Abstract
Abutment and prosthetic screw loosening and fracture remain important mechanical complications of implant-supported restorations and may compromise prosthetic stability, increase maintenance requirements,and contribute to component failure.This critical narrative review evaluates the mechanisms, clinical determinants, prevention, and management of screw-related complications, with emphasis on screw preload, the settling effect, implant–abutment connection design, prosthetic fit, implant angulation, occlusal and parafunctional loading, and tightening protocols. Evidence from clinical trials, observational studies, systematic reviews, meta - analyses, and biomechanical investigations published through 2026 indicates that screw stability is multifactorial and depends on the interaction of preload, connection geometry, component integrity, prosthetic fit, occlusal loading, and functional conditions. In implant-supported single crowns, reported cumulative 5-year incidences are approximately 12.7% for screw or abutment loosening and 0.35% for screw or abutment fracture, although considerable variability exists across implant systems and clinical indications. Morse-taper connections have demonstrated low reported rates of screw loosening, whereas bruxism has been associated with an approximately 3.4-fold increased risk.