Schwarzites and Triply Periodic Minimal Surfaces: From Pure Topology Mathematics to Macroscale Applications.

Schwarzites are porous (spongy-like) carbon allotropes with negative Gaussian curvatures. They are proposed by Mackay and Terrones inspired by the works of the German mathematician Hermann Schwarz on Triply-Periodic Minimal Surfaces (TPMS). This review presents and discusses the history of schwarzites and their place among curved carbon nanomaterials. The main works on schwarzites are summarized and are available in the literature. Their unique structural, electronic, thermal, and mechanical properties are discussed. Although the synthesis of carbon-based schwarzites remains elusive, recent advances in the synthesis of zeolite-templates nanomaterials have brought them closer to reality. Atomic-based models of schwarzites are translated into macroscale ones that are 3D-printed. These 3D-printed models are exploited in many real-world applications, including water remediation and biomedical ones.

Characterization of Microstructure, Optical Properties, and Mechanical Behavior of a Temporary 3D Printing Resin: Impact of Post-Curing Time.

The present study aimed to characterize the microstructure of a temporary 3D printing polymer-based composite material (Resilab Temp), evaluating its optical properties and mechanical behavior according to different post-curing times. For the analysis of the surface microstructure and establishment of the best printing pattern, samples in bar format following ISO 4049 (25 × 10 × 3 mm) were designed in CAD software (Rhinoceros 6.0), printed on a W3D printer (Wilcos), and light-cured in Anycubic Photon for different lengths of time (no post-curing, 16 min, 32 min, and 60 min). For the structural characterization, analyses were carried out using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The mechanical behavior of this polymer-based composite material was determined based on flexural strength tests and Knoop microhardness. Color and translucency analysis were performed using a spectrophotometer (VITA Easy Shade Advanced 4.0), which was then evaluated in CIELab, using gray, black, and white backgrounds. All analyses were performed immediately after making the samples and repeated after thermal aging over two thousand cycles (5-55 °C). The results obtained were statistically analyzed with a significance level of 5%. FT-IR analysis showed about a 46% degree of conversion on the surface and 37% in the center of the resin sample. The flexural strength was higher for the groups polymerized for 32 min and 1 h, while the Knoop microhardness did not show a statistical difference between the groups. Color and translucency analysis also did not show statistical differences between groups. According to all of the analyses carried out in this study, for the evaluated material, a post-polymerization time of 1 h should be suggested to improve the mechanical performance of 3D-printed devices.

Aumento do Rebordo Alveolar com Enxerto em Bloco Impresso Personalizado: Relato de Caso / Alveolar ridge augmentation with custom 3D-printed block graft: Case report

A utilização da tecnologia CAD/CAM (computer aided design/computer aided manufacturing) e 3D (tridimensional) para reconstruções alveolares na implantodontia permite o planejamento pré-operatório detalhado, o design do resultado desejado do enxerto e a avaliação virtual do resultado em relação à reconstrução protética. Este trabalho objetiva detalhar a técnica cirúrgica de enxerto ósseo sintético confeccionado por meio dessa tecnologia, seguido da instalação de implantes osseointegráveis e reabilitação protética em um defeito ósseo na mandíbula. Paciente masculino, 22 anos, compareceu à clínica por avulsão dos elementos 32, 31, 41 e 42 com significativa perda óssea vertical de rebordo alveolar. Devido à extensa perda óssea, realizou-se enxerto em bloco prototipado impresso. O escaneamento intraoral e os arquivos de imagem gerados foram enviados ao centro de planejamento virtual. Primeiramente, foi realizada a cirurgia para instalação do enxerto em bloco. Após o período de cicatrização, foi realizada cirurgia para instalação de dois implantes osseointegráveis. Esperado o período de três meses a partir da instalação dos implantes, foi realizada a confecção de próteses provisórias fixas sobre implantes a fim de realizar o condicionamento dos tecidos moles peri-implantares e o carregamento progressivo dos implantes. O aumento do rebordo alveolar através do uso de enxerto em bloco impresso personalizado apresentou-se como uma técnica com inúmeras vantagens, por não necessitar de sítio doador, reduzir tempo cirúrgico e apresentar perfeita adaptação do bloco ao defeito ósseo, resultando em menor morbidade pós-operatória. Essa técnica é uma indicação para casos de defeitos ósseos severos, visando a otimizar o resultado e a propiciar menor desconforto ao paciente.

