Failure Analysis of Titanium-Based Dental Implant

Metallic materials designed for applications in orthopedic or dental surgical implants must show a group of properties, including biocompatibility, mechanical strength and resistance to degradation (by wear or corrosion) outstand. In order to assure that the properties are achieved, the implant materials must fulfill certain requirements, usually specified in standards. The standards also include chemical composition, microstructure and even macrographic aspects. The main aim of this work was to perform a failure analysis on a titanium-based dental implant and connect the possible causes of failure with the associated material requirements which were previously mentioned. Evaluation techniques included metallographic analysis by optical microscopy and fractographic analysis by scanning electron microscopy (SEM). The results of the examinations suggested that, in spite of their adequate microstructures, the implants fractured due to the overload generated by stress raisers which were found in the implants.     

Failure analysis of surgical implants in Brazil

The present paper summarises cases of metallurgical failure analysis of two femoral compression plates and one femoral nail-plate fabricated in stainless steel, one oral maxillo-facial plate for jaw reconstruction in commercially pure titanium alloy, and several Nitinol wires. The experimental work consisted of visual inspection of the samples, macroscopic and microscopic characterisation of the material, fractographic investigation of the fracture surface and adjacent areas and chemical composition. The present investigation revealed that most of the implants investigated were not in accordance with ISO standards and most of them presented evidence of corrosion assisted fracture. Additionally, some of the components revealed the presence of fabrication and/or processing defects, which contributed to their premature failure. The implantation of materials that are not biocompatible may cause several types of adverse effects in the human body and promote the premature failure of the implants, with immeasurable damages for the patients and losses for the public investment. The local sanitary regulation agencies are strengthening the mechanisms to avoid the commercialisation of surgical implants not in accordance with standards, including the adoption of retrieval analysis of failed implants.     

Retrieval and analysis of surgical implants in Brazil: The need for proper regulation

This paper summarizes several cases of metallurgical failure analysis of surgical implants conducted at the Laboratory of Failure Analysis of IPT, in Brazil. Investigation revealed that most of the samples were not in accordance with ISO standards and presented evidence of corrosion assisted fracture. Additionally, some components were found to contain fabrication/processing defects that contributed to premature failure. The implant of nonbiocompatible materials results in immeasurable damage to patients as well as losses for the public investment. It is proposed that local sanitary regulation agencies create mechanisms to avoid commercialization of surgical implants that are not in accordance with standards and adopt the practice of retrieval analysis of failed implants. This would protect the public health by identifying and preventing the main causes of failure in surgical implants.     

A critical review on polymer-based bio-engineered materials for scaffold development

Since the last decade, tissue engineering has shown a sensational promise in providing more viable alternatives to surgical procedures for harvested tissues, implants and prostheses. Due to the fast development on biomaterial technologies, it is now possible for doctors to use patients’ cells to repair orthopedic defects such as focal articular cartilage lesions. In order to support the three-dimensional tissue formation, scaffolds made by biocompatible and bioresorbable polymers and composite materials, for providing temporary support of damaged body and cell structures have been developed recently. Although ceramic and metallic materials have been widely accepted for the development of implants, its non-resorbability and necessity of second surgical operation, which induces extra for the patients, limit their wide applications. This review article aims at introducing (i) concept of cartilage tissue engineering, (ii) common types of bio-engineered materials and (iii) future development of biomaterial scaffolds.     

Knowledge-based approach towards hydrolytic degradation of polymer-based biomaterials

The concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.1 A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge-based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir-Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided.     

Machine learning recommends affordable new Ti alloy with bone-like modulus

A neural-network machine called “βLow” enables a high-throughput recommendation for new β titanium alloys with Young’s moduli lower than 50 GPa. The machine was trained by using a very general approach with small data from experiments. Its efficiency and accuracy break the barrier for alloy discovery. βLow’s best recommendation, Ti-12Nb-12Zr-12Sn (in wt.%) alloy, was unexpected in previous methods. This new alloy meets the requirements for bio-compatibility, low modulus, and low cost, and holds promise for orthopedic and prosthetic implants. Moreover, βLow’s prediction guides us to realize that the unexplored space of the chemical compositions of low-modulus biomedical titanium alloys is still large. Machine-learning-aided materials design accelerates the progress of materials development and reduces research costs in this work.     

