In vitro and in vivo corrosion properties of new iron-manganese alloys designed for cardiovascular applications.

The principle of biodegradation for the production of temporary implant materials (e.g. stents) plays an important role in the treatment of congenital heart defects.

Machining human dentin by abrasive water jet drilling.

The aim of this experimental in-vitro study was to investigate the machining of human dentin using an abrasive water jet and to evaluate the influence of different abrasives and water pressures on the removal rate. Seventy-two human teeth had been collected after extraction and randomly divided into six homogeneous groups (n=12). The teeth were processed in the area of root dentin with an industrial water jet device.

Intraprosthetic screw fixation increases primary fixation stability in periprosthetic fractures of the femur - a biomechanical study.

Background: The purpose of this study was to develop a new fixation technique for the treatment of periprosthetic fractures using intraprosthetic screw fixation. The goal was to biomechanically evaluate the increase in primary fixation stability compared to unicortical locked-screw plating.

Methods: A Vancouver C periprosthetic fracture was simulated in femur prosthesis constructs.

In vivo degradation of magnesium alloy LA63 scaffolds for temporary stabilization of biological myocardial grafts in a swine model.

Synthetic or biological patch materials used for surgical myocardial reconstruction are often fragile. Therefore, a transient support by degradable magnesium scaffolds can reduce the risk of dilation or rupture of the patch until physiological remodeling has led to a sufficient mechanical durability. However, there is evidence that magnesium implants can influence the growth and physiological behavior of the host's cells and tissue.

Different thermal conductivity in drilling of cemented compared with cementless hip prostheses in the treatment of periprosthetic fractures of the proximal femur: an experimental biomechanical analysis.

Purpose: The purpose of this study was to evaluate the different temperature levels whilst drilling cemented and cementless hip prostheses implanted in bovine femora, and to evaluate the insulating function of the cement layer.

Methods: Standard hip prostheses were implanted in bovine donor diaphyses, with or without a cement layer. Drilling was then performed using high-performance-cutting drills with a reinforced core, a drilling diameter of 5.

The effects of handling and storage on magnesium based implants--first results.

The present work aimed to investigate the influence of acetone and formalin as well as the duration and type of storage on magnesium based implants by means of microscopic, μ-computed tomographic, scanning electron microscopic, EDX and metallographic investigations. In contrast to storing in acetone, storage in formalin led to an increase in surface to volume ratio, and a decrease of the volume and the density. The various types of storage exerted no differing effects on the implants but with increasing storage duration, a spreading of oxygen rich areas on the surface, increased precipitations and a decrease in grain size could be observed.

Temperature control with internally applied cooling in solid material drilling: an experimental, biomechanical study.

Purpose: The purpose of this study was to evaluate the different temperature levels while drilling solid materials and to compare different cooling solutions for possible temperature control. An additional purpose was to develop an internal cooling device which can be connected to routinely used manual drilling devices in trauma surgery.

Methods: Drilling was performed on a straight hip stem implanted in bovine femora without cooling, with externally applied cooling and with a newly developed internal cooling device.

Strong and tough magnesium wire reinforced phosphate cement composites for load-bearing bone replacement.

Calcium phosphate cements are brittle biomaterials of low bending strength. One promising approach to improve their mechanical properties is reinforcement with fibers. State of the art degradable reinforced composites contain fibers made of polymers, resorbable glass or whiskers of calcium minerals.

Influence of cobalt on the properties of load-sensitive magnesium alloys.

In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder rods is utilized which enables the production of magnetic magnesium alloys with a reproducible Co concentration. The efficiency of the casting process is confirmed by SEM analyses.

Intraprosthetic fixation techniques in the treatment of periprosthetic fractures-A biomechanical study.

Aim: To develop new fixation techniques for the treatment of periprosthetic fractures using intraprosthetic screw fixation with inserted threaded liners.

Methods: A Vancouver B1 periprosthetic fracture was simulated in femur prosthesis constructs using sawbones and cemented regular straight hip stems. Fixation was then performed with either unicortical locked-screw plating using the less invasive stabilization system-plate or with intraprosthetic screw fixation using inserted liners.

Biocompatibility of fluoride-coated magnesium-calcium alloys with optimized degradation kinetics in a subcutaneous mouse model.

The principle of biodegradation has been considered for many years in the development of cardiovascular stents, especially for patients with congenital heart defects. A variety of materials have been examined with regard to their suitability for cardiovascular devices. Iron- and magnesium-based stents were investigated intensively during the last years.

Histological and molecular evaluation of iron as degradable medical implant material in a murine animal model.

