A screw lock for single-tooth implant superstructures

Background. The most common complication in a single-tooth implant restoration is abutment screw loosening. Instability of the prosthetic superstructure is expressed by difficulty in chewing and functioning, as well as soft-tissue soreness and/or swelling that could lead to screw fracture. Manufacturers of oral implants have attempted to refine the connecting parts of the prosthesis to achieve a more predictable tightening method for the screws. Methods. To maintain the abutment screw tightly in its correct position, the authors developed a technique in which an elongated hexagonal titanium bar is inserted into the hexed fixed screw head. The screw is locked, and the bar is then fixed with a light-cured composite resin material that serves to seal the retaining screw access hole. The occlusal hexagonal bar thus serves as a secure screw lock that can be easily removed if needed. Results. The authors have used the hexagonal bar for almost three years on 120 single-tooth screw-retained prostheses in 100 patients (65 in the first and second premolar region, 40 in the incisor region and 15 in the posterior molar region). All of these prostheses functioned successfully, including those with wider occlusal planes and increasing occlusal forces. No screw loosening or fractures were noted in any of the fixtures. Clinical Implications. This technique secures and stabilizes the single-tooth prosthesis, reduces chair time on follow-up procedures and reduces unnecessary frustration in patients and dental team members.