柴油机曲轴早期断裂分析

采用宏观断口分析、化学成分分析和显微组织检验等方法对增压柴油发动机曲轴发生断裂的原因进行了分析。结果表明,曲轴材质符合技术要求,而热处理后的校直过程存在问题,由此留下了隐患,造成该曲轴在运行过程中产生疲劳裂纹而断裂。提出了改进措施,杜绝了此类事故的发生。     

Theoretical design and analysis of a honeycomb panel sandwich structure loaded in pure bending

This paper discusses the theoretical and quantitative design and analysis of a honeycomb panel sandwich structure. The initial design is based on specific requirements that the panel must achieve prior to failure under load. Materials to be used for the facing and core are selected based on the given requirements. With the materials chosen, the facing sheets and core are analyzed for failure. Failure occurs when the stresses in the panel exceed the properties of the materials by any mode.     

Antibacterial surface design of biomedical titanium materials for orthopedic applications

Titanium(Ti)and titanium alloys have become widely used as biomedical materials in orthopedics because of their good machinability,corrosion resistance,low elastic modulus and excellent biocom-patibility.However,when Ti-based implants are used for bone repair and replacement,they are easy to cause bacteria adhesion and aggregation,which leads to postoperative infection.In addition,Ti and its alloys,as bio-inert materials,cannot induce desirable tissue responses such as osseointegration after implantation,which will eventually lead to implant loosening.Postoperative bacterial infection and lack of osseointegration directly lead to the failure of implantation surgery and are not conductive to the long-term service of titanium-based implants.Recently,researchers have made many attempts to focus on the surface modification of multifunctional Ti-based implants to endow them with both antibacterial activity and simultaneous osteoinductive property.In this review,we primarily highlighted the recent progresses in the surface design of Ti implants with both antimicrobial and osteoinductive properties for orthopedic applications.First,the challenges for treating implant-associated infections were briefly introduced such as the emergence of antibiotic resistance,the formation of biofilms,and the construction of cell-selective surfaces.Some of the essential fundamentals were concisely introduced to address these emerging challenges.Next,we intended to elaborate the potential strategies of multifunctional surface design to endow good osseointegration for antibacterial Ti implants and highlighted the recent advances of the implants.We hope that this review will provide theoretical basis and technical support for the development of new Ti implant with antibacterial and osteogenic functions.     

Additive Manufacturing of Titanium Alloys for Orthopedic Applications: A Materials Science Viewpoint

Titanium‐based orthopedic implants are increasingly being fabricated using additive manufacturing (AM) processes such as selective laser melting (SLM), direct laser deposition (DLD), and electron beam melting (EBM). These techniques have the potential to not only produce implants with properties comparable to conventionally manufactured implants, but also improve on standard implant models. These models can be customized for individual patients using medical data, and design features, such as latticing, hierarchical scaffolds, or features to complement patient anatomy, can be added using AM to produce highly functional patient‐anatomy‐specific implants. Alloying prospects made possible through AM allow for the production of Ti‐based parts with compositions designed to reduce modulus and stress shielding while improving bone fixation and formation. The design‐to‐process lead time can be drastically shortened using AM and associated post‐processing, making possible the production of tailored implants for individual patients. This review examines the process and product characteristics of the three major metallic AM techniques and assesses the potential for these in the increased global uptake of AM in orthopedic implant fabrication.

     

关节置换植入物用材料临床应用现状及发展趋势

关节置换植入物的应用日趋增多。本文对关节置换植入物用材料的临床应用现状及发展趋势做了综述。首先介绍了关节置换植入物材料的基本要求以及国际、国内标准的相关规定。对各种植入物材料,包括不锈钢、钴基合金、纯钛和钛合金、氧化铝陶瓷、超高分子量聚乙烯和PMMA骨水泥等高分子材料以及羟基磷灰石涂层复合材料的临床应用现状等做了阐述。简要介绍了金属材料和超高分子量聚乙烯材料的发展趋势。     

新型吨袋输送转向装置设计

目的针对目前吨袋在输送转向过程中频繁出现滞留现象、输送传动零部件容易疲劳磨损失效等问题,导致包装能力不能满足客户要求,设计了一套新型输送转向装置。方法通过分析吨袋内物料特性和原吨袋输送转向装置存在问题,提出新型输送转向装置设计方案及装置结构组成。结果新装置包装能力可以达到52.2袋/h,与原装置比较,包装能力提高了35.8%。结论新型输送转向装置克服了粉状和颗粒状物料性质引起的冲击载荷,杜绝了吨袋在转向输送中滞留现象的发生,输送平稳性和传动部件寿命得到提高,包装能力也得到提升。     

