In this work we present a study of demineralization in bovine cortical bone. We selected 9 fresh cortical bone samples from 2 diaphyseal femurs for analysis. Samples were demineralized for 24 h, 48 h, 72 h and 96 h using two concentrations of EDTA with different pH: EDTA 0.1 M (pH 10, alkaline) and EDTA 0.5 M (pH 7.4, neutral). We have employed µ-X-ray fluorescence (µ-XRF) and X-ray diffraction (XRD) to assess the degree of demineralization. EDTA solutions were analyzed for Calcium (Ca) and Phosphorous (P) extractions by Atomic Absorption Spectrophotometry (AAS) and Ion Chromatography (IC), respectively. Results from AAS and IC showed that EDTA 0.5 M (pH 7.4) removed two times more Ca and 3 times more P than EDTA 0.1 M (pH 10) in the first 24 hours. µ-XRF results presented that EDTA has a high capacity to bind Calcium and Phosphorus. On the other hand, despite the differences in concentration and pH, EDTA did not bind Zn and Sr. Results from XRD showed that EDTA with high concentration had a greater impact to the samples' crystallinity causing a severe damage.
Purpose
The purpose of this study is to validate a novel model of resting hand splint manufactured by additive manufacturing (AM) and compare it with the traditional model manufactured by high temperature thermoplastic in terms of cost, weight, volume and thermal comfort.
Design/methodology/approach
A novel resting hand splint model was created from the topology optimization (TO) and analyzed, by finite-element analysis, manufacturing cost and weight, with a traditional resting hand splint. A pilot clinical study was carried out to verify heat diffusion during the use of the two splints.
Findings
The results showed that compared with the traditional model, the novel model reduced the volume of material used by 35.48%, the weight of the orthosis by 17.56% and the maximum surface deformation by 171.17% when subjected to actuation forces. It was also verified that, when manufactured with Nylon by AM, the new model is 1.5 times cheaper than the traditional model made of Polypropylene. The result of the thermographic analysis showed greater temperature variation in the use of the traditional splint (+4.6°C) compared to the temperature variation observed in the nylon splint (2.1°C).
Practical implications
These results have as clinical relevance the demonstration of the feasibility of manufacturing functional orthoses that are more comfortable, cheaper and lighter than traditional ones.
Originality/value
This study describes the use of TO to manufacture a novel resting hand splint, which was compared with the commonly used traditional splint in terms of mechanical resistance, weight, cost and thermal comfort.
Introduction: Although there has been significant progress in the design of implants for osteosynthesis, the occurrence of failures in these medical devices are still frequent. These implants are prone to suffer from fretting corrosion due to micromotion that takes place between the screw heads and plate holes. Consequently, fretting corrosion has been the subject of research in order to understand its influence on the structural integrity of osteosynthesis implants. The aim of this paper is to correlate the surface finish characteristics of bone plate-screw systems with fretting corrosion. Methods: The surface finish (machined and polished) of five specimens taken from three commercial dynamic compression plates (DCP) were evaluated. For testing, the specimens were fixed with bone screws, immersed in a solution of 0.90% NaCl and subjected to a rocking motion with an amplitude of 1.70 mm and frequency of 1.0 Hz for 1.0 × 10 6 cycles, according to the ASTM F897 standard. Both, plate and screws were manufactured in Brazil with ASTM F138 stainless steel. Results: Flaws on the hole countersink area and on the screw thread of some specimens were identified stereoscopically. At the end of the test all the specimens showed evidence of fretting corrosion with an average metal loss of 4.80 mg/million cycles. Conclusion: An inadequate surface finish in some areas of the plates and screws may have favored the incidence of damage to the passive film, accelerating the fretting corrosion at the interfaces between the plate hole countersink and the screw head.
ResumoO presente estudo apresenta a avaliação microestrutural de duas ligas Fe-Ni-Cr com composições químicas distintas submetidas à corrosão em altas temperaturas em tubos de pirólise em uma planta de fabricação de polímeros durante três anos. A superfície e a seção transversal das ligas foram caracterizadas por microscopia eletrônica de varredura e espectroscopia por dispersão de energia de Raios-X. As condições de serviço induziram a formação de uma camada de óxido na superfície das ligas composta por uma região externa e outra interna além de uma região empobrecida em cromo abaixo da camada de óxido. Uma das ligas apresentou também uma zona de oxidação interna. O estágio de modificação microestrutural de ambas as ligas foi analisado e comparado com resultados de outros autores. Palavras-chave: Ligas Fe-Ni-Cr; Alta temperatura; Tubo de pirólise; Corrosão.
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