Bioceramics 29

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Authors: Corrado Piconi
Abstract: Bioinert ceramics in use today are the result of more than 60 years of continuous development. Early studies were concentrated on alumina that in the late 1960s was the most advanced ceramic, and on pyrolytic carbon. After tests in orthopedic bearings, pyrolytic carbon found clinical applications in artificial heart valves, where it is in clinical use so far. After 1970 zirconia-toughened ceramics (YTZP, ZTA, ATZ) were investigated in view of their use as biomaterials in orthopedics. Especially the introduction of YTZP in clinics in the 1990s gave a new momentum to the use of inert bioceramics. So far, zirconia-toughened ceramics are replacing alumina because of their outstanding mechanical properties leading to high reliability in ceramic components. The behavior of ZTAs and ATZs are exploited in several innovative devices. Especially metal-free devices are of interest, because of the increasing number of patients sensitized to metals. Using zirconia-toughened ceramics were achieved remarkable development in ceramic knee replacements, a field pioneered by Japanese researchers, because the behavior of these materials allow the production of devices similar in size to the metallic ones. In dentistry, a number of manufacturers are marketing metal-free dental implants, as well as machinable zirconia blanks for the production of crowns, bridges, copings by CAD/CAM. Besides oxides, that in todays’ orthopedics and dentistry are the state-of-the-art bioinert ceramics, silicon nitride has found application in spinal surgery, and investigations in view of its use in joint replacement bearings are in progress.
Authors: Yoshiyuki Yokogawa, Ryota Fumimoto, Suguru Inamura
Abstract: The preparation of mesoporous silica compact through spark plasma sintering (SPS) and adsorption / desorption of protein onto SPS mesoporous silica (MPS) compact is reported. MPS powders, prepared using triblock copolymer, PEO20PPO70PEO20, were compacted in carbon die and heated at 400 or 500 °C for 5 min under uniaxial pressure. The products are referred to as MPS-400 and MPS-500, respectively. The MPS sinters keep the mesoporous configuration, but the mode diameter of MPS-400 was smaller than that of MPS powders and MPS-500. The adsorbed amounts of protein on MPS-400 was higher than that on MPS-500, while the pore diameter, BET surface area, pore volume of MPS-400 are less than those of MPS-500. The interstices in MPS-500 are narrower than that in MPS-400, which may restrict the protein to penetrate through the narrow channels to reach the mesopores of MPS. The quantity of adsorbed amount of protein on MPS sinters does not depend on mesopore configuration but on the macropore configuration of the MPS sinters.
Authors: Yoshiyuki Yokogawa, Atsumasa Shishido, K. Hiroyasu
Abstract: Mesoporous silica (MPS) coatings on hydroxyapatite (HAp) granules and their protein adsorptive capabilities were studied. MPS particles were coated on HAp granules using a dip-coating method, but the HAp granules were not totally covered by the MPS particles. A silica interlayer was formed on the HAp granules via magnetron sputtering or the sol-gel method prior to the coating of the MPS. The HAp granules coated with the silica interlayer were fully covered by the MPS particles. An silica interlayer may offer bonding between the HAp granules and MPS coating. The adsorption of protein on the MPS-coated HAp granules was evaluated by UV-VIS spectroscopy. The adsorption capacity of protein on the HAp granules was improved by the MPS coatings on the HAp granules, and that of the HAp granules coated with the silica interlayer showed a higher protein adsorption capacity.
Authors: Sota Ushijima, Toshiyuki Ikoma
Abstract: Mesoporous silica thin films were fabricated on gold substrates with a sol-gel method including a cationic surfactant. The interface of gold and silica thin films was fixed with a mercaptosilane. The surface roughness of the thin films and their grain sizes of silica were both increased with the elimination of the cationic surfactant and polyethylene glycol (PEG) modification on its surface. The surface reaction, adsorption of bovine serum albumin (BSA), was monitored with surface plasmon resonance (SPR). Although the adsorption amount of BSA at 1 mg/mL were 7.9 ng/cm2 on the mesoporous silica, the PEG modification can completely desorb BSA. The mesoporous silica thin films on gold substrates fabricated will be a good platform for analyzing surface reaction.
Authors: Arief Cahyanto, Andri Rezano, Myrna Nurlatifah Zakaria, Ahmed El-Ghannam
Abstract: Silica-calcium phosphate composite (SCPC) and carbonate apatite (CO3Ap) have several superior properties as they are bioactive, bioresorbable and elicit excellent tissue response. The CO3Ap surface layer and hydrated silica developed on the surface of the SCPC may be a key factor for achieving dentin regeneration. On the other hand, calcium hydroxide [Ca(OH)2] have antibacterial properties and biocompatible to dental tissue. Therefore, the combination of CO3Ap, SCPC, and Ca(OH)2 in a bone cement may be favorable as a pulp capping agent that enhances pulp tissue formation and dentin regeneration. The aim of the present study is to synthesize and characterize a novel SCPC-CO3Ap cement for pulp capping application in dentistry. The cement is composed of dicalcium phosphate anhydrous (DCPA), vaterite, Ca(OH)2 and SCPC. The set cement was further characterized by Fourier transform infrared (FT-IR). The microstructure of set cement was examined by scanning electron microscopy (SEM) and the mechanical strength was evaluated by diametral tensile strength (DTS). The FT-IR analyses revealed that the additional bands of carbonate were detected in each sample. The SEM samples of set cement showing more compact surface microstructure of group II compared to other groups. Furthermore, the combination of 5% SCPC and 5% Ca(OH)2 in the cement facilitated a compact structure with superior mechanical strength. The novel SCPC-CO3Ap cement has great potential to be used for pulp capping to facilitate dentin regeneration.
