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.