Full-arch prostheses from translucent zirconia: accuracy of fit

The aim of this study was to evaluate the marginal and internal fit of single crowns, compared to 14-unit frameworks made of translucent yttria-stabilized zirconia. We hypothesized that there is an influence of the type of restoration on the marginal and internal fit.

Eight teeth (FDI locations 17, 15, 13, 11, 21, 23, 25 and 27) of a typodont maxillary model were provided with a chamfer preparation to accommodate a 14-unit prosthesis or four single crowns (SCs). Ten 14-unit fixed dental prostheses (FDPs) and 40 single crowns were fabricated using a computer aided design (CAD)/computer aided manufacturing (CAM) system with pre-sintered translucent yttria-stabilized zirconia blanks. The restorations were cemented onto twenty master dies, which were sectioned into four pieces each. Then, the marginal and internal fits were examined using a binocular microscope. In order to detect the differences between the two types of restorations a non-parameteric test (Mann-Whitney-U) was carried out; to detect differences between the abutment teeth and the abutment surfaces non-parametric tests (Kruskal-Wallis) and pairwise post hoc analyses (Mann-Whitney-U) were performed after testing data for normal distribution (method according to Shapiro-Wilk). Level of significance was set at 5%.

The mean (SD) marginal opening gap dimensions were 18 μm (14) for the single crowns and 29 μm (27) for the 14-unit FDPs (p<0.001). Abutment 21 of the FDPs showed statistical differences concerning the location of the teeth in both marginal and internal fit (p<0.001). The measured gaps (types I-IV) revealed statistical differences between all types, when comparing SCs to the FDPs (p<0.001).

Single crowns showed significantly better accuracy of fit, compared to the 14-unit FDPs. However, both restorations showed clinically acceptable marginal and internal fit.