Bioceramics 23

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Authors: Joanna Karaś, Andrzej Roman Olszyna, Ewa Zaczyńska, Anna Czarny, Krzysztof Szamałek
Abstract: The purpose of the study was to identify the influence of the amount of fluoride release from glass ionomer cements on survival of bacterial strains responsible for the development of secondary caries. All developed cements had an antibacterial impact on the strains used in the study. The study demonstrated that the cements exhibit greater antibacterial activity against Streptococcus mutans than Streptococcus sanguinis. The numbers of bacteria count in cultures on the developed cements were approximately 10 times lower compared to the control culture after 24 h, 48 h, 72 h and 7 days. The developed cements had initially (1-2 days) greater antibacterial impact against the strains used in the study, which corresponds to the greatest daily amount of fluoride released from the cements. Following the initial period, the antibacterial activity of all the cements remained roughly at the same level.
Authors: Ali Emrah Çetin, D. Şimşek, M. Çiftçioğlu, Yelda Akdeniz, Filiz Özmıhçı, Arzu Aykut Yetkiner
Abstract: The goal of the present work was to investigate the effects of several cement preparation parameters on setting and hardening reaction mechanisms and hydroxyapatite (HA) cement properties. A central composite experimental design (CCD) was conducted by choosing particle size, solid to liquid ratio, pH, seed concentration and buffer concentration as design parameters along with compressive strength and setting time being the responses. Tetracalcium phosphate (TTCP) powders were prepared by heat treatment of calcium and phosphate source mixtures in the 1200-1400°C temperature range followed by quenching to room temperature in a dessicator. The second phase used in the formulations (brushite) was prepared by aqueous chemical methods. A series of HA pastes/cements were prepared by changing the above mentioned design parameters. Cements were characterized by a standardized setting time test, mechanical testing machine, SEM and XRD. HA cements with the desired properties can be formulated by using CCD in which the responses were expressed by a second order polynomial equation of the parameters. Compressive strengths for the majority of HA cements were determined to be in the 100-160 MPa range which is significantly higher than those reported in the literature.
Authors: F. Dombrowski, Heidi Marx, Ute Ploska, D. Nicolaides, M. Stiller, Christine Knabe, Georg Berger
Abstract: The thrust of the investigations presented here is to point out the degradation behaviour in vitro and the ingrowth behaviour in vivo of four different calcium alkaline phosphate cements. Two of the figuline and mouldable composites consist of the crystalline phase Ca2KNa(PO4)2 and two of the crystalline phase Ca10[K/Na](PO4)2 each containing 2wt% medium gel strength porcine gelatin. Furthermore Α-TCP was added to both Ca10[K/Na](PO4)2 cements as a hardening supporting reactant. The testing material groups differ in small amorphous portions containing either silica phosphate (GB9), magnesium potassium phosphate (GB14) or diphosphates (401545 and 401545(70)). The respective composites show a monomodal particle size distribution (d50~7µm; span~4) and an average total porosity around 28vol%.For the solubility studies cylindrical samples (d=6mm; h=12mm) were stored in a 0.1mol TRIS buffer solution and incubated at 37°C for maximum 50 weeks. The storage solution was analysed and renewed every week. The results are plotted cumulative. For the in vivo studies critical size defects were dissected to mandibles in a sheep model in which a 1cm3 area of the bottom of the mandibles was surgically resected and replaced with the figuline cements whereas the mouldability allows the reconstruction of the original outer contour without draining off even when replacing upside down.
Authors: Simona Cavalu, Viorica Simon, Ipek Akin, Gultekin Goller
Abstract: Polymer-ceramic composites based on polymethyl methacrylate are widely used in orthopaedics as suture materials and fixation devices due to their biocompatibility and ability to support bony growth (osteoconductive) and also bone bioactive (to form a calcium phosphate layer on its surface). The aim of this study is to compare the microstructure, bioactivity and biocompatibility of new acrylic cement containing silver and collagen coated, with a comercial one, by in vitro study in simulated body fluid. In order to evaluate the properties of the surface layer, SEM microscopy and ATR-FTIR spectroscopy are used. The results indicates that both silver content and the presence of collagen layer favourise the mineralisation process at the surface.
Authors: H.A.I. Cardoso, M. Motisuke, Cecília A.C. Zavaglia
Abstract: Among the calcium phosphate cements, the system based on alpha-tricalcium phosphate (α-TCP) combines several interesting properties. However, these cements have their use limited to low load applications. The main objective of this study is to evaluate the influence of three different additives on the setting reaction kinetics and mechanical strength evolution of calcium phosphate cements as a function of time. The cement was obtained by mixing α-TCP powder with four different aqueous solutions containing or not containing disodium hydrogen phosphate (Na2HPO4), citric acid (C6H8O7) and/or tannic acid (C76H52O46). It was observed that two cement samples, one of them containing Na2HPO4 and C6H8O7 and another containing Na2HPO4 and C76H52O46 in the liquid phase, presented faster setting reaction and higher mechanical properties. These cements are more suitable for application as bone cement.
