Dental Implant Systems

Among various dental materials and their successful applications, a dental implant is a good example of the integrated system of science and technology involved in multiple disciplines including surface chemistry and physics, biomechanics, from macro-scale to nano-scale manufacturing technologies and surface engineering. As many other dental materials and devices, there are crucial requirements taken upon on dental implants systems, since surface of dental implants is directly in contact with vital hard/soft tissue and is subjected to chemical as well as mechanical bio-environments. Such requirements should, at least, include biological compatibility, mechanical compatibility, and morphological compatibility to surrounding vital tissues. In this review, based on carefully selected about 500 published articles, these requirements plus MRI compatibility are firstly reviewed, followed by surface texturing methods in details. Normally dental implants are placed to lost tooth/teeth location(s) in adult patients whose skeleton and bony growth have already completed. However, there are some controversial issues for placing dental implants in growing patients. This point has been, in most of dental articles, overlooked. This review, therefore, throws a deliberate sight on this point. Concluding this review, we are proposing a novel implant system that integrates materials science and up-dated surface technology to improve dental implant systems exhibiting bio- and mechano-functionalities

Surface modification of traditional and bioresorbable metallic implant materials for improved biocompatibility

Due to their strength, elasticity, and durability, a variety of metal alloys are commonly used in medical implants. Traditionally, corrosion-resistant metals have been preferred. These permanent materials can cause negative systemic and local tissue effects in the long-term. Permanent stenting can lead to late-stent thrombosis and in-stent restenosis. Metallic pins and screws for fracture fixation can corrode and fail, cause loss of bone mass, and contribute to inflammation and pain at the implant site, requiring reintervention. Corrodible metallic implants have the potential to prevent many of these complications by providing transient support to the affected tissue, dissolving at a rate congruent with the healing of the tissue. Alloys of iron and manganese (FeMn) exhibit similar fatigue strength, toughness, and elasticity compared with 316L stainless steel, making them very attractive candidates for bioresorbable stents and temporary fracture fixation devices. Much attention in recent years has been given to creating alloys with ideal mechanical properties for various applications. Little work has been done on determining the blood compatibility of these materials or on examining how their surfaces can be improved to improve cell adhesion, however. We examined thethrombogenic response of blood exposed to various resorbable ferrous stent materials through contact with porcine blood. The resorbable materials induced comparable or lower levels of several coagulation factors compared with 316L stainless steel. Little platelet adhesion was observed on any of the tested materials. ^ Endothelialization is an important process after the implantation of a vascular stent, as it prevents damage to the vessel wall that can accelerate neointimal hyperplasia. Micromotion can lead to the formation of fibrous tissue surrounding an orthopedic implant, loosening, and ultimately failure of the implant. Nanoscale features were created on the surfaces of noble metal coatings, silicon, and bioabsorbable materials through ion beam irradiation in order to improve endothelialzation and bone cell adhesion. Gold, palladium, silicon, and iron manganese surfaces were patterned through ion beam irradiation using argon ions. The surface morphology of the samples was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM), while surface chemistry was examined through x-ray photoelectron spectroscopy (XPS) and contact angle goniometry measurements. It was not possible to create nanoscale surface features on the surfaces of the gold and palladium films. At near normal incidence, irradiation produced ripples on the surfaces of Si(100), while oblique incidence irradiation produced nanoislands in the presence of impurities on the surface. Iron manganese irradiation resulted in the formation of blade-shaped structures for ion energies between 500eV and 1000eV, and significant iron enrichment at the surface. ^ Chemical treatment can also be used to create surface features that will enhance cell adhesion. Ti6Al4V is one of the most commonly used alloys for permanent orthopedic devices. The creation of a porous surface in order to improve osteoblast adhesion was achieved through chemical etching using acid-peroxide solutions. While phosphoric acid etched the grain boundaries, sulfuric and nitric acid preferentially etched grains of particular orientations, creating a spongy, porous morphology that has the potential to aid in osseointegration

Influence of Surface Modification on Corrosion and Biocompatibility of Titanium Alloys

