Effect of temporary cement on the color of temporary crowns made by conventional pressing methods and substractive CAM/CAD technologies / Efecto del cemento temporal sobre el color de las coronas temporales realizadas mediante métodos de prensado convencionales y tecnologías sustractivas CAM/CAD

Abstract The color stability of temporary restoration is crucial, especially in sensitive areas in terms of aesthetics. This research aimed to determine the effect of temporary cement on the color of temporary crowns made by conventional pressing methods (indirect) and CAM/CAD technologies using milling machines and 3D printers. This study was carried out in a laboratory, utilizing A2 color in all manufacturing methods. The color of the restorations was measured by a spectrophotometer after cementation with semi-permanent resin cement. Subsequently, color changes of the samples (ranging from 0 to 100) were calculated using the Commission International de l'Eclairage (CIE) Lab system. Data analysis was based on descriptive statistics methods and statistical tests, including one-way analysis of variance (ANOVA) and Tukey's post hoc test. According to the results of ANOVA, there was a significant difference between the three groups in terms of the 'a' and 'b' indexes (P<0.001). However, regarding the 'l' index, no significant difference was observed among the three groups (P=0.250). Also, based on Tukey's post hoc test, a significant relationship was seen between the first and second pairs in the 3D printer group, and between the first and third pairs in the milling group (P<0.001). However, no significant difference was observed in the conventional pressing group. The results showed that the 3D printing method exhibited the highest amount of color change among the three methods, while the milling method demonstrated the lowest amount of change.

Resumen La estabilidad del color de la restauración temporal es muy importante, especialmente en zonas sensibles desde el punto de vista estético. En la presente investigación, el objetivo fue determinar el efecto del cemento temporal sobre el color de coronas temporales realizadas mediante métodos de prensado convencionales (indirectos) y tecnologías CAM/CAD utilizando fresadora e impresora 3D. Este estudio se llevó a cabo en un laboratorio y se utilizó color A2 en todos los métodos de fabricación. El color de las restauraciones se midió mediante un espectrofotómetro después de cementarlas con cemento de resina provisional. Luego se calcularon los cambios de color de las muestras (de 0 a 100) utilizando el sistema CIE Lab. El análisis de los datos se basó en métodos de estadística descriptiva y pruebas estadísticas, incluido el análisis de varianza unidireccional (ANOVA) y la prueba post hoc de Tukey. Según los resultados del análisis de varianza unidireccional, hubo una diferencia significativa entre los tres grupos en términos de los índices a y b (P<0,001), pero en términos del índice l, no hubo diferencias significativas entre los tres grupos (P=0,250). Además, según la prueba post hoc de Tukey, se observó una relación significativa entre el primer y el segundo grupo de impresoras 3D y entre el primer y el tercer grupo de fresado (P<0,001). Sin embargo, no se observó ninguna diferencia significativa en el grupo de prensado convencional. Los resultados mostraron que el mayor cambio de color entre los tres métodos fue con el método de impresión 3D, y la menor cantidad fue con el método de fresado.

Optical Strain Gauge Prototype Based on a High Sensitivity Balloon-like Interferometer and Additive Manufacturing.

An optical strain gauge based on a balloon-like interferometer structure formed by a bent standard single-mode fiber combined with a 3D printer piece has been presented and demonstrated, which can be used to measure displacement. The interferometer has a simple and compact size, easy fabrication, low cost, and is repeatable. The sensor is based on the interference between the core and cladding modes. This is caused by the fiber's curvature because when light propagates through the curved balloon-shaped interferometer region, a portion of it will be released from the core limitation and coupled to the cladding. The balloon has an axial displacement as a result of how the artwork was constructed. The sensor head is sandwiched between two cantilevers such that when there is a displacement, the dimension associated with the micro bend is altered. The sensor response as a function of displacement can be determined using wavelength shift or intensity change interrogation techniques. Therefore, this optical strain gauge is a good option for applications where structure displacement needs to be examined. The sensor presents a sensitivity of 55.014 nm for displacement measurements ranging from 0 to 10 mm and a strain sensitivity of 500.13 pm/µÏµ.

Fabrication, morphological, mechanical and biological performance of 3D printed poly(ϵ-caprolactone)/bioglass composite scaffolds for bone tissue engineering applications.

