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PubMed2000

[Studies on properties of biofriction and wear for friction pairs of UHMWPE and Ti matrix-TiN-TiC gradient film materials].

In order to search the possible application of friction pairs of UHMWPE and Ti6Al4V-TiN-TiC etc. gradient materials to total hip joint replacements, we have prepared Ti6Al4V-TiN-TiC etc. gradient film materials by using N ion implant, d. c plasma CVD(PCVD). The properties of biological friction and wear for friction pairs of HUMWPE and Ti6Al4V-TiN-TiC etc. gradient film materials were investigated. The friction coefficient of friction paris and the wear loss of worn UHMWPE were measured; the surface morphology was observed by SEM. It has been shown that in human serum lubrication the wear loss of HUMWPE decreases with the increase in the surface hardness of its pairing ceramic film material. The pairing Ti6Al4V-TiN-TiC gradient film material possesses highest surface hardness, compared with other materials studied; UHMWPE wear loss in lowest. The wear mechanism of studied pairs has been analysed as well in the present paper.

Biocompatible Materials↗

PubMed1997

Effect of metal ions on the formation and function of osteoclastic cells in vitro.

To determine if metal ions play a contributing role in loosening of orthopedic implants, the present work investigated whether sublethal concentrations of ions affect the formation and function of osteoclasts in vitro. Rat bone marrow cells were cultured on slices of devitalized bone and in the presence of ions associated with Co-Cr-Mo and Ti-6A1-4V alloys for up to four weeks. Cultures were assayed for total intracellular protein, used as measure of cell growth, and resorption activity of osteoclastic cells derived from hematopoietic stem cells was quantified using image analysis. Although Co2+ caused delayed toxicity not previously observed during short-term experiments, none of the other ions affected cell proliferation, indicating that the chosen concentrations were sublethal. In general, exposure of bone marrow cultures to ions caused either a decrease or no change in the total area of bone resorption. A decrease in the number of resorption pits formed by osteoclastic cells was primarily responsible for the decrease in total amount of resorption. Therefore, even though cells continued to grow over the entire culture period, less osteoclastic activity was observed. Findings indicate that if metal ions play a role in periprosthetic pathology, they may contribute to implant failure by impairing bone repair while allowing fibrous tissue formation following debris-induced osteolysis.

Alloys↗

PubMed2001

Enhancement of bone ingrowth in a titanium fiber mesh implant by rhBMP-2 and hyaluronic acid.

The present study was designed to evaluate the efficacy of high molecular weight hyaluronic acid (HA) used as a carrier of recombinant human bone morphogenetic protein-2 (rhBMP-2) adsorbed to a titanium fiber mesh implant (TFMI) in vivo. The quantity of HA in the TFMI rapidly decreased during the initial 3-day period after implantation. BMP particles were trapped by the meshwork of HA as observed by scanning electron microscopy (SEM). TFMIs containing LF-6, HA, rhBMP-2, or HA combined with rhBMP-2 were implanted on the cranium of rats. Analysis of digitized SEM images of samples obtained six weeks post-implantation was performed to determine the area occupied by new bone. The area fraction of Ca relative to that of the pores of TFMI in the HA group was larger than that in the Ti group (p<0.05). The area fraction of Ca in both the BMP and HA+BMP groups was larger than that in both the Ti and HA groups (p<0.01), and that in the HA+BMP group was larger than that in the BMP group (p<0.05). It is suggested that HA is not only an effective carrier of BMP, but also it may have a positive effect on the generation of new bone in the TFMI.

Journal Article↗

PubMed1989

Interaction between hydrogen peroxide and titanium: a possible role in the biocompatibility of titanium.

