Bio-Medical Materials and Engineering - Volume 13, issue 3

Authors: Ren, Hai‐Ping | Yang, Hu | Ma, Bing‐Rong | Chen, Sheng‐Zu | Wu, Wen‐Kai

Article Type: Research Article

Abstract: Structures were obtained from images with morphological characteristics to register with voxel‐based method. We applied simple morphological operations to obtain human brain cortex and chose normalized mutual information as similarity measure for the geometric alignment of PET and MR images. Evaluation used nine patients, and the results showed that sub‐voxel accuracy was achieved and the registration process was significantly more rapid. Thus this new automated multi‐modality registration method is more robust and has high accuracy.

Keywords: Morphological tools, MR, PET, 3D registration, mutual information

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 187-196, 2003

Authors: Zhou, X. | Wang, C.X. | Zheng, C.Q. | Zeng, X.C.

Article Type: Research Article

Abstract: Thermokinetics method was used to study the self‐setting kinetics of a new kind of calcium phosphate cement (CPC) in the present study. A calcium‐deficient hydroxyapatite CPC was developed by using α‐TCP and other calcium phosphate bioceramics. The mixing liquids used were deionized water and 0.25 M NaH2 PO4 /Na2 HPO4 , respectively. The calorimetric curves, heat evolution curves and total heat evolution in the setting and hardening process of CPC were determined. It has been found that mixing liquids, reaction temperature had influences on the calorimetric curves and heat evolution, and mixing liquids exhibited the greatest influence on the kinetics …of CPC during the self‐setting and hardening process. Based on the calorimetric curves obtained, the kinetic model equation was simulated, and the reaction control step was determined. Show more

Keywords: Calcium phosphate cement, bioceramics, kinetics, thermokinetics method, hydroxyapatite

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 197-203, 2003

Authors: Zaki, M. | Aljinaidi, A. | Hamed, M.

Article Type: Research Article

Abstract: In recent years, there is an increasing utilization and demand to use magnetic fields in bioengineering applications due to its beneficial effects. Although in the last decade more attention has been given by tribologists to the electromagnetic processes taking place between sliding surfaces, which influence the tribological behaviors, but no attention has been concern with the sliding surfaces of the artificial implant joints. Therefore, the present work aims to elucidate the tribological behavior of an artificial joint implant under the effect of magnetic fields. Experimental investigation was carried out on a specially designed and constructed hip simulator on which …the variations in the coefficients of friction and wear rates of the sliding surfaces were evaluated under the influence of a medium strength magnetic field suitable to apply in the human body. A realistic Ti‐alloy implanted stem was used with an inserted head made from surgical grade stainless steel. This head was allowed to rub against UHMWPE sockets. The utilized type of prosthesis was “The JRI Modular Muller Standard‐Total Hip Design”. The performed experimental tests were conducted under both dry and lubricated sliding conditions using physiological saline solution. The designed simulator allows the coefficients of friction and the wear rates to be evaluated under realistic physiological loading and motion cycles encountered during normal walking of the human body. Comparative results are presented between the artificial joint performance in the presence and absence of the applied magnetic field. The experimental results have indicated that the presence of a medium strength magnetic field of 270 Gauss strength between rubbing surfaces resulted in high beneficial reductions in friction and wear rate of UHMWPE sliding on stainless steel either under dry or saline lubricating conditions. Therefore recommendation was forward to subject artificial implants made of stainless steel/UHMWPE combination of material to such medium strength magnetic field in animal clinical trials aiming to prolong the implant life. Scanning investigation of rubbing surfaces has revealed that the transfer of polymer to the counterface plays a dominant role in dictating the frictional and wear behaviors under dry sliding condition. Smooth molecular profile of the polymer‐transferred leads to progressive reductions in friction and wear while the lumpy polymer transfer, formed at the beginning of sliding, increases both friction coefficient and wear. Two action mechanisms dominate the sliding process; adhesive and abrasive mechanisms. The presence of saline lubricant retards the formation of the beneficial polymer transfer thus leading to faster abrasion of the polymeric counterface which explains the relatively rapid and progressive increases in friction and wear. Show more

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 205-221, 2003

Authors: Koshimune, Masaru | Takamatsu, Kiyohito | Nakatsuka, Hirotada | Inui, Kentaro | Yamano, Yoshiki | Ikada, Yoshito

Article Type: Research Article

Abstract: Enormous effort has been devoted to the generation of a synthetic guidance conduit for nerve repair instead of utilizing autograft. Several studies show neural guidance conduit is more effective when coated with Schwann cells. In this study, we synthesized bioabsorbable conduit consist of L‐lactide and ε‐caprolactone which was useful clinically and examined adhesion of Schwann cells to bioabsorbacle conduits. In vivo studies were done in which these polymer conduits coated with Schwann cells were implanted across a 12 mm gap in the rat sciatic nerve. Silicone conduits were implanted across the same gap as control. At 12 weeks, axonal regeneration …was observed in the midconduit region of these polymer conduits and was not in control. This study assesses the feasibility of a tissue engineering approach to constructing bioabsorbable conduits coated with Schwann cells. Show more

Keywords: Schwann cell, bioabsorbable film, nerve conduit, tissue engineering, regeneration

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 223-229, 2003

Authors: Todo, Shinichi | Blunn, Gordon W. | Harrison, Mark | Freeman, Michael A.R.

