Bio-Medical Materials and Engineering - Volume 6, issue 2

Authors: Nordström, E.G. | Hara, T. | Herø, H.

Article Type: Research Article

Abstract: The solubility of some inorganic materials was studied. It was found that Ca dissolution was high in calcium phosphates with Ca/P ratios 1.67-2.0. Dissolution of P was moderate compared with dissolution of Ca. The composites, HA content 70 wt-%, and HA showed to be corrosion resistant. Dissolution of alumina in the mineral muscovite, used as a filler material, was found to be neglectable and dependent on the density of the composite.

DOI: 10.3233/BME-1996-6201

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 73-78, 1996

Authors: Rao, S. | Ushida, T. | Tateishi, T. | Okazaki, Y. | Asao, S.

Article Type: Research Article

Abstract: The effect of Ti, V and Al ions on the relative growth rate of L929 cells and MC3T3-E1 cells was investigated by a cell culture method with metallic powders. These powders were sterilized under a U.V. lamp for 6 h, suspended in the medium and extracted for 48 h, 72 hand 96 h in the incubator. After filtering with a 0.2 η,m filter, 3.0 × 104 L929 cells and 5 × 104 MC3T3-E1 cells were seeded in these filtrates of the medium with and without (control) the presence of the metallic powder. The number of cells was counted …using a coulter counter from 1 to 7 days. The number of L929 cells after 4 days of incubation was almost similar for Ti and the control, whereas in the case of A1 and V extraction the number of cells was too low as compared to that of the control. The relative growth rate of L929 cells for Ti, Al and V after 4 days of incubation was about 1, 0.2 and 0.02, respectively. A similar trend was also observed for MC3T3-E1 cells. The effect of the relative growth rate of L929 cells at different extraction times of 48 h, 72 h and 96 h was examined. It was found that the relative growth rate of L929 cells for Ti, Al and V extraction was almost the same at all three extraction times. A number of 2.0–5.0 × 104 cells was seeded in the medium of Al extraction. The effect of this initial number of cells on the relative growth rate of L929 cells was investigated. The relative growth rate of L929 cells decreased as the initial number of L929 cells increased. Moreover, dilutions from 1 to 10 times in the case of Al and from 1 to 4000 times in the case of V were made. The relative growth rate became equal to 1 at 5 times dilution for Al and at 4000 times dilution for V, for both L929 and MC3T3-El cells. From the measures of the concentration of the released Al and V ions on the relative growth rate of L929 cells, it could be seen that there was a marked decrease in the concentrations of Al and V ions from 0.3 ppm to 0.1 ppm. Show more

Keywords: Cytocompatibility, titanium, aluminium, vanadium, released ions

DOI: 10.3233/BME-1996-6202

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 79-86, 1996

Authors: Oshida, Yoshiki | Miyazaki, Masashi

Article Type: Research Article

Abstract: Dentin bond strengths are normally evaluated by conducting mechanical tests in tensile and/or shear mode at a certain level of crosshead speed. According to the literature review, crosshead speed is varied in a relatively wide range from 0.1 mm/min to 10.0 mm/min (with the exception of a few studies conducted above 10.0 mm/min). It was also found that crosshead speeds of 0.5, 1.0, 2.0 and 5.0 mm/min were commonly employed to evaluate dentin bond strengths for both tensile and shear modes, although no rationale for selecting the crosshead speed was described in the articles. For testing dentin bond strengths, no …plastic deformation should be involved, and fracture only should take place during the fracturing process. With the Scotchbond Multiple-Purpose/Z100 bonding system, tensile bond strengths were evaluated at crosshead speeds of 0.1, 0.5, 1.0, 5.0 and 10.0 mm/min. It was found that (i) there was no strain rate sensitivity when the test was conducted below the 1.0 mm/min crosshead speed, and (ii) if the crosshead speed exceeded 1.0 mm/min, a strain rate dependency of the tensile bond strengths was observed. Knowledge that the composite resin (Z100) did not exhibit strain rate dependency influenced the conclusion that (iii) the above observed strain rate dependency was solely due to the mechanical response from the bonding interface region. Show more

Keywords: Dentin bond strength, tensile test, crosshead speed, strain rate sensitivity, modulus of elasticity

DOI: 10.3233/BME-1996-6203

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 87-100, 1996

Authors: Barralet, J.E. | Best, S.M. | Bonfield, W.

