Objective. When a new material is released, clinical studies are indicated. For the clinical studies to be defensible, in-vitro studies, which are as clinically relevant as possible, must be performed. The aim of this study was to investigate how the choice of material used for supporting tooth analogues and support complexity influences test results concerning the fracture strength of fixed dental prostheses (FDPs) made from a brittle material: Y-TZP. Material and methods. Twenty-four FDPs were produced in Y-TZP. The FDP cores were subjected to heat treatment to simulate veneering and then thermocycled for 5000 cycles to simulate ageing. The FDPs were divided into three groups and were cemented on tooth-supporting analogues made from aluminium, polymer and DuraLay( ). The FDPs were preloaded for 10,000 cycles and finally loaded to fracture. Results. There were no significant differences in load to fracture or fracture mode between the groups cemented on polymer and DuraLay tooth analogues. The FDPs cemented on aluminium tooth analogues showed a significantly higher load at fracture and a different fracture mode. Conclusions. Within the limitations of this in-vitro study, the following could be concluded. To achieve mutually comparable results there is a need for a standardized, simple test set-up for in-vitro testing of all-ceramic FDPs intended for cementation upon natural teeth. Resilient, non-complex and resilient, complex tooth analogues give comparable test results when the test set-up is unchanged in all other aspects. Non-resilient (with an elastic modulus equivalent to or higher than that of aluminium) tooth analogues give high and unrealistic load-at-fracture values together with adverse fracture modes compared to FDPs failing in clinical situations.

Aim To measure the trueness and precision under repeatable conditions for different intraoral scanners (IOSs) when scanning fully edentulous arch with multiple implants. Materials and Methods Three IOSs and one industrial scanner were used to scan one edentulous master cast containing five implant scan bodies and three spheres. The cast was scanned thirty times with each scanner device. All scans were analyzed in the inspect software, and three-dimensional locations of the implants and the interarch distance between the spheres were measured. The values were compared to measurements made with one coordinate measuring machine (true value). One-way ANOVA was used to calculate the differences between IOSs and in comparison with the true value. Results Significant differences were found between all IOSs. For the implant measurements, Trios 3 had the lowest trueness (≤114 μm), followed by Trios 3 mono (≤63 μm) and Itero element (≤−41 μm). Trios had the lowest precision (≤135 μm), followed by Itero element (≤101 μm) and Trios 3 mono (≤100 μm). With regard to the interarch distance measurements, Trios 3 had the lowest trueness (≤68 μm), followed by Trios 3 mono (≤45 μm) and Itero element (≤40 μm). Trios 3 had the lowest precision (≤206 μm), followed by Itero element (≤124 μm) and Trios 3 mono (≤111 μm). Conclusion The results from this in vitro study suggest that precision is low for the tested IOS devices when scanning fully edentulous arches with multiple implants.

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Aim: The use of colored translucent zirconia may enable restorations of a more natural tooth-like appearance than previous opaque white zirconia. The shift from non-colored to colored zirconia may however entail a risk of reduced strength. The aim of the present study was to compare fracture load and fracture mode of fixed dental prostheses frameworks made of colored translucent zirconia to that of non-colored controls.Methods: A total of forty three-unit FDP frameworks were manufactured from two different high translucent zirconia materials (Zenostar, Wieland Dental, and DD cubeX2, Dental Direkt). Each group contained two subgroups, one colored and one non-colored. Coloring was performed before final sintering using two different infiltration techniques. All FDPs underwent an artificial aging process in the form of heat treatment, thermocycling and preloading whereafter the specimens were subjected to load until fracture. Fracture load and mode was registered.Results: For one of the zirconia materials, Zenostar, the non-colored frameworks showed significantly higher fracture loads (p < .0001) compared to its colored counterpart. No significant difference (p > .05) was found between colored and non-colored frameworks in the other zirconia material, DD cubeX2. All FDPs fractured through the connector. Some fractures ran through the mesial and some through the distal side of the connector but there were no significant differences in fracture mode between groups.Conclusion: Coloring before sintering of high-translucent zirconia may decrease the fracture load of FDP frameworks for certain materials and techniques. Fracture mode however, does not appear to be affected.