Bio-Medical Materials and Engineering - Volume 20, issue 2

Authors: Bergmann, G. | Graichen, F. | Rohlmann, A. | Bender, A. | Heinlein, B. | Duda, G.N. | Heller, M.O. | Morlock, M.M.

Article Type: Research Article

Abstract: The aim here was to define realistic load conditions for hip implants, based on in vivo contact force measurements, and to see whether current ISO standards indeed simulate real loads. The load scenarios obtained are based on in vivo hip contact forces measured in 4 patients during different activities and on activity records from 31 patients. The load scenarios can be adapted to various test purposes by applying average or high peak loads, high-impact activities or additional low-impact activities, and by simulating normal or very active patients. The most strenuous activities are walking (average peak forces 1800 N, high peak …forces 3900 N), going up stairs (average peak forces 1900 N, high peak forces 4200 N) and stumbling (high peak forces 11,000 N). Torsional moments are 50% higher for going up stairs than for walking. Ten million loading cycles simulate an implantation time of 3.9 years in active patients. The in vitro fatigue properties of cementless implant fixations are exceeded during stumbling. At least for heavyweight and very active subjects, the real load conditions are more critical than those defined by the ISO standards for fatigue tests. Show more

Keywords: Hip implant, THR, load, force, telemetry

DOI: 10.3233/BME-2010-0616

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 2, pp. 65-75, 2010

Authors: Kitayama, Shuzo | Nikaido, Toru | Ikeda, Masaomi | Alireza, Sadr | Miura, Hiroyuki | Tagami, Junji

Article Type: Research Article

Abstract: Resin bonding to zirconia ceramic cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. This study was aimed to examine the tensile bond strength of resin cement to zirconia ceramic using a new laboratory technique. Sixty-four zirconia ceramic specimens were air-abraded using Al2 O3 particles and divided into two groups; the control group with no pretreatment (Control), and the group pretreated using the internal coating technique (INT), in which the surface of the zirconia specimens were thinly coated by fusing silica-based ceramic and air-abraded in the same manner. The specimens in each group were …further divided into two subgroups according to the silane coupling agents applied; a mixture of dentin primer/silane coupling agent (Clearfil SE Bond Primer/Porcelain Bond Activator) or a newly developed single-component silane coupling agent (Clearfil Ceramic Primer). After bonding with dual-cured resin cement (Panavia F 2.0), they were stored in water for 24 h and half of them were additionally subjected to thermal cycling. The tensile bond strengths were tested using a universal testing machine. ANOVAs revealed significant influence of ceramic surface pretreatment (p<0.001), silane coupling agent (p<0.001) and thermal cycling (p<0.001); the INT coating technique significantly increased the bond strengths of resin cement to zirconia ceramic, whereas thermal cycling significantly decreased the bond strengths. The use of a single-component silane coupling agent demonstrated significantly higher bond strengths than that of a mixture of dentin primer/silane coupling agent. The internal coating of zirconia dental restorations with silica-based ceramic followed by silanization may be indicated in order to achieve better bonding for the clinical success. Show more

Keywords: Zirconia ceramic, resin cement, internal coating technique, silica-based ceramic, silane coupling agent, thermal cycling

DOI: 10.3233/BME-2010-0617

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 2, pp. 77-87, 2010

Authors: Wu, John Z. | An, Kai-Nan | Cutlip, Robert G. | Dong, Ren G.

Article Type: Research Article

Abstract: Biomechanical models of the hand and fingers are useful tools for hand surgeons to improve surgical procedures and for biomedical researchers to explore the mechanical loading in the musculoskeletal system that cannot be easily measured in vivo. The purpose of the present study was to develop a realistic index finger model for solving practical problems. The model includes the meshes of four bony sections (distal, middle, proximal and metacarpal bones) obtained via micro-CT scans. The tendon attachment sites are adopted from the normative finger model. A total of seven tendon/muscles are included in the model. The predicted tendon excursions and …moment arms were compared with published experimental data. One of the advantages of the current approach over previous studies is that the current model has been developed on a platform of a commercial software package, such that researchers can apply it as a universal tool for practical problems. Show more

Keywords: Index finger, kinematics, muscle–tendon excursion, moment arm, simulations

DOI: 10.3233/BME-2010-0618

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 2, pp. 89-97, 2010

Authors: Coughlan, A. | Scanlon, K. | Mahon, B.P. | Towler, M.R.