Authors: Evangelos Gkogkas, Panagiota T. Dalla, Theodore E. Matikas, Simeon Agathopoulos
Abstract: The influence of the treatment of the surface of IPS Empress II (e-max) glass-ceramic dental material with different silane agents on the surface roughness of this glass-ceramic was evaluated. IPS Empress II (e-max) cores were treated with five different commercial silane agents used in dentistry nowadays, for several periods of time and were finally air dried. After silanization, the surfaces of the glass-ceramic cores were observed with a light profilometer, a scanning electron microscope (SEM), and an atomic force microscope (AFM). The values of surface roughness (Ra) were also measured with the light profilometer. The results showed an important effect of silane treatment applied for different periods of time, especially for prolonged treatment for 24 hours, on the surface roughness of IPS Empress II (e-max). These results can have an important impact on the deep understanding of the cementation protocols applied in modern dentistry.
Authors: Lorena Grima, J.I. Peña, José A. Pardo
Abstract: With age bones lose quality being in some cases necessary their replacement. Research is underway on the development of biomaterials to meet the mechanical and biological requirements. One of the most used alloys is Ti6Al4V. The disadvantage of this biomaterial is the formation of a layer of connective tissue between the implant and the surrounding tissue, which makes it difficult to attach to living bone. Ceramic coatings are made on the surface of these metal biomaterials, which improve the communication between the implant and the living tissue.Ti6Al4V substrates have been coated with a bioactive ceramic with composition 7CaO.P2O5.2SiO2 by Pulsed laser deposition (PLD). Layers have been deposited under different substrate conditions and their microstructure and composition have been characterized by XRD and SEM.
Authors: Hyun Woo Kim, Kyung Nahn Park, Kyung Sik Oh
Abstract: The injection behavior of β-tricalcium phosphate (Ca3(PO4)2: β-TCP) based cement was improved through the granulation of β-TCP. Dense β-TCP granules were obtained by heat treatment after spray drying. The fraction of injected paste under loaded mass in the syringe was measured while varying the granular fraction of β-TCP and the heat treatment temperature. The increase in granular fraction and heating treatment temperature reduced the amount of setting agent required to wet the granules. As the surplus setting agent could be used in the powdery β-TCP to reduce the viscosity, improved injectability was achieved. Inappropriate setting by the excessive setting agent was not observed and the cements tested exhibited normal setting behavior by forming a brushite phase.
Authors: Nina Djustiana, Mitha Amaranila, Nadia Greviana, Myrna Nurlatifah Zakaria, Sunarso, Arief Cahyanto
Abstract: Carbonate Apatite (CO3Ap) cement is considered as an ideal bone substitute due to its biocompatibility and osteoconductivity. Also, CO3Ap cement has the chemical composition that closes to natural bone. During cement preparation, precursors play an important role that affects the properties of CO3Ap cement. Cement hardness is one of the important properties that need to be evaluated before the obtained cement can be applied as a bone substitute. Therefore, the purpose of this study is to determine the effect of precursor ratio of CaCO3 and CaHPO4 on the hardness level of CO3Ap cement. In the present study, the CO3Ap cement was prepared from CaCO3 and CaHPO4. Both Commercial and synthesized CaCO3 were used. The CO3Ap cement obtained from commercial CaCO3 was used as a control group. Synthesized CaCO3 was obtained from Indonesian natural limestone. Three different CaCO3:CaHPO4 ratios, 40:60, 30:70 and 20:80 were mixed with 1 mol/L Na2HPO4. Samples were kept at 37°C with 100% relative humidity for 24 hours then tested using micro Vickers hardness testing machine. The micro Vickers hardness of the control group with CaCO3:CaHPO4 ratio of 40:60, 30:70 and 20:80 were 5.09 VHN, 6.34 VHN, and 6.73 VHN, respectively. Meanwhile, the micro Vickers hardness of the CO3Ap cement obtained from synthesized CaCO3 were 6.22 VHN, 7.50 VHN, and 10.37 VHN for the CaCO3:CaHPO4 ratio of 40:60, 30:70 and 20:80, respectively. The micro Vickers hardness level of CO3Ap cement precursor ratio from the lowest to the highest was 40:60 < 30:70 < 20:80. In conclusion, the precursor ratio significantly affects the hardness level of the CO3Ap cement. The hardness level of CO3Ap cement obtained from synthesized CaCO3 was higher compared with that obtained from commercial CaCO3.

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