Geometric comparison of five interchangeable implant prosthetic retaining screws.

Eight geometric parameters of five interchangeable prosthetic retaining screws (#1-3i Implant Innovation-gold, #2-Impla-Med-gold, #3-Nobelpharma-gold, #4-3i Implant Innovation-titanium, and #5-Implant Support Systems-titanium) were recorded with an Amray 1000-B scanning electron microscope at x20 to x200 magnification. Five screws of each type were measured and eight parameters were evaluated: (A) diameter of head, (B) screw length, (C) thread pitch, (D) major diameter, (E) neck diameter (F) length of neck, (G) crest width, and (H) root width. The Nobelpharma-gold prosthetic retaining screws served as controls. The results revealed significant differences between the control and test screws in all parameters except parameters C and G (ANOVA, p < 0.05) and Duncan's multiple range test (significance level 0.05). On the basis of these differences, it was concluded that interchanging prosthetic retaining screws can introduce unknown variables in treating patients.