A small animal model was established to evaluate the potential of iron as a degradable implant material. After insertion into the tail of mice, the implants gradually degraded over a clinically relevant time period of several months. Histological analysis and gene expression data from whole-genome microarray analyses indicated a limited inflammatory reaction.

In vitro corrosion of ZEK100 plates in Hank's Balanced Salt Solution.

Background: In recent years magnesium alloys have been intensively investigated as potential resorbable materials with appropriate mechanical and corrosion properties. Particularly in orthopedic research magnesium is interesting because of its mechanical properties close to those of natural bone, the prevention of both stress shielding and removal of the implant after surgery.

Methods: ZEK100 plates were examined in this in vitro study with Hank's Balanced Salt Solution under physiological conditions with a constant laminar flow rate.

Novel Repair Concept for Composite Materials by Repetitive Geometrical Interlock Elements.

Material adapted repair technologies for fiber-reinforced polymers with thermosetting matrix systems are currently characterized by requiring major efforts for repair preparation and accomplishment in all industrial areas of application. In order to allow for a uniform distribution of material and geometrical parameters over the repair zone, a novel composite interlock repair concept is introduced, which is based on a repair zone with undercuts prepared by water-jet technology. The presented numerical and experimental sensitivity analyses make a contribution to the systematic development of the interlock repair technology with respect to material and geometrical factors of influence.

Low-temperature degradation of different zirconia ceramics for dental applications.

The aim of this investigation was to determine the influence of simulated ageing on the tetragonal-to-monoclinic phase transformation and on the flexural strength of a 3Y-TZP ceramic, compared to alumina toughened zirconia (ATZ) and ceria-stabilized zirconia (12Ce-TZP). Standardized disc specimens of each material were hydrothermally aged in steam at 134°C and 3bar for 0, 16, 32, 64 or 128h. The phase transformation was determined by X-ray diffraction (XRD) and atomic force microscopy.

Effect of thermal expansion mismatch on the Y-TZP/veneer interfacial adhesion determined by strain energy release rate.

Purposes: The aim of this study was to assess the effect of differences in the thermal expansion behaviour of veneering ceramics on the adhesion to Y-TZP, using a fracture mechanics approach.

Methods: Seven veneering ceramics (VM7, VM9, VM13, Lava Ceram, Zirox, Triceram, Allux) and one Y-TZP ceramic were investigated. Thermal expansion coefficients and glass transition temperatures were determined to calculate residual stresses (σ(R), MPa) between core and veneer.

Ex vivo examination of the biocompatibility of biodegradable magnesium via microdialysis in the isolated perfused bovine udder model.

Purpose: Being biodegradable, magnesium is considered a promising future implant material but very little is known about the biocompatibility for the tissues in direct contact with it. In this study, the degradation of pure magnesium implants in the skin of an isolated bovine udder was examined over a period of five hours.

Methods: Microdialysis technique was used in order to investigate the reactions at the interface of implant and tissue.

Influence of hydrothermal and mechanical conditions on the strength of zirconia.

Low temperature degradation and mechanical and thermal cycling may decrease the strength of zirconia and jeopardize the long-term success of dental restorations made of this material. The objective of this study was to reveal the influence of different environmental and loading conditions on the strength of 3 mol.% yttria-stabilized polycrystalline tetragonal zirconia (3Y-TZP).

Influence of cooling rate on zirconia/veneer interfacial adhesion.

Slow cooling firing schedules have recently been introduced by some manufacturers to reduce chipping complications in zirconia-based core/veneer composites. The aim of this study was to test the hypothesis that these firing schedules may influence the bond strength between the zirconia core and veneering ceramic. Four different veneering ceramics recommended for zirconia (Lava Ceram, Triceram, VM9 and Zirox) were fired onto rectangular shaped Y-TZP specimens (Lava Frame) and cooled using a rapid or a slow cooling rate.

Development and biocompatibility of a novel corrodible fluoride-coated magnesium-calcium alloy with improved degradation kinetics and adequate mechanical properties for cardiovascular applications.

Recently, corrodible magnesium-based alloys have been introduced for use as cardiovascular stents and orthopedic implants. However, rapid corrosion rates have raised questions about their biocompatibility. Therefore, we developed a binary fluoride-coated magnesium-calcium alloy with improved degradation kinetics.

Supra- and subgingival biofilm formation on implant abutments with different surface characteristics.

Purpose: The aim of the present study was to establish a noninvasive method for quantitative analysis of supra- and subgingival biofilm formation on dental implants considering different surface modifications.

Materials And Methods: Patients of both sexes were included. They had to be in generally good health, partially edentulous, and the recipient of at least 1 screw-type implant with an abutment possessing supra- and subgingival areas.