G. Centeno

Two-year prospective study of outcomes following total temporomandibular joint replacement.

The purpose of this 2-year prospective study was to investigate outcomes achieved with a stock temporomandibular joint (TMJ) replacement system in the management of end-stage TMJ disorders. Fifty-two patients requiring reconstruction (36 unilateral/16 bilateral) were operated on during the period 2006-2012; 68 total prostheses were implanted (Biomet Microfixation TMJ Replacement System). The mean age at surgery was 52.6±11.5 years. Changes in the values of inclusion diagnostic criteria at entry were assessed. These included persistent and significant TMJ pain, functional impairment after failure of other surgical therapies, and imaging evidence consistent with advanced TMJ disease of more than 1-year duration. Subjects were excluded if they presented insufficient quantity/quality of bone to support the TMJ replacement, severe hyperfunctional habits, active infectious disease, or an inability to follow postoperative instructions. Over the 2 years of postoperative follow-up, mean pain intensity was reduced from 6.4±1.4 to 1.6±1.2 (P<0.001), and jaw opening was improved from 2.7±0.9cm to 4.2±0.7cm (P<0.001). During the study period, three of 68 implants (4%) were explanted and new TMJ replacements fitted. The results of this study support the view that the surgical placement of stock TMJ prostheses provides significant long-term improvements in pain and function, with few complications.

A functional methodology on the manufacturing of customized polymeric cranial prostheses from CAT using SPIF

Purpose This paper aims to propose a functional methodology to produce cranial prostheses in polymeric sheet. Within the scope of rapid prototyping technologies, the single-point incremental forming (SPIF) process is used to demonstrate its capabilities to perform customized medical parts. Design/methodology/approach The methodology starts processing a patient’s computerized axial tomography (CAT) and follows with a computer-aided design and manufacture (CAD/CAM) procedure, which finally permits the successful manufacturing of a customized prosthesis for a specific cranial area. Findings The formability of a series of polymeric sheets is determined and the most restrictive material among them is selected for the fabrication of a specific partial cranial prosthesis following the required geometry. The final strain state at the outer surface of the prosthesis is analysed, showing the high potential of SPIF in manufacturing individualized cranial prostheses from polymeric sheet. Originality/value This paper proposes a complete methodology to design and manufacture polymer customized cranial prostheses from patients’ CATs using the novel SPIF technology. This is an application of a new class of materials to the manufacturing of medical prostheses by SPIF, which to this purpose has been mainly making use of metallic materials so far. Despite the use of polymers to this application is still to be validated from a medical point of view, transparent prostheses can already be of great interest in medical or engineering schools for teaching and research purposes.

Evaluation of total alloplastic temporo-mandibular joint replacement with two different types of prostheses: A three-year prospective study.

Background Temporo-Mandibular Joint (TMJ) replacement has been used clinically for years. The objective of this study was to evaluate outcomes achieved in patients with two different categories of TMJ prostheses. Material and Methods All patients who had a TMJ replacement (TMJR) implanted during the study period from 2006 through 2012 were included in this 3-year prospective study. All procedures were performed using the Biomet Microfixation TMJ Replacement System, and all involved replacing both the skull base component (glenoid fossa) and the mandibular condyle. Results Fifty-seven patients (38 females and 19 males), involving 75 TMJs with severe disease requiring reconstruction (39 unilateral, 18 bilateral) were operated on consecutively, and 68 stock prostheses and 7 custom-made prostheses were implanted. The mean age at surgery was 52.6±11.5 years in the stock group and 51.8±11.7 years in the custom-made group. In the stock group, after three years of TMJR, results showed a reduction in pain intensity from 6.4±1.4 to 1.6±1.2 (p<0.001), and an improvement in jaw opening from 2.7±0.9 cm to 4.2±0.7 cm (p<0.001). In the custom-made group, after three years of TMJR, results showed a reduction in pain intensity from 6.0±1.6 to 2.2±0.4 (p<0.001), and an improvement in jaw opening from 1.5±0.5 cm to 4.3±0.6 cm (p<0.001). No statistically significant differences between two groups were detected. Conclusions The results of this three-year prospective study support the surgical placement of TMJ prostheses (stock prosthetic, and custom-made systems), and show that the approach is efficacious and safe, reduces pain, and improves maximum mouth opening movement, with few complications. As such, TMJR represents a viable technique and a stable long-term solution for cranio-mandibular reconstruction in patients with irreversible end-stage TMJ disease. Comparing stock and custom-made groups, no statistically significant differences were detected with respect to pain intensity reduction and maximum mouth opening improvement. Key words:Temporo-mandibular joint, temporo-mandibular joint replacement, prosthesis, biomaterials, biomedical engineering, computer-aided design and manufacturing.