Article Type: Research Article

Abstract: A biofilm is an accumulation of micro-organisms and their extracellular products forming a structured community on a surface. Biofilm formation on medical devices has severe health consequences as bacteria growing in this lifestyle are tolerant to both host defence mechanisms and antibiotic therapies. However, silver and zinc ions inhibit the attachment and proliferation of immature biofilms. The objective of this study is to evaluate whether silver and zinc ions eluted from novel glass polyalkenoate cement (GPC) coatings have the ability to inhibit Methicillin-resistant Staphylococcus aureus (MRSA) in vivo. A silver and zinc-containing GPC coating was synthesised, deposited onto Ti6Al4V discs …and placed in a specified amount of analytical water for 1, 7 and 30 days. The resulting elutes were collected and Atomic absorption spectroscopy was used to measure ion release. The elutes were injected into Galleria mellonella larvae infected with MRSA and the antibacterial properties of these elutes were evaluated in vivo. The majority of the zinc and silver ions were released within the first 24 h; this corresponded with the greatest degree of protection observed in infected larvae. Results were compared to a conventional in vitro model where identical elutes were incubated with MRSA on nutrient agar. These results were consistent with those observed in the larval model, demonstrating a reduction in bacterial viability when co-cultured with elutes for 2 h. This work confirms the promise of the Galleria mellonella as a model for the assessment of antimicrobial agents and demonstrates the capacity of novel silver and zinc-containing GPCs to retard the colonisation of MRSA. Show more

Keywords: Glass polyalkenoate cement, antibacterial, zinc, silver

DOI: 10.3233/BME-2010-0620

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 2, pp. 99-106, 2010

Authors: Johnson, Taylor | Bahrampourian, Rahimeh | Patel, Alpesh | Mequanint, Kibret

Article Type: Research Article

Abstract: Tissue engineering holds great promise as an alternative strategy to current treatment modalities of diseased or otherwise failed tissues. Most strategies of tissue engineering rely on three-dimensional porous scaffolds to mimic the natural extracellular matrix (ECM) as templates onto which cells attach, multiply, migrate and function. When cells are harvested from a donor and seeded, scaffolds facilitate the organization of these cells into a three-dimensional architecture, control cell behavior and subsequently direct the formation of organ-specific tissue. In view of its role, scaffold fabrication methods target the creation of highly porous and interconnected pore structures. Among the different scaffolds fabrication …methods explored, solvent casting followed by precipitation or particulate leaching is one of the most straightforward methods. In this paper, we conducted a comparative study of two methods to prepare spherical porogens using poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) as dispersing agents and we used these porogens to fabricate cylindrical porous scaffolds using a combination of pressure differential and solvent casting/particulate leaching method. Porogen particle size analyses showed that at 0.6% dispersing agent concentration, PVP produced smaller particles with narrower distribution (100–300 μm) than poly(vinyl alcohol) (100–500 μm) presumably due to the fast adsorption kinetics of the former. Scaffolds fabricated from PVP-stabilized porogens had higher open porosities and high pore interconnectivity than those based on porogens prepared using PVA stabilizer. Preliminary cell culture work also showed that scaffolds fabricated using PVP-stabilized porogens support attachment and spreading of human coronary artery smooth muscle cells (HCASMC) better than the PVA counterparts. This is the first time that such direct comparative studies on the porogen preparation methods and its effect on the scaffold porosity and cell attachment property is reported. Show more

Keywords: Scaffolds, poly(vinyl pyrrolidone), particle size, porogen, porosity

DOI: 10.3233/BME-2010-0621

Citation: Bio-Medical Materials and Engineering, vol. 20, no. 2, pp. 107-118, 2010