Key Engineering Materials Vols. 396-398

Abstract: The aim of this paper was to evaluate the usefulness of coupling digital image analysis with immunohistochemistry and histomorphometry data to the study of tissue response to hydroxyapatite in a model of critical size bone defect in calvaria of rats. A transosseous defect measuring 8 mm in diameter was performed with a surgical trephine in the parietal bone of 40 rats and divided into two experimental groups according to the treatment: group I (blood clot, control), group II (HA) and killed 1, 3, 6 and 9 months after implantation (n=5/group/period). The skullcaps with overlaying skin were collected and processed for paraffin embedding. The specimens were cut in the laterolateral direction into 5-µm thick semi-serial sections and stained with hematoxylin-eosin for identification and counting of polymorphonuclears cells, mastocytes, and multinucleated giant cells, MNG, or immunolabeled with anti- lysozyme, -factor VIII and –PCNA. Digital images were obtained and analyzed with the ImagePro-Plus® software for cell couting (polymorphonuclears cells, mastocytes, macrophages and MNG) and microvessel density. Image segmentation of anti-PCNA immunostaining was used for cell proliferation analysis. The digital images obtained allowed clear identification of cells of interest by through morphological aspects or immunostaining. Data recording and analysis was facilitated by the use of specific software for image processing and graphical and statistical analysis. It can be concluded that the techniques applied were usefull to identify and count cells, structures and process of interest making easier the effectiveness of hydroxyapatite in the critical size defect in rat calvaria model.

Abstract: The purpose of this study is to figure out the effect of maintaining period of PTFE membrane used in GBR with autogeonous bone, heterogeneous bone and synthetic bone on bone formation on rabbits' cranial defect. Eight adult New Zealand white rabbits were used in this study. Four defects were surgically made in their calvaria. Using a trephine bur, 4 'through and through' defects were created and classified into 4 groups, which were consisted of control (no graft), experimental group 1 (autogeonous bone) and experimental group 2 (deproteinized bovine bone: OCS-B®; NIBEC, Korea), experimental group 3 (synthetic bone: MBCP; Biomatlante, France). The defects were covered with PTFE membrane (Cytoplast®, Innova, Canada). Membranes were removed after 1, 2, 4 and 8 weeks post-GBR in each 2 rabbits. And then, all rabbits were sacrificed; specimens were taken and observed histologically..: After removing the membranes after 1 week of the experiment, bone formation was not evident in a control group but the area was replaced with only loose fibrous connective tissue. In group 1(autogeonous bone), thin bone formation and infiltration of connective tissue on the superficial layer were observed. Initial bone formation and infiltration of fibrous connective tissue were evident in group 2(deprotenized bovine bone) and 3(synthetic bone). When the membranes were removed after 2 weeks of the experiment, bridge shaped bone formation was shown in control group but mostly connective tissue took place. More increased bone thickness was evident in group 1 and increased bone formation than first week was shown in group 2 and 3. When the membranes were removed after 4 weeks of the experiment, 2/3 of normal bone thickness was formed in control group still with infiltration of connective tissue. In group 1, regular bone formation with normal bone thickness was shown and in group 2 and 3, similar bone thickness to the normal was evident. After the removal of the membranes in 8 weeks, bone thickness formed in control group was more increased than 4th week, but could not reach normal bone thickness. In group 1, normal bone thickness was formed and similar bone thickness to that of the normal was observed in group 2 and 3. Within the limited study, when performing the GBR procedure, at least 4-week period of the membrane retention is required, and more retention time of the xenograft or synthetic bone is needed than that of autogenous bone for better bone regeneration.

Abstract: Production of calcium phosphates from homogeneous solutions of Ca2+ and PO43- are studied in presence of complexing agents such as acetic acid, lactic acid, etilendiaminotetracetic acid (EDTA), iminodietanoic acid, and malic acid; solids are characterized with infrared spectroscopy (IR), powder x-ray diffraction, scanning electron microscopy (SEM) and electron dispersion spectra (EDS). The objective for this experiment was to find a suitable complexing agent to produce hydroxyapatite under mild reaction conditions. With the methodology described only tree phases are produced: brushite, monetite and hydroxyapatite. It is found a relationship among the ligand and the calcium phosphate phase obtained, where the complexing agent that provides the best working conditions for hydroxyapatite production is EDTA.

Abstract: The antibacterial effects of titanium oxide/calcium phosphate and calcium phos-phate/copper phosphate composite coatings have been investigated. Implant-like rough blasted tita-nium substrates are covered by a native titanium oxide layer. Together with the electrodeposited calcium phosphate layer a clear antibacterial effect has been observed. Electrodeposited calcium phosphate coatings were also dipped in aqueous copper sulphate solutions to convert partly calcium phosphate to copper phosphate. The antibacterial properties of such coatings can be controlled and adjusted to the clinical setting and to specific indications. Patient-tailored antibacterial treatments seem to be possible and may be of special interest for high-risk operations.

