Marginal fit of 14-unit zirconia fixed dental prosthesis retainers

The marginal fit of 14-unit fixed dental prosthesis retainers and single-crown copings fabricated by the same computer-aided design (CAD)/computer-aided manufacturing (CAM) system were evaluated in vitro hypothesizing that the marginal opening might be independent of the type of restoration. Eight ivorine maxillary teeth (FDI locations 27, 25, 23, 21, 11, 13, 15 and 17) were prepared to accommodate a 14-unit prosthesis. Ten fixed dental prosthesis retainers and 40 single-crown-copings were fabricated using Zeno CAD/CAM on 20 master dies. Four cross-sections were made from each tooth and the marginal gap dimensions were measured. One-way anova was used to test the difference between the experimental groups and two-way anova and a post hoc test (Student-Newman-Keuls) were carried out to determine the influence of the location of the abutment tooth and the measurement location within the abutment tooth in the experimental groups (P < 0.05). Mean marginal gap dimensions and standard deviations for fixed dental prosthesis retainers and single-crown copings were 25 +/- 29 and 13 +/- 12 microm, respectively. The type of restoration showed a significant influence (P < 0.001) on the marginal gap. The location of the abutment tooth (P < 0.001) and the measurement location (P < 0.001) exhibited significant influence on marginal gaps of fixed dental prosthesis retainers while no influence on single-crown copings could be detected. The highest marginal gaps were found at the palatal surface of the incisor and canine of the 14-unit fixed dental prosthesis retainers. Fourteen-unit fixed dental prosthesis showed significantly higher marginal openings than single crowns fabricated under the same conditions. However, both restorations showed clinically acceptable marginal openings.