Hydroxyl radicals formed from hydrogen peroxide during an inflammatory response are potent agents for cellular deterioration. The behaviour of implanted material in terms of its ability to sustain or stop free radical formation may be therefore very important. In vitro studies of titanium which is known to be biocompatible and osseointegrates into human bone were carried out. In our model studies, the production of free radicals from H2O2 at Ti and TiO2 surfaces was measured by spin trapping techniques. Our findings suggest that there is no sustained hydroxyl radical production at a titanium (oxide) surface. We propose that this is due to the quenching of the Fenton reaction through both trapping and oxidation of superoxide radicals in a TiOOH adduct.

Biocompatible Materials↗

PubMed2004

Corneal topographic changes after phacoemulsification through steep axis incision.

PURPOSE: To evaluate the effect of 5.5 mm sutured and 4.0 mm sutureless corneal incisions after phacoemulsification on corneal topograpy. MATERIAL AND METHODS: Twenty eyes of 20 patients that underwent phacoemulsification with IOL implantation were randomly divided into two. The first group received a PMMA IOL through a sutured 5.5 mm corneal incision. The second group received a foldable hydrophilic acrylic IOL through a sutureless 4.0 mm incision. Complete ocular examination and computerized corneal topography (Keratron Corneal Analyzer, Software version 3.2, Optikon 2000, Italy) were performed preoperatively, at 1 week, and 1 month postoperatively. The Maloney indices [best fit sphere (BFS), best fit cylinder (BFC) and topographic irregularity (TI)] were provided by the Keratron Corneal Analyzer. RESULTS: There was no statistically significant difference in the mean BFS between the groups preoperatively (p = 0.305), at postoperative week 1 (p = 0.362), and at postoperative month 1 (p = 0.160). The BFC was significantly higher in the 5.5 mm incision group than in the 4.0 mm incision group preoperatively (p = 0.025), however, there was no statistically significant difference between the groups at postoperative week 1 (p = 0.909), and at postoperative month 1 (p = 0.382). There was no statistically significant difference in the mean TI between the groups preoperatively (p = 0.494) and at postoperative week 1 (p = 0.271). However the mean TI at postoperative month 1 was significantly higher in the 5.5 mm incision group than the 4.0 mm incision group (p = 0.05). CONCLUSION: The 5.5 mm sutured incisions caused an increase in TI at 1 week and 1 month postoperatively. For a more rapid visual rehabilitation, 4.0 mm sutureless incisions are recommended.

Aged↗

PubMed2003

In vitro osteoblast response to anodized titanium and anodized titanium followed by hydrothermal treatment.

In this study, Titanium (Ti) surfaces were modified using anodization. The electrolyte used for anodization was a mixture of calcium glycerophosphate and calcium acetate. The anodized surfaces were divided into three groups. Hydrothermal treatments were performed on two of the anodized groups for either 2 or 4 h. In vitro osteoblast response to anodized oxide and the hydrothermal treated oxide after anodization was evaluated in this study. Calcium and phosphorus ions were deposited on the Ti oxide during anodization. Anodized surfaces following a 4-h hydrothermal treatment were observed to promote the growth apatite-like crystals as compared with anodized surfaces after a 2-h hydrothermal treatment. Cellular function and onset of mineralization, as indicated by protein production and osteocalcin production, respectively, also were observed as enhanced on hydrothermal-treated surfaces. It was thus concluded from this study that calcium phosphate and apatite-like crystals could be deposited on Ti surfaces using anodization and a combination of anodization and hydrothermal treatment. It was also concluded that the phenotypic expression of osteoblast was enhanced by the presence of calcium phosphate or apatite-like crystals on anodized or hydrothermally treated Ti surfaces.

Alkaline Phosphatase↗

PubMed2005

Phases in titanium alloys.

Titanium (Ti) provides the basis for many alloys used in medical technology. These alloys have been discussed many times in this column over the past decade. In recent years in particular, there have been a number of developments in Ti metallurgy, which suggests that a reappraisal of these alloy systems is timely.

Alloys↗

PubMedDate not supplied

One piece ultracompact totally implantable electromechanical total artificial heart for permanent use.