Titanium alloys enhance the quality and longevity of human life by replacing or treating various parts of the body. However, the aggressive body fluids lead to corrosion and metal ions dissolution. These ions leach to the adjacent tissues and causes adverse reactions. Surface modifications improve corrosion resistance and biological activity. In this investigation, electropolishing, magnetoelectropolishing, titanium coating and hydroxyapatite coating were carried out on commercially pure titanium (CPTi), Ti6Al4V and Ti6Al4V-ELI (Extra Low Interstitials). These surface modifications are known to affect surface chemistry, morphology, wettability, corrosion resistance and biocompatibility of these materials. In vitro cyclic potentiodynamic polarization tests were conducted in phosphate buffer saline in compliance with ASTM standard. The surface morphology, roughness and wettability of these alloys were studied using scanning electron microscope, atomic force microscope and contact angle meter, respectively. Moreover, biocompatibility of titanium alloys was assessed by growing MC3T3 pre-osteoblast cells on the surfaces

Surface characterization of 316L stainless steel for biomedical applications

Stainless steel alloys play an important role in the field of biomaterials due to their exceptional corrosion resistance and biocompatibility. These alloys have the capability to enhance the quality of a human life by altering various structures of human physiology. The close proximity these alloys have with destructive body fluids, ion dissolution is a detrimental cause from the corrosion initiative and may cause unfavorable reactions. A view on developing an improved compatible surface for the human body leads to implementation of different chemical surface modifications used for creating features that must be corrosion resistant and biologically active without changing the overall bulk property. In this study, multiple technics for chemical treatments of above and below enhanced oxidation evolution will undergo a process of electropolishing and magnetoelctropolishing produced on commercial 316 L stainless steel. These surface modifications attempt to refine and improve critical features: corrosion resistance, biocompatibility, morphology, wettability, and chemistry

On surface electropolishing for the development of metallic stents

Les maladies cardiovasculaires sont responsables d'environ le tiers de tous les cas de décès au Canada. L'une des solutions utilisées pour résoudre ce problème consiste à utiliser un dispositif métallique constitué d'un maillage ayant une forme d’un filet et appelé stent. Les stents sont de petits dispositifs implantés dans des vaisseaux sanguins rétrécis pour rétablir la circulation sanguine et éviter une crise cardiaque ou un accident vasculaire cérébral et pour traiter les anévrismes du cerveau. Un contrôle précis de la surface de ces stents est nécessaire pour assurer la compatibilité de l'alliage choisi avec le milieu biologique dont il va être en contact avec. Les stents métalliques doivent satisfaire à des conditions précises définies en fonction de leur application finale. Ils doivent respecter des exigences strictes en termes de propriétés mécaniques, d'interaction électrochimique (corrosion) et de cytocompatibilité. Les alliages suivants sont traditionnellement utilisés dans les applications biomédicales et plus précisément pour les applications cardiovasculaires: l'alliage AISI316L est considéré comme une référence dans ce domaine, mais l'alliage L605, un alliage à base de Cobalt, prend de plus en plus d'importance grâce à ses propriétés mécaniques élevées (haute ductilité et haute résistance à la traction) et résistance élevée à la corrosion. L'utilisation d'alliages de titane est la nouvelle frontière pour les biomatériaux dans les applications cardiovasculaires, il est considéré comme un nouveau candidat potentiel pour les stents cardiovasculaires. Les alliages de titane présentent une combinaison unique de haute résistance et de grande ductilité (résistance à la traction et déformation uniforme supérieures à 1000 MPa et 30% respectivement). L’électropolissage est une étape de prétraitement appliquée à ces alliages métalliques pour obtenir des surfaces chimiquement homogènes, recouvertes d'une couche d'oxyde uniforme et amorphe, généralement de rugosité très lisse. Ce processus permet non seulement de contrôler les propriétés physiques de la surface, mais également celles chimiques. Le processus d'électropolissage comporte certaines variables, telles que le courant, la tension, la solution électrolytique et la température de l'électrolyte. En les contrôlant, il est possible de comprendre et d'améliorer les propriétés de la surface. Le but de ce projet est d’étudier les effets des différents variables d’électropolissage (courant, tension, solution électrolytique) sur les caractéristiques / propriétés de surface (morphologie, composition chimique et mouillabilité) des alliages utilisés pour la fabrication de stents.Cardiovascular diseases (CVD) are responsible for about one-third of all death cases in Canada. One of the solutions used to solve this problem is using a metallic device made of a mesh and called a stent. Stents are small devices that are implanted in narrowed blood vessels to restore blood flow and to avoid a heart attack or stroke and to treat brain aneurysms. An accurate surface control is needed to assure the cytocompatibility of the chosen alloy with its biologic environment. Metallic stents must satisfy precise conditions defined according to their final application. They need to respect strict requirements, in terms of mechanical properties, electrochemical interaction (corrosion) and cytocompatibility. The following alloys are traditionally used in biomedical applications and more precisely for cardiovascular applications: the alloy AISI316L is considered a reference in this field, but the alloy L605, a Co-based material, is gaining more and more importance, due to its high mechanical properties (high ductility and high ultimate tensile strength) and high corrosion resistance. The use of Titanium alloys is the new frontier for biomaterials in cardiovascular applications, it is considered as a new potential candidate for cardiovascular stents. Titanium alloys, shows a unique combination of high strength and high ductility (ultimate tensile strength and uniform deformation higher than 1000 MPa and 30%, respectively). Electropolishing is a pre-treatment step applied to these alloys to obtain chemically homogeneous surfaces, covered with a uniform and amorphous oxide layer, generally with a very smooth roughness. This process not only makes it possible to control the physical properties of the surface, but also the chemical ones. The electropolishing process has some changeable variables, such as current, voltage, electrolytic solution and temperature of electrolyte. By controlling them, it is possible to understand and improve the surface properties. This work is aimed at studying the effects of electropolishing changeable variables (current, voltage, electrolytic solution) on surface characteristics/properties (morphology, chemical composition and wettability) of those alloys used for the manufacture of stents

