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Influence of water content on hardening and handling of a premixed calcium phosphate cement
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)
2013 (English)In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 33, no 1, 527-531 p.Article in journal (Refereed) Published
Abstract [en]

Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring tosyringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15)N to 39 (±9)N, the compression strength was almost doubled, and the setting time decreased from 29 (±4)min to 19 (±2)min, while the working time remained 5 to 6 h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

Place, publisher, year, edition, pages
2013. Vol. 33, no 1, 527-531 p.
Keyword [en]
monetite, brushite, injectability, handling, bone void filler
National Category
Ceramics Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-168648DOI: 10.1016/j.msec.2012.09.026ISI: 000313155500072OAI: oai:DiVA.org:uu-168648DiVA: diva2:501739
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme
Available from: 2012-02-14 Created: 2012-02-14 Last updated: 2017-12-07
In thesis
1. Premixed Acidic Calcium Phosphate Cements
Open this publication in new window or tab >>Premixed Acidic Calcium Phosphate Cements
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Calcium phosphate cements are used in medicine to fill bone defects or give support to screws and plates in fracture fixation. The cements are formed via mixing a powder with water and the mixture harden through a dissolution-precipitation reaction. Today the cement mixing is performed in the operating room and consists of several complicated steps that need to be performed under sterile conditions. This renders the mixing a risk factor, potentially leading to harm for the patient e.g. unsatisfactory healing or infection. To reduce this risk, premixed cements have been developed using glycerol as mixing liquid. The premixed cement sets when it is exposed to body liquids. Therefore, premixed cement can be delivered to the operating room in prefilled syringes ready for use, thus eliminating the mixing step.

The aim of this thesis is to describe differences between premixed and water-mixed cements and their advantages and drawbacks. The differences will be discussed based on results obtained from bench testing of specific cement properties as function of cement formulations as well as in vitro and in vivo studies.

Several cement formulations were evaluated e.g. the influence of powder to liquid ratio (P/L), powder particle size and addition of water on key properties. The results showed that premixed cements have excellent handling properties and have mechanical properties similar to water-based cements. Both P/L and particle size can be used to control these properties. It was shown that small amounts of water improve certain cement properties while dry raw materials were important for long shelf life. To better understand the setting of premixed cements new methods for evaluating working time and setting of premixed cements were developed. In vivo studies showed that the formulations developed in this thesis are biocompatible, resorbable and show good tissue response in bone.

This thesis concludes, that the premixed cements are a promising biomaterial with excellent handling properties and good biological response. The most important challenge for the premixed cements, in order to become commercially successful, is to obtain clinically relevant setting time and shelf life simultaneously. An increasing use of premixed cements in the clinics should shorten operation times and reduce infection rates to the benefit of both patients and medical staff.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 904
Keyword
monetite, brushite, bone void filler, injecatilbity, in vivo, in vitro
National Category
Biomaterials Science Ceramics
Identifiers
urn:nbn:se:uu:diva-168650 (URN)978-91-554-8285-5 (ISBN)
Public defence
2012-03-29, Å2001, Ångstrsömslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-03-08 Created: 2012-02-14 Last updated: 2013-04-08Bibliographically approved
2. 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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Engstrand, JohannaÅberg, JonasEngqvist, Håkan

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