Several techniques, such as additive manufacturing, have been used for the manufacture of polymer-ceramic composite scaffolds for bone tissue engineering. A new extruder head recently developed for improving the manufacturing process is an experimental 3D printer Fab@CTI that enables the use of ceramic powders in the processing of composite materials or polymer blends. Still, the manufacturing process needs improvement to promote the dispersion of ceramic particles in the polymer matrix. This article addresses the manufacture of scaffolds by 3D printing from mixtures of poly(ϵ-caprolactone) (PCL) and a glass powder of same composition of 45S5Bioglass®, labeled as synthesized bioglass (SBG), according to two different methods that investigated the efficiency of the new extruder head. The first one is a single extrusion process in a Fab@CTI 3D printer, and the other consists in the pre-processing of the PCL-SBG mixture in a mono-screw extruder with a Maddock® element, followed by direct extrusion in the experimental Fab@CTI 3D printer. The morphological characterization of the extruded samples by scanning electron microscope showed an architecture of 0°/90° interconnected struts and suitable porosity for bone tissue engineering applications. Scaffolds fabricated by two methods shows compressive modulus ranging from 54.4 ± 14.2 to 155.9 ± 20.4 MPa, results that are compatible to use in bone tissue engineering. Cytotoxicity assays showed non-toxic effects and viability forin vitroMG-63 cell proliferation. Alizarin Red staining test showed calcium deposition in all scaffolds, which suggests PCL/SBG composites promising candidates for use in bone tissue engineering. Results of cell morphology suggest more cell growth and adhesion for scaffolds fabricated using the pre-processing in a mono-screw extruder.

Trocar shortening for pediatric vitreoretinal surgery with a 3D printed trocar spacer: Report of two cases.

PURPOSE: To show the results of a trocar spacer for pediatric vitreoretinal surgery with a 3D printed trocar spacer in 2 cases. METHODS: We used standard 27 gauge (ga) and 25 ga trocars and cannulae, and prototyped 1.5 mm × 3 mm spacers with a Prusa MK3 3D printer (0.4 mm nozzle) with Fuse deposition melting (FDM) technology. Parts were printed with a 50 µm layer height in polylactic acid or polylactide (PLA). The spacer was placed in two places: between the blade's base and the trocar, and between the trocar and the sclera depending on the desired amount of shortening. This prototype was used in 2 vitrectomy cases in pediatric patients. RESULTS: We used this trocar spacer in 2 cases with positive results. CONCLUSIONS: This 3D printed spacer has proved to effectively shorten the introduced trocar into two different small eyes. More studies are needed to validate the efficacy and safety of this spacer in clinical practice.

Congruencia entre modelos dentales impresos 3D y el archivo digital de origen: estudio in vitro comparativo de 5 impresoras 3D / Congruence between 3D printed dental models and the original digital file: comparative in vitro study of 5 3D printers

Este trabajo tuvo como objetivo conocer la fiabilidad de la impresora 3D (i3D) aditiva por Matriz de Proceso Digital de Luz (MDLP) Hellbot modelo Apolo®, a través de verificar la congruencia dimensional entre las mallas de modelos impresos (MMi) y su correspondiente archivo digital de origen (MMo), obtenido del software de planificación ortodontica Orchestrate 3D® (O3D). Para determinar su uso en odontología y sus posibilidades clínicas, fue comparada entre cinco i3D de manufactura aditiva, dos DLP, dos por estereolitografía (SLA) y una por Depósito de Material Fundido (FDM). La elección de las cinco i3D se fundamentó en su valor de mercado, intentando abarcar la mayor diversidad argentina disponible. Veinte modelos fueron impresos con cada i3D y escaneados con Escáner Intraoral (IOS) Carestream modelo 3600® (Cs3600). Las 120 MMi fueron importadas dentro del programa de ingeniería inversa Geomagic® Control X® (Cx) para su análisis 3D, consistiendo en la superposición de MMo con cada una de las MMi. Luego, una evaluación cualitativa de la desviación entre la MMi y MMo fue realizada. Un análisis estadístico cuidadoso fue realizado obteniendo como resultado comparaciones en 3d y 2d. Las coincidencias metrológicas en la superposición tridimensional permitieron un análisis exhaustivo y fácilmente reconocible a través de mapas colorimétricos. En el análisis bidimensional se plantearon planos referenciados dentariamente desde la MMo, para hacer coincidir las mediciones desde el mismo punto de partida dentaria. Los resultados fueron satisfactorios y muy alentadores. Las probabilidades de obtener rangos de variabilidad equivalentes a +/- 50µm fueron de un 40,35 % y de +/- 100µm un 71,04 %. Por lo tanto, te- niendo en cuenta las exigencias de congruencia dimensional clínicas de precisión y exactitud a las cuales es sometida nuestra profesión odontológica, se evitan problemas clínicos arrastrados por los errores dimensionales en la manufactura (Cam) (AU)

