Improvement in zirconia osseointegration by means of a biological glass coating: An in vitro and in vivo investigation

The biocompatibility and osseointegration of zirconia (ZrO(2)), either coated with RKKP bioglazeor uncoated, were evaluated in vitro and in vivo. The in vitro test was performed in human osteoblasts, whereas maximal sensitization was performed in 23 Dunkin Hurtley guinea pigs. RKKP bioglaze-coated and uncoated (controls) ZrO(2) cylinders were implanted in the distal femoral epiphyses of 14 Sprague-Dawley rats under general anesthesia, and animals were sacrificed at 30 and 60 days. Lactate dehydrogenase, alkaline phosphatase, and Thiazolyl Blue (MTT) were tested in vitro. A graded score was used for evaluating the results of the sensitization test. Histomorphometry and microhardness testing were performed to quantify the osseointegration rate, as well as bone quality around the implants. Neither in vitro cytotoxicity nor sensitization were observed. Histomorphometry demonstrated that at 30 days, the affinity index was significantly higher in coated implants than in uncoated ones (p < 0.05); at 60 days, the behavior of coated implants was better than that of uncoated ones, but differences were not significant. Significant increases in bone microhardness were found at 1000 microm from the interface area for both uncoated (p < 0.0005) and RKKP bioglaze-coated (p < 0.0005) ZrO(2), and also within 200 microm from the interface (p = 0.014) but only for coated ZrO(2.) These results suggest that RKKP bioglaze-coated ZrO(2) permits biocompatible devices with improved osseointegration properties to be manufactured.     

Isolation and characterization of osteoblast cultures from normal and osteopenic sheep for biomaterials evaluation

Being very useful in the analysis of bone cell differentiation and activity, osteoblast cultures are also used in the in vitro biocompatibility study of new materials. The aim of this work was to evaluate sheep osteoblast cultures derived from normal and ovariectomized animals, and then to assess the in vitro biomaterial behavior on these cultures, taking into account the quality of bone where orthopedic devices are clinically used. For this purpose, we characterized sheep osteoblast cultures, isolated from iliac crest bone of normal (NB osteoblast culture) and osteopenic after ovariectomy (OB osteoblast culture) sheep. Moreover, we studied cell behavior when cultured on different biomaterials (titanium and two biological glasses, RKKP and AP40). Cell characterization at baseline demonstrated that both cultures (NB and OB) showed normal osteoblastic behavior. On the contrary, osteoblasts derived from osteopenic bone and cultivated on AP40 for 6 days revealed a different behavior in terms of both cell morphology and metabolic activity. Statistical analysis (one-way analysis of variance and Scheffé's post hoc multiple-comparison tests) revealed significant differences in Ca level (p<0.0005), MTT test (p<0.0005) and OC production (p<0.05). These in vitro tests demonstrated that sheep osteoblast cultures can be useful when determining biocompatibility and osteointegration of orthopedic materials, and also when evaluating for the presence of osteoporosis.     

In vitro characterisation of zirconia coated by bioactive glass

An in vitro evaluation of a biomedical device, which combines the mechanical properties of zirconia substrates with the bioactivity of two different glass layers (AP40 and RKKP), was performed. In this work, data on different kinds of analysis were reported both on as-sintered zirconia samples and on RKKP- and AP40-coated zirconia substrates. Structure, composition and morphology of the apatite layer growth on the coated samples after 30 days of soaking in an acellular simulated body fluid, serum protein adsorption, fibroblasts and human osteoblast-like cells adhesion, growth, morphology and biochemical aspects were studied. Results of soaking test in SBF, revealed the growth of an apatite layer on the surface of the glass-coated samples. Proteins adsorbed to the materials were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and results evidenced that the two glass-coated materials bound a higher amount of total protein than did the zirconia substrate. Fibroblasts and osteoblast-like cells cultured on RKKP- and AP40-coated zirconia showed a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of osteoblast alkaline phosphatase activity in comparison with zirconia substrate. In conclusion, our results indicate that the surface chemical characteristics of the two glass coatings AP40 and RKKP, with no great differences between them, substantially enhance zirconia integration with bone cells at least in vitro. This effect may be of significance in the stability of glass-coated zirconia orthopaedic and dental implants.     

