nan Lopes

Biological and Physical-Chemical Characterization of Phase Pure HA and SI-Substituted Hydroxyapatite by Different Microscopy Techniques

Two different microscopy techniques were used to investigate the re sponse of human osteoblasts to hydroxyapatite (HA) and silicon substituted hydroxyapati te (Si-HA), namely, fluorescence and confocal microscopy The changes in the surface of HA and Si-HA, after incubation for different periods of time in simulated body fluid, were a ssed using atomic force microscopy and environmental electron scanning microscopy. Cell prolifer ation was higher on SiHA compared to HA. In addition more focal points of adhesion were seen i n Si-HA than on HA. Using atomic force microscopy and environmental scanning electron mic roscopy it was possible to observe changes in the surface of both materials, namely dissolution f eatures and the formation of an apatite layer. These findings support the results of a previous st udy, which showed that Si-HA had a higher dissolution with the preferential release of silicon i nto the medium and this fact may account for the changes observed in the cell behaviour.

In Vitro Analysis of Protein Adhesion to Phase Pure Hydroxyapatite and Silicon Substituted Hydroxyapatite

The adhesion of bovine collagen type I, bovine serum albumin, bovine IgG, 1 % and 10 % (v/v) human serum to hydroxyapatite (HA), silicon-substituted hydroxyapatite (Si-HA) and tissue culture plastic were studied. The materials were incubated at 37 °C for 30 minutes, after which the protein solution was removed and analyzed. The adsorbed protein was evaluated by electrophoresis and immunoassay after extraction from the materials. The degree of adhesion was higher for collagen, followed by IgG and albumin on all materials. However there was no difference in the amount of collagen adsorbed onto the surface of each material and this was also the finding with albumin and IgG. These results suggest that the increased bioactivity seen with Si-HA is not due to the degree of protein adhesion, but may possibly be due to changes in the conformation of the bound proteins.

Biological Behaviour of Bonelike® Graft Implanted in the Tibia of Humans

This paper reports the ability of Bonelike® to regenerate bone defected areas when implanted in the tibia of 3 patients (average age of 59 years) during a high tibial osteotomy (HTO) to treat medial compartment osteoarthritis of the knee. Bonelike® is a synthetic bone graft designed to mimic the inorganic composition of bone using a patent process that consists of liquid sintering hydroxyapatite in the presence of CaO-P2O5 based glass. The preliminary clinical evaluation performed showed that an intimate contact between new formed bone and Bonelike® was established (67±10 %), with no fibrous interface. Therefore, Bonelike® is a single-handedly viable osteoconductive synthetic grafting material as it has been demonstrated from the profiles of radiological, histological and scanning electron microscopy analyses for the six months implantation period.

Assessment of the Potential of Bonelike® Graft for Bone Regeneration by Using an Animal Model

BonelikeÒ graft that mimics the inorganic composition of bone tissue has been developed and characterized over the last decade. To evaluate the osteoconductivity of BonelikeÒ two granule size ranges, one ranging from 150-250µm and the other from 250-500µm were implanted in the femurs of New Zealand White rabbits, aiming at being clinically used in different medical applications, such as dentistry and orthopaedics. In order to facilitate the medical application of the BonelikeÒ graft the use of a commercially available polymeric vehicle was also analyzed. Radiological examination, histological studies and scanning electron microscopy (SEM) analyses revealed that the surface of Bonelike® granules was almost completely surrounded by new bone formation after 12 weeks of implantation, which proves its highly osteoconductive behaviour.

Production of Porous Biomaterials Based on Glass-Reinforced Hydroxyapatite Composites

