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  • 1
    Electronic Resource
    Electronic Resource
    Flexural and fatigue properties of a bone cement based upon polyethylmethacrylate and hydroxyapatite (1995)
    Springer
    Journal of materials science 6 (1995), S. 799-803 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Polymethylmethacrylate (PMMA) bone cement is commonly used in surgery to fix joint replacements into the bone. Although the operations are generally successful, loosening of the prosthesis does occur with fracture of the bone cement treated as the source of failure in some instances. Polyethylmethacrylate (PEMA) bone cement offers a promising alternative to PMMA due to its high ductility, low toxicity and low exotherm. In addition, hydroxyapatite (HA) particles can be added, while retaining the ductile properties of the material. In this study, the flexural and fatigue properties of this experimental cement, with and without HA reinforcement, have been examined. It was found that up to 40wt.% HA could be added with increases in both flexural strength and modulus. Specimens were subjected to tensiontension cyclic loading at a number of stress levels until catastrophic failure occurred. In comparison with a commercial PMMA cement, tested at relatively high stresses, the PEMA cement failed at lower cycles to failure. However, the data converged at the lower stresses employed which are closer to the physiological loading situation. With the addition of HA, although the cycles to failure were decreased, the deformation experienced by the PEMA-HA cement whilst being cycled was reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134320
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of sterilization upon a range of properties of experimental bone cements (1997)
    Springer
    Journal of materials science 8 (1997), S. 849-853 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Bone cement, used to fix prostheses into the bone, must be sterilized prior to implantation. Two sterilization techniques, γ and β radiation, were investigated, examining the influence upon molecular weight, static and dynamic mechanical characteristics and rheological properties. A number of experimental cements were studied prepared from methylmethacrylate (MMA) co-polymers, either single powders or powder blends, mixed with MMA monomer. It was found that with both γ and β radiation, there was a decrease in molecular weight of all powders, including a MMA/styrene co-polymer, in relation to the radiation dose. This fall in molecular weight resulted in a drop in tensile strength, Young’s modulus and strain to failure of all cements tested. However, the deterioration in mechanical strength was highlighted by the dynamic testing. Fatigue lives of cements after testing in tension–tension, at 2 Hz under load control and irradiated with 25 kGy γ radiation, displayed significant decreases. This result indicated the utmost importance of conducting such tests upon experimental bone cements prior to in vivo use. The rheological time profiles of curing cements were also found to be influenced by 25 kGy γ radiation, with a reduction of complex viscosity after sterilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018545519964
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanical properties of hydroxyapatite reinforced poly(ethylmethacrylate) bone cement after immersion in a physiological solution: influence of a silane coupling agent (2000)
    Springer
    Journal of materials science 11 (2000), S. 491-497 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract PEMA–based bone cement has previously been shown to possess many advantages over traditional PMMA cements. One of these is the option of adding up to 40 wt % HA without a decrease in static mechanical strength, thus providing the potential for enhanced bioactivity. Bone cement, in vivo, is subjected to an aqueous environment and therefore, it is important to understand the influence of this upon the mechanical integrity of experimental cements. In this current investigation the static and dynamic properties of PEMA cement, with and without 30 wt % untreated and silanated HA, were examined after periods of immersion in Ringer’s solution. A commercial PMMA cement was also tested in a similar manner. Relatively small changes in static mechanical properties were observed after 12 weeks storage for the PEMA cements, the largest change being for the PEMA cement reinforced with silanated HA. The PMMA cement exhibited the largest change in static strength with a decrease of 16.6%. In contrast to these results, the fatigue properties of the PEMA cements were found to decrease significantly after storage in Ringer’s solution, again with the largest changes to the PEMA cement reinforced with silanated HA. This effect was attributed to the reduction in efficiency of the silane coupling agent in the presence of water. The fatigue resistance of the PMMA cement was not reduced after immersion in a saline environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013057724268
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Isothermal and non-isothermal polymerization of a new bone cement (1998)
    Springer
    Journal of materials science 9 (1998), S. 317-324 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A new bone cement based on poly(ethylmethacrylate) (PEMA), hydroxyapatite powder (HA) and n-butylmethacrylate monomer (n-BMA) has been studied using isothermal and non-isothermal polymerization. Methacrylate monomers are highly reactive and release a considerable amount of heat during polymerization. A quantitative understanding of the methacrylate polymerization is necessary because the thermal history of the polymerization has considerable influence on the final properties of a bone cement. In the first part, polymerization kinetics are analysed by means of differential scanning calorimetry (DSC). DSC data are used to evaluate a phenomenological model describing the cure kinetics of this new bone cement. In the second part, a kinetic model coupled with the energy balance is used to obtain temperature and degree of conversion profiles in the bone–cement–prosthesis system, under non-isothermal conditions, as function of initial temperature and thickness of the cement. Material properties, boundary and initial conditions and the kinetic behaviour are the input data for the numerically solved heat-transfer model. The temperature at the bone/cement interface, can be considered as a weak point, often responsible for total joint replacement failure. For this particular bone cement exhibiting a low exotherm and low glass transition temperature, the interfacial temperature is lower than the threshold level for thermal tissue damage (50 °C). The conversion occurs almost completely, avoiding problems with unreacted monomers that can be released by the cement, giving rise to tissue damage. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008898712929
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison between the polymerization behavior of a new bone cement and a commercial one: modeling and in vitro analysis (1998)
    Springer
    Journal of materials science 9 (1998), S. 835-838 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The polymerization behavior of a new bone cement based on poly(ethylmethacrylate), hydroxyapatite powder and n-butylmethacrylate monomer and a commercial cement have been studied. Polymerization kinetics were analyzed by means of differential scanning calorimetry (DSC). DSC data have been used to evaluate a phenomenological model describing the cure kinetics of this new bone cement. The kinetic model coupled with the energy balance was then used to obtain temperature and degree of conversion profiles in the bone–cement–prosthesis system, under non-isothermal conditions, as function of initial temperature and thickness of the cement. Material properties, boundary and initial conditions and the kinetic behavior were the input data for the numerically solved heat-transfer model. The modeling results have been compared with in vitro results. © 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008996112042
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    In vitro evaluation of a new polymethylmethacrylate cement reinforced with hydroxyapatite (1999)
    Springer
    Journal of materials science 10 (1999), S. 793-796 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The nature of the orthopedic implant surface affects the interaction between cells and subsequent bone formation. The bone/cement interface in cement-held prostheses is considered to be the main cause of fracture leading to implant revision. It is thought that the introduction of a bioactive phase, such as hydroxyapatite (HA), to cement may permit a stronger implant by encouraging direct bone apposition rather than encapsulation of the implant by fibrous tissue. Thus, a poly(methylmethacrylate) (PMMA) cement incorporating 17.5% HA by weight has been investigated. In this study, in order to analyze the interaction at the cellular level, the in vitro biological response of the HA/PMMA to a similar PMMA without HA incorporation has been studied. Primary human osteoblast-like cells (HOB) were used as they are a model of the cell type the cements might encounter in vivo. Cell proliferation and growth were assessed by measurement of total cellular DNA and tritiated thymidine ([3H]-TdR) incorporation. Alkaline phosphatase (ALP) production was measured as an indicator of HOB phenotype upon the cements. The results showed that HA/PMMA was a better substrate for HOB cells, resulting in increased proliferation and ALP activity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that HOB cells cultured on the HA-filled PMMA preferentially anchored to HA particles exposed at the cement surface, with a close intimacy observed between HA and HOB cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008907218330
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    Paper (German National Licenses)
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