Optical Impression Method for Fixed Prosthodontics

Abstract

Following a revision of Japanʼs medical fees in FY2014, CAD/CAM resin composite restorations for premolars that are fabricated from a block of composite resin using a computer assisted design and manufacturing system（a dental CAD/CAM device）were approved for insurance reimbursement. Later, in 2016, insurance coverage was expanded to include molars as well for patients with metal allergies caused by dental alloys, and as a result, these crowns have come into broad use in clinical application. Dental CAD/CAM devices comprise a measurement device, a design device, and a machining device. There are two kinds of measuring devices；with the conventional method, silicone rubber impression material is used, and after the impression is taken, a stone die is used to fabricate a working cast which is then scanned. With the other method, a scanner is used inside the oral cavity to directly scan the row of teeth that includes the abutment tooth（optical impression method）. In addition to these, there are numerous reports describing research in which the fixed dental prosthesis（FDP）is fabricated using only the data from the optical impression, without fabricating a working cast. When an optical impression is taken, direct optical scanning is used in the oral cavity to scan the row of teeth that includes the abutment tooth, while monitoring the scan. An advantage of this method is that the FDP can be fabricated without going through the technical process of fabricating a working cast. In this paper, recent research findings are used to present the following regarding the optical impression method used for fabricating a FDP：impression accuracy as compared with the conventional method；the accuracy of FDP and time efficiency as compared with the indirect method；and evaluations by prosthodontists and patients as well as clinical course.