A complete arch fixed/detachable implant prosthesis has been developed that is supported by a fiber-reinforced composite (FRC) substructure in place of cast metal. This prosthesis is attached to implant abutments via screw-retained porcelain-coated titanium cylinders. There are generally five to six cylinders (one screwed on to each abutment) integral within the pre-impregnated, unidirectional glass FRC used for each substructure. Acrylic denture teeth and polymethyl methacrylate (PMMA) are processed over the FRC substructure analogously to metal-supported prostheses. Objective: This in-vitro study assessed the fit between cylinders and abutments at two levels of screw tighness (as a measure of dimensional stability): (A) prior to FRC substructure fabrication; (B) after FRC substructure fabrication; and (C) after processing of denture teeth and PMMA. Methods: Fit measurements were made with a traveling microscope at four sites around each of cylinder following both low (1.5 Ncm) and medium (15 Ncm) torque screw tightening. Three frameworks, each containing five cylinders, were evaluated. Results: At medium screw tightness the mean (± SD) marginal gaps (ìm) were: A = 96.85 ± 20.92; B = 98.78 ± 20.58; and, C = 122.20 ± 32.41. Group C differed significantly from groups A & B (ANOVA; 95% Tukey) which were indistinguishable (p > 0.05). Similar results were seen with low screw tightness measurements. Conclusions: The FRC substructure exhibited good dimensional stability during its fabrication, but the processing of PMMA onto an FRC substructure affected the cylinder-abutment relationship and hence the dimensional stability in full-arch FRC implant prostheses.

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