The use of the technology CAD/CAM (computer aided design/computer aided manufacturing) and 3D (three dimensional) to alveolar reconstructions in implant dentistry allows detailed preoperative planning, the design of the desired grafting result, and the virtual evaluation of the result in relation to the prosthetic reconstruction. This paper aims to details the synthetic bone graft made through this technology, followed by the installation of osseointegrated implants and prosthetic rehabilitation in a bone imperfection in the jaw. A 22-year-old man attended the clinic due to a tooth avulsion of the four lower incisors with significant vertical bone loss of alveolar ridge. Because of the extensive bone loss, it was made a prototyped printed block graft. The intraoral scan and the generated image files were sent to the virtual planning center. First, it was necessary a surgery to install the block graft. After the healing process, it was made a surgery to put two osseointegrated implants. Three months later, temporary fixed prostheses on implants were made to conditioning the peri-implant soft tissues and the progressive loading of the implants. The increase of the alveolar ridge using personalized printed block graft was presented as a technique with numerous advantages, since it does not require a donor site, reduces the surgical time and presents perfect adaptation of the block to the bone imperfection, resulting in a less postoperative morbidity. This technique is indicated to cases of severe bone imperfections, aims to optimize results, and provide less discomfort to the patient.

3D wildlife skull models for wildlife veterinary training.

Wildlife veterinarians are necessary for zoonotic diseases and species loss management, and there is a rising interest to enroll at veterinary schools with the wish to work in zoo and wildlife medicine. However, teaching wildlife is challenging due to the difficulty faced by universities to work with wild animal specimens. The aim of the present was to evaluate the understanding efficiency of some anatomical and behavioral aspects using 3D printed models of four wildlife species skulls, the kinkaju (Potos flavus), the white-nosed coati (Nasua narica), the northern anteater (Tamandua mexicana), and the nine-banded armadillo (Dasypus novemcinctus). This study was performed on 85 third-year veterinary students, divided into an experimental and a control group, who used and not used 3D printed skulls, respectively. Results show that the experimental group shows higher scores, in three of the four variables evaluated, than the control group. Then, 3D wildlife printed skulls constitute a promising teaching tool for veterinary students. In fact, it may be as good as real skulls, since new 3D printers can print on high endurance and firmness stock with high accuracy at reduced costs. In this context, it is important to encourage its use for the training of new generations and keep professionals up to date.

Adhesion of biofilm, surface characteristics, and mechanical properties of antimicrobial denture base resin.

PURPOSE: This study incorporated the nanomaterial, nanostructured silver vanadate decorated with silver nanoparticles (AgVO3), into heat-cured resin (HT) at concentrations of 2.5%, 5%, and 10% and compared the adhesion of multispecies biofilms, surface characteristics, and mechanical properties with conventional heat-cured (HT 0%) and printed resins. MATERIALS AND METHODS: AgVO3 was incorporated in mass into HT powder. A denture base resin was used to obtain printed samples. Adhesion of a multispecies biofilm of Candida albicans, Candida glabrata, and Streptococcus mutans was evaluated by colony-forming units per milliliter (CFU/mL) and metabolic activity. Wettability, roughness, and scanning electron microscopy (SEM) were used to assess the physical characteristics of the surface. The mechanical properties of flexural strength and elastic modulus were tested. RESULTS: HT 10%-AgVO3 showed efficacy against S. mutans; however, it favored C. albicans CFU/mL (P < .05). The printed resin showed a higher metabolically active biofilm than HT 0% (P < .05). There was no difference in wettability or roughness between groups (P > .05). Irregularities on the printed resin surface and pores in HT 5%-AgVO3 were observed by SEM. HT 0% showed the highest flexural strength, and the resins incorporated with AgVO3 had the highest elastic modulus (P < .05). CONCLUSION: The incorporation of 10% AgVO3 into heat-cured resin provided antimicrobial activity against S. mutans in a multispecies biofilm did not affect the roughness or wettability but reduced flexural strength and increased elastic modulus. Printed resin showed higher irregularity, an active biofilm, and lower flexural strength and elastic modulus than heat-cured resin.

