CAD/CAM Conic Crowns for Predictable Retention in Implant-Supported Prostheses.

PURPOSE To evaluate CAD/CAM conic crowns to obtain a reversible and predictable retention in implant-supported prostheses. MATERIALS AND METHODS Five 1- to 8-degree CAD/CAM abutments and their respective copings (n = 40) were designed and manufactured to measure the retention strength (in N) on a Zwick/Roell testing frame. RESULTS The mean retention strength values found, in descending order of cone angle, were as follows: 8 degrees, 21.02 N; 7 degrees, 23.16 N, 28 N, and 36.40 N; 6 degrees, 40.46 N; 5 degrees, 66.36 N; 4 degrees, 61.23 and 76.12 N; 3 degrees, 93.44 N, 103.21 N, and 112.04 N; 2 degrees, 154.20 N; and 1 degree, 204.74 N, 261 N, and 293.40 N. These data describe a high-intensity ratio with a curvilinear trend that can be used to develop predictive models. CONCLUSION With the limits of this study, it can be concluded that retention strength increased as the cone angle decreased. The data described a curve from which two predictive models were developed to find retention strength from the cone angle used and the cone angle that would be needed to deliver a given retention strength. This study is the first step in searching for an alternative to cemented and screw-retained implant-supported prostheses and new retaining elements in implant-retained prostheses.