development of a dlp 3d printer for orthodontic applications

Abstract Recent advances in Additive Manufacturing (AM) technologies have allowed a widespread diffusion of their use in different fields. 3D printing is becoming commonplace for biomedical applications requiring the custom fabrication of prostheses and appliances fitting patient-specific anatomies. In this work, the feasibility of a vat photopolymerization technology, based on Digital Light Processing (DLP), has been investigated for the manufacturing of polymeric orthodontic appliances. A custom DLP 3D printer has been developed by exploiting an off-the-shelf digital projector, with the aim at studying the influence of printing parameters on the surface roughness. The feasibility of using Dental LT Clear resin, a biocompatible photopolymer specifically designed for SLA technology, has been finally verified

Sustainability in Healthcare Sector: The Dental Aligners Case

Additive manufacturing is a technology gaining ground in fields where a high degree of product customization is required; in particular, several aspects need to be explored concerning traditional technologies, such as the variety of materials and their consumption. It also remains to be clarified whether these technologies can contribute to the ecological transition when applied in healthcare. This study compares two technologies for producing clear dental aligners: thermoforming and direct 3D printing. The former method thermoforms a polymeric disc over 3D-printed, customized models. The second, more innovative approach involves directly printing aligners using Additive Manufacturing (AM), specifically applying Digital Light Processing (DLP) technology. The study conducts a comparative Life Cycle Assessment (LCA) analysis to assess the environmental impact of these two different manufacturing processes. The research results highlight that adopting direct printing through AM can bring advantages in terms of environmental sustainability, thanks to the reduction in raw materials and electricity consumption. These drops are drivers for the decreased potential environmental impacts across all impact categories considered within the EF 3.1 method. Furthermore, lowering the amount of raw material needed in the direct printing process contributes to a notable decrease in the overall volume of waste generated, emphasizing the environmental benefits of this technique

A Digital Process for Manufacturing Customized Trays for Dental-Whitening Treatments

This study presents an alternative process for designing and manufacturing customized trays for dental-whitening treatments. The process is based on a digitized approach consisting of three main stages: design of a reference model, its manufacturing by AM, and thermoforming of the tray. The aim of the study was to develop a high-performance tray, able to guarantee comfort, safety, and efficacy for whitening treatments. To evaluate the patient’s experience, some tests under real operating conditions were performed. Twenty people carried out a nighttime treatment of 14 days. Each patient was asked to assess the overall level of satisfaction and the comfort of the tray and its ability to retain the gel. Tooth whitening was also determined according to the VITAPAN scale. All patients involved in the study were satisfied and provided positive feedback about comfort and tightness of the tray. At the end of the treatment, 15 out of 20 patients achieved shade A1 on the VITAPAN scale. The mean improvement in color shades was about 7. These results confirmed the great potential of the proposed dental tray. Its use was proven to guarantee a high level of quality, flexibility, and customization of dental-whitening treatments, improving comfort, safety, and efficacy

An examination of auxetic componentry for applications in human-centred biomedical product design settings

This paper explores how the examination of additively manufactured auxetic componentry can be applied in human-centred design settings with particular focus on biomedical products. Firstly, the design applications of auxetics are detailed followed by a review of the key problems facing practical researchers in the field with the treatment of boundary conditions identified as a key issue. The testing setup that is then introduced utilises a novel method of part mounting and facilitates optical analysis and real-time force–displacement measurements. A study is advanced that analyses three different auxetic structures (re-entrant, chiral, and semi-rigid), a set of samples of which were additively manufactured in flexible TPU material. A range of parameters were varied across the three designs including interior geometry and wall thicknesses in order to demonstrate the effectiveness of the setup for the examination of the different structures. The results from these examinations are subsequently discussed and a number of suggestions made regarding how this kind of analysis may be integrated into novel design development workflows for achieving human-centred biomedical devices which often require detailed consideration of ergonomic and usability factors

Investigation of the Material Extrusion Additive Manufacturing of an Inconel-718 Filament

Material Extrusion Additive Manufacturing (MEAM) for metals is becoming increasingly appealing compared to other metal AM techniques, which are typically energy-intensive and require equipment expensive to install and maintain. In MEAM a polymeric feedstock filled with metal particles is extruded through a heated nozzle; subsequently, the 3D-printed green parts are debound and sintered. This study investigates the feasibility of producing functional Inconel-718 components with a commercial filament and a desktop printer, using a one-step thermal debiding and sintering procedure. To this purpose, the feedstock was extensively characterized, and optimal printing parameters were determined using the design of experiment technique and statistical analysis. Then tensile specimens were printed, debound, sintered and their mechanical and physical properties were measured. The specimens reached a maximum relative density of 83.4% and a maximum ultimate tensile strength of 223 MPa. A decrease in the debinding heat rate was required to avoid macro-void formation

Effects of Coating Post-processing on Mechanical Properties of Strut-and-Node-Based SLA Lattice Structures