Development and implementation of a significantly low-cost 3D bioprinter using recycled scrap material.

The field of 3D bioengineering proposes to effectively contribute to the manufacture of artificial multicellular organ/tissues and the understanding of complex cellular mechanisms. In this regard, 3D cell cultures comprise a promising bioengineering possibility for the alternative treatment of organ function loss, potentially improving patient life expectancies. Patients with end-stage disease, for example, could benefit from treatment until organ transplantation or even undergo organ function restoration. Currently, 3D bioprinters can produce tissues such as trachea cartilage or artificial skin. Most low-cost 3D bioprinters are built from fused deposition modeling 3D printer frames modified for the deposition of biologically compatible material, ranging between $13.000,00 and $300.000,00. Furthermore, the cost of consumables should also be considered as they, can range from $3,85 and $100.000,00 per gram, making biomaterials expensive, hindering bioprinting access. In this context, our report describes the first prototype of a significantly low-cost 3D bioprinter built from recycled scrap metal and off-the-shelf electronics. We demonstrate the functionalized process and methodology proof of concept and aim to test it in different biological tissue scaffolds in the future, using affordable materials and open-source methodologies, thus democratizing the state of the art of this technology.

Efeito de diferentes tratamentos de superfície na resistência ao cisalhamento entre uma resina nanohíbrida para impressão 3D e cimento resinoso / Effect of different surface treatments on the shear strength between a nanohybrid resin for 3D printing and resin cement

O objetivo deste trabalho foi avaliar a resistência de união entre uma resina nanohíbrida para impressão 3D com cimento resinoso após diferentes tratamentos de superfície e envelhecimento. Foram fabricados 120 blocos da resina nanohíbrida (Nanolab 3D, Wilcos do Brasil) em tamanhos de 10 x 8 x 2 mm, desenhados no software Rhinoceros 7 e depois impressos (W3D PRINT, Wilcos do Brasil) por método digital de processamento de luz (LCD). Foram produzidos também blocos de mesmo tamanho obtidos a partir de blocos de CAD/CAM de uma resina híbrida (Hybrid, Blue Dent), como grupo controle. Cinco tratamentos de superfície foram realizados nos blocos de resina: nenhum tratamento, condicionamento ácido com ácido fluorídrico, jateamento com Al3O2, imersão em monômero de metilmetacrilato (primer) e um grupo somando o jateamento com imersão em primer. Foram construídos cilindros (< 1 mm2) de cimento resinoso convencional dual sobre as superfícies tratadas com auxílio de matriz de silicone. A resistência de união foi medida usando uma máquina de ensaio universal e um teste de microcisalhamento com fio. Metade das amostras de cada grupo foram testadas sete dias após a cimentação, já a outra metade foi termociclada por 12.000 ciclos térmicos (5-55 ºC, 30 segundos cada) e ensaiadas a seguir. Os modos de falha foram analisados por um estereomicroscópio e imagens representativas foram realizadas com o auxílio do microscópio eletrônico de varredura. Após a análise inferencial com ANOVA 3-fatores foi possível observar que houve diferença estatisticamente significante tanto para os fatores material, tratamento de superfície e envelhecimento isoladamente, como para as interações entre eles. A resina híbrida de impressão mostrou maior resistência de união quando comparada com os blocos CAD/CAM. A ciclagem térmica aumentou a resistência de união das resinas impressas e diminuiu a mesma nos blocos de CAD/CAM. É possível concluir que a aplicação de silano é o melhor tratamento de superfície para as resinas de impressão 3D já que proporcionou bons valores de resistência de união e confiabilidade da interface adesiva. A resistência adesiva a longo prazo da resina híbrida de impressão 3D (Nanolab) é influenciada positivamente pelo envelhecimento (AU)

