Contraction Dynamics of Rod Microtissues of Gingiva-Derived and Periodontal Ligament-Derived Cells

Tissue engineering strategies using microtissues as “building blocks” have high potential in regenerative medicine. Cognition of contraction dynamics involved in the in vitro self-assembly of these microtissues can be conceived as the bedrock of an effective periodontal tissue regenerative therapy. Our study was directed at evaluating the shrinkage in the rod-shaped structure of a directed self-assembly of human gingiva-derived cells (GC) and periodontal ligament-derived cells (PDLC) and developing insights into the potential mechanisms responsible for the shrinkage. GC and PDLC were seeded in non-adherent agarose molds to form rod microtissues. Cells used for the experiments were characterized using fluorescence-activated cell sorting (FACS). To assess the viability, resazurin-based cytotoxicity assays, trypan blue dye exclusion assay, MTT and live/dead staining, and histological evaluation of rods based on hematoxylin and eosin staining were performed. Rod contraction was evaluated and measured at 0, 2, 6, and 24 h and compared to L-929 cells. The role of transforming growth factor (TGF)-β signaling, phosphoinositide 3-kinase (PI3K)/AKT, and mitogen activated protein kinase (MAPK) signaling was analyzed. Our results show that the rod microtissues were vital after 24 h. A reduction in the length of rods was seen in the 24 h period. While the recombinant TGF-β slightly reduced contraction, inhibition of TGF-β signaling did not interfere with the contraction of the rods. Interestingly, inhibition of phosphoinositide 3-kinase by LY294002 significantly delayed contraction in GC and PDLC rods. Overall, GC and PDLC have the ability to form rod microtissues which contract over time. Thus, approaches for application of these structures as “building blocks” for periodontal tissue regeneration should consider that rods have the capacity to contract substantially. Further investigation will be needed to unravel the mechanisms behind the dynamics of contraction

3D printed plates based on generative design biomechanically outperform manual digital fitting and conventional systems printed in photopolymers in bridging mandibular bone defects of critical size in dogs

Conventional plate osteosynthesis of critical-sized bone defects in canine mandibles can fail to restore former functionality and stability due to adaption limits. Three-dimensional (3D) printed patient-specific implants are becoming increasingly popular as these can be customized to avoid critical structures, achieve perfect alignment to individual bone contours, and may provide better stability. Using a 3D surface model for the mandible, four plate designs were created and evaluated for their properties to stabilize a defined 30 mm critical-size bone defect. Design-1 was manually designed, and further shape optimized using Autodesk®Fusion 360 (ADF360) and finite element analysis (FE) to generate Design-2. Design-4 was created with the generative design (GD) function from ADF360 using preplaced screw terminals and loading conditions as boundaries. A 12-hole reconstruction titanium locking plate (LP) (2.4/3.0 mm) was also tested, which was scanned, converted to a STL file and 3D printed (Design-3). Each design was 3D printed from a photopolymer resin (VPW) and a photopolymer resin in combination with a thermoplastic elastomer (VPWT) and loaded in cantilever bending using a customized servo-hydraulic mechanical testing system; n = 5 repetitions each. No material defects pre- or post-failure testing were found in the printed mandibles and screws. Plate fractures were most often observed in similar locations, depending on the design. Design-4 has 2.8–3.6 times ultimate strength compared to other plates, even though only 40% more volume was used. Maximum load capacities did not differ significantly from those of the other three designs. All plate types, except D3, were 35% stronger when made of VPW, compared to VPWT. VPWT D3 plates were only 6% stronger. Generative design is faster and easier to handle than optimizing manually designed plates using FE to create customized implants with maximum load-bearing capacity and minimum material requirements. Although guidelines for selecting appropriate outcomes and subsequent refinements to the optimized design are still needed, this may represent a straightforward approach to implementing additive manufacturing in individualized surgical care. The aim of this work is to analyze different design techniques, which can later be used for the development of implants made of biocompatible materials

