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The effect of composition on mechanical properties of brushite cements
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. (Materials in Medicine)
2014 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, Vol. 29, 81-90 p.Article in journal (Refereed) Published
Abstract [en]

Due to a fast setting reaction, good biological properties, and easily available starting materials, there has been extensive research within the field of brushite cements as bone replacing material. However, the fast setting of brushite cement gives them intrinsically low mechanical properties due to the poor crystal compaction during setting. To improve this, many additives such as citric acid, pyrophosphates, and glycolic acid have been added to the cement paste to retard the crystal growth. Furthermore, the incorporation of a filler material could improve the mechanical properties when used in the correct amounts. In this study, the effect of the addition of the two retardants, disodium dihydrogen pyrophosphate and citric acid, together with the addition of β-TCP filler particles, on the mechanical properties of a brushite cement was investigated. The results showed that the addition of low amounts of a filler (up to 10%) can have large effects on the mechanical properties. Furthermore, the addition of citric acid to the liquid phase makes it possible to use lower liquid-to-powder ratios (L/P), which strongly affects the strength of the cements. The maximal compressive strength (41.8 MPa) was found for a composition with a molar ratio of 45:55 between monocalcium phosphate monohydrate and beta-tricalcium phosphate, an L/P of 0.25 ml/g and a citric acid concentration of 0.5 M in the liquid phase.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 29, 81-90 p.
Keyword [en]
Brushite, Calcium phosphate cement, Compressive strength, Porosity, X-ray diffraction, Rietveld analysis
National Category
Biomaterials Science Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
URN: urn:nbn:se:uu:diva-208134DOI: 10.1016/j.jmbbm.2013.08.024ISI: 000330085700008OAI: oai:DiVA.org:uu-208134DiVA: diva2:650947
Swedish Research Council
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2015-02-03Bibliographically 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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