Abstract: Cell behaviour such as adhesion, morphology, proliferation and functional activity are highly influenced by surface properties including hydrophobicity, roughness, texture and morphology. These surface properties may be controlled using a mixture of additive coating techniques to produce glass coatings by sol-gel process and soft lithography on dental ceramics. The purpose of this work was to compare cell adhesion and early orientation of Human Bone Marrow (HBM) cells cultured on micro-patterned (micro-PGC) and on flat glass coatings (FGC) produced by sol-gel processing. Spin coating was used to apply SiO2 flat coatings on glass substrates as model surfaces. Photolithography was applied to produce master patterns with microscale dimensions. A moulding technique was used to print micropatterned SiO2 glass coatings produced by a sol-gel process. The coatings were then sintered, sterilized and cultured with HBM cells derived from primary cultures, using a standardized protocol, for 1 and 7 days. Cell morphology and orientation were observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Flat and MPGC with line shaped features were produced. Cells presented a typical osteoblastic morphology on flat surfaces while slimmer, preferentially oriented and more elongated morphologies could be seen on line micro-patterned surfaces. HBM cells cultured on flat glass coatings showed increased tendency to spread and to assume more randomized proliferation when compared to the cells on the micro-patterned glass coatings. Micro-patterned glass coatings showed higher orientation control and smaller delay in the rate of proliferation, in early stages of in vitro culture as compared to flat coatings. These preliminary studies revealed that Micro-PGC induce significant morphological changes and controlled orientation of HBM cells during early stages of cell proliferation.

Abstract: Synthetic Hydroxyapatite (HA) has been used as coating in order to enhance biocompatibility of titanium implants. Osseointegration at the implant-bone interface can be positively affected by the presence of HA coating and other biocompatible calcium phosphates (CaP) deposited on titanium implants, due to the high biocompatibility of these bioceramics. The biomimetic process is based on the nucleation and growth of a bioceramic film onto a substrate immersed in a body fluid solution (SBF) and it can be applied to deposit CaP coatings onto metallic substrates. The present work presents results on the characterization by SEM of CaP coating deposited on porous titanium samples by a biomimetic process.

Abstract: Metals are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. A promising alternative to avoid those effects is to protect the implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic coatings made by sol gel technique with the adding of silica particles, in order to increase the barrier effect of the coating, and glass-ceramic (GC) particles with the aim of generating bioactivity. X-ray photoelectron spectroscopy (XPS) and electrochemical techniques were used to analyze the bioactive and protective response of this silica reinforced coatings with the adding GC particles applied on surgical grade stainless steel.

Abstract: The commercially pure titanium (cp Ti) biocompatibility is due to its chemical stability in organism because of the presence of a fine film and impermeable of titanium oxide over the metal surface that confirms its corrosion resistance, changing this material's surface has been the direction of many research groups, these modifications may have influence in corrosion resistance. In this work was investigated the electrochemical behavior of cp Ti, without and with coating of the hydroxyapatite, commonly used implant materials, in artificial saliva and simulated body fluid (SBF) solution at 25oC and pH=7.4. The potentiodynamic polarization curves, shows that there is a passive region with low current’ density, indicating that in the investigated conditions the formation of a surface protective film occurs. In the studied conditions it was observed that hydroxyapatite layer has influence on corrosion resistance properties.

Abstract: Incorporation of bioceramics on the surface of dental implants has been utilized in an attempt to increase biological response of bone to materials. This paper reports the in vitro biological evaluation of Ca/P-based nanothickness bioceramic coated alumina-blasted/acid-etched titanium implants (AB/AE nanotite implant) and compare its performance to the untreated and uncoated implants, Ca/P-based nanothickness bioceramic coated untreated implants (untreated nanotite implant), alumina-blasted/acid-etched titanium implants (AB/AE implant) and hydroxyapatite plasma-sprayed implants (PSHA Implant). Balb/c 3T3 fibroblasts were used to asses the cytocompatibility of implant materials according to ISO-10993-5 protocols. Osteoblasts from Balb/c femurs seeded onto different implant surfaces showed the effect of surface topography and chemistry on cell adhesion. The results showed that all implants were not cytotoxic and that PSHA and AB/AE nanotite implants favored osteoblasts adhesion.

Abstract: Anodic oxidation is a promising technique to become titanium surfaces bioactive, by simultaneously changing the surface morphology, structure and chemical properties. Calcium and phosphorus based electrolytes were used to produce anodic films on c.p. Ti with two different current densities, 150 mA/cm2 and 300 mA/cm2. Morphology and structure were examined by SEM, EDS and XRD, and elastic modulus and hardness of the surfaces by instrumented indentation. Besides rutile and anatase TiO2 phases, hydroxyapatite was also identified on the films, as well as the segregation of very soft Ca and P-rich zones. Low values for the elastic modulus and hardness values close to the Ti corroborate to the applicability of Ca and P based TiO2 anodic films in biomedical titanium implants.