Objectives: Inconsistent characterization of oral implant microtopography makes it difficult to compare and evaluate available data on microtopography and the biological response to topographical characteristics. The aim of this investigation was therefore to identify a surface texture parameter panel that enables a discriminative characterization of differently processed oral implant surfaces. Materials and methods: Surface micromorphologies of titanium- and ceramic-based biomaterials processed by machining or by machining and subsequent post-processing, including blasting, etching, anodization or porous sintering, were analyzed by scanning electron microscopy and white light interferometry. It was then analyzed which of the parameters Sa, Sq, Sz, Ssk, Sku, Str, Sal, Spd, Spc, Sdq and Sdr best characterized morphological surface features and hence should be reported as minimum parameter panel for implant surface characterization. Results: SEM demonstrated that each surface processing resulted in a specific and biomaterial-dependent micromorphology. The data revealed that the micromorphology of machined surfaces was best characterized by Sa, Sdr, Str and Ssk, and that for post-processed surfaces Spd and Spc were additionally required. Based on these data, Sa, Sdr, Str, Ssk, Spd and Spc were identified as minimum parameter panel for discriminative description of the investigated implant microtopographies. Significance: The present investigation identified Sa, Sdr, Str, Ssk, Spd and Spc as minimum parameter panel for discriminative oral implant surface characterization. The widespread use of such a panel combined with biological data will help to identify cell-relevant implant surface structures, thus enabling the design of oral implants with predefined biological response. 

Graphene layers have a very high basal plane thermal conductivity, but a low conductivity out-of-plane. When placed on a heat source, they can efficiently spread heat laterally, but not vertically. To fully exploit ultrahigh basal plane thermal conductivity of graphene layers, they can be assembled vertically. We examine the efficiency of vertically aligned graphene layers as thermal interface material (TIM) for gallium nitride (GaN) high electrons mobility transistors (HEMTs) with ceramic packages. The junction temperature (Tj) is directly measured using thermocouples bonded to the die. The measurements are done under free convection in the ambient. The graphene results are compared with two conventional TIMs. It is shown the graphene TIM can lower the Tj by at least 5 °C. More temperature reduction is expected when testing with forced cooling. A transient thermal finite element model is also used for temperature prediction, showing good agreement with the experimental data.

This work presents a literature study over how additive manufacturing can be used to improve the performance of windings for traction machines when it comes to materials, loss minimization and thermal management, especially for concentrated windings. It continues to present the additive manufacturing methods most suitable for additively manufacturing windings. The lessons from manufacturing coils with metal binder jetting are presented, concluding that some support structures are needed which can be chemically removed later in the process which means that the full detail capability of metal binder jetting can not be utilized fully. Finally different approaches to thermal management with additively manufactured coils are modelled. The results show that compared to direct air cooled windings, additively manufactured copper coils with direct cooling can increase the maximum current by 50 %. If aluminium (AlSiMg) windings are made with both additive manufacturing and improved end-turn cooling they can match the performance of non-AM direct air cooled copper windings. 

To date, it is unknown whether 3D printed fixed oral implant-supported prostheses can achieve comparable soft tissue integration (STI) to clinically established subtractively manufactured counterparts. STI is mediated among others by gingival fibroblasts (GFs) and is modulated by biomaterial surface characteristics. Therefore, the aim of the present work was to investigate the GF response of a 3D printed methacrylate photopolymer and a hybrid ceramic-filled methacrylate photopolymer for fixed implant-supported prostheses in the sense of supporting an STI. Subtractively manufactured samples made from methacrylate polymer and hybrid ceramic were evaluated for comparison and samples from yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), comprising well documented biocompatibility, served as control. Surface topography was analyzed by scanning electron microscopy and interferometry, elemental composition by energy-dispersive x-ray spectroscopy, and wettability by contact angle measurement. The response of GFs obtained from five donors was examined in terms of membrane integrity, adhesion, morphogenesis, metabolic activity, and proliferation behavior by a lactate-dehydrogenase assay, fluorescent staining, a resazurin-based assay, and DNA quantification. The results revealed all surfaces were smooth and hydrophilic. GF adhesion, metabolic activity and proliferation were impaired by 3D printed biomaterials compared to subtractively manufactured comparison surfaces and the 3Y-TZP control, whereas membrane integrity was comparable. Within the limits of the present investigation, it was concluded that subtractively manufactured surfaces are superior compared to 3D printed surfaces to support STI. For the development of biologically optimized 3D printable biomaterials, consecutive studies will focus on the improvement of cytocompatibility and the synthesis of STI-relevant extracellular matrix constituents.