Coatings on zirconia for medical applications

In order to combine the mechanical properties of a high-strength inert ceramic (yttria-stabilised zirconia, ZrO2-3%Y2O3, defined as zirconia in the text) with the specific properties of bioactive materials, some zirconia samples were coated by two bioactive phosphosilicate glasses and glass-ceramics: RKKP and AP40. Coatings of about 200-300 microm thickness were prepared by a simple and low-cost firing method. They were characterised by optical and scanning electron microscopy (SEM) and compositional analysis (EDS). The adhesion of the coatings on zirconia was tested by shear tests. Vickers indentations at the coating/zirconia interface were performed in order to observe the crack propagation path. The reactivity of glasses and glass-ceramics coatings towards a simulated body fluid (SBF), having the same ion concentration as that of human plasma, was evaluated and compared to that of the bulk glass and glass-ceramics, by examining the morphology of the reaction layer formed on the surface of the coated zirconia after one month of soaking in the SBF at 37 degrees C.     

Biocompatibility and bioactivity enhancement of Ce stabilized ZrO(2) doped HA coatings by controlled porosity change of Al(2) O(3) substrates

Al(2) O(3) substrates with controlled porosity were manufactured from nanosized powders obtained by plasma processing. It was observed that when increasing the sintering temperature the overall porosity was decreasing, but the pores got larger. In a second step, Ce stabilized ZrO(2) doped hydroxyapatite coatings were pulsed laser deposited onto the Al(2) O(3) substrates. It was shown that the surface morphology, consisting of aggregates and particulates in micrometric range, was altered by the substrate porosity and interface properties, respectively. TEM studies evidenced that Ce stabilized ZrO(2) doped HA particulates ranged from 10 to 50 nm, strongly depending on the Al(2) O(3) porosity. The coatings consisted of HA nanocrystals embedded in an amorphous matrix quite similar to the bone structure. These findings were congruent with the increased biocompatibility and bioactivity of these layers confirmed by enhanced growing and proliferation of human mesenchymal stem cells.     

Ceramic and PMMA particles differentially affect osteoblast phenotype

There is increasing evidence that wear debris particles present in periprosthetic tissues have direct effects on osteoblasts. The nature of the cell response varies with the chemistry of the particle and the number of particles. Most studies have used Ti, Ti-6Al-4V, and ultrahigh molecular weight polyethylene (UHMWPE) particles since these materials are most frequently used in implants and as a result, these particles predominate in peri-prosthetic tissues. Ceramics have also been used successfully as load-bearing surfaces in implants for years, although it is unknown how wear debris from these surfaces may contribute to aseptic bone loss. Further, particles resulting from polymethylmethacrylate (PMMA) cements used for fixation may also be involved in aseptic loosening of implants, but how these particles may affect bone formation is unknown. In the present study, we examined whether aluminum oxide (Al2O3), zirconium oxide (ZrO2), and PMMA particles exert effects on osteoblast proliferation, phenotypic expression, and local factor production, and if so, whether the effects were specific to the particle type. ZrO2 particles were produced in a custom-made axial mixer in which ZrO2 containers were filled with ZrO2 bars and 95% ethanol and then rotated continuously at room temperature. PMMA particles were prepared in a ZrO2 roller mill. Al2O3 was produced and provided by Aesculap AG. Particles were endotoxin-free with equivalent circle diameters <3 microm; Al2O3 particles were significantly smaller than ZrO2 or PMMA particles. Particle suspensions were added to confluent cultures of MG63 osteoblast-like cells after diluting them 1:100, 1:10, and 1:1 with culture medium. Cells were incubated with the particles for 24 h. Transmission electron microscopy showed that MG63 cells phagocytosed Al2O3 particles and exhibited ultrastructural changes consistent with cytotoxicity. This was supported by biochemical changes as well. Proliferation, alkaline phosphatase activity, and TGF-beta1 levels were decreased. ZrO2 and PMMA particles increased proliferation and alkaline phosphatase specific activity. The effect of ZrO2 on alkaline phosphatase was targeted to matrix vesicles, the effect of PMMA was greater on the cells. All particles increased prostaglandin E2 production. These results show that Al2O3, ZrO2, and PMMA particles elicit direct effects on osteoblasts and that cell response depends on the particle type. None of the particles tested had the same effect as noted previously for UHMWPE: increased proliferation and decreased alkaline phosphatase. These results may indicate that the response of peri-prosthetic tissues to wear particles may be modulated by the relative contributions of the various particle types present.     