Realistic 3D printed imaging tumor phantoms for validation of image processing algorithms

Medical imaging phantoms are widely used for validation and verification of imaging systems and algorithms in surgical guidance and radiation oncology procedures. Especially, for the performance evaluation of new algorithms in the field of medical imaging, manufactured phantoms need to replicate specific properties of the human body, e.g., tissue morphology and radiological properties. Additive manufacturing (AM) technology provides an inexpensive opportunity for accurate anatomical replication with customization capabilities. In this study, we proposed a simple and cheap protocol to manufacture realistic tumor phantoms based on the filament 3D printing technology. Tumor phantoms with both homogenous and heterogenous radiodensity were fabricated. The radiodensity similarity between the printed tumor models and real tumor data from CT images of lung cancer patients was evaluated. Additionally, it was investigated whether a heterogeneity in the 3D printed tumor phantoms as observed in the tumor patient data had an influence on the validation of image registration algorithms. A density range between -217 to 226 HUs was achieved for 3D printed phantoms; this range of radiation attenuation is also observed in the human lung tumor tissue. The resulted HU range could serve as a lookup-table for researchers and phantom manufactures to create realistic CT tumor phantoms with the desired range of radiodensities. The 3D printed tumor phantoms also precisely replicated real lung tumor patient data regarding morphology and could also include life-like heterogeneity of the radiodensity inside the tumor models. An influence of the heterogeneity on accuracy and robustness of the image registration algorithms was not found

Deferoxamine but Not Dimethyloxalylglycine, L-Mimosine, or Cobalt Dichloride Can Interfere with the MTT Assay

Hypoxia mimetic agents (HMAs) have been shown to have a positive influence on cellular functions in a multitude of tissue regenerative strategies. Novel experimental approaches use biomaterials as carriers for controlled delivery of these HMAs. Here, the cytotoxic aspects of biocompatibility are of key relevance. The MTT assay is widely used to evaluate cytotoxicity and proliferation. Based on the implications from the proceeding research we hypothesized that specific HMAs such as deferoxamine at high concentrations can interfere with the MTT assay. Thus, the aim of this study was to test the repercussions of the HMAs dimethyloxalylglycine, deferoxamine, L-mimosine, and CoCl2 on the validity of the MTT assay. Murine MC3T3-E1 cells were cultured in serum-free alphaMEM and in alphaMEM supplemented with 10 % fetal bovine serum with the HMAs dimethyloxalylglycine, deferoxamine, L-mimosine, and CoCl2, respectively, at 3 mM-0.3 mM for 24 h (experimental groups). Cells without HMAs served as control (control groups). The same experiments were performed with medium and phosphate buffered saline (PBS) without cells. In all settings MTT solution was added to PBS-washed or unwashed culture plates for the last two hours of the incubation period. Then MTT solution was removed and dimethyl sulfoxide was added to dissolve the formazan crystals and absorption was measured. Our data show that the presence of deferoxamine can interfere with the MTT assay if not removed before the addition of MTT. This is particularly important when evaluating cell viability in setups where deferoxamine-loaded biomaterials are used

Frontiers in Bioengineering and Biotechnology / 3D PrintingEncompassing the Facets of Dentistry

This narrative review presents an overview on the currently available 3D printing technologies and their utilization in experimental, clinical and educational facets, from the perspective of different specialties of dentistry, including oral and maxillofacial surgery, orthodontics, endodontics, prosthodontics, and periodontics. It covers research and innovation, treatment modalities, education and training, employing the rapidly developing 3D printing process. Research-oriented advancement in 3D printing in dentistry is witnessed by the rising number of publications on this topic. Visualization of treatment outcomes makes it a promising clinical tool. Educational programs utilizing 3D-printed models stimulate training of dental skills in students and trainees. 3D printing has enormous potential to ameliorate oral health care in research, clinical treatment, and education in dentistry.(VLID)470940