In this study, the effect of coating a zirconia-based ceramic oral implant with a material of the same composition to build a relatively smooth surface with three different porosity features was evaluated in vivo, at 4 and 8 weeks after implantation in sheep femoral condyles. The results showed that at 4 weeks, the three coated zirconia-based implants with smoother surface topographies behaved similarly and promoted faster bone healing compared to the results obtained in the same zirconia- or titanium-based implants, but with rougher sandblasted and acid-etched surfaces. In addition, higher pull-out strengths were estimated in the coated-ceramic sample compared to titanium sandblasted and etched one. The present work showed that zirconia coatings with smoother surfaces than those conventionally used in the market improved the early phase of bone healing, paving the way for shorter treatment times and improved patient outcomes. 

This study centers on investigating the influence of conductive additives, carbon black (Super P) and graphene, within the context of LiFePO4 (LFP)-impregnated carbon fibers (CFs) produced using the powder impregnation method. The performance of these additives was subject to an electrochemical evaluation. The findings reveal that there are no substantial disparities between the two additives at lower cycling rates, highlighting their adaptability in conventional energy storage scenarios. However, as cycling rates increase, graphene emerges as the better performer. At a rate of 1.5C in a half-cell versus lithium, electrodes containing graphene exhibited a discharge capacity of 83 mAhgLFP−1; those with Super P and without any additional conductive additive showed a capacity of 65 mAhgLFP−1 and 48 mAhgLFP−1, respectively. This distinction is attributed to the structural and conductivity advantages inherent to graphene, showing its potential to enhance the electrochemical performance of structural batteries. Furthermore, LFP-impregnated CFs were evaluated in full cells versus pristine CFs, yielding relatively similar results, though with a slightly improved outcome observed with the graphene additive. These results provide valuable insights into the role of conductive additives in structural batteries and their responsiveness to varying operational conditions, underlining the potential for versatile energy storage solutions. © 2024 The Authors

Vanadis 4E (V4E) is a powder metallurgical cold work tool steel predominantly used in application with demand for wear resistance, high hardness, and toughness. It is of interest to have a processing route that enables full density starting from clean gas-atomized powder allowing component shaping capabilities. This study presents a process involving freeze granulation of powder to facilitate compaction by means of cold isostatic pressing, followed by sintering to allow for capsule-free hot isostatic pressing (HIP) and subsequent heat treatments of fully densified specimens. The sintering stage has been studied in particular, and it is shown how sintering in pure nitrogen at 1150 °C results in predominantly closed porosity, while sintering at 1200 °C gives near full density. Microstructural investigation shows that vanadium-rich carbonitride (MX) is formed as a result of the nitrogen uptake during sintering, with coarser appearance for the higher temperature. Nearly complete densification, approximately 7.80 ± 0.01 g/cm3, was achieved after sintering at 1200 °C, and after sintering at 1150 °C, followed by capsule-free HIP, hardening, and tempering. Irrespective of processing once the MX is formed, the nitrogen is locked into this phase and the austenite is stabilised, which means any tempering tends to result in a mixture of austenite and tempered martensite, the former being predominate during the sequential tempering, whereas martensite formation during cooling from austenitization temperatures becomes limited. 