An ultracompact, one piece, totally implantable electromechanical total artificial heart (TAH) has been developed as a permanent replacement for failing hearts. It consists of left and right pusher plate blood pumps (stroke volume 55 ml) made of titanium alloy (Ti-6Al-7Nb) sandwiching a miniaturized electromechanical actuator between them. The diameter of the TAH is 90 mm, with a thickness of 70 mm, yielding an overall volume of 400 ml. It weighs 450 g. Although it is miniaturized, it provided a maximum pump output of 8 L/min against a left afterload of 100 mm Hg. It required approximately 12 watts to provide a pump output of 6.5 L/min with maximum efficiency of 13.5%. To balance left and right flow, the right stroke length was made 10% shorter than the left, and an auxiliary compliance chamber was used to compensate for additional flow differences between them. Motor commutation pulses and a Hall effect pusher plate sensor signal were used in the controller to implement the left master alternate variable rate mode. The calf fitting study revealed excellent anatomic compatibility, and the first successful survivor was obtained in December 2001. Studies of system endurance and biocompatibility are required to ensure long-term reliability. This TAH is promising for permanent replacement of the failing heart as well as for bridge to heart transplantation for the smaller size group of end-stage cardiac patients.

Animals↗

PubMed2003

Distinct clinical features in the recipients of the implantable cardioverter defibrillator in Taiwan: a multicenter registry study.

Little information about the ICD is available from the Asian Pacific region. The purpose of this study was to characterize the clinical features in ICD patients in Taiwan and to compare these features with those in patients in the Western populations, mainly the Canadian Implantable Defibrillator Study (CIDS), the Antiarrhythmics versus Implantable Defibrillator (AVID) trial, and the Cardiac Arrest Study Hamburg (CASH) trial. From February 1995 to October 2001, 101 ICDs were implanted in 92 patients (78 [84%] men) in 12 hospitals. Clinical presentations included sudden cardiac death due to VF/VT in 35 (38%) patients, syncopal VT in 25 (27%), drug refractory nonsyncopal VT in 27 (29%), and unexplained syncope with inducible sustained VT/VF in 5 (6%). The mean age was significantly younger than that in CIDS or AVID (59 +/- 16 vs 63 +/- 9 years in CIDS, P = 0.02; vs 65 +/- 11 years in AVID, P < 0.001), but was comparable to that in CASH (59 +/- 16 vs 58 +/- 11 years in CASH, P = 0.75). The mean LVEF was significantly higher than that in CIDS or AVID (48 +/- 19% vs 34 +/- 15% in CIDS, P < 0.001; vs 32 +/- 13% in AVID, P < 0.001), but was comparable to that in CASH (48 +/- 19 vs 46 +/- 19% in CIDS, P = 0.83). The ICD patients in the current study also showed a higher incidence of normal heart (23 vs 4% in CIDS, P < 0.001; vs 3% in AVID, P < 0.001; vs 9% in CASH, P < 0.001) and cardiomyopathy (41% vs 10% in CIDS, P < 0.001; vs 15% in AVID, P < 0.001; vs 11% in CASH, P < 0.001), but a lower incidence of coronary artery disease (29% vs 83% in CIDS, P < 0.001; vs 82% in AVID, P < 0.001; vs 73% in CASH, P < 0.001). During a mean follow-up of 28 +/- 24 months, 13 (14%) patients died. Older age was the only factor associated with poorer survival after ICD implantation. Forty-seven (51%) patients received appropriate ICD discharges during follow-up. History of prior myocardial infarction was the only factor associated with an earlier first appropriate ICD discharge and LVEF < 0.35 the only factor associated with subsequent poorer survival after the first ICD discharge. In conclusion, this study demonstrated many distinct clinical features in our ICD population that were different from those in the Western populations.

Aged↗

PubMed1993

In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling.

