We used stereolithography to print polymer nanocomposite samples of stimuli-responsive spin crossover materials in the commercial photo-curable printing resins DS3000 and PEGDA-250. The thermomechanical analysis of the SLA-printed objects revealed not only the expected reinforcement of the polymer resins by the introduction of the stiffer SCO particles, but also a significant mechanical damping, as well as a sizeable linear strain around the spin transition temperatures. For the highest accessible loads (ca. 13-15 vol.%) we measured transformation strains in the range of 1.2-1.5%, giving rise to peaks in the coefficient of thermal expansion as high as 10-3 °C-1, which was exploited in 3D printed bilayer actuators to produce bending movement. The results pave the way for integrating these advanced stimuli-responsive composites into mechanical actuators and 4D printing applications.

Three-dimensional (3D) scaffolds provide cell support while improving tissue regeneration through amplified cellular responses between implanted materials and native tissues. So far, highly conductive cardiac, nerve, and muscle tissues have been engineered by culturing stem cells on electrically inert scaffolds. These scaffolds, even though suitable, may not be very useful compared to the results shown by cells when cultured on conductive scaffolds. Noticing the mature phenotype the stem cells develop over time when cultured on conductive scaffolds, scientists have been trying to impart conductivity to traditionally nonconductive scaffolds. One way to achieve this goal is to blend conductive polymers (polyaniline, polypyrrole, PEDOT:PSS) with inert biomaterials and produce a 3D scaffold using various fabrication techniques. One such technique is projection micro-stereolithography, which is an additive manufacturing technique. It uses a photosensitive solution blended with conductive polymers and uses visible/UV light to crosslink the solution. 3D scaffolds with complex architectural features down to microscale resolution can be printed with this technique promptly. This chapter reports a protocol to fabricate electrically conductive scaffolds using projection micro-stereolithography.

One of the advancements of the transdermal drug delivery system (TDDS) is the development of microneedles (MNs). These micron-sized needles are used for delivering various types of drugs to address the disadvantage of other transdermal techniques as well as oral drug delivery systems. MNs have high patient acceptance due to self-administration with minimally invasive and pain compared to the parenteral drug delivery. Over the years, various methods have been adopted to evolve the MNs and make them more cost-effective, accurate, and suitable for multiple applications. One such method is the 3D printing of MNs. The development of MN platforms using 3D printing has been made possible by improved features like precision, printing resolution, and the feasibility of using low-cost raw materials. In this review, we have tried to explain various types of MNs, fabrication methods, materials used in the formulation of MNs, and the recent applications that utilize 3D-printed MNs.

OBJECTIVE: To formulate an experimental methacrylate-based photo-polymerizable resin for 3D printing with ytterbium trifluoride as filler and to evaluate the mechanical, physicochemical, and biological properties.
METHODS: Resin matrix was formulated with 60 wt% UDMA, 40 wt% TEGDMA, 1 wt% TPO, and 0.01 wt% BHT. Ytterbium Trifluoride was added in concentrations of 1 (G1 %), 2 (G2 %), 3 (G3 %), 4 (G4 %), and 5 (G5 %) wt%. One group remained without filler addition as control (GC). The samples were designed in 3D builder software and printed using a UV-DLP 3D printer. The samples were ultrasonicated with isopropanol and UV cured for 60 min. The resins were tested for degree of conversion (DC), flexural strength, Knoop microhardness, softening in solvent, radiopacity, colorimetric analysis, and cytotoxicity (MTT and SRB).
RESULTS: Post-polymerization increased the degree of conversion of all groups (p < 0.05). G2 % showed the highest DC after post-polymerization. G2 % showed no differences in flexural strength from the G1 % and GC (p > 0.05). All groups showed a hardness reduction after solvent immersion. No statistical difference was found in radiopacity, softening in solvent (ΔKHN%), colorimetric spectrophotometry, and cytotoxicity (MTT) (p > 0.05). G1 % showed reduced cell viability for SRB assay (p < 0.05).
CONCLUSIONS: It was possible to produce an experimental photo-polymerizable 3D printable resin with the addition of 2 % ytterbium trifluoride as filler without compromising the mechanical, physicochemical, and biological properties, comparable to the current provisional materials.

BACKGROUND: The purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB).
METHODS: A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced.
CONCLUSIONS: ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry.