In this study, porous GR-HA composites were produced using a calcium-phosphate glass with the composition, in mol%, 75P2O5-15CaO-10CaF2. The composites were obtained by wet mixing 4.0% (w/w) of the glasses with hydroxyapatite (HA) powder (batch P120) (Plasma Biotal; Tideswell, U.K.), pressing and sintering. Two different organic additives were used as pore formers: potato starch and almond crust. This processing route was effective in producing a homogeneous microstructure of equiaxed grains. The bulk density of the samples decreased with the volume fraction increase in the content of pore formers. Scanning electron microscopy and mercury porosimetry analyses showed to be complementary techniques in characterising the pore size and distribution. Introduction Porous biomaterials have been produced in a variety of ways [1-2] for numerous biomedical applications, such as drug delivery systems and as osteoconductive implants for bone ingrowth. These macroporous bioceramics require pores larger than 100μm to allow proper vascularisation of the newly formed bone tissue. Several glass systems have been used to produce glass reinforced hydroxyapatite (GR-HA) composites. A previous study has demonstrated that glass reinforced hydroxyapatite composite materials based on HA and 4wt% of the 75P2O5-15CaO-10CaF2 glass are partially resorbable in vivo using rabbit model [3]. During sintering, the CaO-P2O5 glass reacts with HA and some -TCP ( -tricalcium phosphate) is formed in the microstructure as demonstrated by X-ray diffraction analysis [3]. The amount of TCP depends upon the sintering temperature used and the content of glass added to prepare the composite. This phase is known to be more biodegradable than HA and therefore this composite material should augment bone ingrowth compared to unmodified HA. Furthermore, the degree of biodegradability of this type of composites may be controlled by the content of glass and the sintering temperature. Experimental procedure The composite material was developed by J.D. Santos and co-workers [4]. To produce the composite, the glass was melted in a platinum crucible at 1450°C during 1 hour with a heating rate of 2°Cmin -1 . The produced glass was firstly crushed in an agate mortar up to a granule size less than 75 μm. The composites were obtained by wet mixing 4.0% (w/w) of the glasses with hydroxyapatite (HA) powder (batch P120) (Plasma Biotal; Tideswell, U.K.). Composite powders were then dried, sieved and dispersed in ethanol in the presence of a suitable dispersant, followed by planetary ball milling for 1 hour, achieving a particle size distribution with 90% below of 5 μm. Two different organic additives were used as pore formers: a potato starch with an average granule size of about 55 μm and almond crust with an average granule size of about 410 μm (90% below 600 μm), and added to portions of the stock suspension together with a binder [Poly-vinylbutyralco-vinyl alcohol-co-cinyl acetate]. The fraction of starch was maintained constant, at 20% in Key Engineering Materials Online: 2002-10-25 ISSN: 1662-9795, Vols. 230-232, pp 483-486 doi:10.4028/www.scientific.net/KEM.230-232.483

In Vitro Mineralisation of Human Bone Marrow Cells Cultured on Bonelike

Bonelike is a CaO-P2O5 based glass-reinforced hydroxyapatite (HA) designed to mimic the inorganic composition of the bone tissue. This work evaluates the response of human bone marrow cells to Bonelike uf6da concerning cell proliferation and osteoblast differentiation. HA was used as control material. Results showed that Bonelike uf6da allowed the proliferation of bone marrow cells and their complete differentiation, as evidenced by t he formation of cell-mediated mineralisation. In comparison with HA, Bonelike uf6da had a positive effect on the expression of alkaline phosphatase and also on the formation of a mineralised matrix, two osteobla st markers. Introduction Bonelike is a synthetic hydroxyapatite (HA) that is sintered in the pr esence of CaO-P 2O5-based glasses using a patented process [1]. This synthetic bone graft w as designed to improve the mechanical properties of calcium phosphate ceramics and mimic the inorganic composition of bone tissue. The physicochemical and mechanical behaviour of Bonelike uf6da hav been extensively reported in literature [1-3]. Previous in vitro biological studies showed that glass-reinforced HA composites al low the proliferation of MG63 osteoblast-like cells and human bone marrow ce lls and the expression of osteoblast markers [4-6]. Also, in vivo studies performed in a rabbit model demonstrated that Bonelike composites induced earlier new bone formation around implants than HA [7]. Recently, a composite prepared by the addition (4 wt %) of a glass with the composition of 65P2O5-15CaO-10CaF 2-10Na2O (in % mol) to HA was subject of clinical trials in implantol ogy and maxillofacial surgery [8]. This study demonstrated extensive new bone formation around implanted granules and continuous replacement by new bone. Osteoblasts a re the cells responsible for the formation of the bone tissue at the bone/material interface and the present work evaluates the response of human bone marrow cells to Bonelike uf6da composite, with the same chemical composition, concerning cell proliferation and osteoblast differentiation. HA was used as control material. Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 821-824 doi:10.4028/www.scientific.net/KEM.254-256.821

Application of Glass Reinforced Hydroxyapatite Composite in the Treatment of Human Intrabony Periodontal Angular Defects – Two Case Reports

Bony defects caused by periodontitis are often treated by regenerative therapy using autografts and/or allografts. Alloplasts such as hydroxyapatite or ceramics and bioactive glasses are used as osteoconductive materials that serve as scaffold for new bony ingrowth. The purpose of this study was to ascertain the possible regenerative capability of glass reinforced hydroxyapatite (Bonelikeuf0e2¬)¬¬¬ an osteoconductive synthetic graft in the treatment of human periodontal intrabony angular defects. The material was placed in 2 defects in 2 individual patients and clinical parameters such as probing depth (PD) and clinical attachment level (CAL) have been included. Bone fill was determined using an intra oral periapical radiograph (IOPA) and Autocad Software. After 3 months implantation period, there was an improvement in CAL and reduction in PD along with bone fill was observed.

