The mechanical complications and behavior of angulated dental implant abutment systems versus conventional abutments, a narrative review

Background: Angulated screw channel (ASC) abutment allows off-axis dental implants to be used in dental restorations without the need for cementation. As this is a relatively new system, research on its clinical performance is limited. Objectives: To summarize the available in-vitro and in-vivo studies on the mechanical and technical issues associated with the ASC system and compare its clinical performance with that of conventional implantsupported abutments. Methods: A comprehensive literature search in PubMed, Web of Science, and ScienceDirect databases was performed, focusing on articles about angulated (angled) screw channel (ASC) systems published in English between January 2015 and November 2023. Only in-vitro and in-vivo studies were included. Results: After analyzing the recorded articles, 26 studies (11 in vivo and 15 in vitro) were included in the final discussion and review. Conclusion: Although the ASC system is still relatively new, and is presently outperformed by conventional abutment systems in terms of technical and mechanical properties, in short- and medium-term in-vivo studies, it was shown reliable for retaining single or multiple-unit implant restorations in both posterior and anterior zones. Still, further long-term clinical research is needed to fully elucidate the risk factors associated with ASC failures.