The objective of this work was to evaluate the bond strength between a nanohybrid resin for 3D printing with resin cement after different surface treatments and aging. 120 blocks of nanohybrid resin (Nanolab 3D, Wilcos do Brasil) were manufactured in sizes of 10 x 8 x 2 mm, designed in the Rhinoceros 7 software and then printed (W3D PRINT, Wilcos do Brasil) by digital light processing method (LCD ). Blocks of the same size obtained from CAD/CAM blocks of a hybrid resin (Hybrid, Blue Dent) were also produced as a control group. Five surface treatments were performed on the resin blocks: no treatment, acid etching with hydrofluoric acid, sandblasting with Al3O2, immersion in methylmethacrylate monomer (primer) and one group adding the sandblasting with immersion in primer. Cylinders (< 1 mm2) of conventional dual resin cement were built on the surfaces treated with the aid of a silicone matrix. Bond strength was measured using a universal testing machine and a wire microshear test. Half of the samples from each group were tested seven days after cementation, while the other half was thermocycled through 12,000 thermal cycles (5-55 ºC, 30 seconds each) and then tested. Failure modes were analyzed using a stereomicroscope and representative images were taken using a scanning electron microscope. After the inferential analysis with 3-way ANOVA, it was possible to observe that there was a statistically significant difference both for the material, surface treatment and aging factors alone, as well as for the interactions between them. The hybrid impression resin showed higher bond strength when compared to the CAD/CAM blocks. Thermal cycling increased the bond strength of printed resins and decreased it in CAD/CAM blocks. It is possible to conclude that silane application is the best surface treatment for 3D printing resins as it provided good bond strength values and reliability of the adhesive interface. The long-term adhesive strength of the 3D printing hybrid resin (Nanolab) is positively influenced by aging. (AU)

3D-printed resins for provisional dental restorations: Comparison of mechanical and biological properties.

OBJECTIVES: To characterize the mechanical and biological properties of three commercially available resins, which are currently used for provisional restorations and to compare them to an experimental resin intended for definitive fixed dental prostheses. MATERIALS AND METHODS: Three commercially available resins: Crowntec (CT, Saremco), Temporary C&B (FL, Formlabs), C&B MFH (ND, Nextdent), and the experimental resin: Permanent Bridge (PB, Saremco) were printed and subjected to biaxial flexural strength test, finite element analysis, Weibull analysis, scanning electron microscopy, cell proliferation, immunohistochemistry and cytotoxicity assays. Samples from CT, PB, and ND were provided directly from the manufacturers ensuring ideal workflow. FL was printed using the workflow as recommended by the manufacturer, using a Formlabs 2 printer and their post-processing units Form Wash and Form Cure. RESULTS: From the tested resins, PB yielded the best overall results in terms of mechanical properties. Cell proliferation and cytotoxicity did not show any significant differences among materials. PB showed higher values for probability of survival predictions (35%) when subjected to 250 MPa loads, whereas the other materials did not reach 10%. SIGNIFICANCE: Despite mechanical differences between the evaluated materials, the outcomes suggest that 3D printed provisional resins may be used in clinical settings, following the manufacturers indications. New materials intended for long-term use, such as the PB resin, yielded higher mechanical properties compared to the other materials. Alternative printing and post-processing methods have not yet been evaluated and should be avoided until further literature is available. CLINICAL SIGNIFICANCE: 3D printed resins for provisional restorations have become popular with the emergence of new technologies. In this study, we evaluated three different commercially available resins for provisional restorations and one new experimental resin. The results from this study indicate that commercially available resins could be used in clinical settings under certain conditions and limited periods of time. Following the manufacturers protocols is of paramount importance to not compromise these properties.

Low-cost Gent type sampler constructed for urban atmospheric aerosol sampling.

