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Porosity prediction of calcium phosphate cements based on chemical composition
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Technical University of Catalonia, Spain.
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2015 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 26, no 7, 210Article in journal (Refereed) Published
Abstract [en]

The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% beta-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37 degrees C and 100 % relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 degrees C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (<2.0 %). In conclusion, a theoretical model for porosity prediction was developed and validated for brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

Place, publisher, year, edition, pages
2015. Vol. 26, no 7, 210
National Category
Ceramics Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
URN: urn:nbn:se:uu:diva-233632DOI: 10.1007/s10856-015-5497-0ISI: 000358671200009OAI: diva2:753216
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), GA IG2011-2047EU, FP7, Seventh Framework Programme, GA 262948Swedish Research Council, 621-2011-6258Swedish Research Council, 2011-3399
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2016-07-14Bibliographically approved
In thesis
1. Physical Properties of Acidic Calcium Phosphate Cements
Open this publication in new window or tab >>Physical Properties of Acidic Calcium Phosphate Cements
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example, cement with increased strength could be used as load bearing support in selected applications. The focus of this thesis is, therefore, on how the physical properties of acidic calcium phosphate cements (brushite cements) are affected by compositional variations, with the ultimate aim of making it possible to formulate brushite cements with desired properties.

In this thesis a method to measure the porosity of a cement was developed. This method is advantageous over existing methods as it is easy to use, requiring no advanced equipment. A model estimating the porosity of the hardened cement from the initial chemical composition was further formulated and the accuracy affirmed. Utilization of this model allows the porosity to be optimized by calculations rather than extensive laboratory work. The effect on strength and porosity of several compositional variations were also assessed and it was found that the optimal composition to achieve a high strength was: monocalcium phosphate particles in sizes <75µm, 10 mol% excess of beta-tricalcium phosphate, 1 wt% disodium dihydrogen pyrophosphate, and 0.5 M citric acid in a liquid-to-powder ratio of 0.22 ml/g. This composition gave the highest compressive strength historically measured for this type of cement, i.e., 74.4 (±10.7) MPa. Although such a high strength may not be necessary for all applications, it allows for the use of brushite cements in new applications. Furthermore, a high strength of the bulk allows for alterations to the cement that cause a decrease in strength. One application is fast degrading materials, allowing rapid bone ingrowth. A fast degradation is obtained with a high macroporosity, which would reduce strength. The high strength composition was therefore utilized to achieve brushite cement with a high macroporosity.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 73 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1195
National Category
Biomaterials Science Ceramics Medical Materials
urn:nbn:se:uu:diva-233637 (URN)978-91-554-9081-2 (ISBN)
Public defence
2014-12-05, Polhemsalen, Ångströmlaboratoriet, Uppsala, 09:15 (English)
EU, FP7, Seventh Framework ProgrammeSwedish Research Council
Available from: 2014-11-14 Created: 2014-10-07 Last updated: 2015-02-03

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