Direct Writing Of Polymeric Coatings For Corrosion Control And Tunable Release Of Bioactive Materials

The interface between a medical device and its surrounding tissue can be critical to biocompatibility, performance and therapeutic effectiveness. Careful choice and application of materials at this interface is therefore a key to the success of any medical device. This research employed a novel direct-write inkjet printing technique for polymeric surface modification of bioresorbable AZ31 Mg alloy towards corrosion control and tunable release of bioactive agents. In the first phase of this research, the direct-write inkjet printing technique was successfully used to fabricate thin films of different blends of poly (ester-urethane) urea embedded with taxol coatings on mechanically polished AZ31 Mg coupons. A corrosion study was performed using the electrochemical impedance spectroscopy (EIS) technique. The polarization resistance values obtained using the equivalent circuit model were analyzed using the ECHEM analyst commercial software developed by Gamry®. The polarization resistances obtained indicated that the corrosion resistance of the polymeric materials increases in this order: uncoated AZ31 \u3c PEUU-SB \u3c PEUU-PC \u3c PEUU-V

The Science and Technology of 3D Printing

Three-dimensional printing, or additive manufacturing, is an emerging manufacturing process. Research and development are being performed worldwide to provide a better understanding of the science and technology of 3D printing to make high-quality parts in a cost-effective and time-efficient manner. This book includes contemporary, unique, and impactful research on 3D printing from leading organizations worldwide

Eisenbasierte, Freitragende Filme Hergestellt durch Magnetron Sputtern für Biodegradierbare Anwendungen

