Bio-Medical Materials and Engineering - Volume 3, issue 3

Authors: Oshida, Yoshiki | Munoz, Carlos A. | Winkler, Mark M. | Hashem, Azza | Itoh, Michio

Article Type: Research Article

Abstract: Aluminum oxide particles are commonly used as a sandblasting media, particularly in dentistry, for multiple purposes including divesting the casting investment materials and increasing effective surface area for enhancing the mechanical retention strengths of succeedingly applied fired porcelain or luting cements. Usually fine aluminum oxide particles are recycled within the sandblasting machine. Ceramics such as aluminum oxides are brittle, therefore, some portions of recycling aluminum oxide particles might be brittle fractured. If fractured sandblasting particles are involved in the recycling media, it might result in irregularity metallic materials surface as well as the recycling sandblasting media itself be contaminated. Hence, …it is necessary from both clinical and practical reasons to monitor the particle conditions in terms of size/shape and effectiveness of sandblasting, so that sandblasting dental prostheses can be fabricated in optimum and acceptable conditions. In the present study, the effect of recycling aluminum oxide particles on the surface texture of metallic materials was evaluated by Fractal Dimension Analysis (FDA). Every week the alumina powder was sampled and analyzed for weight fraction and contaminants. Surface texture of sandblasted standard samples was also characterized by FDA. Results indicate very little change in particle size, while the fractal dimension increased. Fractal dimension analysis showed that the aluminum oxide particle as a sandblasting media should be replaced after 30 or 40 min of total accumulated operation time. Show more

Keywords: fractal dimension analysis, sandblasting, aluminum oxide particle, contamination, X-ray diffraction

DOI: 10.3233/BME-1993-3301

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 117-126, 1993

Authors: Brossa, F. | Cigada, A. | Chiesa, R. | Paracchini, L. | Consonni, C.

Article Type: Research Article

Abstract: Using Air Plasma Spraying (APS) and Vacuum Plasma Spraying (VPS) techniques, hydroxylapatite (HA) and mixtures of HA and titanium (Ti) were deposited on a Ti6Al4V alloy (and on an AISI 316L steel) subjected to different surface treatments. The deposits were investigated for their crystallinity, thickness, and adhesion properties. Higher adhesion values were obtained with VPS rather than with APS. By utilising VPS, the deposition conditions were selected in order to achieve crystallinity values between 70 and 90%. The adhesion results depend on the crystallinity (increasing with its decrease), on the thickness (decreasing slightly with its increase) and especially on the …surface finish of the metallic substrate. A porous Ti precoat was more effective than either chemical etching in HCl or sandblasting; sandblasting being the least effective. In particular, the double deposits consisting of a porous Ti precoat and a successive layer of HA proved to be most interesting for their higher adhesion properties and for their capability of providing primary stability due to the presence of the HA and secondary stability, in the case of its reabsorption, due to the porous metal. Show more

Keywords: plasma spray coatings, hydroxylapatite, porous Ti, osteo-integration, adhesion

DOI: 10.3233/BME-1993-3302

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 127-136, 1993

Authors: Ioku, Koji | Yanagisawa, Kazumichi | Yamasaki, Nakamichi | Kurosawa, Hisashi | Shibuya, Kazuyuki | Yokozeki, Hitoshi

Article Type: Research Article

Abstract: Hydroxyapatite (Ca10 (PO4 )6 (OH)2 ;HA) is one of the most biocompatible materials with bones, and porous HA is promising bone substitute materials for clinical applications. While there are reports that β-tricalcium phosphate (Ca3 (PO4 )2 ;TCP) has higher resorbability than HA when the material is implanted in a bone defect. In the present study, porous HA coated with β-TCP was prepared by our unique method. The porous HA of about 60% porosity with interconnecting pore structure was soaked in diammonium hydrogen phosphate solution, and then the HA was sintered at 900°C for 3 h. β-TCP was revealed by X-ray …diffractometry on the surface of porous HA. It was possible to control the content of surface-formed β-TCP arbitrary by varying the concentration of the solution. The obtained HA coated with 33 wt% β-TCP (33TCP) had about 60% open porosity with the pore size from 150 to 400 μm. The average compressive strength of this porous ceramics was 17.5 MPa. Surface coated HA with β-TCP deprived of the brittleness in handling. The weight of HA implanted into muscles was increased obviously at 4 weeks because of formation of carbonate hydroxyapatite on the surface of HA. The weight of 33TCP was scarcely changed up to 12 weeks, but the weight tended to increase at 24 weeks. The carbonate hydroxyapatite was not formed on 33TCP at 4 weeks, but formed on it at 24 weeks. Therefore β-TCP coated porous HA behaved like β-TCP initially after implantation, and then behaved like HA. Show more