Enhancing the bioactivity of zirconia and zirconia composites by surface modification

Among bioceramics, zirconia (ZrO(2)) and alumina (Al(2)O(3)) possess exceptional mechanical properties suitable for load-bearing and wear-resistant applications but the poor bioactivity of these materials is the major concern when bonding and integration to the living bone are desired. This article investigates two different approaches and their underlying mechanisms to improve the bioactivity of zirconia (3Y-TZP) and a zirconia composite with alumina (10Ce-TZP/Al(2)O(3)). Chemical treatment approach applied on 3Y-TZP where the substrates were soaked in 5M H(3)PO(4) to create chemically functional groups on the surface for inducing apatite nucleation. X-ray photoelectron spectroscopy (XPS) was used to detect chemical changes and X-ray diffraction (XRD) to monitor phase changes on the surface before and after acid treatment. Alternate soaking approach applied on 10Ce-TZP/Al(2)O(3) consisted of soaking the composite substrates in CaCl(2) and Na(2)HPO(4) solutions alternately to make a precursor for apatite formation. The bioactivity was evaluated by apatite-forming ability of surface-treated materials in simulated body fluid (SBF). Both methods resulted in the formation of hydroxyapatite on the surface of materials; however, alternate soaking approach showed to be a simpler, faster, and more effective method than the chemical treatment approach for enhancing the bioactivity of zirconia materials.     

In vitro and in vivo assessment of bone-implant interface: a comparative study.

The present in vitro and in vivo comparison of three bioactive (HA, AP40, RKKP) and three bioinert (Ti6-Al4-V, Al2O3, ZrO2) materials was undertaken to identify which of them provide(s) the most suitable coating for prostheses implanted in patients with altered metabolic status. The experimental design included in vitro tests with human osteoblasts and morphological observations by scanning electron microscopy. For the in vivo evaluation, the materials were implanted in the femoral condyle of ovariectomised and intact female rats, and two months after surgery an X-ray microanalytical study was performed. The in vitro study showed good biocompatibility with all materials. Microanalysis evidenced a similar behaviour with all materials except the two biological glasses. The differences in Ca and P content observed between intact and ovariectomised rats can be explained by the intrinsic capability of biological glasses to undergo surface modifications in the presence of alterations of the bone metabolism. Thus, their use seems to be indicated in recipients with osteoporotic pathologies.     

Alumina and zirconia coated vitallium oral endosteal implants in beagles.

