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This study compares the mechanical properties of 5-mol% yttria partially stabilized zirconia (5Y-PSZ) materials, designed for 3D printing or milling. Three 5Y-PSZ materials were investigated: printed zirconia (PZ) and two milled zirconia materials, VITA-YZ-XT (MZ-1) and Cercon xt (MZ-2). PZ samples were made from a novel ceramic suspension via digital light processing and divided into three subgroups: PZ-HN-ZD (horizontal nesting, printed with Zipro-D Dental), PZ-VN-Z (vertical nesting, printed with Zipro-D Dental) and PZ-VN-Z (vertical nesting, printed with Zipro Dental). Key outcomes included biaxial flexural strength (ISO 6872) and Vickers hardness (n ≥ 23 samples/subgroup). Microstructure and grain size were analyzed using light and scanning electron microscopy. Printed specimens exhibited biaxial flexural strengths of 1059 ± 178 MPa (PZ-HN-ZD), 797 ± 135 MPa (PZ-VN-ZD), and 793 ± 75 MPa (PZ-VN-Z). Milled samples showed strengths of 745 ± 96 MPa (MZ-1) and 928 ± 87 MPa (MZ-2). Significant differences (α = 0.05) were observed, except between vertically printed groups and MZ-1. Vickers hardness was highest for PZ-VN-Z (HV0.5 = 1590 ± 24), followed by MZ-1 (HV0.5 = 1577 ± 9) and MZ-2 (HV0.5 = 1524 ± 4), with significant differences, except between PZ and MZ-1. PZ samples had the smallest grain size (0.744 ± 0.024 µm) compared to MZ-1 (0.820 ± 0.042 µm) and MZ-2 (1.023 ± 0.081 µm). All materials met ISO 6872 standards for crowns and three-unit prostheses in posterior regions. [ABSTRACT FROM AUTHOR]

Objectives: Cleaning splints (CSs) can facilitate interdental brush (IDB) insertion and guide IDBs during cleaning movement. Cleaning efficacy with and without CSs was to be assessed and compared for a fully dentate (FD) and a partially edentulous (PE) situation. Methods: For two maxillary typodont models simulating either an FD situation or a PE situation with every second tooth missing, suitable IDBs were selected and each cleaning splint was designed and fabricated by 3D-printing. Before and after standardized cleaning, model teeth were photographed at three timepoints: (T1) clean surface, (T2) surface coated with artificial plaque, and (T3) after IDB cleaning. For each of the four test groups differing in dental status (FD, PE) and CS use (without, with), n = 10 tests/group were completed. After aligning corresponding photographs, pixel-based color difference ratios (T2-T3)/(T2-T1) were calculated. Approximal cleaning efficacy was set as the mean value over predefined regions of interest. Effects of CS use and dental status were analyzed with two-way ANOVA (α = 0.05). Results: CS use significantly improved mean approximal cleaning efficacy for the PE model (p = 0.001), whereas no difference was found with the FD model (p = 0.381). Improved cleaning efficacy with the PE model was only found in combination with a CS (factor combination model × CS use: p = 0.003). Conclusions: Cleaning splints might have the potential to improve interproximal hygiene and can be recommended for clinical use. Clinical studies should validate the results of this in vitro study and clarify if CSs could be beneficial for patients with restricted manual skills. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the fracture resistance of veneered incisor crowns made from highly translucent zirconia frameworks. Materials and Methods: Ninety‐six all‐ceramic single crowns were based on either a coping with minimum wall thickness or a cutback framework fabricated from highly translucent zirconia (5Y‐PSZ). Each one‐third of the specimens was finalized with different veneering ceramics using standardizations and glaze firing. Crowns were luted to cobalt–chromium dies with MDP‐containing composite cement. Half of the entire sample underwent artificial aging (chewing simulation and thermocycling) before fracture load tests were conducted using a 6 mm steel sphere applied in a 90° angle to the oral aspect of the crowns with 1.3 mm distance to the incisal edge. Besides descriptive presentation of recorded forces at first damage (F1d) and fracture (Fu), Kruskal Wallis and Mann–Whitney U tests were used to analyze data at α = 0.05. Results: Directly after manufacturing, incisor crowns of all test groups showed sufficient mean fracture resistances. After artificial aging, crack formation was observed in a high percentage for fully veneered crowns of all test groups, but only for one veneering ceramics with cutback crowns. Mean test forces of unaged crowns were F1d,mean ≥ 422 N | Fu,mean ≥ 749 N (fully veneered) and F1d,mean ≥ 644 N | Fu,mean ≥ 706 N (cutback) dropped significantly to F1d,mean ≥ 131 N | Fu,mean ≥ 223 N (fully veneered) and F1d,mean ≥ 324 N | Fu,mean ≥ 524 N (cutback). Conclusions: Within the limitations of this laboratory study, 5Y‐PSZ based anterior crowns can be a viable treatment option. Framework design, choice of the veneering ceramics and artificial aging show relevant effects on the fracture resistances. Concerted veneering ceramics should be used and partially veneering of the zirconia frameworks should be favored over full veneers. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the impact of surface conditioning of titanium, zirconia thickness, and cement type on the final color of zirconia luted to the titanium. Methods: A total of 192 grade 5 titanium specimens with the final dimensions 10 mm × 10 mm × 2 mm were fabricated and subjected to four different surface conditioning including, that is, sandblasting, etching, and anodization. In addition, 192 zirconia specimens with the same dimensions as the titanium specimens but altered thicknesses of 0.7 (n = 96) and 1.0 (n = 96) mm were fabricated using 5Y‐TZP zirconia. Color as expressed by L∗ (lightness), a∗ (red–green axis), and b∗ (blue–yellow axis) of titanium and zirconia specimens as well as the joined titanium–zirconia complex, total assembly (Panavia V5 clear, PC; opaque, PO, each n = 96) were determined under standardized conditions using a spectroradiometer (SpectraScan P‐650). Color differences were calculated using the ΔE00 formula. ANOVA supplemented with post hoc Tukey test for group comparisons was compiled to estimate possible effects of titanium conditioning, zirconia thickness, and type of cement used on the final zirconia color (SPSS Ver. 28; α = 0.05). Results: All investigated factors affected the zirconia color of the total assembly (p < 0.001). Using PO mean values of all groups were still close to baseline colors (ΔE00 between 5.5 and 6.2). When using PC, the final color was significantly altered, irrespective of the other parameters. Specimens luted with PO appeared lighter, less reddish (a∗ was affected predominately by sample thickness), and more bluish, while luting with PC resulted in reduced lightness combined with large shifts along the red and yellow axes. Significance: Color changes of zirconia luted to titanium are primarily affected by the color of the substrate if a translucent cement was used. Vice versa, the application of an opaque cement effectively masked the dark substrate color. Substrate color and choice of cement have to be taken into consideration when performing shade selection. [ABSTRACT FROM AUTHOR]

The efficacy of retainers is a pivotal concern in orthodontic care. This study examined the biomechanical behaviour of retainers, particularly the influence of retainer stiffness and tooth resilience on force transmission and stress distribution. To do this, a finite element model was created of the lower jaw from the left to the right canine with a retainer attached on the oral side. Three levels of tooth resilience and variable retainer bending stiffness (influenced by retainer type, retainer diameter, and retainer material) were simulated. Applying axial or oblique (45° tilt) loads on a central incisor, the force transmission increased from 2% to 65% with increasing tooth resilience and retainer stiffness. Additionally, a smaller retainer diameter reduced the uniformity of the stress distribution in the bonding interfaces, causing concentrated stress peaks within a small field of the bonding area. An increase in retainer stiffness and in tooth resilience as well as a more oblique load direction all lead to higher overall stress in the adhesive bonding area associated with a higher risk of retainer bonding failure. Therefore, it might be recommended to avoid the use of retainers that are excessively stiff, especially in cases with high tooth resilience. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the dimensional accuracy of impressions made using a new fast-setting polyether material.Materials and Methods: A metallic reference model with two crown preparations, one inlay preparation, and three stainless steel precision balls was digitized to create a digital reference model. Sixteen one-step impressions were made for each of the four study groups, differing in impression material (regular-setting polyether [RSP] vs fast-setting polyether [FSP]) and technique (monophase vs dualphase), for a total of 64 specimens. Plaster casts fabricated from these impressions were digitized using 3D scans. Global accuracy was studied by evaluating distance and angle deviations between the replica and the reference model. Local accuracy was described in terms of trueness and precision of the aligned individual abutment tooth surfaces.Results: For all impression