Prosthetic screw retention in full-arch implant-supported rehabilitations using the All-on-4 concept

Abstract

Prosthetic screw retention represents a critical factor for the mechanical stability and long-term success of full-arch implant-supported rehabilitations using the All-on-4 concept. Preload loss resulting from tribological phenomena and functional biomechanical loading is considered one of the main causes of prosthetic screw loosening in this treatment modality. This study aimed to critically analyze scientific evidence regarding factors associated with prosthetic screw retention in full-arch implant-supported rehabilitations published over the last ten years. A qualitative narrative literature review was conducted. The bibliographic search was performed between November 2025 and January 2026 using PubMed/MEDLINE, Scopus, Web of Science, and Embase databases, employing descriptors related to the All-on-4 protocol, preload maintenance, screw loosening, angled screw channels, and mechanical complications. After applying eligibility criteria, 18 studies were included in the final analysis. The findings indicate that prosthetic screw stability depends on both preload magnitude and maintenance, being influenced by friction coefficient, screw surface treatment, settling effect, implant angulation, distal cantilever extension, and passive fit accuracy of the prosthetic framework. Laboratory evidence suggests improved reverse torque maintenance with tribological surface modifications; however, long-term prospective clinical studies remain limited. It can be concluded that prosthetic screw retention in the All-on-4 protocol is multifactorial, requiring an integrated biomechanical approach involving proper torque application, occlusal control, accurate prosthetic fit, and periodic clinical monitoring to minimize mechanical complications and enhance treatment predictability.