Promoting Bone Mesenchymal Stem Cells and Inhibiting Bacterial Adhesion of Acid-Etched Nanostructured Titanium by Ultraviolet Functionalization

Titanium(Ti) and its alloys are used extensively in orthopedic implants because of their excellent biocompatibility,mechanical properties and corrosion resistance. However,titanium-based implant materials face many severe complications,such as implant loosening due to poor osseointegration and bacterial infections,which may lead to implant failure. Hence,preparing a biomaterial surface,which enhances the interactions with host cells and inhibits bacterial adhesion,may be an optimal strategy to reduce the incidence of implant failure. This study aims to improve osseointegration and confer antibacterial properties on Ti through a combination of two surface modifications including nanostructuring generated by acid etching and ultraviolet(UV) light treatment.Our results showed that without UV treatment,the acid etching treatment of Ti surface was effective at both improving the adhesion of bone mesenchymal stem cells(BMSCs) and increasing bacterial adhesion. A further UV treatment of the acid-etched surface however,not only significantly improved the cell adhesion but also inhibited bacterial adhesion. The acid-etched nanostructured titanium with UV treatment also showed a significant enhancement on cell proliferation,alkaline phosphatase(ALP) activity and mineralization. These results suggest that such nanostructured materials with UV treatment can be expected to have a good potential in orthopedic applications.     

Nanospikes on Customized 3D-Printed Titanium Implant Surface Inhibits Bacterial Colonization

Additive manufacturing has opened the door to patient-tailored orthopedic implants, which can significantly minimize implant failures associated with prosthesis-to-bone mismatch. Success of an implant also depends on the choice of implant materials, effective osseointegration, implant quality, and the mechanical properties together with its capability to limit infection due to bacterial contamination. Herein, nanospikes are created on 3D-printed titanium-alloyed implant surfaces, which can kill bacteria to minimize any implant-associated infections. For the first time, orthopedic implants with a fracture to the proximal phalanx are fabricated using selective laser melting (SLM) followed by a heat-treatment step and the hydrothermal process. It is showed in the results that by optimizing SLM parameters, dimensionally consistent parts can be produced and tensile properties of the 3D-printed implants can be significantly improved via a simple cyclic heat-treatment process compared to the traditionally manufactured implants. Nanospikes similar to those present on dragonfly wings fabricated on 3D-printed implants surface are able to kill above 90% of adhering bacteria by rupturing the membranes upon contact. These results indicate that fabrication of patient-specific 3D-printed implants with inherent bactericidal properties has the potential to eliminate postsurgical infections and possible implant failures.     

航空材料在外科植入物骨关节假体中的应用

在现代材料科学与技术的发展历程中,航空材料一直扮演着先导和基础作用.航空材料中的高温合金(主要是钴基合金)、钛合金、不锈钢、陶瓷、高耐磨非金属等材料以其轻质、高强、高抗疲劳性、高耐热、高可靠性,并且具有良好的生物相容性等优良性能,已成为临床中较为理想的植入材料,并被广泛应用于外科植入物方面.国内外人工关节得以迅猛发展很大程度上依赖于航空材料在外科植入物骨关节假体中的应用.本文旨在介绍目前航空材料在外科植入物骨关节假体应用方面的常用材料、性能及使用要求.     

Meeting the challenges related to material issues in chemical industries

Reliable performance and profitability are two important requirements for any chemical industry. In order to achieve high level of reliability and excellent performance, several issues related to design, materials selection, fabrication, quality assurance, transport, storage, inputs from condition monitoring, failure analysis etc. have to be adequately addressed and implemented. Technology related to nondestructive testing and monitoring of the plant is also essential for precise identification of defect sites and to take appropriate remedial decision regarding repair, replacement or modification of process conditions. The interdisciplinary holistic approach enhances the life of critical engineering components in chemical plants. Further, understanding the failure modes of the components through the analysis of failed components throws light on the choice of appropriate preventive measures to be taken well in advance, to have a control over the overall health of the plant. The failure analysis also leads to better design modification and condition monitoring methodologies, for the next generation components and plants. At the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, a unique combination of the expertise in design, materials selection, fabrication, NDT development, condition monitoring, life prediction and failure analysis exists to obtain desired results for achieving high levels of reliability and performance assessment of critical engineering components in chemical industries. Case studies related to design, materials selection and fabrication aspects of critical components in nuclear fuel reprocessing plants, NDT development and condition monitoring of various components of nuclear power plants, and important failure investigations on critical engineering components in chemical and allied industries are discussed in this paper. Future directions are identified and planned approaches are briefly described     