Article Type: Research Article

Abstract: Femoral lift‐off has been reported in total knee arthroplasty using dynamic fluoroscopic analysis. However, the effect of femoral lift‐off on ultra‐high‐molecular‐weight polyethylene (UHMWPE) is not clear. The objective of this study was to evaluate the effect of lift‐off movement on the wear of UHMWPE using a pin‐on‐disc testing machine. Using oxidised UHMWPE, delamination was observed in 70% of the discs with lift‐off movement, as against none in without lift‐off movement (p=0.0603). In non‐oxidised UHMWPE the depth of the wear track was increased in the impact area after lift‐off, but there was no delamination and no increase in wear as measured …by weight loss. UHMWPE can sustain the impact of after lift‐off with neither delamination nor wear by other mechanisms. In contrast, degraded (i.e., oxidised) UHMWPE undergoes delamination after lift‐off. Since it is probable that lift‐off cannot be prevented, oxidised UHMWPE should never be used in TKA. Show more

Keywords: Total knee arthroplasty, UHMWPE, lift‐off, delamination, wear

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 231-234, 2003

Authors: Sarma, P.A. | Pidaparti, R.M. | Moulik, P.N. | Meiss, R.A.

Article Type: Research Article

Abstract: The aim of this study is to investigate the hyperelastic material models to describe the non‐linear stress–strain behavior of tracheal smooth muscle tissue. Specifically, the goal is to validate the material model with experimental data using different finite element models and discuss the trends in stress–strain behavior of smooth muscle tissue. Both 2D and 3D finite element analyses were carried out to estimate the stress–strain behavior of the smooth muscle tissue. The results obtained indicate that the developed Ogden material model is valid and useful in explaining the stress strain behavior of tracheal smooth muscle tissue under different conditions. Finite …element simulation results of the stress–strain behavior in the transverse direction are presented. Show more

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 235-245, 2003

Authors: Hirakata, Luciana M. | Kon, Masayuki | Asaoka, Kenzo

Article Type: Research Article

Abstract: The purpose of this study was to estimate the availability of α‐tricalcium phosphate (α‐TCP) on/in hydroxyapatite (HAP) ceramics for bioactivity as bone‐substitute materials by immersion in a simulated body fluid (SBF; Hanks' solution) containing ion concentrations similar to those in human blood plasma. Two α‐TCP‐surface‐modified HAP and α‐TCP‐HAP composite materials were prepared by orthophosphoric acid treatment of sintered HAP and controlling the crystal phases of calcium phosphate cement, respectively. After immersion in SBF, the sintered HAP modified on the surface in an approximately 0.2 μm α‐TCP layer was more effective for the precipitation of carbonated apatites than an approximately 2 …μm α‐TCP layer and HAP‐only layer. In the calcium phosphate cements consisting of HAP and α‐TCP phases, after immersion for 1 week, the specimens precipitated large amounts of apatites having α‐TCP contents of approximately 25% and 50% in the cement. The results of immersion tests imply the possibility that the α‐TCP on/in HAP ceramics may be a bioactive agent for bone‐substituting HAP materials. Show more

Keywords: Hydroxyapatite ceramic, α‐tricalcium phosphate, simulated body fluid, precipitation, bioactivity

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 247-259, 2003

Authors: Ito, Michio | Nagasawa, Sakae | Yoshida, Takamitsu | Kamijo, Kuni | Khabbaz, Zahra | Oshida, Yoshiki

Article Type: Research Article

Abstract: The success of the oral rehabilitation of implant patients depends not only on the osseointegration of implant fixtures but also on maintaining the integrity of the connection of prosthetic superstructures to these fixtures. It was an objective of the present study to evaluate and compare cement bond strengths among rolled (R), cast (C) and metal‐injection‐molded (M) commercially pure titanium plates which were bonded with Panavia 21 (Kuraray) and Imperva (Shofu) cements. Two plates (15×5×1 mm) of each R, C, and M were lap‐jointed (lap length: 5 mm). The joints were stored in 37°C distilled water for 24 h, followed by …tensile tests with an INSTRON system under 1 mm/min crosshead speed. It was found that the bond strength of R with Panavia 21 (PAN) was 5.31 (SD : 1.5) MPa and 2.30 (0.83) MPa with Imperva (IMP) cement. These were improved by applying an alloy primer to 7.08 (1.31) MPa and 6.72 (1.63) MPa, respectively. Using PAN with primer application, C and M samples showed bond strengths of 7.99 (1.31) and 7.20 (2.50) MPa, while they were 5.83 (2.15) and 6.79 (2.09) MPa using IMP with primer. There was a significant difference (p<0.01) between PAN and IMP cements for C samples. Additionally, samples were pre‐oxidized at 100°C in air for 10 min. Bond strengths of PAN with the primer were 5.69 (2.25), 9.14 (1.28), and 5.60 (3.13) MPa for R, C, and M sample groups. If the cement with the primer was applied immediately after the polishing (instead of pre‐oxidized surfaces), bond strengths were improved to 9.14 (1.78) for R, 9.29 (1.85) for C, and 9.36 (1.81) MPa for M sample group. At p<0.05 level, there was a significant difference between surface pre‐condition of R and M, but no significance with C. Show more

Keywords: Luting cement, cement; titanium, cement bond strength, metal primer, pre‐oxidation effects

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 261-269, 2003

Authors: Ozeki, K. | Yuhta, T. | Aoki, H. | Fukui, Y.

