Axial displacement in cement-retained prostheses with different implant-abutment connections.

Abstract

The purpose of this study was to evaluate axial displacement in cement-retained prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM) abutments with three different types of implant-abutment connections. CAD/CAM abutments made with two types of titanium blocks (made by the same manufacturer as the implant manufacturer and by a manufacturer with a patent for CAD/CAM abutment fabrication) were connected with three types of implant connections: external, internal butt, and internal conical connection. Titanium custom abutments and zirconia prostheses were fabricated using the CAD/CAM system for each specimen. The geometries and surface morphologies of CAD/CAM abutments and ready-made abutments were comparatively evaluated using scanning electron microscopy. Cemented prostheses on abutments were mounted on a universal testing machine and subjected to 250-N sine wave cyclic loads. Cumulative axial displacement was measured at loading cycles of 3, 10, 100, and 106 and analyzed by repeated measures analysis of variance (ANOVA). Surface geometries and morphologies of CAD/CAM abutments varied according to the implant-abutment connection and manufacturers of the titanium block. The internal conical connection exhibited the greatest axial displacement, while the external connection showed the lowest axial displacement. The CAD/CAM abutment made with a compatible titanium block exhibited a greater axial displacement than that exhibited by the abutment fabricated using a titanium block made by the implant manufacturer. In implant connections with a vertical stop, axial displacement occurred primarily in the early loading period and was self-limited. However, long-term axial displacement can occur with internal conical connection implants. Therefore, in internal conical connection implants, axial displacement should be managed more carefully using a provisional restoration, with consideration of the abutment fabrication method.