Influence of different implant-abutment connection designs on the mechanical and biological behavior of single-tooth implants in the maxillary esthetic zone: A systematic review

Statement of problem. A consensus regarding which implant-abutment connection type would perform best in the anterior maxilla is lacking. Purpose. The purpose of this systematic review was to determine the best implant-abutment connection type for anterior single-tooth implants considering esthetics, success, and survival rates. Material and methods. An electronic search was conducted in MEDLINE, Scopus, Embase, and the Cochrane Library databases to identify clinical studies on single-tooth implants with external and internal hexagon, and/or Morse taper connections. These studies needed to describe at least one of the following outcomes: esthetic score, survival/success rate, or marginal bone loss. The included studies and reports were assessed for bias using the Cochrane risk of bias tool. Results. Of the 891 articles identified, 29 were selected and analyzed. The most common technical complications were abutment screw loosening and crown-cement loosening, while dehiscence and recession were the most common biological complications. The most frequent complications were dehiscence for external hexagon, crown-cement loosening for the internal hexagon, and ceramic fracture for the Morse taper. Esthetics were favorable for all connections, but the internal hexagon performed better. However, better results for marginal bone loss, success, and survival were found for the Morse taper. The global annual failure rate was 0.90% and 0.2% for Morse taper, 0.3% for external hexagon, and 2.2% for internal hexagon. Conclusions. This review suggests that Morse taper performs better for survival, success, and marginal bone loss. Internal hexagon performed better for esthetic parameters. Additional controlled studies are needed to provide stronger evidence because the evidence generated in this study was considered low.