Objectives: Surface characteristics of implant reconstructions determine the gingival fibroblast (GF) response and thus soft tissue integration (STI). However, for monolithic implant reconstructions it is unknown whether the (hybrid) ceramic biomaterial type and its surface treatment affect GF response. Therefore, this investigation examined the influence of the implant reconstruction biomaterials hybrid ceramic (HC), lithium disilicate ceramic (LS), 4 and 5 mol% yttria partially stabilized zirconiumdioxide ceramics (4/5Y-PSZ) and their surface treatment - machining, polishing or glazing - on surface characteristics and GF response. Methods: After characterization of surface topography and wettability by scanning electron microscopy, interferometry and contact angle measurement, the adhesion, morphology, metabolic activity and proliferation of GFs from six donors was investigated by fluorescent staining and a resazurin-based assay at days 1, 3 and 7. Titanium (Ti) served as control. Results: Biomaterial type and surface treatment affected the GF response in a topography-dependent manner. Smooth polished and glazed surfaces demonstrated enhanced GF adhesion and earlier proliferation onset compared to rough machined surfaces. Due to minor differences in surface topography of polished and glazed surfaces, however, the GF response was similar for polished and glazed HC, LS, 4- and 5Y-PSZ as well as Ti. Significance: Within the limits of the present investigation, polishing and glazing of machined HC, LS and 4/5Y-PSZ can be recommended to support STI-relevant cell functions in GF. Since the GF response on polished and glazed HC, LS, 4- and 5Y-PSZ surfaces and the Ti control was comparable, this investigation proofed equal cytocompatibility of these surfaces in vitro. © 2024 The Authors

The purpose of the present study was to assess the fracture resistance of a two-piece alumina-toughened zirconia implant system with a carbon-reinforced PEEK abutment screw. Methods: Thirty-two implants with screw-retained zirconia abutments were divided into four groups of eight samples each. Group 0 (control group) was neither loaded nor aged in a chewing simulator; group H was hydrothermally aged; group L was loaded with 98 N; and group HL was subjected to both hydrothermal aging and loading in a chewing simulator. One sample of each group was evaluated for t-m phase transformation, and the others were loaded until fracture. A one-way ANOVA was applied to evaluate differences between the groups. Results: No implant fracture occurred during the artificial chewing simulation. Furthermore, there were no statistically significant differences (p > 0.05) between the groups in terms of fracture resistance (group 0: 783 ± 43 N; group H: 742 ± 43 N; group L: 757 ± 86 N; group HL: 740 ± 43 N) and bending moment (group 0: 433 ± 26 Ncm; group H: 413 ± 23 Ncm; group L: 422 ± 49 Ncm; group HL: 408 ± 27 Ncm). Conclusions: Within the limitations of the present investigation, it can be concluded that artificial loading and hydrothermal aging do not reduce the fracture resistance of the investigated implant system. 

Objective: To investigate the fracture strength and potential phase transformation of an injection-molded two-piece zirconia implant restored with a zirconia abutment after loading and/or aging. Methods: Thirty-two two-piece zirconia implants (4.0 mm diameter) restored with zirconia abutments were embedded according to ISO 14801 and divided into four groups (n = 8/group): Three groups were either exclusively hydrothermally treated (group HT; 85°C), dynamically loaded (group DL; 107 cycles; 98 N), or subjected to both treatments simultaneously (group DL/HT). One group remained untreated (group 0). A sample from each group was cross-sectioned and examined by scanning electron microscopy for possible crystal phase transformation. The remaining samples were then loaded to fracture in a static loading test. A one-way ANOVA was used for statistical analyses. Results: During dynamic loading, three implants of group DL and six implants of group DL/HT fractured at a load of 98 N. The fracture strength of group DL/HT (108 ± 141 Ncm) was significantly reduced compared to the other groups (group 0: 342 ± 36 Ncm; HT: 363 ± 49 Ncm; DL: 264 ± 198 Ncm) (p <.05). Fractures from group 0 and HT occurred at both implant and abutment level, whereas implants from group DL and DL/HT fractured only at implant level. A shallow monoclinic transformation zone of approximately 2 μm was observed following hydrothermal treatment. Conclusions: Within the limitations of this study, it can be concluded that dynamic loading and the combination of loading and aging reduced the fracture strength of the implant abutment combination. Hydrothermal treatment caused a shallow transformation zone which had no influence on the fracture strength. © 2022 The Authors.