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| 2. |
- Engstrand, Johanna, et al.
(author)
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Hydroxyapatite formation on a novel dental cement in human saliva
- 2012
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In: ISRN Dentistry. - : Hindawi Limited. - 2090-438X. ; , s. 624056-
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Journal article (peer-reviewed)abstract
- Dental materials have to meet high standards regarding mechanical strength and handling properties. There is however only a limited amount of research that has been devoted to natural formation of hydroxyapatite (HA) in contact with the materials. The objective of the current investigation was to study the surface reactions occurring in human salvia on a novel dental cement. Ceramir Crown & Bridge, a bioceramic luting agent intended for permanent cementation of conventional oral prosthetics, was evaluated by immersing discs made from the cement in human saliva and phosphate buffered saline (PBS) for seven days, after which they were dried and analyzed. The analytical methods used in order to verify HA formation on the surface were grazing incidence X-ray diffraction (GI-XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). All results showed that HA was formed on the surfaces of samples stored in saliva as well as on samples stored in PBS. The possibility of a dental luting cement to promote natural formation of HA at the tooth interface increases the stability and durability of the system and could help prevent secondary caries.
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| 3. |
- Engstrand Unosson, Johanna, et al.
(author)
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An evaluation of methods to determine the porosity of calcium phosphate cements
- 2015
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In: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 103:1, s. 62-71
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Mestres, Gemma, et al.
(author)
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Changes in the drug release pattern of fresh and set simvastatin-loaded brushite cement
- 2016
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In: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 58, s. 88-96
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Journal article (peer-reviewed)abstract
- Calcium phosphate cements are synthetic bone graft substitutes able to set at physiological conditions.They can be applied by minimally invasive surgery and can also be used as drug delivery systems.Consequently, the drug release pattern from the cement paste (fresh cement) is of high clinical interest.However, previous studies have commonly evaluated the drug release using pre-set cements only.Therefore, the aim of this work was to determine if the time elapsed from cement preparation untilimmersion in the solution (3 min for fresh cements, and 1 h and 15 h for pre-set cements) had aninfluence on its physical properties, and correlating these to the drug release profile. Simvastatin wasselected as a model drug, while brushite cement was used as drug carrier. This study quantified howthe setting of a material reduces the accessibility of the release media to the material, thus preventingdrug release. A shift in the drug release pattern was observed, from a burst-release for fresh cements toa sustained release for pre-set cements.
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| 5. |
- Persson, Cecilia, et al.
(author)
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Nano grain sized zirconia–silica glass ceramics for dental applications
- 2012
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In: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 32:16, s. 4105-4110
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Journal article (peer-reviewed)abstract
- Glass ceramics based on lithium disilicates are commonly used in dental veneers and crowns. Alternative materials with improved mechanical properties may be of interest for more demanding applications, e.g. bridgeworks. In this study, a sol-gel method was optimized to produce nano grain-sized zirconia-silica glass ceramics with properties adequate for dental applications. The material properties were compared to those of IPS e.max (R) CAD, a commercially available lithium disilicate. The zirconia-silica glass ceramic was found to be translucent, with a transmittance of over 70%, and possessed excellent corrosion resistance. It also presented a somewhat lower elastic modulus but higher hardness than the lithium disilicate, and with the proper heat treatment a higher fracture toughness was achieved for the zirconia-silica glass ceramic. In conclusion, the material produced in this study showed promising results for use in dental applications, but the production method is sensitive and large specimen sizes may be difficult to achieve.
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| 6. |
- Unosson, Johanna, et al.
(author)
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Brushite foams - the effect of Tween® 80 and Pluronic® F-127 on foam porosity and mechanical properties
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In: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - 1552-4973 .- 1552-4981.
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Journal article (other academic/artistic)abstract
- Resorbable calcium phosphate based bone void fillers should work as temporary templates for new bone formation. The incorporation of macropores with sizes of 100 -300 µm has been shown to increase the resorption rate of the implant and speed up bone ingrowth. In this work, macroporous brushite cements were fabricated through foaming of the cement paste, utilizing two different synthetic surfactants, Tween® 80 and Pluronic® F-127. The macropores formed in the Pluronic samples were both smaller and less homogeneously distributed compared with the pores formed in the Tween samples. The porosity and compressive strength were comparable to previously developed hydroxyapatite foams. The cement foam containing Tween, 0.5 M citric acid in the liquid, 1 mass% of disodium dihydrogen pyrophosphate mixed in the powder and a liquid to powder ratio of 0.43 mL/g, showed the highest porosity values (76 % total and 56 % macroporosity), while the compressive strength was higher than 1 MPa, i.e. the hardened cement could be handled without rupture of the foamed structure. The investigated brushite foams show potential for future clinical use, both as bone void fillers and as scaffolds for in vitro bone regeneration.
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| 7. |
- Unosson, Johanna, et al.
(author)
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Brushite foamsthe effect of Tween (R) 80 and Pluronic (R) F-127 on foam porosity and mechanical properties
- 2016
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In: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 104:1, s. 67-77
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Journal article (peer-reviewed)abstract
- Resorbable calcium phosphate based bone void fillers should work as temporary templates for new bone formation. The incorporation of macropores with sizes of 100 -300 mu m has been shown to increase the resorption rate of the implant and speed up bone ingrowth. In this work, macroporous brushite cements were fabricated through foaming of the cement paste, using two different synthetic surfactants, Tween (R) 80 and Pluronic (R) F-127. The macropores formed in the Pluronic samples were both smaller and less homogeneously distributed compared with the pores formed in the Tween samples. The porosity and compressive strength (CS) were comparable to previously developed hydroxyapatite foams. The cement foam containing Tween, 0.5M citric acid in the liquid, 1 mass% of disodium dihydrogen pyrophosphate mixed in the powder and a liquid to powder ratio of 0.43 mL/g, showed the highest porosity values (76% total and 56% macroporosity), while the CS was >1 MPa, that is, the hardened cement could be handled without rupture of the foamed structure. The investigated brushite foams show potential for future clinical use, both as bone void fillers and as scaffolds for in vitro bone regeneration.
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| 8. |
- Unosson, Johanna, et al.
(author)
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Development of a Resorbable Calcium Phosphate Cement with Load Bearing Capacity
- 2014
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In: Bioceramics Development and Applications. - : OMICS Publishing Group. - 2090-5017 .- 2090-5025. ; 4:1, s. 1000074-
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Journal article (peer-reviewed)abstract
- Compared to cortical bone and polymeric bone cements, the mechanical properties of calcium phosphate cements are generally poor. This has resulted in them being used in non-load bearing clinical applications. The aim of this study was to investigate the possibility of producing a brushite cement with mechanical properties closer to those of cortical bone (i.e., >100 MPa in compression), i.e. with a potential to be used in load bearing applications. With a compressive strength of 74.4 (± 10.7) MPa, maximum at 91.8 MPa, the cement presented herein is comparable with the non degradable polymeric counterparts and the strongest hydroxyapatite cements, and is close in strength of cortical bone. Furthermore, it has a high injectability (>90%) and a setting time of approximately 17 minutes. A cement comprising these properties has great potential of changing the future clinical indications for calcium phosphate cements, and could potentially reduce the use of non-degradable polymeric cements.
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| 9. |
- Unosson, Johanna, 1985-
(author)
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Physical Properties of Acidic Calcium Phosphate Cements
- 2014
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Doctoral thesis (other academic/artistic)abstract
- 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.
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