One hundred forty-eight retrieved modular hip prostheses of both mixed (Ti-6Al-4V/Co-Cr) and similar (Co-Cr/Co-Cr) metal combinations were examined and positive evidence of corrosive attack was found in the conical taper region between head and stem. Significant corrosion was observed in both mixed and similar metal combinations with 16% of necks and 35% of heads (for mixed-metal cases), and 14% of necks and 23% of heads (for similar-metal cases) showing moderate to severe corrosive attack. There was a significant correlation between the percentage of prostheses with moderate to severe corrosion and the duration of implantation for both mixed and similar metal cases, indicating that this corrosion process is progressive in time. Moderate to severe corrosion was seen as early as 2.5 and 11 months (mixed and similar metals, respectively). Scanning electron microscopy and x-ray analysis identified several forms of corrosive attack in the cobalt-based component of the taper. These included, for both mixed and same metal combinations: preferential dissolution of cobalt, fretting, and pitting; mixed metals only: the formation of a Ti-Cr-Mo interfacial phase and interdendritic corrosion; and for similar metals: intergranular attack adjacent to grain boundaries enriched in molybdenum and silicon. It is hypothesized that the restricted crevice environment, coupled with high cyclic stresses which cause repeated fracture of the passive oxide films in the taper, result in an unstable electrochemical environment within the crevice for both the cobalt alloy and Ti-alloy passive films. The passivity of these alloys is subsequently lost and active attack of the taper results. Also, the repeated fracturing of the passive films will result in large amounts of corrosion products being formed. This corrosion and particulate accumulation could result in loss of mechanical integrity of the implants in vivo, create particles for third body wear, and release particles into the surrounding tissues.

Alloys↗

PubMed2000

Surface analysis of a femoral stem after failed total hip replacement.

We analysed the surface of a Ti alloy femoral stem in a cementless total hip replacement with early failure. A specific protocol consisting of non destructive and destructive tests was used in the evaluation of the retrieved stem. The tests confirmed that implant fretting due to bone abrasion constitutes an early phase of loosening.

Aged↗

PubMed1993

Localization of interleukin-1 type I receptor and interleukin-1 beta in human endometrium throughout the menstrual cycle.

Previous studies in the human suggest that the interleukin-1 (IL-1) system, may be an important paracrine/autocrine mediator in local intercellular interaction in endometrial tissue. In this study we have determined that IL-1 receptor type I (IL-1R tI) is expressed at the messenger RNA (mRNA) and protein levels in glandular cells and its ligand, IL-1 beta has been localized by immunohistochemical methods in endothelial cells and isolated stromal cells in the human endometrium throughout the menstrual cycle. IL-1R tI mRNA was detected in glandular epithelium using both specific complementary DNA and complementary RNA 32P-labeled probes. Human glandular epithelium contains a 5.1-kilobase mRNA transcript throughout the complete menstrual cycle. Quantitative densitometric analysis of slot blot hybridization signals shows an increase of IL-1R tI mRNA in both early and mid-late secretory phases in comparison with the proliferative phase (P < 0.05). IL-1R tI protein was localized in endometrial glandular epithelial cells using both indirect immunofluorescence and avidin-biotin-peroxidase methods. However, more intense staining for IL-1R tI was observed in lumenal epithelial cells compared with the staining present deep in the endometrial glands. Using the same methods, IL-1 beta was detected in endothelial cells of spiral vessels and isolated stromal cells throughout the menstrual cycle, and an increased staining from proliferative to secretory phase was observed. The detection of IL-1R tI in the human endometrial epithelium and its ligand, IL-1 beta, in isolated stromal cells and endothelial cells, is another example of possible communication between the immune and reproductive systems with special relevance to human implantation.

Adult↗

PubMed2003

The influence of niobium and vanadium on passivity of titanium-based implants in physiological solution.