Microfluidic devices have immense potential for widespread community use, but a current bottleneck is the transition from research prototyping into mass production because the gold standard prototyping strategy is too costly and labor intensive when scaling up fabrication throughput. For increased throughput, it is common to mold devices out of thermoplastics due to low per-unit costs at high volumes. However, conventional fabrication methods have high upfront development expenses with slow mold fabrication methods that limit the speed of design evolution for expedited marketability. To overcome this limitation, we propose a rapid prototyping protocol to fabricate thermoplastic devices from a stereolithography (SLA) 3D printed template through intermediate steps akin to those employed in soft lithography. We apply this process towards the design of self-operating capillaric circuits, well suited for deployment as low-cost decentralized assays. Rapid development of these geometry- and material-dependent devices benefits from prototyping with thermoplastics. We validated the constructed capillaric circuits by performing an autonomous, pre-programmed, bead-based immunofluorescent assay for protein quantification. Overall, this prototyping method provides a valuable means for quickly iterating and refining microfluidic devices, paving the way for future scaling of production.

OBJECTIVE: To share our experience in creating precise anatomical models using available open-source software.
METHODS: An affordable method is presented, where from a DICOM format of a computed tomography, a segmentation of the region of interest is achieved. The image is then processed for surface improvement and the DICOM format is converted to STL. Error correction is achieved and the model is optimized to be printed by stereolithography with a desktop 3D printer.
RESULTS: Precise measurements of the dimensions of the DICOM file (CT), the STL file, and the printed model (3D) were carried out. For the C6 vertebra, the dimensions of the horizontal axis were 55.3 mm (CT), 55.337 mm (STL), and 55.3183 mm (3D). The dimensions of the vertebral body were 14.2 mm (CT), 14.551 mm (STL), and 14.8159 mm (3D). The length of the spinous process was 18.2 mm (CT), 18.283 mm (STL), and 18.2266 mm (3D), while its width was 8.5 mm (CT), 8.3644 mm (STL), and 8.3226 mm (3D). For the C7 vertebra, the dimensions of the horizontal axis were 58.6 mm (CT), 58.739 mm (STL), and 58.7144 mm (3D). The dimensions of the vertebral body were 14 mm (CT), 14.0255 mm (STL), and 14.2312 mm (3D). The length of the spinous process was 18.7 mm (CT), 18.79 mm (STL), and 18.6458 mm (3D), and its width was 8.9 mm (CT), 8.988 mm (STL), and 8.9760 mm (3D).
CONCLUSIONS: The printing of a 3D model of bone tissue using this algorithm is a viable, useful option with high precision.
OBJECTIVE: Compartir nuestra experiencia para crear modelos anatómicos precisos utilizando software con licencia abierta disponibles.
UNASSIGNED: Se presenta un método asequible, en donde a partir de un formato DICOM de una tomografía computarizada se logra una segmentación de la región de interés. Posteriormente se procesa la imagen para una mejora de superficie y se realiza la conversión de formato DICOM a STL. Se logra la corrección de errores y se optimiza el modelo para luego ser impreso por medio de estereolitografía con una impresora 3D de escritorio.
RESULTS: Se efectuaron mediciones precisas de las dimensiones del archivo DICOM (TC), del archivo STL y del modelo impreso (3D). Para la vértebra C6, las dimensiones del eje horizontal fueron 55.3 mm (TC), 55.337 mm (STL) y 55.3183 mm (3D). Las dimensiones del cuerpo vertebral fueron 14.2 mm (TC), 14.551 mm (STL) y 14.8159 mm (3D). La longitud de la apófisis espinosa fue de 18.2 mm (TC), 18.283 mm (STL) y 18.2266 mm (3D), mientras que su ancho fue de 8.5 mm (TC), 8.3644 mm (STL) y 8.3226 mm (3D). Para la vértebra C7, las dimensiones del eje horizontal fueron 58.6 mm (TC), 58.739 mm (STL) y 58.7144 mm (3D). Las dimensiones del cuerpo vertebral fueron 14 mm (TC), 14.0255 mm (STL) y 14.2312 mm (3D). La longitud de la apófisis espinosa fue de 18.7 mm (TC), 18.79 mm (STL) y 18.6458 mm (3D), y su ancho fue de 8.9 mm (TC), 8.988 mm (STL) y 8.9760 mm (3D).
UNASSIGNED: La impresión de un modelo en 3D de tejido óseo mediante este algoritmo resulta una opción viable, útil y con una alta precisión.