The purpose of this study was to assess the addition of a ceramic coating upon a Vitallium implant to increase the implant's biologic acceptability in the oral environment. The mandibular premolar teeth in 9 adult beagle dogs were removed bilaterally and these areas allowed to heal for 6 weeks. Ceramic coating with either Al2O3 or ZrO2 was carried out by flame spray deposition upon Vitallium anchor implants (9 of each), and the implants placed into the 18 healed premolar areas. Clinical and radiographic evaluation was conducted by 2 independent investigators over a 32 week period. Implants which exhibited mobility greater than II on a scale of 0 to III, at intervals of one-half, were judged unsatisfactory. After 19 weeks, all 9 Al2O3 coated implants and 5 ZrO2 coated implants were rated unsatisfactory. After 32 weeks, 4 ZrO2 coated implants were in situ with 0 or I mobility. Radiographically the width of the peri-implant space increased in direct proportion to both time and mobility. Histologic sections demonstrated encapsulating dense fibrous connective tissue which was oriented parallel to both ZrO2 and Al2O3 implants. Results suggest the zirconia used is a superior ceramic coating to the alumina. Neither seemed to increase biologic acceptability over uncoated Vitallium implants.     

A new model formulation of the SiO2-Al2O3-B2O3-MgO-CaO-Na2O-F glass-ceramics

Mono-phase glass-ceramics of akermanite were successfully produced from a Ca-mica and wollastonite via low-temperature sintering and crystallization. Doping with P(2)O(5) considerably improves sintering behaviour since P(2)O(5) increases the stability of glass against crystallization at the temperature of sintering onset. The resulting glass-ceramics feature good in vitro acceptance from osteoblasts, and moderate bioactivity due to the enrichment of the glassy phase with Ca and Si. The good quality of the white colour at the surface and throughout the bulk, the matching of microhardness with tooth enamel, and the possibility to coat other biomaterials such as ZrO(2), Ti or hydroxyapatite make these materials promising for medical applications.     

Osteointegration of bioactive glass-coated zirconia in healthy bone: an in vivo evaluation

Osteointegration of yttria stabilised tetragonal zirconia (YSTZ), either coated with bioactive glass named RKKP bioglaze (RKKP) or uncoated, was evaluated in an animal model. RKKP-coated and uncoated (controls) YSTZ cylinders were implanted in the distal femoral epiphyses of 14 Sprague Dawley rats under general anaesthesia. At the experimental times of 30 and 60 days after sacrifice, histomorphometry and SEM microanalysis were performed on methylmethacrylate-embedded undecalcified sections to determine the osteointegration rate. At 30 days, a significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in RKKP-coated versus uncoated YSTZ implants p < 0.05); at 60 days, the coated implants behaved better than controls (affinity index of + 32%), but the difference observed lay within the statistical uncertainty. SEM analysis demonstrated better bone adhesion to the material in RKKP-coated YSTZ at both 30 and 60 days. These findings suggest that YSTZ coated with the bioactive glass named RKKP enhances osteointegration of ceramics.     

Influence of physicochemical reactions of bioactive glass on the behavior and activity of human osteoblasts in vitro

Bioactive glasses are characterized by a bond to bone with a hydroxyl carbonate apatite layer. They enhance bone tissue formation and for this purpose are used in orthopedic surgery and in dental implantology. In the current work, we studied the biological response of human osteoblasts with a bioactive glass. This bioactive glass is based on 50% Si0(2), 20% Na(2)O, 16% CaO, 6% P(2)O(5), 5% K(2)0, 2% Al(2)O(3) and 1% MgO and designated A9. Cracks and irregularities were observed on the material surface when it was immersed in the culture medium. In addition, energy dispersive X-ray analyses highlighted a selective release of the elements at the surface of the bioactive glass, such as Na(+) and K(+) ions, released from the first day, contrary to the Si, Al, Ca, P, and Mg elements, which were released more slowly. Cell proliferation kinetics, total protein synthesis, and DNA content of the osteoblasts in contact with bioactive glass were similar to control cells. The morphological studies by light and scanning electron microscopy revealed an increasing cellular density in culture with bioactive glass without contact inhibition. The immunohistochemical studies highlighted the expression of types I, III, and V collagens by osteoblasts cultured in the presence of bioactive glass. The pH measurement of the culture medium in the presence of bioactive glass demonstrated a slight alkalinization. We thus conclude that human osteoblasts preserve their properties in the presence of bioactive glass (A9).     