The objective of this study was to determine the reliability of the Hellbot Apollo® model additive 3D printer (i3D) by Matrix Digital Light Processing (MDLP) by verifying the dimensional congruence between the printed model meshes (MMi) and their corresponding digital source file (MMo), obtained from the Orchestrate 3D® (O3D) orthodontic planning software. A comparison was made between five i3D of additive manufacturing, two DLP, two by stereolithography (SLA), and one by Fused Material Deposition (FDM), to determine its use in dentistry and its clinical possibilities. The choice of the five i3D was based on their market value, trying to cover most of the Argentinean diversity available. Twenty models were printed with each i3D and scanned with Carestream Intraoral Scanner (IOS) model 3600® (Cs3600). The 120 MMi were imported into the reverse engineering program Geomagic® Control X® (Cx) for 3D analysis, consisting of overlaying MMo with each MMi. Then, a qualitative evaluation of the deviation between MMi and MMo. Also, a careful statistical analysis was performed, resulting in 3d and 2d comparisons. Metrological coincidences in three-dimensional overlay allowed a comprehensive and easily recognizable analysis through colorimetric maps. In the two-dimensional analysis, dentally referenced planes were proposed from the MMo, to match the measurements from the same dental starting point. The results were satisfactory and very encouraging. The probabilities of obtaining ranges of variability equivalent to +/- 50µm were 40.35 % and +/- 100µm 71.04 %. Therefore, considering the demands of clinical dimensional congruence, precision, and accuracy to which our dental profession it is subjected, clinical problems caused by dimensional errors in manufacturing (Cam) are avoided (AU)

Disinfection of 3D-printed protective face shield during COVID-19 pandemic.

This study assessed the disinfection using 70% ethanol; H2O2-quaternary ammonium salt mixture; 0.1% sodium hypochlorite and autoclaving of four 3D-printed face shields with different designs, visor materials; and visor thickness (0.5-0.75 mm). We also investigated their clinical suitability by applying a questionnaire to health workers (HW) who used them. Each type of disinfection was done 40 times on each type of mask without physical damage. In contrast, autoclaving led to appreciable damage.

A Low-Cost Open Source Device for Cell Microencapsulation.

Microencapsulation is a widely studied cell therapy and tissue bioengineering technique, since it is capable of creating an immune-privileged site, protecting encapsulated cells from the host immune system. Several polymers have been tested, but sodium alginate is in widespread use for cell encapsulation applications, due to its low toxicity and easy manipulation. Different cell encapsulation methods have been described in the literature using pressure differences or electrostatic changes with high cost commercial devices (about 30,000 US dollars). Herein, a low-cost device (about 100 US dollars) that can be created by commercial syringes or 3D printer devices has been developed. The capsules, whose diameter is around 500 µm and can decrease or increase according to the pressure applied to the system, is able to maintain cells viable and functional. The hydrogel porosity of the capsule indicates that the immune system is not capable of destroying host cells, demonstrating that new studies can be developed for cell therapy at low cost with microencapsulation production. This device may aid pre-clinical and clinical projects in low- and middle-income countries and is lined up with open source equipment devices.

A low-cost didactic module for testing advanced control algorithms.

Commercial modules for learning advanced control systems are not quite common and some are very expensive due to their sensors, electronic and license. There is an open area to develop and to build didactic modules to improve the learning process using experimentation in real physical systems. Particularly, a cart inverted pendulum is a classical physical system very commonly used in recent decades. We propose a cart inverted pendulum named MoDiCA-X as a low-cost didactic module with open source hardware and software. It is an electromechanical system feasible to build and easy to be modified. The mechanical parts of the module are 3D printed solids and can also be easily replicated. In terms of programming, the control applied to the system can be modified, since it uses C/C++ programming languages that are widely used in the academic community. The module is equipped with two very commercial sensors, are easy to install and to remove; both acquire the pendulum attitude and the car position. The actuators are four electric DC motors coupled to the car wheels to provide suitable velocity and torque to each axle independently. We validate the performance of the module by applying a multivariable linear quadratic regulator algorithm (LQR).