Article Type: Research Article

Abstract: The effect of carbonate in reducing the crystal size of precipitated hydroxyapatite by approximately an order of magnitude has not been used previously in the preparation of gel monoliths for the fabrication of carbonate hydroxyapatite ceramics. The aim of this study was to devise a method whereby gel monoliths of carbonate hydroxyapatite could be repeatably produced without cracking. A precipitation reaction was used for the preparation of carbonate hydroxyapatites with carbonate contents of 5.8 and 7.8 wt%, Biaxial vacuum filtration was used to form disc shaped monoliths. The rate of filtration of a 7,8 wt% carbonate hydroxyapatite sol was measured …throughout the gelation process. Gel monoliths were dried slowly in air and the mass and dimensions of the gel were recorded once approximately every 24 hours. Using this data, the permeability, water volume fraction with time, rate of water loss, gelation point and gel density were determined. The pore size distribution was measured using mercury porosimetry for a carbonate apatite gel and a pressed powder pellet of a commercial hydroxyapatite, Intact monoliths were formed with masses up to 9.9 g, It was found that gelation behaviour was independent of monolith size and carbonate content and the final green density of all monoliths was 37%, Gelation was found to occur at 50–55 vol% water Gel monoliths were found to have a monomodal pore size distribution with a mean pore size of 9.1 nm, whereas a pressed pellet of hydroxyapatite had a bimodal pore size distribution. Show more

Keywords: Carbonate, hydroxyapatite, sol, gel, processing

DOI: 10.3233/BME-1996-6204

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 101-112, 1996

Authors: Lewis, Gladius | Manickam, Saravanakumar | Wharton, Darrison

Article Type: Research Article

Abstract: The finite element analysis method was used to obtain values of the von Mises equivalent stress (SEQV) at selected locations within the adhesive layer of two-dimensional models of bonded orthodontic brackets. In all, 39 model cases were analyzed involving 4 overall bracket configurations, 3 combinations of materials of fabrication of the bracket, 3 types of debonding forces and 4 adhesives. The results are presented to show the sensitivity of SEQV to each of the parameters studied. Comments are made on the usefulness of the results in the development of a standard protocol for experimental determination of the bond strength of …adhesives used in securing orthodontic brackets. Show more

Keywords: Orthodontic bracket, debonding, adhesive layer, finite element stress analysis

DOI: 10.3233/BME-1996-6205

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 113-121, 1996

Authors: Khang, Gilson | Park, Joon B. | Lee, Hai Bang

Article Type: Research Article

Abstract: Using a custom-made PVC medical tube ateriovenous (A-V) shunt and a porous polysulfone (PSf) catheter, an ex vivo and in vivo experiment were carried out to study the effectiveness of saline solution perfusion to prevent adhesion of platelets without using anticoagulants. The critical perfusion rate for preventing adhesion of platelets onto the PSf catheter tubes is about 0.45 ml min−1 cm−2 . The higher perfusion rate resulted in a lesser platelet adhesion. At the highest perfusion rate tested, 0.92 ml min−1 cm−2 , the number of adhered platelets decreased by 98% in the in vivo experiment. From …the results of ex vivo and in vivo canine experiments, the saline perfusion catheters can be used as a very useful clinical armamentarium to prevent platelet and blood cell adhesion without using anticoagulants. Show more

Keywords: Platelet adhesion, blood compatibility, polysulfone porous catheter tube, saline perfusion, ex vivo and in vivo, canine experiment

DOI: 10.3233/BME-1996-6206

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 2, pp. 123-134, 1996