牙科氧化锆氧化铝陶瓷复合材料的生物相容性

BACKGROUND: The physiological environment of oral cavity is very complex. Dental restoration materials exposed to the weakly acidic body fluids in the long term, and were in the complex influences including physical, chemical, biological and mechanical and other factors. Therefore, the evaluation of biocompatibility for dental materials is the focus of research before entering the clinical trials, and also the important technical indicators to  ensure the clinical safety. OBJECTIVE: To preliminarily evaluate the biocompatibility of ZrO2 and Al2O3 ceramic composites. METHODS: The experiment was divided into six groups: ZrO2 and Al2O3 (1:1) 100% extract group, ZrO2 and Al2O3 (1:1) 50% extract group, ZrO2 and Al2O3 ( 4:1) 100% extract group, ZrO2 and Al2O3 (4:1) 50% extract group, and the volume fraction of 0.64% phenol positive control group and 100% fresh medium of negative control group. Acute hemolysis and in vitro cytotoxicity experiments were conducted according to the biological evaluation standards and requirements of GB-T16886 15-2003 medical devices. The effects of the above six groups of extracts on rabbit blood cells and L-929 mouse fibroblast cells were tested respectively. RESULTS AND CONCLUSION: There was no significant difference in the absorbance values between different concentrations of experimental groups and negative control group (P > 0.05). The cytotoxicity rating of all experimental groups was 0-1 grade. The hemolysis rates in the ZrO2 and Al2O3 (1:1) 100% extract and ZrO2 and Al2O3 (4:1) 100% extract groups were 1.27% and 2.4% respectively, less than the accepted safety standards of 5%. These results demonstrate that the acute hemolytic experiment and in vitro cytotoxicity experiment of (1:1), (4:1) ZrO2 and Al2O3 ceramic composites are all negative, and all have good cytocompatibility and blood compatibility.       

Fatigue characteristics of bioactive glass-ceramic-coated Ti-29Nb-13Ta-4.6Zr for biomedical application

A new surface-coating method by which CaP invert glass is used to improve the bioactivity of titanium alloys has been developed recently. In this method, the powder of CaP invert glass (CaO-P2O5-TiO2-Na2O) is coated on the surface of titanium alloy samples and heated between 1073 and 1123 K. With this treatment, a calcium phosphate layer mainly containing beta-Ca3(PO4)2 phase can be coated easily on titanium alloy samples. In the present study, the effect of this coating process on the fatigue properties of Ti-29Nb-13Ta-4.6Zr, a new metastable beta alloy for biomedical applications, has been investigated. The fatigue endurance limit of the coated alloy was found to be about 15% higher than that of uncoated alloy, as a result of the formation of a hard (alpha + beta) layer and a small amount of the omega phase during the coating process. The coating exhibits excellent adhesion to the substrate during the tensile and fatigue tests. Subsequent ageing at 673 K for 259.2 ks greatly improves the fatigue resistance of the coated alloy due to isothermal omega phase precipitation, and does not have obvious detrimental effect on the coating properties.     

Deposition of highly adhesive ZrO(2) coating on Ti and CoCrMo implant materials using plasma spraying

ZrO(2) (4% CeO(2)) and ZrO(2) (3% Y(2)O(3)) coatings were deposited on titanium (Ti) and CoCrMo implants using plasma spraying and the adhesive, morphological and structural properties of the plasma-sprayed coatings were evaluated. Characterization of these coatings was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness, hardness, and adhesive strength. XRD patterns showed that both the coatings appeared to be primitive tetragonal phase. SEM observations showed that both the ZrO(2) coatings appeared to be rough, porous and melted. The cross-section surface morphology of the coatings, coating-substrate interfaces and substrates without acid etching was very dense and smooth. After acid etching, as compared to the dense ZrO(2) coating-CoCrMo substrate interfaces, the thin gaps appeared within the ZrO(2) coating-Ti substrate interfaces. It is suggested that plasma spraying probably formed an amorphous Ti layer in the coating-Ti substrate interface that can be removed by acid etching. The average surface roughness of ZrO(2) (3% Y(2)O(3)) and ZrO(2) (4% CeO(2)) coatings was correlated to the starting powder size and substrates. No significant difference between the hardness of all coatings and substrates was observed. The adhesive strengths of ZrO(2) (4% CeO(2)) coating to Ti and CoCrMo substrates were higher than 68MPa and significantly greater than that of ZrO(2) (3% Y(2)O(3)) coatings.     

