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An evaluation of methods to determine the porosity of calcium phosphate 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.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
2015 (English)In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 103, no 1, 62-71 p.Article in journal (Refereed) Published
Abstract [en]

The porosity of a material can be determined using a diversity of methods; however, the results from these methods have so far not been compared and analyzed for calcium phosphate cements (CPCs). The aim of this study was to compare a fast and easy method for porosity measurements with some commonly used porosity methods for CPCs. The investigated method is based on the assumption that when a wet cement sample is dried, the volume of the evaporated water is equal to the volume of pores within the cement. Moreover, different methods of drying the cements were evaluated for acidic CPCs. The results showed that drying at room temperature (22°C ±1°C) is preferable, since a phase transformation was observed at higher temperatures. The results also showed that drying for 24 hours in vacuum was sufficient to achieve water free cements. The porosity measured was found to vary between the porosity methods evaluated herein, and to get a complete picture of a cement’s porosity more than one method is recommended. Water evaporation, is, however, a fast and easy method to estimate the porosity of CPCs and could simplify porosity measurements in the future.

Place, publisher, year, edition, pages
2015. Vol. 103, no 1, 62-71 p.
Keyword [en]
porosity, calcium phosphate, ceramic
National Category
Ceramics Medical Materials
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-233543DOI: 10.1002/jbm.b.33173ISI: 000346191600008OAI: oai:DiVA.org:uu-233543DiVA: diva2:753153
Funder
EU, FP7, Seventh Framework ProgrammeSwedish Research Council
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1195
National Category
Biomaterials Science Ceramics Medical Materials
Identifiers
urn:nbn:se:uu:diva-233637 (URN)978-91-554-9081-2 (ISBN)
Public defence
2014-12-05, Polhemsalen, Ångströmlaboratoriet, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
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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Publisher's full texthttp://onlinelibrary.wiley.com/doi/10.1002/jbm.b.33173/abstract;jsessionid=CE7FB4083411C4E093D41AB78161D6DF.f03t04

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Engstrand Unosson, JohannaPersson, CeciliaEngqvist, Håkan

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