Jorge Vicente Lopes da Silva

Dimensional error in selective laser sintering and 3D-printing of models for craniomaxillary anatomy reconstruction

BACKGROUND Selective laser sintering (SLS) and three-dimensional printing (3DPtrade mark) are rapid prototyping (RP) techniques to fabricate prototypes from biomedical images. To be used in maxillofacial surgery, these models must accurately reproduce the craniofacial skeleton. PURPOSE To analyze the capacity of SLS and 3DPtrade mark models to reproduce craniomaxillary anatomy and their dimensional error. MATERIAL Dry skull, helical computed-tomography images, SLS and 3DPtrade mark prototypes, and electronic calliper. METHODS Tomographic images of a dry skull were manipulated with the InVesalius biomedical software. Prototypes were fabricated using SLS and 3DPtrade mark techniques. Ten linear measurements were made on the models and compared with corresponding dry skull measurements (criterion standard) carried out with an electronic calliper. RESULTS We observed a dimensional error of 2.10 and 2.67% for SLS and 3DPtrade mark models, respectively. The models satisfactorily reproduced anatomic details, except for thin bones, small foramina and acute bone projections. The SLS prototypes showed greater dimensional precision and reproduced craniomaxillary anatomy more accurately than the 3DPtrade mark models. CONCLUSION Both SLS and 3DPtrade mark models provided acceptable precision and may be useful aids in most maxillofacial surgeries.

Surgical planning for resection of an ameloblastoma and reconstruction of the mandible using a selective laser sintering 3D biomodel

Ameloblastoma is a benign locally aggressive infiltrative odontogenic lesion. It is characterized by slow growth and painless swelling. The treatment for ameloblastoma varies from curettage to en bloc resection, and the reported recurrence rates after treatment are high; the safety margin of resection is important to avoid recurrence. Advances in technology brought about great benefits in dentistry; a new generation of computed tomography scanners and 3-dimensional images enhance the surgical planning and management of maxillofacial tumors. The development of new prototyping systems provides accurate 3D biomodels on which surgery can be simulated, especially in cases of ameloblastoma, in which the safety margin is important for treatment success. A case of mandibular follicular ameloblastoma is reported where a 3D biomodel was used before and during surgery.

Effect of process parameters on the properties of selective laser sintered Poly(3-hydroxybutyrate) scaffolds for bone tissue engineering

Porous scaffolds are biocompatible and bioactive temporary substrates. They should present appropriated microstructure, mechanical properties and surface properties for guiding bone tissue regeneration. In this work, scaffolds of Poly(3-hydroxybutyrate) (PHB) were printed by Selective Laser Sintering (SLS). The effect of scan spacing (SS) and powder layer thickness (PLT) on the morphology, mechanical properties and dimensional deviations related to the digital model of sintered scaffolds was evaluated. Curling was observed in the first built layers of scaffolds, mainly for scaffolds printed with the lowest PLT. Besides designed pores, the scaffolds also presented micropores derived from the incomplete sinterisation of PHB particles. This morphology can be advantageous for bone regeneration. The variation of PLT caused a higher difference between the values of scaffold mechanical properties than the variation of SS. The scaffolds, except the one printed with the highest PLT or SS, showed mechanical properties within the lower range of human trabecular bone.

Burr-like, laser-made 3D microscaffolds for tissue spheroid encagement.

The modeling, fabrication, cell loading, and mechanical and in vitro biological testing of biomimetic, interlockable, laser-made, concentric 3D scaffolds are presented. The scaffolds are made by multiphoton polymerization of an organic-inorganic zirconium silicate. Their mechanical properties are theoretically modeled using finite elements analysis and experimentally measured using a Microsquisher(®). They are subsequently loaded with preosteoblastic cells, which remain live after 24 and 72 h. The interlockable scaffolds have maintained their ability to fuse with tissue spheroids. This work represents a novel technological platform, enabling the rapid, laser-based, in situ 3D tissue biofabrication.

Design, physical prototyping and initial characterisation of ‘lockyballs’

Directed tissue self-assembly or bottom-up modular approach in tissue biofabrication is an attractive and potentially superior alternative to a classic top-down solid scaffold-based approach in tissue engineering. For example, rapidly emerging organ printing technology using self-assembling tissue spheroids as building blocks is enabling computer-aided robotic bioprinting of three-dimensional (3D) tissue constructs. However, achieving proper material properties while maintaining desirable geometry and shape of 3D bioprinted tissue engineered constructs using directed tissue self-assembly, is still a challenge. Proponents of directed tissue self-assembly see the solution of this problem in developing methods of accelerated tissue maturation and/or using sacrificial temporal supporting of removable hydrogels. In the meantime, there is a growing consensus that a third strategy based on the integration of a directed tissue self-assembly approach with a conventional solid scaffold-based approach could be a potential optimal solution. We hypothesise that tissue spheroids with ‘velcro®-like’ interlockable solid microscaffolds or simply ‘lockyballs’ could enable the rapid in vivo biofabrication of 3D tissue constructs at desirable material properties and high initial cell density. Recently, biocompatible and biodegradable photo-sensitive biomaterials could be fabricated at nanoscale resolution using two-photon polymerisation (2PP), a development rendering this technique with high potential to fabricate ‘velcro®-like’ interlockable microscaffolds. Here we report design studies, physical prototyping using 2PP and initial functional characterisation of interlockable solid microscaffolds or so-called ‘lockyballs’. 2PP was used as a novel enabling platform technology for rapid bottom-up modular tissue biofabrication of interlockable constructs. The principle of lockable tissue spheroids fabricated using the described lockyballs as solid microscaffolds is characterised by attractive new functionalities such as lockability and tunable material properties of the engineered constructs. It is reasonable to predict that these building blocks create the basis for a development of a clinical in vivo rapid biofabrication approach and form part of recent promising emerging bioprinting technologies.