Induction of macrophage apoptosis by ceramic and polyethylene particles in vitro

The purpose of this study was to investigate in vitro the presence of apoptotic cell death after macrophage stimulation with different ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles. We also analyzed the effects of particle size, concentration, and composition. The J774 mouse macrophage cell line was exposed to commercial particles of different sizes (up to 4.5 microm) and concentrations (up to 500 particles per macrophage). Fluorescence microscopy and DNA laddering were used to investigate the presence of apoptosis in cell cultures after 24 h of incubation. Fluorescence microscopy of propidium iodide stained cells showed two characteristic morphological features that occur in apoptotic cells, namely nuclear condensation and heterogeneity of stain uptake. The effect of ceramic particles on apoptotic nuclear morphology was size- and concentration-dependent and reached a plateau above 150 particles per macrophage at 1.3 microm. With regards to composition, we did not find any difference in cell morphology between Al2O3 and ZrO2. Ceramic and HDP particles induced DNA fragmentation into oligonucleosomes as evidenced by DNA laddering, another characteristic of apoptosis. The induction of DNA laddering was size- and concentration-dependent whereas particle composition (Al2O3 vs. ZrO2 and Al2O3 vs. HDP) had no effect. In conclusion, our results demonstrated that ceramic and HDP particles induce macrophage apoptotic cell death in vitro and open doors for possible modulation of debris-induced periprosthetic osteolysis.     

Bioactive glass ceramics: properties and applications

Heat treatment of an MgO-CaO-SiO2-P2O5 glass gave a glass ceramic containing crystalline apatite (Ca10(PO4)6O,F2] and beta-wollastonite (CaO,SiO2) in an MgO-CaO-SiO2 glassy matrix. It showed bioactivity and a fairly high mechanical strength which decreased only slowly, even under load-bearing conditions in the body. It is used clinically as artificial vertebrae, iliac bones, etc. The bioactivity of this glass ceramic was attributed to apatite formation on its surface in the body. Dissolution of calcium and silicate ions from the glass ceramic was considered to play an important role in forming the surface apatite layer. It was shown that some new kinds of bioactive materials can be developed from CaO,SiO2-based glasses. Ceramics, metals and organic polymers coated with bone-like apatite were obtained when such materials were placed in the vicinity of a CaO,SiO2-based glass in a simulated body fluid. A bioactive bone cement which was hardened within 4 min and bonded to living bone, forming an apatite, was obtained by mixing a CaO,SiO2-based glass powder with a neutral ammonium phosphate solution. Its compressive strength reached 80 MPa comparable to that of poly(methyl methacrylate) within 3 d. A bioactive and ferromagnetic glass ceramic containing crystalline magnetite (Fe3O4) in a matrix of CaO,SiO2-based glassy and crystalline phases was obtained by a heat treatment of a Fe2O3-CaO.SiO2-B2O3-P2O5 glass. This glass ceramic was shown to be useful as thermoseeds for hyperthermia treatment of cancer.     

