Cyclic loading of implant-supported prostheses: changes in component fit over time

Area of Science:

• Dental Implantology
• Biomaterials Science
• Prosthodontics

Background:

• Achieving a passive fit in implant-supported prostheses is crucial to prevent mechanical failures like implant fracture and component loosening.
• Clinical goals often shift to achieving minimal misfit, as perfect passive fit is practically unattainable.
• The specific threshold of misfit that differentiates minimal from catastrophic failure remains undefined.

Purpose of the Study:

• To investigate if cyclic loading alters the fit of implant-supported prostheses.
• To quantify changes in the gap between the gold cylinder and implant abutment over time under cyclic loading.

Main Methods:

• Fifteen implant-supported frameworks were fabricated using conventional casting.
• Frameworks underwent cyclic loading (200 N up to 200,000 cycles) under three conditions: anterior loading, unilateral posterior cantilever loading, and bilateral posterior cantilever loading.
• Gap measurements between the prosthetic cylinder and abutment were recorded at four points before, and after 50,000 and 200,000 cycles.

Main Results:

• A significant decrease in gap dimensions was observed at individual reference points (P=.024) and on average (P=.031) when cyclic load was applied to the anterior framework portion.
• No significant gap closure was detected when loading was applied to the unilateral (P=.33) or bilateral (P=.35) posterior cantilevers.

Conclusions:

• Simulated functional loading on the anterior portion of implant-supported prostheses can alter the fit between the superstructure and abutment.
• Cyclic loading on posterior cantilever portions of the prosthesis did not lead to measurable changes in gap size within this study's parameters.