Surface films play a key role in corrosion and osteointegration processes of titanium-based orthopedic implants. The influence of niobium and vanadium as alloying elements on titanium alloy passivity have been investigated in Hanks' Balanced Salt Solution (HBSS), at 37 degrees C and pH 6.9.Ti6Al4V and Ti6Al6Nb have been considered. The excellent passivating properties of the anodically formed Ti(IV)-based surface oxide film and high corrosion resistance of the Ti6Al6Nb alloy have been attributed to the stabilizing effect of Nb(5+) cations on the passive film, by annihilation of stoichiometric defects (anion vacancies) caused by the presence of titanium suboxides. Localized corrosion sensitivity of the Ti6Al4V alloy has been correlated to the dissolution of vanadium at the surface film/electrolyte interface coupled with generation of cation vacancies and their diffusion through the film as a part of the solid-state diffusion process. The presence of a high concentration of chloride ions (0.15gl(-1)) in HBSS further accelerates these processes.

Alloys↗

PubMed2000

[Standardized testing of bone implant surfaces with an osteoblast cell culture cyste. III. PVD hard coatings and Ti6Al4V].

The effect of titanium-based PVD coatings and a titanium alloy on the proliferation and differentiation of osteoblasts was investigated using a standardised cell culture system. Human fetal osteoblasts (hFOB 1.19) were cultured on titanium-niobium-nitride ([Ti,Nb]N), titanium-niobium-oxy-nitride coatings ([Ti,Nb]ON) and titanium-aluminium-vanadium alloy (Ti6Al4V) for 17 days. Cell culture polystyrene (PS) was used as reference. For the assessment of proliferation, the numbers and viability of the cells were determined, while alkaline phosphatase activity, collagen I and osteocalcin synthesis served as differentiation parameters. On the basis of the cell culture experiments, a cytotoxic effect of the materials can be excluded. In comparison with the other test surfaces, [Ti,Nb]N showed greater cell proliferation. The [Ti,Nb]N coating was associated with the highest level of osteocalcin production, while all other differentiation parameters were identical on all three surfaces. The test system described reveals the influence of PVD coatings on the osteoblast differentiation cycle. The higher oxygen content of the [Ti,Nb]ON surface does not appear to have any positive impact on cell proliferation. The excellent biocompatibility of the PVD coatings is confirmed by in vivo findings. The possible use of these materials in the fields of osteosynthesis and articular surfaces is still under discussion.

Alloys↗

PubMedDate not supplied

Shape memory effect and super elasticity. Its dental applications.

The shape memory alloys are quite fascinating materials characterized by a shape memory effect and super elasticity which ordinary metals do not have. This unique behaviour was first found in a Au-47.5 at % Cd alloy in 1951, and was published in 1963 by the discovery of Ti-Ni alloy. Shape memory alloys now being practically used as new functional alloys for various dental and medical applications.

Dental Alloys↗

PubMed1999

Valve-preserving treatment of Ebstein's anomaly: perioperative and follow-up results.

BACKGROUND: Ebstein's anomaly is a rare congenital cardiac defect of the tricuspid valve (TV) leading to severe tricuspid insufficiency (TI). METHODS: In ten patients, 6 adults (39-53 years) and 4 children (5-10 years), operated between 1989 and 1995 echocardiography was performed pre and post repair and at follow-up. Patients were assessed in our institution at two cut-off points, resulting in a mean first follow-up of 17 +/-15 months and a mean second follow-up of 53+/-23 months. All patients had additional congenital cardiac defects (ASD,VSD). In all patients the TV was repaired by techniques described by Carpentier et al. with some modifications. The goal of this reparative attempt is to mobilize restricted leaflet tissue and aid coaptation through implantation of a ring. RESULTS: Echocardiographically we were able to identify significant characteristics for the successful repair of Ebstein's anomaly. The severity of the disease is represented by the size and function of the right ventricle and the atrialized chamber, the most advanced cases exhibiting a dilated right ventricle with poor contractility. There was severe preoperative TI ( mean grade 3.2 +/- 0.3). Postoperatively TI was significantly reduced to a mean grade of 2+/-0.2. 60% of the patients demonstrated an improvement in the ratio of atrialized chamber to functional right ventricle. Right-ventricular function was improved, the mean score being 2.8+/-0.1. At follow-up I and II right-ventricular function and tricuspid insufficiency was improved in most patients and all patients benefited in quality of life. CONCLUSION: These results suggest that surgical correction should not be delayed until severe right heart failure develops as, particularly in children, good results are achieved, improving the quality of life.