Article Type: Research Article

Abstract: To alleviate the effects of Ni allergy from NiTi alloy implants, hydroxyapatite (Ca10 (PO4 )6 (OH)2 ; HA), alumina (Al2 O3 ), or titanium (Ti) was coated onto NiTi alloy plates to form 1‐μm thick films using radio frequency magnetron sputtering. The coatings on the plates were characterized using XRD. After the plates had been immersed in physiological saline for periods of one, four, or eight weeks, the concentration of Ni ions released in each solution was detected using a microwave induced plasma mass spectrometer. After eight weeks, the concentration of Ni ions released from the non‐coated, the Ti‐coated, the …HA‐coated, and the alumina‐coated plates were 238, 19.7, 183, and 106 ppb, respectively. The bonding strength of the Ti film, the HA film, and the alumina film to the NiTi substrate were 3.8±1.2, 2.6±0.7, and 3.1±1.2 MPa, respectively. The non‐coated, the HA‐coated, the alumina‐coated, and the Ti‐coated plates were implanted into the femurs of a dog for four weeks for histological observation. In case of the non‐coated plates, connective tissue more than 300 μm thick was observed, whereas for the coated plates the thickness of the connective tissue was around 100 μm. Show more

Keywords: NiTi alloy, Ni allergy, sputtering, titanium, hydroxyapatite, alumina

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 271-279, 2003

Authors: Chang, Jui‐Chung | Oshida, Yoshiki | Gregory, Richard L. | Andres, Carl J. | Barco, Thomas M. | Brown, David T.

Article Type: Research Article

Abstract: Microbiology‐related corrosion has been noted in industry for many years. It is widely recognized that microorganisms affect the corrosion of metal and alloys immersed in aqueous environments. Under similar conditions, the effect of bacteria in the oral environment on the corrosion of dental metallic materials remains unknown. The purpose of this study is to investigate the corrosion behavior of dental metallic materials in the presence of Streptococcus mutans and its growth byproducts. Samples were commercially pure titanium (CPT), Ti‐6Al‐4V (TAV), Ti‐Ni (TN), Co‐Cr‐Mo alloy (CCM), 316L stainless steel (SSL), 17Cr‐4Ni PH‐type stainless steel (PH), and Ni‐Cr alloy (NC). Using Gamry …corrosion test system, surfaces were exposed to (1) sterilized Ringer's solution as a control for (2), (2) S. mutans mixed with sterilized Ringer's solution; (3) sterilized tryptic soy broth as a control for (4), and (4) byproducts of S. mutans mixed with sterilized tryptic soy broth. Corrosion parameters (EOCP , ECORR , ICORR , etc.) were corrected for all tested samples. Averaged values of these parameters were statistically analyzed by t‐test to identify significant differences. It was concluded that (1) S. mutans reduced the EOCP of CPT, TAV, TN, and SSL, and the byproducts of S. mutans reduced the EOCP of TAV, TN, SSL, and PH. (2) S. mutans increased the ICORR of PH, and byproducts of S. mutans increased the ICORR of all the samples. (3) S. mutans reduced the ECORR of CPT, TAV and TN, and the byproducts of S. mutans reduced the ECORR of TN, SSL, PH, and NC. (4) S. mutans increased the IPASS of CPT, and the byproducts of S. mutans increased the IPASS of CPT, PH, and NC. Show more

Keywords: Bacteria corrosion, microbiology, titanium, passivation, transpassivation

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 281-295, 2003

Authors: Murdoch, A.H. | Shepherd, D.E.T. | Mathias, K.J. | Stevenson, E.C.

Article Type: Research Article

Abstract: This paper describes the design of a retractable intramedullary nail for the humerus that does not require inter‐locking screws. The developed nail has a series of fins which open out from the casing to grip the medullary canal of the bone, thus securing it in position. Prototypes of the nail have been mechanically tested using static compression, dynamic compression and static torsion tests. During the compression tests no nails were found to fail. Statically a mean force of 809 N was withstood. During dynamic testing all the nails survived 1 million cycles, with a maximum applied load of 400 N. …In torsion the two nails failed at 1.0 and 2.2 N m. Based on the mechanical testing, the retractable intramedullary nail would appear strong enough to withstand the expected loading conditions in the human body. Show more

Keywords: Design, finite element analysis, intramedullary nail, mechanical testing, torsion

Citation: Bio-Medical Materials and Engineering, vol. 13, no. 3, pp. 297-307, 2003