Ortodontia Digital com Alinhadores Ortodônticos ­ Sistema Cleartek / Digital Orthodontics with Orthodontic Aligners ­ Cleartek System

Atualmente, a maior parte dos pacientes ortodônticos gostaria de ser tratado com alinhadores transparentes, preferindo esses aos brackets metálicos ou estéticos. Assim se torna fundamental o ortodontista dominar a técnica desde as fases iniciais (fluxo de trabalho) até a condução dos casos. O tratamento ortodôntico com alinhadores possui uma série de vantagens em relação ao convencional, pois é mais discreto, estético, confortável, permite uma higienização mais fácil e não há restrição de alimentação. Entretanto algumas desvantagens aparecem, tais como a necessidade de cooperação por parte do paciente e algumas limitações biomecânicas. Alguns sistemas têm se destacado no mercado por oferecerem aos dentistas serviços de planejamento digital e produção de alinhadores ortodônticos, tornando esses aptos a conduzirem de forma mais direta e com maior autonomia os seus tratamentos com alinhadores. Dessa forma o propósito desse artigo é apresentar de forma simplificada o sistema de alinhadores Cleartek e alguns casos clínicos e assim fornecer subsídios para o ortodontista que pretende utilizá-lo, desde o planejamento até o acompanhamento clínico e finalização dos casos tratados.(AU)

Currently, most orthodontic patients would like to be treated with transparent aligners, preferring these to metal or aesthetic brackets. So it becomes essential to the orthodontist to master the technique from the initial phases to the conduction of the cases. Orthodontic treatment with aligners has a number of advantages compared to conventional ones, because it is more discreet, aesthetic, comfortable, allow easier hygiene and there is no food restriction. However, some disadvantages appear, such as the need of patient cooperation and some biomechanical limitations. Some systems have excel out in the market for offering dentists services of digital planning and production of orthodontic aligners, allowing them to be able to lead in a more direct form and with more autonomy their treatments with aligners. So the purpose of this article is to present in a simplified way Cleartek aligners system and some clinical cases and thus to provide subsidies for the orthodontist that intends to use them, from the planning to the clinical follow-up and completion of the treated cases. (AU)

3D printing for electroanalysis: From multiuse electrochemical cells to sensors.

This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the 3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and $ 6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of $ 1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 µmol L-1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k0) for the redox probe Ru(NH3)6+3 revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.

Development of esthetic prosthesis for a patient with severe stigmatizing facial lesions due to cancer: a pilot study.

PURPOSE: Severe physical facial deformities due to surgical interventions can have significant psychosocial consequences to patient's relationships with friends and family and thus, has a considerable impact on their quality of life. We have developed a 3D prosthesis for a 56-year-old woman diagnosed with epidermoid carcinoma at the right hemiface, to improve her quality of life. METHODS: The patient started radiotherapy with modulated intensity. To deal with the advance of the process, a maxilectomy of supra structure with modified radical cervical emptying on the right hemiface was performed. Reconstruction of areas surgically affected by the displacement of islands of skin and muscle (flaps) from healthy regions was initiated. Although the procedure occurred without intercurrences, the patient developed necrosis and loss of the myocutaneous flap. After the removal of the flap, the esthetic result of the treatment was evident causing exposure of subcutaneous and granulation tissues. RESULTS: A computational model was used to develop a 3D structure of the affected area and then used to construct the prosthesis. The prosthesis was applied over the affected area, and the patient was able see her face on the mirror for the first time in years. The patient was grateful and hopeful. CONCLUSION: We have found that the application of this new technology greatly improves the social interaction of patients with deformities due to surgical interventions.

Developing an Ear Prosthesis Fabricated in Polyvinylidene Fluoride by a 3D Printer with Sensory Intrinsic Properties of Pressure and Temperature.

An ear prosthesis was designed in 3D computer graphics software and fabricated using a 3D printing process of polyvinylidene fluoride (PVDF) for use as a hearing aid. In addition, the prosthesis response to pressure and temperature was observed. Pyroelectric and piezoelectric properties of this ear prosthesis were investigated using an astable multivibrator circuit, as changes in PVDF permittivity were observed according to variations of pressure and temperature. The results show that this prosthesis is reliable for use under different conditions of pressure (0 Pa to 16,350 Pa) and temperature (2 °C to 90 °C). The experimental results show an almost linear and inversely proportional behavior between the stimuli of pressure and temperature with the frequency response. This 3D-printed ear prosthesis is a promising tool and has a great potentiality in the biomedical engineering field because of its ability to generate an electrical potential proportional to pressure and temperature, and it is the first time that such a device has been processed by the additive manufacturing process (3D printing). More work needs to be carried out to improve the performance, such as electrical stimulation of the nervous system, thereby extending the purpose of a prosthesis to the area of sensory perception.