Authors: H.A.I. Cardoso, M. Motisuke, A.C.D. Rodas, O.Z. Higa, Cecília A.C. Zavaglia
Abstract: An application of calcium phosphates is as bone cements, among which the system based on alpha-tricalcium phosphate (α-TCP) exhibits excellent properties. The aim of this study is to analyze pH evolution and cytotoxicity of α-TCP cement with three different additives. Changes on the pH were measured at intervals of 12h during seven days. But initial measurements were executed at each 15 minutes. Indirect cytotoxicity test was performed according to ISO (10993-5, 1992) employing CHO-k1 cells and RPMI 1640 as culture medium. It was used a colorimetric method which uses the tetrazolium compound. The additives used on the liquid phase were disodium hydrogen phosphate (Na2HPO4) and/or citric acid (C6H8O7) and/or tannic acid (C76H52O46). The results indicate that the cement without additives does not have requirements to be applied like bone cement, while the other cements composition exhibit different responses in the pH and the cytotoxicity test. In conclusion, due to the presence of additives it was possible to control pH evolution during setting and cytotoxic response. However, further investigation is necessary in order to determine the influence of these additives, mainly tannic acid, on the in vivo behavior of these bone cements.
Authors: Jing Tao Zhang, Franck Tancret, Jean Michel Bouler
Abstract: Calcium phosphate cements have been widely used in medical and dental applications for decades. However, their intrinsic high brittleness and low strength prohibit their use in many stress-bearing locations, which would require an improvement in mechanical properties. The influence of microstructural parameters on the latter have nevertheless barely been investigated in a systematic manner. Furthermore, due to their inferior reproducibility which is sensitive to the variations introduced during the preparation and the way they are measured, mechanical properties of CPC cannot simply be characterized using mean values, but request a more reliable method. In this aim, apatite cements have been fabricated by mixing liquid and powders based on α-TCP (α-tricalcium phosphate), and their mechanical properties have been measured (Young’s modulus, fracture toughness, compressive strength and flexural strength) in wet environment as a function of various parameters (liquid-to-powder ratio; amount and morphology of porosity, including macropores created by porogens). The reliability of compressive strength of CPC is analysed using Weibull statistics. The above results indicate that fabrication and microstructural features of CPC significantly influence their mechanical properties.
Authors: N.J. Dunne, R. O’Hara, F. Buchanan, J. Orr
Abstract: Due to their insufficient mechanical stability and brittle nature, calcium phosphate cements (CPCs) have not been used for the treatment of vertebral fractures. Mechanical stability of human bone is provided by a complex interaction of type I collagen fibres and hydroxyapatite crystals. In the present study, fibre reinforcement of an apatitic calcium phosphate prepared at different liquid/powder ratio (LPR) was investigated. Different lengths of type I collagen fibres sourced from bovine Achilles tendon were used. Compressive strength and fracture behaviour were examined. Fibre addition of up to 5 wt.% had a significant influence on the compressive properties of the CPC. The mechanism of fibre reinforcement appeared to be crack bridging. Setting time and injectability of the CPC with fibre reinforcement was also investigated and decreased with fibre volume fraction. Increasing the LPR, improved the injectability and delayed the setting reaction. However, the compressive properties of the hardened cement were reduced as a consequence.
Authors: Koji Goto, Haruhiko Akiyama, Keiichi Kawanabe, Kazutaka So, Takashi Nakamura
Abstract: We used a composite of uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-l-lactide (PLLA) to fix the acetabular bone graft in total hip arthroplasty (THA) in a clinical trial in six patients, and followed them for over 10 years. The patients were evaluated clinically and radiologically to assess the safety and efficacy of the screws and the characteristics of their absorption. No patient in this series experienced revision or radiographic loosening during the follow-up period. The configurations of the HA–PLLA composite screws were confirmed on early post-operative radiographs in every case, whereas they appeared obscure on radiographs within 5 years after surgery, and only osteosclerotic traces remained in the screw positions at the final follow-up. Some screw heads were covered with bone within 3 months of surgery, and some screw heads migrated laterally with breakage, but were absorbed in situ within 5 years. The screws seemed to have no negative effect on the mid-term clinical results of the THAs.
Authors: Junichi Tazaki, Masaru Murata, Y. Nakanishi, M. Ochi, Y. Hirose, T. Akazawa, S. Yodogawa, J. Hino, K. Ito, H. Kitajo, M. Arisue, T. Shibata
Abstract: In our previous clinical study, autogenous demineralized dentin matrices (DDM) prepared from the functional vital teeth (#38, #41) of thirty-five-year-old female were grafted on the bone defect, using newly developed mill, and then received to the host without troubles. In this study, we implanted the human tooth dentin adjusted previously and the dental implants into the regions of missing tooth simultaneously. Fifty-seven-year-old female presented with missing teeth (#35-#37, #45-#47). First, a non-functional vital tooth (#18) were extracted and cryopreserved immediately. 11 months after extraction, the tooth was crushed by newly developed auto-crash mill using ZrO2 vessel and ZrO2 blade for 1 minute. The crushed granules were demineralized completely in 2% HNO3 solution, rinsed in cold distilled water and lyophilized (granule size: 0.5-2.0mm). The bacteria-free of the DDM were confirmed by the bacteriological examination before use. Drilling of the prospective implant beds were then performed according to the manufacture’s protocol and a screw-type rough surface implants (Nobel Biocare® Mk III) were placed. The adjusted DDM granules were implanted into the bone defect (#45). There are no postoperative complications at 3 years after implantation. This case indicates that the preserved autogenous DDM can be used as collagenous biomaterials with osteoinductive potency.

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