Ultimate tensile strength of five interchangeable prosthetic retaining screws

Implant prosthetic retaining screws have been reported to serve as built-in safety factors to protect against overload in the implant's "vertical stack," although loosening and fracture of retaining screws are often considered complications. Manufacturers have responded by introducing interchangeable prosthetic retaining screws, which can give the clinician the impression that interchanging screws will not have an adverse effect on the remainder of the implant complex and/or the integration of the implant itself. The objective of this investigation was to measure the ultimate tensile strength of four retaining screws from three manufacturers and two alloy types (gold and titanium) using the Nobelpharma gold prosthetic retaining screws as a standard for the comparisons. Five screws of each type were loaded in tension in an Instron Universal Testing Machine until fracture occurred. A Tukey-Kramer Test (significance level = .05) analysis of the data showed that all of the interchangeable prosthetic retaining screws were significantly different from the control screws in respect to ultimate tensile strength. The data suggest that interchanging prosthetic retaining screws will influence their built-in safety feature.