Contraction Dynamics of Rod Microtissues of Gingiva-Derived and Periodontal Ligament-Derived Cells

Tissue engineering strategies using microtissues as “building blocks” have high potential in regenerative medicine. Cognition of contraction dynamics involved in the in vitro self-assembly of these microtissues can be conceived as the bedrock of an effective periodontal tissue regenerative therapy. Our study was directed at evaluating the shrinkage in the rod-shaped structure of a directed self-assembly of human gingiva-derived cells (GC) and periodontal ligament-derived cells (PDLC) and developing insights into the potential mechanisms responsible for the shrinkage. GC and PDLC were seeded in non-adherent agarose molds to form rod microtissues. Cells used for the experiments were characterized using fluorescence-activated cell sorting (FACS). To assess the viability, resazurin-based cytotoxicity assays, trypan blue dye exclusion assay, MTT and live/dead staining, and histological evaluation of rods based on hematoxylin and eosin staining were performed. Rod contraction was evaluated and measured at 0, 2, 6, and 24 h and compared to L-929 cells. The role of transforming growth factor (TGF)- signaling, phosphoinositide 3-kinase (PI3K)/AKT, and mitogen activated protein kinase (MAPK) signaling was analyzed. Our results show that the rod microtissues were vital after 24 h. A reduction in the length of rods was seen in the 24 h period. While the recombinant TGF- slightly reduced contraction, inhibition of TGF- signaling did not interfere with the contraction of the rods. Interestingly, inhibition of phosphoinositide 3-kinase by LY294002 significantly delayed contraction in GC and PDLC rods. Overall, GC and PDLC have the ability to form rod microtissues which contract over time. Thus, approaches for application of these structures as “building blocks” for periodontal tissue regeneration should consider that rods have the capacity to contract substantially. Further investigation will be needed to unravel the mechanisms behind the dynamics of contraction.(VLID)470685

Perspectives on medical 3D printing at the point-of-care from the new European 3D Printing Special Interest Group

Abstract This editorial presents the vision for the newly formed (2022) European 3D Special Interest Group (EU3DSIG) in the landscape of medical 3D printing. There are four areas of work identified by the EU3DSIG in the current landscape, namely: 1) creating and fostering communication channels among researches, clinicians and industry, 2) generating awareness of hospitals point-of-care 3D technologies; 3) knowledge sharing and education; 4) regulation, registry and reimbursement models

Medical 3D printing with polyjet technology: effect of material type and printing orientation on printability, surface structure and cytotoxicity

Abstract Due to its high printing resolution and ability to print multiple materials simultaneously, inkjet technology has found wide application in medicine. However, the biological safety of 3D-printed objects is not always guaranteed due to residues of uncured resins or support materials and must therefore be verified. The aim of this study was to evaluate the quality of standard assessment methods for determining the quality and properties of polyjet-printed scaffolds in terms of their dimensional accuracy, surface topography, and cytotoxic potential. Standardized 3D-printed samples were produced in two printing orientations (horizontal or vertical). Printing accuracy and surface roughness was assessed by size measurements, VR-5200 3D optical profilometer dimensional analysis, and scanning electron microscopy. Cytotoxicity tests were performed with a representative cell line (L929) in a comparative laboratory study. Individual experiments were performed with primary cells from clinically relevant tissues and with a Toxdent cytotoxicity assay. Dimensional measurements of printed discs indicated high print accuracy and reproducibility. Print accuracy was highest when specimens were printed in horizontal direction. In all cytotoxicity tests, the estimated mean cell viability was well above 70% (p < 0.0001) regardless of material and printing direction, confirming the low cytotoxicity of the final 3D-printed objects. Graphical Abstrac

Additional file 1 of Medical 3D printing with polyjet technology: effect of material type and printing orientation on printability, surface structure and cytotoxicity

Additional file 1