Adult↗

PubMed2004

The modulation of osteogenesis in vitro by calcium titanium phosphate coatings.

Calcium phosphate coated titanium and titanium alloy are widely used as dental and orthopaedic implants. This study examines the effect of novel calcium titanium and calcium titanium zirconium phosphates suitable for plasma-spraying onto titanium substrata on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that on native titanium and hydroxyapatite-coated titanium. Test materials were an acid etched and sand-blasted titanium surface (Ti-DPS), a plasma-sprayed hydroxyapatite coating (HA), and five materials which were created from CaTi(4)(PO(4))(6) (CTP) and CaZr(4)(PO(4))(6) (CZP): sintered CaTi(4)(PO(4))(6) (CTP-S1), sintered 46CaO.23TiO(2).31P(2)O(5) (CTP-S2), sintered CaTiZr(3)(PO(4))(6), (CTZP-S1), sintered 46CaO.23ZrO(2).31P(2)O(5) (CTZP-S2) and sintered 55CaO.20TiO(2).31P(2)O(5) (CTP-S3). HBDC were grown on the substrata for 3, 7, 14 and 21 d, counted and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrates significantly affected cellular growth and the temporal expression of an array of bone-related genes and proteins. At 14 and 21 d, cells on CTP-S3 displayed significantly enhanced expression of all osteogenic mRNAs. Surfaces of CTP-S1 and CTP-S3 had the most effect on osteoblastic differentiation inducing a greater expression of an array of osteogenic markers than recorded for cells grown on Ti-DPS and HA, suggesting that these novel materials may possess a higher potency to enhance osteogenesis.

Alkaline Phosphatase↗

PubMed1999

[Biological mechanism of macrophage activation by wear particles at the bone-implant interface].

OBJECTIVE: To observe the response of membrane Ca(2+) channel of macrophage-like cells (MCs) to wear particles and analyze the cytoplasmic [Ca(2+)]i change in macrophage activation at the bone-implant interface. METHODS: The synoviocyte system of normal hip joint was established in vitro. Immunohistochemical technique (SABC) with CD68 Mab was used to differentiate MCs and fibroblast-like cells (FCs) in the system, and the time when MCs begin to perform phagocytosis was determined by SEM. 1.5 mg/ml (W/V) Ti alloy, Co-Cr alloy or UHMWPE particles suspension was added into the system to monitor the [Ca(2+)]i change in the MCs by confocal laser scanning microscope (CLSM). RESULTS: Phagocytosis of MCs happened after 6 hours, but within 1 hour the Ca(2+) channel of their cell membrane opened for 1 - 6 times and caused rapid and transient pulses of [Ca(2+)]i in cytoplasm after different period of incubation. There was no significant difference between times or range of the [Ca(2+)]i pulse (P > 0.05). The group of UHMWPE particles had the longest incubation period (P < 0.05), but the interval of pulses was shorter than that in the group of Co-Cr alloy particles (P < 0.05). [Ca(2+)]i pulses still appeared when MCs were incubated by indomethecin (P > 0.05), but the phenomenon could be blocked by nimodipin. CONCLUSIONS: Activation of macrophages at the bone-implant-interface could happen before they phagocytose wear particles. The primary switch-on mechanism of osteolysis mediated by cytokines at the bone-implant interface may be the opening of membrane Ca(2+) channel and pulse-like Ca(2+) influx of macrophages when stimulated by wear particles.

Biocompatible Materials↗