In the work structured pure iron, iron-gold and binary FeMn alloys with different Mn contents are successfully fabricated by magnetron sputtering and characterized. For the characterization of the microstructure X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) was applied. In addition, the mechanical properties were determined by uniaxial tensile tests. Electrochemical polarization and immersion test were performed in Hanks solution in order to determine the corrosion rates. Furthermore, vibrating sample magnetometry was used in order to characterize the material in terms of its magnetic properties. It was found that in general the sputtered material exhibits a high mechanical strength compared to literature values for comparable materials. This is mainly attributed to the fine grained microstructure of sputtered material. A significant acceleration of the corrosion rates were reached by the addition of gold, due to the formation of micro galvanic elements. Against expectations the corrosion rates of FeMn alloys were found to be slower than pure iron. However, the low corrosion rate is compensated by the superior strength up to 1242 MPa. Additionally it was shown that the Mn concentrations > 15 % are sufficient in order to stabilize the non- ferromagnetic epsilon and gamma phase and in turn distinctly enhance the magnetic resonance imaging compatibility of the material. The work proofed the concept of using magnetron sputtering in combination with UV-lithography as promising alternative fabrication method of filigree structured, biodegradable iron based implants. Due to the advantages, the method offers a great potential to tailor the material properties.In der Arbeit wird gezeigt, dass Magnetron-Kathodenzerstäubung (Sputtern) in Kombination mit UV-Lithografie, eine geeignete Methode zur Herstellung von Eisen basierten biodegradierbaren Implantaten darstellt. Die Nutzung dieser Art der Herstellung bietet viele Vorteile. Zunächst einmal besitzt gesputtertes Material eine einzigartige Mikrostruktur und somit auch Materialeigenschaften. Darüber hinaus können neben der Abscheidung aller Arten von Legierungen auch Systeme aus nicht mischbaren Komponenten hergestellt werden. In dieser Arbeit wurden strukturierte Filme aus Reineisen, Eisen-Gold sowie verschiedene binäre Eisen-Mangan Legierungen erfolgreich hergestellt und charakterisiert. Es wurde gezeigt, dass im Vergleich zu Literaturwerten vergleichbarer Materialien, das gesputterte Material eine allgemein hohe Festigkeit besitzt. Dies ist hauptsächlich auf die charakteristische feinkörnige Mikrostruktur zurückzuführen. Weiterhin wurde eine signifikante Steigerung der Korrosionsrate durch das Einbringen von Goldausscheidungen erreicht, da diese als mikrogalvanische Elemente fungieren. Entgegen den Erwartungen, führte das Hinzulegieren von Mn führte zu einer geringfügigen Abnahme der Korrosionsrate. Dies wird jedoch durch die sehr hohe Festigkeit von bis zu 1147 MPa kompensiert. Zusätzlich konnte gezeigt werden, dass Mn Konzentrationen >15 %ausreichen, um die nicht-ferromagnetischen Epsilon und Gamma Phasen zu stabilisieren, was die Materialkompatibilität mit Magnet Resonanz Tomographie Untersuchungen deutlich verbessert. Die Arbeit zeigt, dass es möglich ist Magnetronsputtern in Kombination mit UV-Lithografie als alternatives Herstellungsverfahren für feinstrukturierte Implantate zu nutzen. Durch die Vorteile dieser Herstellungstechnik erscheint diese als vielversprechend um die Materialeigenschaften gemäß den Anforderungen zu optimieren

Coating stent materials with polyhedral oligomeric silsesquioxane-poly(carbonateurea)urethane nanocomposites

The long-term efficacy of coronary or peripheral stenting is limited by in-stent restenosis (ISR), which occurs in 15 to 30% of patients and is attributed primarily to neointimal hyperplasia. By adding a drug-eluting coating, this rate has been reduced to about 5% or less. However, recently longer-term follow-up data has highlighted problems with drug-coated stents, including late stage thrombosis. A bio-stable poly(carbonate-urea)urethane has been used for stent coating and the surface properties of the polymer have been optimised by incorporating the polyhedral oligomeric silsesquioxane molecule. These POSS polymers improve the adhesion and the growth of endothelial cells. The work described in this thesis, presents an innovative approach in self-expanding/balloon expandable coronary stent design that incorporates a NiTi/stainless steel alloy scaffold with a polyhedral oligomeric silsesquioxane- poly (carbonate-urea) urethane nanocomposite polymer (POSS-PCU) coating. Electrohydrodynamic spraying and ultrasonic atomization spraying of the non-biodegradable nanocomposite polyhedral oligomeric silsesquioxane (POSS) polymer have been investigated in detail for coating metallic stent materials and compared with dip coating. Because of the tight geometry of coronary stents, these new coating techniques have been shown to offer advantages over traditional coating techniques. These advantages include, reduced polymer consumption, precise coating thickness as low as 10 μm and a highly controllable spray which leads to consistent reproducible results. However, poor adhesion, or bond deterioration over the lifespan/ deployment of the device could reduces the efficiency and could impart even more complexity to the implant including formation of debris which can induce thrombus formation. Changing the surface physical property/chemical composition through the proposed protocol has been shown to increase the bonding strength by up to three times. This study has identified a new process and conditions which can be used in stent coating research

Failure Analysis of Biometals

Metallic biomaterials (biometals) are widely used for the manufacture of medical implants, ranging from load-bearing orthopaedic prostheses to dental and cardiovascular implants, because of their favourable combination of properties, including high strength, fracture toughness, biocompatibility, and wear and corrosion resistance. Owing to the significant consequences of implant material failure/degradation, in terms of both personal and financial burden, failure analysis of biometals has always been of paramount importance in order to understand the failure mechanisms and implement suitable solutions with the aim to improve the longevity of implants in the body. Failure Analysis of Biometals presents some of the latest developments and findings in this area. This includes a great range of common metallic biomaterials (Ti alloys, CoCrMo alloys, Mg alloys, and NiTi alloys) and their associated failure mechanisms (corrosion, fatigue, fracture, and fretting wear) that commonly occur in medical implants and surgical instruments