Inaccurate fit of implant superstructures. Part 1: Stresses generated on the superstructure relative to the size of fit discrepancy.

This laboratory study used a photoelastic-coating technique to investigate the relationship between the magnitude and location of discrepancies of fit and the amount and distribution of surface stresses on an implant superstructure. For the test superstructure involving four abutments and a single fit discrepancy, maximum surface stress was found over the intermediate abutment, regardless of the location of the fit error. The results show a positive relationship between the size of the fit discrepancy and the magnitude of stress on the superstructure for gaps of up to 104 micrometers at an end abutment and 55 micrometers at an intermediate abutment, when the gold screws were tightened at 10-Ncm torque.