materials and techniques, the local accuracy at the abutment tooth level was excellent. For surfaces prepared for crowns, mean trueness was < 10 μm, and mean precision < 12 μm. Inlay surfaces were associated with higher inaccuracies (mean trueness < 21 μm and mean precision < 37 μm). The greatest global inaccuracies were generally measured for the cross-arch span, with mean distance changes between -55 μm and -94 μm. For all aspects of studied accuracy, impressions with FSP were at least comparable to those fabricated with RSP.Conclusion: Within the limitations of this study, all tested polyether materials would allow for clinically acceptable impression making. The new fast-setting material could be an alternative to regular-setting polyether materials, especially for single crowns and small fixed partial dentures. [ABSTRACT FROM AUTHOR]

To evaluate the resistance to fracture in cantilevered fixed dental prostheses (cFDPs) of single implant-supported zirconia cantilevers in the anterior region. Materials and Methods: Thirty-two cemented and solely screw-retained cFDPs consisting of an implant-supported crown replacing the central incisor and an attached cantilever unit in the position of the lateral incisor in the maxilla were constructed by computer-aided design (CAD) and machined by computer-aided manufacturing (CAM). For the cemented solution, a cFDP was designed on top of a customized abutment luted to an adhesive base. For screw-retained cFDPs, abutment, cement gap, and restoration of the cementable design were combined. All cFDPs were veneered manually on the facial side. Half of the samples underwent artificial aging (thermocycling and chewing simulation) before fracture tests were conducted with loads applied to the pontic either parallel to the implant axis (axial loading on the pontic) or tilted lingually by α = 45 degrees (oblique loading on the pontic). Thus, there were eight groups differing in cFDP design, artificial aging, and load application (n = 8/group). If fracture (Fu,total) occurred within the implant components, the adhesive base was replaced by a cast CoCr base, and the cFDP’s fracture resistance (Fu,cFDP) was also determined. Using statistical analyses (SPSS 24, IBM), factors affecting fracture resistance were identified. Results: Fu,total was mainly correlated to screw fractures and therefore not affected by cFDP design. Oblique loading on the pontic (Fu,total = 231 N – 352 N), however, led to a significant (P < .001) decrease in ultimate load compared with axial loading on the pontic (Fu,total = 611 N – 815 N). In relation to Fu,total, Fu,cFDP was approximately twice as high for both loading conditions. Conclusion: When relating the results to maximum occlusal forces exerted in the maxillary anterior region, single implant-supported cFDPs can be a viable restorative treatment option. [ABSTRACT FROM AUTHOR]

Aims: To develop a German version of the Dental Environment Stress (DES) questionnaire, and to evaluate its reliability and validity. Methods: The original English DES questionnaire was translated into German using a forward–backward translation process. To evaluate construct stability, a subgroup of dental students (n = 43) completed the DES twice (interval: 1 week). To evaluate how the DES responds to anticipated changes in stress, all dental students' (n = 64) DES scores and saliva cortisol levels administered from a clinical study were compared between holiday and term time. Furthermore, the Depression, Anxiety and Stress Scale (DASS) and a stress self‐assessment were used to determine the validity of the DES. Reliability analyses were calculated using Kendall's tau correlations. To estimate reliability strength, correlation coefficients and intraclass correlations (ICCs) were used. Results: Regarding construct stability, 24 of 25 DES items had at least moderate correlations, and most items showed strong correlations. Correlations for the seven subdomains were good (range: 0.778–1.000). The same was true for the total DES score (ICC: 0.944). Correlations for response to term‐time stress were weaker and more varied. Validity analyses revealed fair correlations between the DES and students' self‐assessment (Pearson's r =.592) and DASS score (Pearson's r =.392), suggesting satisfactory validity. Stress levels were quite similar between baseline and follow‐up. Conclusion: The German DES is a reliable tool for evaluating stress in dental students. Because it can be used to identify individual stressors in various categories, it might enable the detection of specific stress situations in educational situations and facilitate solutions (adjustment of curricula, tailored consulting services). [ABSTRACT FROM AUTHOR]