Load‐Bearing Capacity of Monolithic Zirconia Fixed Dental Prostheses Fabricated with Different Connector Designs and Embrasure Shaping Methods

Abstract

Purpose To investigate the load‐bearing capacity and failure mode of monolithic zirconia fixed dental prostheses (FDPs) fabricated with different connector designs and embrasure shaping methods. Materials and Methods Seventy four‐unit zirconia FDPs (with two premolar pontics) were fabricated and divided into seven groups (n = 10) according to the different connector designs gained by using different embrasure shaping methods. The groups were as follows: monolithic FDPs fabricated with sharp embrasures, monolithic FDPs fabricated with blunt embrasures, monolithic FDPs fabricated with blunt embrasures and no occlusal embrasures, two groups of monolithic FDPs fabricated with blunt embrasures and interproximal separations made with diamond discs at the soft stage and at the fully sintered stage, and monolithic FDPs fabricated with blunt embrasures and interproximal separation accentuated by localized porcelain build‐up. A final group was used as a control group, where fully veneered traditional zirconia FDPs were fabricated with default milling settings. The FDPs were artificially aged and loaded to fracture. Load to fracture and failure modes were analyzed by one‐way ANOVA, Tukey's post hoc test, and Fisher exact test (α = 0.05). Results The FDPs fabricated with interproximal porcelain separation showed significantly the highest load to fracture (1038 N ± 82) of all groups (p < 0.001), with no significant difference compared to the FDPs with no occlusal embrasures (934 N ± 175; p ˃ 0.29). The FDPs fabricated with blunt embrasures showed significantly higher load to fracture (873 N ± 115) compared to the FDPs in the control group (689 N ± 75) and the FDPs with sharp embrasures (417 N ± 87; p < 0.001). There were no significant differences between the FDPs with sharp embrasures (417 N ± 87) and the FDPs with interproximal disc separations (467 N ± 94; p ˃ 0.23). Failure mode of the FDPs fabricated with sharp embrasures and interproximal disc separations differed significantly compared to the FDPs in the other groups (p < 0.001). Conclusions Sharp embrasures and interproximal separations made with diamond discs significantly decrease the load‐bearing capacity of monolithic zirconia FDPs compared to FDPs made with blunt embrasures. Blunt embrasures in combination with localized porcelain build‐up produce FDPs with high load‐bearing capacity in relation to loads that might be expected under clinical use.

Comparison of porcelain veneer fracture in implant‐supported fixed full‐arch prostheses with a framework of either titanium, cobalt–chromium, or zirconia: An in vitro study

“…Therefore, manual supervision and halt were added. In contrast to other studies, there were difficulties in detecting an audible crack in the veneer (Bakitian et al, 2019). However, care was taken to register the first sound, visible crack, or loading drop.…”

“…However, this is the reality in a clinical situation and thus relevant for the outline of the study. The design of the FDPs may also affect the load‐bearing capacity (Bakitian et al, 2019 ; Larsson et al, 2007 ). Usually, when comparing different materials or designs, in vitro studies are based on the same models where teeth or implant placement are identical (Bakitian et al, 2019 ; Karl et al, 2007 ; Larsson et al, 2007 ; Löfgren et al, 2017 ).…”

“…The design of the FDPs may also affect the load‐bearing capacity (Bakitian et al, 2019 ; Larsson et al, 2007 ). Usually, when comparing different materials or designs, in vitro studies are based on the same models where teeth or implant placement are identical (Bakitian et al, 2019 ; Karl et al, 2007 ; Larsson et al, 2007 ; Löfgren et al, 2017 ). In this study, the models were identical within the metal framework groups.…”

“…Previous results have shown that if there is a complete fracture of the Y‐TZP framework, it usually happens in the weakest point of the FDP, often the connector (Bakitian et al, 2019 ; Le et al, 2015 ). None of the FDP in this study was loaded to complete fracture but the fracture of the veneer occurred more often in the area of loading.…”

Reliability and aging behavior of three different zirconia grades used for monolithic four-unit fixed dental prostheses

“…To the present, such laboratory data, subjecting ready to be delivered dental reconstructions to aging and loading conditions closely approximating clinical reality, is not available for multi-unit fixed dental prostheses made from different and market-available zirconia grades. Available studies are addressing the connector design and embrasure shaping method [16], evaluating the stress distribution using finite element analysis [17], marginal and internal fit [18], optical characteristics [19][20][21], the effect of speed sintering [22], or mechanical properties of implant supported anterior FDPs [23]. Of these studies, only a single one investigated the fracture resistance of anatomically shaped tooth-supported FDPs, however not dynamically loading or hydrothermally aging the samples [16].…”