Background:

Screw loosening is a common mechanical complication in full-arch fixed complete dental prostheses (FCDPs). While marginal bone loss has been widely studied, the biomechanical role of apical or periapical bone loss (PBL) remains unclear.

 

Objective:

This study aimed to investigate the influence of implant-level PBL characteristics, along with patient and prosthesis-related factors, on screw loosening in FCDPs.

 

Methods:

A retrospective analysis of 54 patients rehabilitated with FCDPs supported by 4 or 6 implants was conducted. Clinical records and panoramic radiographs were evaluated. Logistic regression analysis was performed to identify significant risk factors for screw loosening.

 

Results:

Screw loosening occurred in 75.9% of prostheses within a 3-year period. A greater number of implants with PBL significantly reduced the likelihood of screw loosening, suggesting adaptive load redistribution. Nightguard use was associated with lower screw loosening risk, while implant position, arch type, and demographic factors were not significant predictors.

 

Conclusion:

Both biological and mechanical factors influence screw stability in FCDPs. Periapical bone loss may modulate biomechanical forces and could serve as an early indicator of mechanical changes rather than merely a radiographic defect. Recognizing this may support a shift from reactive repair to proactive maintenance strategies in FCDPs.