Rapid Prototyping Applications in the Treatment of Craniomaxillofacial Deformities - Utilization of Bioceramics

The aim of this article is to develop a methodology for the select ion of suitable biomaterials for the treatment of craniofacial deformities usi ng rapid prototyping as a support tool. This research is carried out by a multidisciplinary team of el ectronic, chemical and computer engineers, and surgeons. The main motivation for the team is to put avai lable, disseminate and integrate computer systems, methodologies, and rapid prototyping usage i n order to reduce postoperative costs and risks from the insufficiency of information. It is also useful for the effective surgical planning and for the selection of the suitable biomaterial o create a customized implant for the patient. The present work dealt with bioceramics for the production of customized implants considering small injuries.

Monoscopic photogrammetry to obtain 3D models by a mobile device: a method for making facial prostheses

PurposeThe aim of this study is to present the development of a new technique to obtain 3D models using photogrammetry by a mobile device and free software, as a method for making digital facial impressions of patients with maxillofacial defects for the final purpose of 3D printing of facial prostheses.MethodsWith the use of a mobile device, free software and a photo capture protocol, 2D captures of the anatomy of a patient with a facial defect were transformed into a 3D model. The resultant digital models were evaluated for visual and technical integrity. The technical process and resultant models were described and analyzed for technical and clinical usability.ResultsGenerating 3D models to make digital face impressions was possible by the use of photogrammetry with photos taken by a mobile device. The facial anatomy of the patient was reproduced by a *.3dp and a *.stl file with no major irregularities. 3D printing was possible.ConclusionsAn alternative method for capturing facial anatomy is possible using a mobile device for the purpose of obtaining and designing 3D models for facial rehabilitation. Further studies must be realized to compare 3D modeling among different techniques and systems.Clinical implicationFree software and low cost equipment could be a feasible solution to obtain 3D models for making digital face impressions for maxillofacial prostheses, improving access for clinical centers that do not have high cost technology considered as a prior acquisition.

InVesalius: An Interactive Rendering Framework for Health Care Support

This work presents InVesalius, an open-source software for analysis and visualization of medical images. The tool has supported several surgeries in hospitals and has been downloaded from more than a hundred countries around the world. Its main characteristics, aspects of implementation, and applications in areas such as image segmentation, mesh generation, volume rendering, and 3D printing of anatomic models are described.

3D Scanning Using RGBD Imaging Devices: A Survey

The capture and digital reconstruction of tridimensional objects and scenarios are issues of great importance in computational vision and computer graphics, for the numerous applications, from navigation and scenario mapping, augmented reality to medical prototyping. In the past years, with the appearance of portable and low-cost devices such as the Kinect Sensor, which are capable of acquiring RGBD video (depth and color data) in real-time, there was a major interest to use these technologies, efficiently, in 3D surface scanning. In this paper, we present a survey of the most relevant methods from recent literature on scanning 3D surfaces using these devices and give the reader a general overview of the current status of the field in order to motivate and enable other works in this topic.

Computer Fluid Dynamics Analysis for Efficient Cooling and Lubrication Conditions in Micromilling of Ti6Al4V Alloy

Titanium alloy Ti6Al4V is a material that has been used extensively in industries, such as the medical field for prostheses and surgical instruments, because of its biocompatibility. However, it is considered a difficult-to-machine material owing to its inherent mechanical and thermal properties (which cause severe tool wear and shorten tool life), diminished surface quality, and it conducts low productivity. The aim of this work is to evaluate the efficiency of minimum quantity lubrication (MQL) in micromilling in terms of dry machining and jet application. The effect of cutting fluid flow was analyzed through Computational Fluid Dynamics (CFD) analysis and jet application, in the context of the microscale, was found to cause a disordered flow that did not reach the desired target, in this case the two flutes of the tool. These results were accordant with those obtained in the micromilling experiments. In addition, recent machining concerns are related to sustainability and aim to reduce or even eliminate the use of cutting fluids altogether; in this sense, applying MQL in micromilling would represent a substantial reduction in cutting fluid consumption.