Abstract: The purpose of this study was to investigate the effect of albumin on the potentiodynamic anodic polarisation of commercially available pure titanium (CP Ti). The polarisation was performed starting at 1200 mV and terminating at 3500 mV vs. Saturated Calomel Electrode (SCE) in 3.5wt% NaCl with and without additions of egg albumin. The surfaces of untreated and treated disks by terminating at 1400 mV and at 1800 mV were characterised using the N1s peak via X-ray Photoelectron Spectroscopy (XPS). It was found that the adsorption of albumin obstructed the
passivation and that the corrosion rate in transpassive region was significantly increased.
Abstract: Surface microscopic patterns can enhance osteointegration of titanium implants in
orthopedic and dental applications. It is a challenge to produce regular topographic patterns on titanium. We have developed two techniques, jet-electrochemical micromachining (Jet-EMM) and the confined etchant technique (CELT) to produce topographic patterns on titanium. The results demonstrate that Jet-EMM has the ability to produce micro-hole arrays on either flat or curved surfaces and CELT can fabricate complex micro patterns with limited depth on a flat surface.
Abstract: The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on a novel low temperature degradation-free zirconia/alumina composite material and on the conventional ceramics (alumina and zirconia) used for a femoral head in total hip joint replacement. The wear of UHMWPE pins against these ceramic disks was evaluated by performing linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in a bovine serum. The weight loss of polyethylene against the novel low temperature degradation-free zirconia/alumina composite disks was much less than conventional ceramics for all tests. The mean
weight loss of the polyethylene pins was more in the linear reciprocal sliding test than in the repeat pass rotational sliding test for all kinds of disk materials. Neither the coherent transfer film nor the surface damage was observed on the surface of the novel zirconia/alumina composite disks during the test. In conclusion, the novel zirconia/alumina composite leads the least wear of polyethylene among the tested ceramics and demonstrates the potential as the alternative materials for femoral
head in total hip joint replacement.
Abstract: Wear is the primary cause of the failure of joint replacement prostheses. In this paper, the ultra-high molecular weight polyethylene (UHMWPE) as an artificial joint acetabular material was filled with nano-powder of SiO2 of various mass fractions. The effect of SiO2 mass fraction on the tensile strength, tensile modulus, wetting property and tribological properties of the SiO2-UHMWPE composites were investigated when sliding against Ti-6Al-4V under lubrication of physiological saline water. The morphologies of the worn surfaces of composites were observed with optical microscope. As a result, the tensile strength, tensile modulus, wettability and wear resistance of the composites were all improved by filling with SiO2, and the composites had largely decreased friction coefficients under lubrication of physiological saline water compared with the unfilled UHMWPE. This was attributed to the reinforcing function of the nano-powder of SiO2 in the composites and the lubricating action of the water boundary film. The wear of pure UHMWPE was dominated by plowing, plastic deformation, while the SiO2-UHMWPE was characterized the mild fatigue wear.
Abstract: PE is manufactured by Transysteme with the method of thermocompression of PE powder. This company irradiates PE by YAG LASER. We compared the physical behavior of both samples. The DSC reveals a high and similar crystallinity of PE, before and after YAG LASER treatment. Weattability between PE and Li-PE are similar at about 37 mJ/cm². The difference appears with respect to the surface profile and composition: the roughness is 0.20 µm for PE and 0.29µm for Li- PE. XPS reveals many traces of stripping agents on PE. YAG Laser produces a surface cleaning effect. Biological tests reveal a non-toxicity of the polyethylene powder, an improved proliferation and vitality of L132 cells on Li-PE with respect to untreated PE. We have a 4-fold improvement of proliferation and a 2-fold improvement of vitality on Li-PE with respect to PE. As to morphology and cell adhesion behavior, we have no differences between both samples. Thus the irradiation process of PE by YAG LASER improved the biological behaviors of this polymer due to changes in roughness and to surface cleaning.