Continuous Variable Transmission With an Inertia-Regulating System

This article describes a power transmission system applicable to vehicles. It consists of an oscillating, ratcheting-type, continuously variable transmission (CVT) system governed by an inertia mechanism. The inertia-regulating mechanism adds an additional degree of freedom and gives the system a dynamic character. The transmission consists of three different subsystems. The first of these converts the rotation of the engine or motor into an oscillating angular velocity movement and regulates the amplitude of this movement. The oscillating rotation from the first subsystem is used to drive a second subsystem, which acts as a regulating device by means of an inertial mechanism. The oscillating movement at the output of the second subsystem is rectified in the third, resulting in a unidirectional angular velocity. As a result, a unidirectional torque is generated at the output of the CVT, commensurate with the operating condition of the transmission, and this is capable of overcoming a torque resistance. A prototype of this transmission was built and tested to check the experimental results against those predicted by a series of computational simulations. As a result, the experimental graphs that characterize the operation of this type of transmission system were obtained, demonstrating its ability to function in an efficient manner.

Teaching Experience for the Virtualization of Machine Tools and Simulation of Manufacturing Operations

This work aims to generate the digital documentation related to a number of manufacturing processes on different machine tools. The project is developed with the contribution of engineering students doing their final thesis within this field. Different machine tools and machining and incremental forming processes have been virtualized by using the CAD/CAM software CATIA V5. Some of the modeled parts were finally manufactured after checking and post-processing the NC code. Digital documentation is developed on different formats (e.g. photographs, videos, images and simulations) in order to be used as a teaching complement.

Experimental study of impact on SMC composites used in the automotive industry

The signal from a piezoelectric sensor received by a data acquisition system was used to record the temporal evolution of the force transmitted by an impactor on specimens of an SMC composite. A high-speed motion analyser recorded the sequence of images of the impact and fracture of the material. The subsequent processing of this sequence using an image analysis programme provided data for the calculation of various energy magnitudes. The behaviour under impact of this material was then characterised on the basis of these energy magnitudes and the temporal evolution of the force.

Multidisciplinary Learning of Manufacturing Engineering through Bachelor and Master Theses in Incremental Sheet Forming

This work presents a novel teaching experience in the framework of final master and bachelor theses within the research line on incremental sheet forming processes. This forming process involves a series of competences dealing with manufacturing technology at a wide multidisciplinary level. This paper analyses these different manufacturing topics and the knowledge acquired by students doing their final theses within this field. This knowledge will be very useful during their future professional career.

Self-Evaluation E-Learning System for Manufacturing Engineering Subjects

This work presents a project of teaching innovation on the subject Technology of Manufacturing that has been developed for the last five years. The objective is to stimulate students for training through a self-evaluation system based on e-learning tools, in agreement with the guidelines of the European Higher Education Area (EHEA). The system includes a methodology to perform a series of evaluations about theoretical and practical knowledge which allows the student self-learning. The data obtained with the proposed system are analyzed and the effect on student results is discussed. The evolution in time of the student grades, their involvement and satisfaction with the project, and its influence in their final score are presented.

Teaching Experience on Metal Forming Processes through Case Study Methodology

The aim of this contribution is to promote the use of FEM based numerical simulations for teaching the fundamentals of manufacturing processes. In particular, it focuses on metal forming processes, which by their mathematical modelling complexity can only be tackled in a very elementary way using traditional methods. This enables an active teaching based on realistic problem solving, through which students acquire both theoretical and practical knowledge on the subject. This approach is consistent with the guidelines of the European Higher Education Area (EHEA) on the use of participatory learning tools.

Novel experimental techniques for the determination of the forming limits at necking and fracture

Abstract Forming limit diagrams (FLDs) are currently the most useful and used tool for evaluating the workability of metal sheets. FLDs provide the failure locus at the onset of necking (commonly designated as the forming limit curve [FLC]) and at the onset of fracture in the principal strain space. The FLC is usually determined by means of Nakazima and Marciniak tests following the ISO 12004-2:2008 standard but the procedure for evaluating the necking strains presents difficulties that often lead to the fact that FLCs of the same material provided by different sources present sensible differences from each other. The interest in the determination of the onset of fracture has always been limited because most of the conventional sheet metal forming processes reach their formability limits at the onset of necking. However, this trend is progressively changing as a result of the growing interest and rapid development of new increment sheet forming processes in which plastic deformation is successfully accomplished for strain loading paths well above the FLC. On the other hand, a recently developed analytical framework built upon the fundamental concepts of anisotropic plasticity, ductile damage, and fracture mechanics helps better understanding of the relation between formability limits by fracture and crack opening modes. Both fracture limits by tension (also known as the fracture forming limit line [FFL]) and by in-plane shear (also known as the shear fracture forming limit line [SFFL]) will be characterized and experimentally determined. This chapter focuses on the innovative methods and procedures that were recently developed by the authors for the determination of the formability limits by necking (FLC) and fracture (FFL/SFFL), and on the application of FLDs to stretch-bending and single-point incremental forming processes. Results are comprehensively described and illustrated by a series of examples retrieved from experimental testing on steel and aluminum alloys and allow understanding of the influence of bending on formability.