The importance of studying the atmospheric pollution due to its effects on human health and other ecosystems, the inexistence of national production of equipment for air sample collection, and the high cost of the imported equipment (especially in developing countries) led the authors of the present work to construct a low-cost Gent type sampler. The construction of the sampler was carried out by combining low-cost materials with good mechanical strength (such as nylon 6.0), hydraulic piping PVC, and the use of a 3D printer. The innovation of the present work is the employment of a 3D printer using ABS polymer to create the grids that cannot be machined. In addition to the sampler, the system is composed of a vacuum pump, a gas meter, and a rotameter. The total cost of the sampling system amounted at about 1200 USD, and the cost of the manufactured Gent type sampler did not reach 100 USD. The results obtained while using this set for sampling atmospheric aerosol for a period of 11 months were compared with the mass concentration of PM10 obtained from the official environmental company, CETESB of São Paulo State, Brazil, showing good correlation with those from CETESB - which confirmed its effectiveness and suitability for use. The low cost, easy operation, and versatility of the built Gent type sampler enable its use for scientific and academic purposes. The equipment can be useful in environmental monitoring networks, in low-income regions, and as an instrument for environmental education used in universities.

A Low-Cost Calibration Method for Low-Cost MEMS Accelerometers Based on 3D Printing.

A ubiquitous sensor in embedded systems is the accelerometer, as it enables a range of applications. However, accelerometers experience nonlinearities in their outputs caused by error terms and axes misalignment. These errors are a major concern because, in applications such as navigations systems, they accumulate over time, degrading the position accuracy. Through a calibration procedure, the errors can be modeled and compensated. Many methods have been proposed; however, they require sophisticated equipment available only in laboratories, which makes them complex and expensive. In this article, a simple, practical, and low-cost calibration method is proposed. It uses a 3D printed polyhedron, benefiting from the popularisation and low-cost of 3D printing in the present day. Additionally, each polyhedron could hold as much as 14 sensors, which can be calibrated simultaneously. The method was performed with a low-cost sensor and it significantly reduced the root-mean-square error (RMSE) of the sensor output. The RMSE was compared with the reported in similar proposals, and our method resulted in higher performance. The proposal enables accelerometer calibration at low-cost, and anywhere and anytime, not only by experts in laboratories. Compensating the sensor's inherent errors thus increases the accuracy of its output.

Error Measurement Between Anatomical Porcine Spine, CT Images, and 3D Printing.

RATIONALE AND OBJECTIVES: 3D printers are increasingly used in medical applications such as surgical planning, creation of implants and prostheses, and medical education. For the creation of reliable 3D printed models of the vertebral column, processing must be performed on CT images. This processing must be assessed and validated so that any error of the printed model can be recognized and minimized. MATERIAL AND METHODS: In order to perform this validation, 10 CT scans of porcine lumbar spinal vertebra were used, which were then dissected and scanned again. CT image processing was performed to obtain a mesh and perform 3D printing. RESULTS: There was no statistical difference among the four different levels of vertebrae measurements (first CT images, second CT images, anatomical piece of porcine bone and 3D printing of porcine bone; One Way repeated measure ANOVA, F < F_crit, p value > α = 0.05). The Intraclass Correlation also revealed a mean intraclass correlation coefficient (3,1) = 0.9553, which describes the reliability of all four levels in addition to the reliability of the data between porcine samples subjected to different levels of measurement. This shows that the average error is less than 1 mm. CONCLUSIONS: The measurements of models created with 3D printers using the pipeline described in this paper have an average error of 0.60 mm with CT images and 0.73 mm with anatomical piece. Thus, 3D printed models accurately reflect in vivo bones and provide accurate 3D impressions to assist in surgical planning.

Uso de nuevos recursos tecnológicos en la docencia de un curso de anatomía con orientación clínica para estudiantes de medicina / Use of new technological resources in the teaching of a clinical anatomy course for medicine students