Abstract: The friction and wear behavior of dental feldspathic ceramics, treated distinctively by
three routine surface strengthening techniques (auto-glazing, ion exchange and polishing), were investigated by cyclic sliding against pure titanium ball on a modified fretting friction and wear test rig under imitating oral enviorment. The wear scars of the samples were characterized with 3-D con focused laser-scanning microscope. The wear depths were analyzed statistically and the element concentrations of Ti, Al and Si on the scar before and after surface treatments were determined with energy dispersion spectrometry. The correlations between the wear behaviors and micro hardness or toughness were also compared. The results show the present routine surface strengthening methods have little effects on the friction coefficient of dental porcelain, but play an role in improving the wear behavior of ceramics at the early stage of sliding cycles. The effect of surface ion exchange is
better than that of auto-glazing or polishing. The friction and wear behavior of dental ceramics depend on the material itself especially after the surface-strengthening layer disappeared. Abrasive wear, adhesion and micro cracking characterize the wear mechanism of dental feldspathic ceramics after the surface-strengthening treatments.
Abstract: Influence of heat-treatment conditions on wear resistance of titanium was investigated. Titanium plates were subjected to heat-treatment in air and water vapor respectively. Heat-treatments increased micro-hardness of titanium. The plate heat-treated in air (H) has the highest roughness and the plate treated in water vapor (W) lowest. After heat-treatment surface oxide was rutile. The friction coefficient of W was the lowest and almost stable at about 0.18. Non-heat--treated titanium plate (S) had a highest coefficient up to 1.1. Wear resistance of heat--treated titanium, especially W was significantly superior to non-treated titanium. The wear of
S resulted mainly from adhesion failure, H involved with abrasive wear and fatigue failure. For W, a complex wear mechanism was probably existed.
Abstract: In this study, the wear characteristics of five different dental composite resins cured by conventional halogen light and LED light sources were investigated. Five different dental composite resins of Surefil, Z100, Dyract AP, Fuji II LC and Compoglass were worn against a zirconia ceramic ball using a pin-on-disk type wear tester with 15 N contact force in a reciprocal sliding motion of sliding distance of 10 mm/cycle at 1Hz under the room temperature dry condition. The wear variations of dental composite resins were linearly increased as the number of cycles increased. It was observed that the wear resistances of these specimens were in the order of Dyract AP >
Surefil > Compoglass > Z100 > Fuji ı LC. On the morphological observations by SEM, the large crack formation on the sliding track of Fuji ıLC specimen was the greatest among all resin composites. Dyract AP showed less wear with few surface damage. There is no significant difference in wear performance between conventional halogen light curing and light emitting diodes curing sources. It indicates that a light emitting diodes (LED) source can replace a halogen light
source as curing unit for composite resin restorations.
Abstract: As the aseptic loosening induced by polyethylene wear debris is the main cause of
long-term failure of total joint replacements, increasing the wear resistance of ultrahigh molecular weight polyethylene (UHMWPE) will be very important to obtain long-life artificial joint. In this paper the UHMWPE was implanted with 450 keV N+ ions to three doses of 5×1014/cm2, 2.5×1015/cm2 and 1.25×1016/cm2. The friction and wear behaviors of UHMWPE were studied under lubrication of distilled water and blood plasma using a ball-on-disk tribometer with a ZrO2 ceramic ball as a counterface. Experimental results showed that the friction coefficient of ions implanted UHMWPE are higher than un-implanted UHMWPE. Under blood plasma lubrication condition, the wear rate of implanted UHMWPE was lower than un-implanted UHMWPE, and the wear rate decreased with increasing implantation dose. The plow, plastic deformation and fatigue were wearing mechanism for un-implanted UHMWPE and the abrasive wear for implanted UHMWPE.
Abstract: Stress shielding, which occurred always around traditional one part implant applied for prosthetic artificial lower limb attachment, would cause osteoporosis and thus result in the loose and extrusion, and then the malfunction of the implant. To improve the structure of the implant, a new type of implant—multi-part implant was developed in this article. Based on CT data and under the maximal load during a normal walking cycle, 3D finite element analysis (FEA) was carried out to analyze the stress of bone around the new implant in three cases of distally truncated femur at high position、middle-position and low-position. Results reveal that stress shielding and stress concentration under the new type of implant reduced effectively compared with the traditional one-part implant, and the stress distribution is much close to the natural bone. Application for distally truncated femur at middle-position and low-position was much better, while stress concentration was marked at high-position. Meanwhile, the stability in vivo can also be maintained with the multi-part implant. The new implant is promising applied for prosthetic limb.