Bio-Medical Materials and Engineering - Volume 6, issue 4
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Bio-Medical Materials and Engineering is to promote the welfare of humans and to help them keep healthy. This international journal is an interdisciplinary journal that publishes original research papers, review articles and brief notes on materials and engineering for biological and medical systems.
Articles in this peer-reviewed journal cover a wide range of topics, including, but not limited to: Engineering as applied to improving diagnosis, therapy, and prevention of disease and injury, and better substitutes for damaged or disabled human organs; Studies of biomaterial interactions with the human body, bio-compatibility, interfacial and interaction problems; Biomechanical behavior under biological and/or medical conditions; Mechanical and biological properties of membrane biomaterials; Cellular and tissue engineering, physiological, biophysical, biochemical bioengineering aspects; Implant failure fields and degradation of implants. Biomimetics engineering and materials including system analysis as supporter for aged people and as rehabilitation; Bioengineering and materials technology as applied to the decontamination against environmental problems; Biosensors, bioreactors, bioprocess instrumentation and control system; Application to food engineering; Standardization problems on biomaterials and related products; Assessment of reliability and safety of biomedical materials and man-machine systems; and Product liability of biomaterials and related products.
Abstract: The biomedical study of NiTi shape memory alloys has been undertaken in China since 1978. A series of stimulating corrosion tests, histological observations, toxicity tests, carcinogenicity tests, trace nickel elements analysis and a number of clinical trials have been conducted. The results showed that the NiTi shape memory alloy is a good biomaterial with good biocompatibility and no obvious local tissue reaction, carcinogenesis or erosion of implants were found experimentally or clinically. In 1981, on the basis of fundamental studies, a shape memory staple was used for the first time inside the human body. Subsequently, various shape memory devices were…designed and applied clinically for internal fixation of fractures, spine surgery, endoprostheses, gynaecological and craniofacial surgery. Since 1990, a series of internal stents have been developed for the management of biliary, tracheal and esophageal strictures and urethrostenosis as well as vascular obturator for tumour management. Several thousand cases have been treated and had a 1-10 year follow-up and good clinical results with a rather low complication rate were obtained.
Abstract: NiTi Shape Memory Alloys (SMA) are potential biomaterial candidates for medical devices such as osteosynthesis staples. However, Ni dissolution induced by uniform or localized corrosion could lead to toxicity. In this work, plasma polymerized tetrafiuoroethy1ene (PPFTE) coating is used to improve the corrosion resistance of NiTi plates and corresponding NiTi staples. The scratch test indicates a good surface adhesion of the film but that it lacks cohesiveness. Potentiodynamic tests in physiological Hank's solution show that PPTFE coating improved the pitting corrosion resistance. The passivation range is increased from 35% to 96% compared to the untreated sample and the pit diameter…is decreased from 100 μm to 10 μm. The uniformity of the deposited film is a very important parameter. When the film is damaged, the corrosion seems to increase in comparison to the untreated samples. Otherwise, if the staple is carefully manipulated, the coating follows the large deformations induced by the memory effect of the alloy without cracking, and then, protects efficiently the staple from pitting.
Abstract: Nitinol alloys (Nitinol) exhibit a dramatically enhanced elasticity, known as “superelasticity”, which is becoming integral to the design of a variety of new medical products. Elasticity is the most apparent of the advantages afforded by this material, but by no means the only or most important. Also discussed in this paper are features such as biocompatibility, kink resistance, constancy of stress, physiological compatibility, shape memory deployment, dynamic interference and fatigue resistance. Each of these properties is discussed and highlighted through example. Examples presented include stents, filters, retrieval baskets, and surgical tools.
Abstract: Nitinol based shape memory alloys were introduced to Medicine in the late seventies. They posses a unique combination of properties including shape memory, superelasticity, great workability in the martensitic state, resistance to fatigue and corrosion. Despite these exceptional physical, chemical and mechanical properties the worldwide medical application has been hindered for a long time because of the lack of knowledge on the nature of the biocompatibility of these enriched by nickel alloys. A review of biocompatibility with an emphasis on the most recent studies, combined with the results of X-ray surface investigations, allows us to draw conclusions on the origin…of the good biological response observed in vivo. The tendency of Nitinol surfaces to be covered with TiO2 oxides with only a minor amount of nickel under normal conditions is considered to be responsible for these positive results. A certain toxicity, usually observed in in vitro studies, may result from the much higher in vitro Ni concentrations which are probably not possible to achieve in vivo. The essentiality of Ni as a trace element may also contribute to the Nitinol biocompatibility with the human body tissues. Examples of successful medical applications of Nitinol utilizing shape memory and superelasticity are presented.
Abstract: In the last twenty-five years a large variety of research has been carried out in Russia using Shape Memory Alloys (SMA), particularly nearly equiatomic NiTi alloys, for medical applications. In this field of activity, Russian research centers have been quite successful in treating different kinds of diseases, from bone fractures to dental implants. This review is intended to give a panorama of SMA medical applications in Russia in order to illustrate the remarkable possibilities offered by SMA materials in the medical field.
Abstract: Since ten years the NiTi alloys have gained an ever increasing place in orthodontic practice: that is due to their peculiar mechanical properties ascribed to a martensitic thermoelastic transformation which can be thermally or, in a proper temperature range, stress-induced. In the last case, when martensite is stress-induced at body temperature, the stress-strain behaviour is pseudoelastic with large deformations gained or recovered at constant stress, respectively in direct/reverse transformation: this behaviour exploited in orthodontics allowed to overcome the drawbacks intrinsic to the use of conventional alloys as stainless steel or Co-Mo alloys, where small displacements can be achieved at decreasing…loads. From the phase state diagram of NiTi alloys it appears that at body temperature they are stable, but out of equilibrium: thermal treatments at intermediate temperatures can therefore modify the equilibrium state and as a consequence the transformation temperatures respect to body temperature. That allows to modify the recovery stress level according to the requirements of practice and thus disclosing new roads: the capability to foresee NiTi archwires pre-programmed in different sections, with a personalized scheme. Attention has not currently been paid to the modifications in the recovery stress induced by a temperature change inside the oral cavity. Recent results have shown that the thermal changes in the oral cavity induced by cold/hot liquid intake can considerably modify the stress level to which the dentition is exposed: though confined to the time extent connected with drinking, similar effects can be expected also for meals intake and should be taken into account for a correct procedure.
Keywords: NiTi alloy, shape memory alloys, orthodontics, superelasticity, martensitic transformation
Abstract: Thirty-six metatarsal osteotomies using internal fixation of a shape memory metal compression staple for hallux valgus were performed in 21 women with a mean age of 42.3 years (30–66 years). The time for return to light work averaged 19.0 days, and to full work and normal walk 41.2 days after the operation. Twenty patients (35 feet) had complete relief from pain. Only in one foot, the pain was transferred under the second metatarsal head. The appearance of the feet was apparently improved and the width of the forefeet was decreased by a mean of 0.90 cm after the operation. Radiographic…analysis of feet showed that all osteotomies united, and the average angle of hallux valgus was improved from 31.2° to 16.3° and the mean intermetatarsal angle from 12.0° to 6.4°. No external fixation of plaster splintage was needed and the distal fragment during healing of the osteotomy was stable. The time of bone healing was shortened and patients were allowed to bear weight at an early time.
Keywords: NiTi staple, metatarsal osteotomy, hallux valgus