In Vitro Biodegradability of Chitosan-Organosiloxane Hybrid Membrane

Chitosan-silicate hybrid membranes were prepared using g-glycidoxy-propyltrimethoxysilane (GPSM) through a sol-gel process. The amino groups of chitosan chains were reacted with the epoxy groups of GPSM and GPSM have a function as the agent to cross-link the chitosan chains. The cross-linking degree of the hybrid membranes was determined by ninhydrin assay. Fourier-transform infrared (FT-IR) spectroscopy and 29Si cross-polarization (CP) magic-angle spinning (MAS)-NMR spectroscopy were used to assess the structure of the hybrid membranes. The biodegradability of the hybrid membranes in phosphate-buffered saline solution or lysozyme solution was investigated as a function of the GPSM concentration.

Biological Activity of Two Glass Ceramics in the Meta- and Pyrophosphate Region: a Comparative Study

Based upon the CaO-P 2O5 glass system, two glass ceramics were prepared in the me taand pyrophosphate regions. The present work describes preliminary res ults concerning the biological activity of MK5B (45CaO-45P 2O5-5MgO-5K2O, in mol %) and MT13B (45CaO-37P 2O55MgO-13TiO2, in mol %) using MG63 osteoblast-like cells. Both materials support ed cell growth and proliferation which increased with the incubation time. However, ce ll growth was significantly lower on seeded MK5B samples. SEM observation showed that cell adhe sion and spreading were hampered on this material. Evident degradation of the material sur face was observed with simultaneous cell proliferation and material precipitation. By contr ast, MT13B presented a relatively stable surface throughout the culture time. Results suggest that the in vitro biological behaviour of MK5B and MT13B is related with differences in the degradation r ates of the two materials during the culture time. Introduction Several efforts have been made to obtain allografts for bone regene atio processes with controlled biodegradability. For several medical applications e.g. implantology these allografts should be capable of being degraded with simultaneously new bone regeneration without gaps formation at bone/implant interface. Based upon the CaO-P 2 5 glass system two glass ceramics were prepared in the metaand pyrophosphate regions [1-3]. K 2O and TiO2 oxides were also added to promote the precipitation of biodegradable and bioactive phases. By working in the m etaand pyrophosphate regions it is possible to obtain calcium phosphate biomaterials wi th ta lored degradability and enough mechanical strength and therefore to modulate their behaviour t o specific clinical applications. The present work aims at analysing the biological ac tivity of the two glass ceramics using MG63 osteoblast-like cells. Materials and methods Glass ceramics MK5B (45CaO-45P 2O5-5MgO-5K2O, in mol %) and MT13B (45CaO-37P 2O55MgO-13TiO2, in mol %) were prepared by controlled crystallisation and powder s intering technique, respectively. Sintering and crystallisation heat-treatm ents were conducted according to differential thermal analysis results. Crystallisation of MK 5B was performed using two-step heattreatment of nucleation followed by crystal growth to obtain volume c rystallisation [1] and MT13B was sintered at 703 C [1,2]. For cell culture studies, samples were ground down to 1000 mesh of SiC paper and sterilised by autoclaving. Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 825-828 doi:10.4028/www.scientific.net/KEM.254-256.825

Hybrid Chitosan Membranes Tested in Sheep for Guided Tissue Regeneration

Previous in vitro studies confirmed an improved cytocompatibility of chitosan-silicate hybrid membranes over chitosan membranes. The main goal of this study was to assess the in vivo histocompatibility of both membranes through subcutaneous implantations at different time periods, 1 week, 1, 2 and 3 months, using a sheep model. Chitosan membranes elicited an exuberant inflammatory response and were consequently rejected. The hybrid chitosan membranes were not rejected and the degree of inflammatory response decreased gradually until the third month of implantation. Histological evaluation also showed that these membranes can be resorbed in vivo. This study demonstrates that the incorporation of silicate into the chitosan solution improves its histocompatibility, indicating that the hybrid chitosan-silicate membranes are suitable candidates to be used in clinical applications.