Keywords: hydroxyapatite, tricalcium phosphate, porous material, composite, ceramics

DOI: 10.3233/BME-1993-3303

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 137-145, 1993

Authors: Hirota, Kazushi | Nishihara, Katsunari | Tanaka, Hidehiko

Article Type: Research Article

Abstract: Preparation of a composite consisting of apatite and collagen was attempted. Starting from an aqueous solution of collagen, phosphoric acid, and calcium hydroxide suspension, an apatite (90wt%)-collagen (10wt%) composite of 1.75 g/ml in apparent density, with 2 GPa in Young's modulus, and 6.5 MPa in compression strength was synthesized at 40°C, 200 MPa, successfully. It was found that the presence of liquid water in the system was essential for the sintering of the composite under high pressures. Without liquid water, the specimen that was pressure treated and brought in atmospheric pressure, broke into small pieces due to residual strain. The …prepared composite could be cut by a razor blade, and was stable against immersion in water. The mean size of the apatite crystals in the composite was 10 nm in width and 40 nm in length. Show more

Keywords: collagen, hydroxyapatite, composite, pressure, sintering

DOI: 10.3233/BME-1993-3304

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 147-151, 1993

Authors: Nakamura, Takao | Hayashi, Kozaburo | Yamane, Hideyuki

Article Type: Research Article

Abstract: An electric motor-driven ventricular assist device has been developed for long-term use inside the body. The system is composed of a pusher-plate-type blood pump and an actuator consisting of an electrical motor and a ball screw. Cyclic change of the direction of motor rotation makes a back-and-forth axial movement of the ball screw shaft. The shaft, which is detached from the pump diaphragm, pushes the diaphragm via a pusher plate to eject blood during systole; blood is sucked by the diaphragm resilience during diastole. Using the output signals from a newly designed, incremental-type, miniature optical rotary encoder mounted inside the …actuator, the input voltage of the motor is optimally controlled referring to the phase difference between the current position of the moving rotor and the electrical reference signal of the rotation generated by a microprocessor-based controller. In vitro performance tests indicated that the system fulfills required specifications. The maximum efficiency was 11%, which was about twice as high as that obtained with the previous open-loop prototype system. In the air, the surface temperature of the actuator elevated to 20°C above the room temperature. An acute in vivo test showed its feasibility as a left ventricular assist device. Analysis of the energy loss in each component of the system indicated that redesign and precise assembly of the mechanical parts could increase the system efficiency. Show more

Keywords: efficiency, electric motor, left ventricular assist device, mechanical actuator, optical rotary encoder

DOI: 10.3233/BME-1993-3305

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 153-165, 1993

Authors: Lewis, Gladius

Article Type: Research Article

Abstract: The mode-I plane-strain fracture toughness values of eight posterior restorative composite materials were determined using straight-sided chevron-notch short-rod specimens and a special loading module. These results, together with the values of the modulus of elasticity, modulus of resilience, and flexural strength of these materials (as given in a paper by a previous worker) were used in a detailed correlational exercise, with the values of the clinical wear of restorations made from these materials (as given in the aforementioned paper) being the dependent variable. It was found that clinical wear may best be predicted using values of all four aforementioned mechanical …properties. Show more

Keywords: clinical wear, fracture toughness, dental composite materials

DOI: 10.3233/BME-1993-3306

Citation: Bio-Medical Materials and Engineering, vol. 3, no. 3, pp. 167-174, 1993