A layer-by-layer approach to natural polymer-derived bioactive coatings on magnesium alloys

The development of polyelectrolyte multilayered coatings on magnesium alloy substrates that can be used for controlled delivery of growth factors and required biomolecules from the surface of these degradable implants could have a significant impact in the field of bone tissue regeneration. The current work reports on the fabrication of multilayered coatings of alginate and poly-l-lysine on alkaline- and fluoride-pretreated AZ31 substrates using a layer-by-layer (LbL) technique under physiological conditions. Furthermore, these coatings were surface functionalized by chemical cross-linking and fibronectin immobilization, and the resultant changes in surface properties have been shown to influence the cellular activity of these multilayered films. The physicochemical characteristics of these coated substrates have been investigated using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cytocompatibility studies using MC3T3-E1 osteoblasts show that the fluoride-pretreated, cross-linked and fibronectin-immobilized LbL-coated substrates are more bioactive and less cytotoxic than the hydroxide-pretreated, cross-linked and fibronectin-immobilized LbL-coated samples. The in vitro degradation results show that the multilayered coatings of these natural polysaccharide- and synthetic polyamino acid-based polyelectrolytes do not alter the degradation kinetics of the substrates; however, the pretreatment conditions have a significant impact on the overall coating degradation behavior. These preliminary results collectively show the potential use of LbL coatings on magnesium-based degradable scaffolds to improve their surface bioactivity.     

In vitro cytotoxicity of amorphous carbon films

Amorphous carbon (a-C), carbon nitride (a-CN) and titanium films were deposited on stainless steel substrates (SS) using a dc magnetron sputtering system attached to a high vacuum chamber. Films were deposited using a base pressure of 1.3x10(-4) Pa. For the carbon films a pure graphite target was eroded in an Argon plasma. For the case of the a-CN films, the Ar flux was substituted by 100% N2 gas. Titanium films were deposited in a different chamber, using a pure Ti target and an argon plasma. In vitro studies were carried out on the coated samples using human osteoblasts cells. Cytotoxicity of carbon films was assessed by cellular adhesion and proliferation, as determined by direct cellular counting using a spectroscopic technique and a well-defined standard curve. Osteoblasts cells were also grown on uncoated steel and prepared Petri dishes for comparison. The percentage of osteoblasts adhesion measured at 24 hrs attained maximum values for the a-C films. Similarly, cellular proliferation evaluated at three, five and seven days showed an outstanding increase of osteoblasts cells for the a-C and Ti coatings in contrast to the uncoated steel. The cell functionality was evaluated by the MTT test after incubation periods of 3, 5 and 7 days. The absorbance values obtained for a-C, a-CN and Ti surfaces resulted significantly higher with respect to the positive control, indicating that the surface did not induce any toxic effect. Preliminary bio-mineralization was evaluated by measuring the elemental composition of the mineral grown on the substrates after periods up to 14 days.     

Osteointegration of bioactive glass-coated and uncoated zirconia in osteopenic bone: an in vivo experimental study

In elderly and osteoporotic patients an age-related loss of osteoinductivity could be the biological cause of implant failure regardless of the high quality of the implanted device. yttria stabilized tetragonal zirconia (YSTZ), either coated with the bioactive glass named RKKP bioglaze (RKKP) or uncoated, was implanted in the distal femurs of sham-operated and ovariectomized female rats. Animals were sacrificed at 30 and 60 days. Histomorphometry and microhardness tests were performed to assess osteointegration rate as well as bone quality around the implants. Significant decreases (p < 0.0005) in trabecular bone volume, BV/TV (41%), trabecular bone surface BS/TV (33%), trabecular thickness Tb.Th (20%), and trabecular number Tb.N (32%), together with a significant increase in trabecular separation Tb.Sp (184%), were found for the osteopenic rats compared with the sham-operated rats. At both experimental times the RKKP coating ensured a better osteointegration rate with higher AI values than the uncoated YSTZ, even when osteopenic rats were used (48% at 30 days and 12% at 60 days). No differences were observed at the bone-biomaterial interfaces for either material when comparing sham-operated with osteopenic rats. The present results demonstrate that the RKKP bioactive glass used as a coating ensures a high osteointegration rate even in osteoporotic bone, which is already visible from postoperative day 30 and is still apparent on day 60.