El uso de recursos tecnológicos como material de apoyo en la docencia de anatomía humana tiene antecedentes históricos en Chile desde el siglo 19, con la llegada del primer modelo anatómico artificial. En conjunto con las tradicionales clases magistrales y lectura de los textos clásicos sobre la materia, durante los trabajos prácticos se presentaba al estudiante una serie de contenidos estrictamente anatómicos que posteriormente serían evaluados. Esta metodología de enseñanza se mantuvo hasta muy avanzado el siglo 20. Posteriormente con los avances en tecnología médica de las últimas décadas incorporados a la práctica clínica habitual, también debieron integrarse conocimientos sobre las estructuras anatómicas, en cuanto a su representación en los exámenes obtenidos mediante técnicas de imágenes médicas. Por esta razón para la formación de las nuevas generaciones de médicos, se han debido actualizar paulatinamente; la literatura básica integrando a ella contenidos clínicos, la metodología docente haciéndola participativa hacia el estudiante y en el último tiempo los materiales para trabajos prácticos, de manera que se logre un aprendizaje duradero, cuyos contenidos sean utilizados posteriormente en otras asignaturas básicas y clínicas. Previo a iniciar las actividades docentes en el laboratorio de anatomía de la nueva Escuela de Medicina de la Universidad de Tarapacá, Chile, la institución adquirió material de apoyo docente de última generación para complementar la enseñanza en los trabajos prácticos de anatomía. En este artículo se describirá la implementación de los nuevos recursos tecnológicos de apoyo docente en anatomía para nuestra escuela de medicina, entre los cuales se encuentran: modelos anatómicos impresos en tres dimensiones (3D) Erler-Zimmer®, cadáver humano sintético Syndaver®, mesa de disección digital 3D SECTRA® y su estación de trabajo complementaria. Todos estos materiales se unieron al uso de otros recursos tradicionales en la enseñanza de esta disciplina, para entregar los contenidos de la anatomía con un enfoque combinado.

The use of technological resources as assisting material in the teaching of human anatomy has been referenced in Chile since the 19th century with the first artificial anatomical model. In conjunction with traditional lectures and classical texts on the subject during practical work, the student was presented with a series of strictly anatomical contents that would later be evaluated. This teaching methodology was maintained until well into the 20th century. Subsequently, medical technology progress and innovation was integrated in clinical practice over the last decades. Further, knowledge of anatomical structures, in terms of their representation in exams obtained through medical imaging techniques was also consolidated. For this reason for the education of the new generations of medical doctors, a gradual update was required. These included basic clinical content literature, a teaching methodology with student participation, and use of materials for practical work to achieve learning techniques that would be useful in later courses. Prior to the beginning of the school year, the School of Medicine of the Universidad de Tarapacá acquired state of the art material to complement teaching in practical anatomy work for its anatomy laboratory. This article describes implementation of the new technological resources for educational support in anatomy for our school of medicine, among these are: anatomical models printed in three dimensions (3D) Erler-Zimmer®, synthetic human cadaver Syndaver®, SECTRA® 3D digital dissection table and complementary workstation. All of this material will be used in conjunction with other traditional resources when teaching anatomy, so as to provide an overall view of the contents in this subject area.

Clinical application of atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template

OBJECTIVES: To investigate the primary clinical value of atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template. METHODS: We retrospectively analyzed the cases of 17 patients treated from June 2015 to September 2016 with atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template. All procedures were performed prior to surgery, including thin-slice CT scanning, medical image sampling and computerized 3D modeling of the atlantoaxial joint, optimal pedicle screw trajectory determination, and anatomical trait acquisition for the atlantoaxial pedicle, spinous process of the axis, vertebral lamina and posterior lateral mass, and design of a reverse template. During surgery, a navigation template was tightly attached to the atlantoaxial joint to assist in pedicle screw placement. Surgeons subsequently used an electric drill to remove the template through a guide channel and then placed the atlantoaxial pedicle screw. Observed indexes included the VAS score, JOA improvement rate, surgery duration, and blood loss. RESULTS: Surgery was successful in all 17 patients, with an average operation duration of 106±25 min and an average blood loss of 220±125 ml. Three days postoperatively, the VAS score decreased from 6.42±2.21 to 3.15±1.26. Six months postoperatively, the score decreased to 2.05±1.56. The postoperative JOA score increased significantly from 7.68±2.51 to 11.65±2.72 3 d after surgery and to 13.65±2.57 after 6 months. Sixty-eight pedicle screws were inserted successfully, with 34 in the atlas and 34 in the axis. According to the Kawaguchi standard, 66 screws were in grade 0 (97.06%), and 2 were in grade 1 (2.94%). The pre- and postoperative transverse and sagittal screw angles showed no significant differences. CONCLUSIONS: Atlantoaxial pedicle screw placement assisted by a modified 3D-printed navigation template is worth recommending due to the improved accuracy in screw placement, improved patient safety and beneficial clinical effects.