The capacity of additive manufacturing and three-dimensional (3D) printing to quickly construct intricate structures and accurate geometries sets them apart from traditional production techniques. The fourth industrial revolution and the digitalization of production were fueled by the emergence of 3D printing, which was made possible by the increasing demand for goods with various designs, functions, and materials. The global influence of 3D printing on healthcare has resulted in the replacement of generic implanted medical devices with patient-customized implants. In the field of oral and maxillofacial surgery, where surgeons use precision medicine daily, this revolution has had a huge influence. Treatments enhanced by 3D technology include orthognathic surgery, complete joint replacement therapy, and trauma. Surgical teams now engage in the 3D design and production of devices at point-of-care treatment facilities with internal infrastructure thanks to the growing and broad adoption of 3D technology in clinical settings. The way doctors approach treatment planning and clinical results are affected greatly by 3D technology. While outlining significant clinical applications, the article presents our viewpoint on the use of 3D-based technology in the field of oral and maxillofacial surgery and the road ahead with the advent of Four-dimensional (4D) printing.

UNASSIGNED: With the increasing application of guided endodontics to treat complex root canal treatment, the entire process of root canal treatment has become more precise, reducing damage to tooth structure and improving success rates. However, due to the limitations of the operating space, the use of guided endodontic templates in posterior root canal treatment is less common. This study aims to compare the accuracy and reliability of selective laser melting (SLM) and traditional stereolithography etching (SLA) guided endodontic templates for posterior root canals, providing better treatment strategies for posterior root canal treatment.
UNASSIGNED: The teeth were randomly assigned to either SLM or SLA group. Preoperative cone-beam computed tomography (CBCT) and a three-dimensional (3D) scanner were used to establish the 3D root canal system and the accurate occlusal models of the teeth. The virtual access to the canal access was designed using Mimics 19.0 and 3-Matic 11.0. The endodontic access was performed based on either SLM or SLA templates. The accuracy of endodontic preparation was measured in three-dimensions by calculating deviations from planned accesses. The template height and tooth substance loss rates in each group were measured.
UNASSIGNED: SLM-guided templates have a low average deviation at the entry point and apical portion of the bur of total posterior teeth (including premolars and molars) and individual molars (P < 0.05). Moreover, there was a significant difference in angular deviations and height of template in total posterior teeth and individual molars (P < 0.05). The mean substance loss rate of the SLA group was slightly greater than that of the SLM group, but the difference was not statistically (P > 0.05).
UNASSIGNED: SLM-guided endodontics provides a more predictable and precise location of root canal orifice for the treatment of posterior teeth.

OBJECTIVE: To evaluate the fabrication trueness of additively manufactured maxillary definitive casts with various tooth preparations fabricated with different 3-dimensional (3D) printers and print orientations.
METHODS: A maxillary typodont with tooth preparations for a posterior 3-unit fixed partial denture, lateral incisor crown, central incisor and canine veneers, first premolar and second molar inlays, and a first molar crown was digitized with an industrial scanner. This scan file was used to fabricate definitive casts with a digital light processing (DLP) or stereolithography (SLA) 3D printer in different orientations (0-degree, 30-degree, 45-degree, and 90-degree) (n = 7). All casts were digitized with the same scanner, and the deviations within each preparation site were evaluated. Generalized linear model analysis was used for statistical analysis (α = 0.05).
RESULTS: The interaction between the 3D printer and the print orientation affected measured deviations within all preparations (P ≤ 0.001) except for the lateral incisor crown and canine veneer (P ≥ 0.094), which were affected only by the main factors (P < 0.001). DLP-90 mostly led to the highest and DLP-0 mostly resulted in the lowest deviations within posterior tooth preparations (P ≤ 0.014). DLP-30 led to the lowest deviations within the first premolar inlay and DLP-45 led to the lowest deviations within the central incisor veneer preparation (P ≤ 0.045).
CONCLUSIONS: Posterior preparations of tested casts had the highest trueness with DLP-0 or DLP-30, while central incisor veneer preparations had the highest trueness with DLP-45. DLP-90 led to the lowest trueness for most of the tooth preparations.
CONCLUSIONS: Definitive casts with tooth preparations fabricated with the tested DLP 3D printer and the print orientation adjusted on tooth preparation may enable well-fitting restorations. However, 90-degree print orientation should be avoided with this 3D printer, as it led to the lowest fabrication trueness.