral structures. The reversible hydrocolloid agar and the irreversible hydrocolloid alginate exhibit poor dimensional stability because of the imbibition or loss of water, respectively, when sitting in wet or dry conditions, as well as in having low tear...