Lattice structures play an increasingly crucial role in Additive Manufacturing (AM) to enhance the performance of parts for industrial and biomedical applications. Among AM technologies, VAT photopolymerization is one of the most suitable in producing shapes characterized by a good resolution and fine details as required for lattice structures. High stiffness and strength photoresins are commonly adopted when strut-and-node lattice structures, based on stretch-dominated unit cells, are printed. However, this choice can lead to brittle and sudden structural failures, undermining the use of these structures due to safety reasons. This work evaluates the effect of chemical post-processing on the deformation behavior and the tensile properties of SLA strut-and-node-based lattice structures. FCC (Face-Centered Cubic) lattice structures with two different layer heights were tested, and a highly deformable UV resin was used as a coating product. Results evidenced an increase in specimen elongation up to 64% for coated FCC lattice structures with respect to as printed samples. Chemical post-processing based on resin coating demonstrated to be an effective solution to get additively manufactured strut-and-node-based lattice structures characterized both by high strength and high strain

A Depth-Camera Based System for the Real-Time Scanning of Upper Limb Anatomy

The 3D reconstruction of upper limb anatomy plays a significant role in many biomedical fields as ergonomics, motion rehabilitation, prosthesis design. Conventional manual measurements have been progressively replaced by 3D optical scanning in collecting and storing 3D anatomical data, thus increasing reliability and data accuracy, shortening, at the same time, the overall acquisition process. However, the real-time scanning of human body parts still represents a complex task since it is challenging to keep the arm in a stable position and avoid artifacts in the collected data. Also, optical undercut geometries often impair the 3D reconstruction’s completeness. In this paper, a compact and low-cost 3D scanning system has been developed by integrating three D415 Intel RealSense cameras. The three depth cameras have been assembled in a circular rig to define a lightweight handheld scanner capable of carrying out 3D data acquisition in different scenarios. The optical system has been validated through anthropometric measurements on different subjects

Effects of Coating Post-processing on the Compressive Properties of Strut-and-Node-Based FDM Lattice Structures

Lattice structures have many outstanding properties, and their use in diversified industrial and biomedical fields is widely studied. The advent of additive manufacturing (AM) technologies has further pushed the design of these cellular structures allowing for the fabrication of complex trusses and tailored local geometries. However, geometrical defects introduced by the AM process into printed lattice structures significantly affect their mechanical properties. In this work, the effect of chemical post-processing on the compressive properties of FDM-PLA strut-and-node-based lattice structures is evaluated. A UV resin has been used as a coating film on samples fabricated using Simple Cubic (SC) and Face-Centered Cubic (FCC) unit cells. Results demonstrated a 65% increase in compressive strength for SC unit cells and a 12% increase for FCC unit cells with respect to as-printed samples. Resin coating demonstrated to represent an effective approach to minimize defects of strut-and-node-based lattice structures, thus enhancing mechanical properties

Laparoscopic hepatic segmentectomy 4a for HCC on cirrhosis: Cranio-ventral approach to the middle hepatic vein

Dear Editor, Hepatocellular carcinoma (HCC) represents the most frequent surgical indication for minimally invasive approach.1 Anatomical liver resection is considered as the gold-standard of treatment, however the anatomical resection of the posterior segments by laparoscopic approach may be complex.2e4 The major hepatic veins are known to run between the segments. For this reason, the hepatic vein guided approach is helpful for anatomical liver resection because these veins can be considered as landmarks to divide the liver parenchyma. In this approach the major hepatic vein is exposed continuously along its root.5 In this video, a cranio-caudal approach to the middle hepatic vein (MHV) is shown in order to perform an anatomical hepatic segmentectomy 4a for an HCC on cirrhosis. After identifying the course of the MHV and of the portal pedicle to segment 4a (P4a) by intraoperative ultrasound, P4a was intraparenchymally isolated and divided. Indocyanine green was intravenously injected and the negative staining showed the segmental area to be removed. Liver transection started with a cranio-caudal approach to the MHV that was isolated along its ventral side. Liver resection was performed without pedicle clamping. Postoperative course was uneventful and the patient was discharged on postoperative day 3. In conclusion the cranio-caudal approach, by exposing the hepatic veins from the root side to the peripheral side branches, may be considered as an effective technique for anatomical resections and safe because it avoids injuries of the veins at the level of their bifurcation

Properties Enhancement of Carbon PA 3D-Printed Parts by Post-processing Coating-Based Treatments

In recent years, Fused Deposition Modelling (FDM) has become one of the most attractive Additive Manufacturing (AM) techniques, due to the advantages in the production of complex shapes with a wide range of materials and low investment costs. The thermoplastic polymers used for FDM technology are characterized by low mechanical properties if compared to those of composites and metals. This issue is usually overcome by reinforcing the thermoplastic polymer with chopped fibres or particles. Moreover, a second issue arises, which is represented by the water absorption with a relevant impact on mechanical properties and dimensional stability of printed models. In this paper, an experimental study is presented with the aim at evaluating the water absorption influence on mechanical properties of Carbon PA (Polyamide matrix reinforced with Carbon Fiber at 20%) specimens fabricated with the FDM technique. Two post-processing treatments, based on the use of acrylic spray and photosensitive resin, have been also proposed to improve the behaviour of Carbon PA printed parts. Results of water absorption tests and tensile tests demonstrated a significant improvement in terms of weight stability and mechanical properties by adopting the proposed post-processing treatments