CAD/CAM Conic Crowns for Predictable Retention in Implant-Supported Prostheses
F ixed implant-supported prostheses are currently categorized as one of two types: cement-retained or screw-retained. Each has advantages and drawbacks, and the two types consequently are recommended for different purposes. Conic crowns provide an interesting alternative with advantages over both. Prostheses can be made that can be retained without cement or screws but are reversible and predictable. Since their introduction, the efficacy and advantages of conic crowns and their good long-term prognosis in prosthodontics have been shown.1 Retention depends on physical-mechanical factors such as friction between the retaining surfaces, metallic surface adherence, negative pressure, and technical characteristics of the primary and secondary structure design, such as cone angle, height, materials, and surface polishing.1-4 Conic crowns may be electroformed, using gold essentially, which affords very precise internal fitting, ‘Associate Professor, Department of Buccofacial Prostheses, College o f Dentistry, Complutense University of Madrid, Madrid, Spain. 2Full-Time Professor, Department of Buccofacial Prostheses, College of Dentistry, Complutense University of Madrid, Madrid, Spain. Correspondence to: Dr Jose L. Antonaya, Complutense University of Madrid, College of Dentistry, Ramon y Cajal Square, Madrid, Spain. Email: [email protected] ©2016 by Quintessence Publishing Co Inc. or conventionally sprued with nonprecious metals. Computer-aided design/computer-assisted manufacture (CAD/CAM) procedures allow for the use of homogenous and cheaper materials, control of many of these parameters, and the tolerance to ensure a reversible retention force.5 The aim of the present study was to explore and evaluate in vitro CAD/CAM conic crowns to obtain a reversible retention strength, possibly generate a predictive model to find the retention form cone angle and vice versa, and open a new line of research.