Biomaterials for ossicular chain reconstruction. A review

This review gives a survey of biomaterials used for ossicular chain reconstruction. The survey is focussed on application, biophysical requirements, properties and goals for future developments. The implantation site middle ear differs from others due to aeration and potential bacterial colonization. As a consequence, implant materials must exhibit excellent biocompatibility, biostabilty and sound conducting properties. In vitro and in vivo biocompatibility investigations and clinical observations determine the choice of material. Additionally the implants must provide the possibilty of intraoperative shaping or should be available in different variations in order to allow reconstruction appropriate to the individual conditions. Ceramics, metals and plastics are materials in current use. Based on thorough experimental and long term clinical experiences, the bioinert aluminum oxide is favorable amoung the ceramics. Bioactive ceramics may have minor biostability and the risk of fixation to surrounding bone which impairs sound conduction. This is also true for hydroxyapatite although biodegradation occurs only rarely. Today, titanium is the metal best established in middle ear implantation, reflected by excellent biocompatibility in vitro and in vivo, and good clinical results. Titanium is preferred by many surgeons, considering that sound transmission properties are mainly dependent on the implant weight. In stapes surgery, when the implant has direct contact to inner fluids, gold was accused to cause granuloma formation with subsequent inner ear damage in selected cases. In frequent past and present use, plastics (porous polyethylene and teflon) have proven to be of limited value in ossicular chain replacement because of high extrusion rates and the observation of material desintegration and bacterial colonization. In order to individually manage the pathological conditions in the middle ear, the implant design is of crucial importance. It is dependent on the ossicle to be replaced and the implant material. Future investigations have to minimize implant extrusions possibly by modifying and improving implant surfaces.     

Biodegradable Hydroxyapatite–Polymer Composites

The fracture of bone due to trauma or due to natural aging is one of the most frequent types of tissue failures. Treatment frequently requires the implantation of a temporary or permanent prosthesis. The implanted materials may include the components of artificial joints, plates, and screws for fracture fixation. Typically, such implants are intended only to provide structural support or to serve as templates for bone re‐growth. In general they are intended to remain in place for the life of the patient or to be removed in a second surgical procedure. This report provides a short review of the synthetic reconstructive bone implants. Following this, the rationale and basics of the biodegradable hydroxyapatite–polymer composite approach are described.     

Anforderungen an Hochtemperaturwerkstoffe für Gasturbinen-Flugtriebwerke

High-Temperature Material Requirements for Gas Turbine Aero Engines. The special requirements to be met by the materials used for aero engines are due to three facts: Engine stressing is characterized by a rather extreme combination of mechanical, chemical and thermal stresses. The typical engine materials based on nickel, cobalt and titanium involve difficulties in the manufacturing and processing techniques due to the high tolerance requirements. The high risk for human life as a result of a failure of such components calls for an exceptionally high reliability standard. Requirements as a result of the stresses are dealt with by means of the rotor blades and disks. This example shows that, in addition to the conventional requirements for creep and oxidation resistance, further requirements resulting from the additional stresses (load and temperature cycles, corrosion effects) must be treated on an equivalent basis. In the field of processing typical problems are discussed which are associated with manufacturing ability, weldability and distortion. The reliability to be specified results in requirements for cleanliness, structure, homogeneity, isotropy, suitability for nondestructive testing and approval of suppliers. These requirements are reflected in the relevant procurement specifications.     

Research and application problems in fracture of materials and structures in the united states air force

This paper reviews current and projected Air Force R&D activities in the area of fracture mechanics for materials and structures and cites systems problems which have been essentially responsible for the recent flurry of activity in this area. The specific technology areas reviewed in this paper range from basic material property data generation to the improvement of fracture analysis procedures which account for the complex structural geometries, chemical and stress environment. The emphasis, direction and guidance for selecting specific topics of research has been assisted by recent past failure incidents, and knowledge of the technological deficiencies gained from current attempts to formulate and apply requirements to design, analyze and test for safe crack growth and residual strength.While the current R&D efforts are directed toward improving the material data base and analytical capability needed to effectively implement fracture control procedures, unknowns and areas of concern still exist. Examples of these include the accurate assessment of cost weight and performance impacts caused by the imposition of fracture requirements, the need for, and magnitude of safety or confidence factors for residual strength or safe crack growth analyses and the scope and magnitude of test and/or analysis required to prove conformance with specifications.