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Leif Hermansson - One of the best experts on this subject based on the ideXlab platform.
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wear of a bioceramic Dental Restorative Material by tooth brushing
Ceramic engineering and science proceedings, 2008Co-Authors: Anna Pallas, Harkan Engqvist, La Linden, Leif HermanssonAbstract:To study the wear from tooth brushing of a new bioceramic Dental Restorative Material, a toothbrush test has been conducted. The bioceramic is composed of calcium aluminate hydrate as binder and Dental glass as filler. The Material is intended to be used in small and medium sized posterior class I, II and V fillings. Twenty years of tooth brushing was simulated in an accelerated wear test with an exchange of the brushes every half-year. During testing, the brushes were covered with a mixture of artificial saliva and toothpaste. The volumetric wear was measured in a stereomicroscope and a profilometer was used to measure the changes in surface roughness. For comparison a glass-ionomer cement and a polymer composite were also tested. The worn surfaces were studied using scanning electron microscopy. Two different wear regimes could be detected on the samples, severe wear at the corners and mild wear at the top. The bioceramic had less severe wear than the composite and about the same as the glass-ionomer cement but the steady state wear rates were similar. The surface roughness (the mild wear) of the bioceramic was lower than that of the glass-ionomer and higher than that of the composite. The difference in surface roughness could be related to the microstructure (particle size and distribution) of the Materials.
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Flexural strength measurement of ceramic Dental Restorative Materials
Journal of Advanced Materials, 2007Co-Authors: Håkan Engqvist, Lars Kraft, Karin Lindqvist, N-o Ahnfelt, Leif HermanssonAbstract:Flexural strength of a Dental Material reflects its ability to withstand tensile stresses and as such has an impact of the fracture risk of a filling. There are several methods to measure flexural strength of a Material. The flexural strength of a bioceramic calciumaluminate-based Dental Restorative Material (DoxaDent) has been measured in three different methods with a composite (Tetric Ceram), a glass ionomer cement (Fuji 11) and a phosphate cement (Harward) as references. The three test methods were: a) ISO 4049 for Dental composites, three-point bend test of 2*2*25 mm rods, non-polished surface, b) EN 843-1 for ceramic Materials, three-point bend test of 3*4*40 mm, polished surface, and c) biaxial ball-on-disc for ceramic Materials (ASTM F-394), polished surface. The results obtained clearly show the difficulty in performing flexural strength testing of a bioceramic Material. By using the ball-on-disc method the defect size was reduced and thus the resulting flexural strength higher. The strength of DoxaDent tested in the ball-on-disc method is close to the theoretical strength based on the microstructure of the Material (maximum grain size of 15 mu m). The composite Material and the phosphate cement were rather insensitive to the test method whereas the glass ionomer cement also showed sensitivity towards the test method. Based on fracture mechanics the flexural strength of bioceramic Materials is discussed. A modified biaxial test method for evaluation of strength of Dental Materials in a close to real-life component is proposed.
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microleakage of a Dental Restorative Material based on biominerals
Advances in Bioceramics and Biocomposites: Ceramic Engineering and Science Proceedings Volume 26 Number 6, 2005Co-Authors: Håkan Engqvist, Jesper Loof, Emil Abrahamsson, Leif HermanssonAbstract:Since the introduction of the resin composites on the market marginal leakage causing secondary caries has been one of the major clinical topics. As the composites shrink during hardening they tend to develop a gap between the filling and the tooth, where bacteria can enter. This can be overcome by using bonding techniques, but bonding does not give complete success. An alternative to use shrinking composites could be the use of fully ceramic filling Material based on biominerals that harden via a acid base reaction with water. The biomineral technology based on Ca-aluminate has been proven to yield a bond to living tissue and as such the filling Material would naturally avoid marginal leakage without the use of any pre-treatment or extra bonding systems. In this paper the influence of thermo cycling on the marginal leakage of a Restorative Material based on biominerals is evaluated and compared to that of a resin composite.
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Early-age deformation, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on calcium aluminate cement
Cement and Concrete Research, 2004Co-Authors: Lars Kraft, Håkan Engqvist, Leif HermanssonAbstract:Abstract Dimensional changes during the first hour of hydration for small specimens of a Dental Material based on calcium aluminate cement (CAC) was examined. The study was conducted on specimens prepared in two different ways. First, intact tablets (three pieces per test) dipped in water were measured. Second, compacted specimens from four tablets were measured after 10 min of hydration. The dimensional changes were studied in both wet and dry conditions at 37 °C and in a dry condition at 25 °C. In the wet environment at 37 °C no dimensional change of the samples was observed. At normal room humidity (RH 55%) at both temperatures, shrinkage of 0.35–0.40% was observed. For comparison to the early-age drying shrinkage, a study of the drying shrinkage in mature Material, hydrated for 50 and 100 days, respectively, was conducted. Furthermore the thermal expansion coefficient was determined and found to be close to that of tooth substance.
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Early-age dimensional changes, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on Calcium aluminate
2004Co-Authors: Lars Kraft, Håkan Engqvist, Leif HermanssonAbstract:Early-age dimensional changes, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on Calcium aluminate
Håkan Engqvist - One of the best experts on this subject based on the ideXlab platform.
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Flexural strength measurement of ceramic Dental Restorative Materials
Journal of Advanced Materials, 2007Co-Authors: Håkan Engqvist, Lars Kraft, Karin Lindqvist, N-o Ahnfelt, Leif HermanssonAbstract:Flexural strength of a Dental Material reflects its ability to withstand tensile stresses and as such has an impact of the fracture risk of a filling. There are several methods to measure flexural strength of a Material. The flexural strength of a bioceramic calciumaluminate-based Dental Restorative Material (DoxaDent) has been measured in three different methods with a composite (Tetric Ceram), a glass ionomer cement (Fuji 11) and a phosphate cement (Harward) as references. The three test methods were: a) ISO 4049 for Dental composites, three-point bend test of 2*2*25 mm rods, non-polished surface, b) EN 843-1 for ceramic Materials, three-point bend test of 3*4*40 mm, polished surface, and c) biaxial ball-on-disc for ceramic Materials (ASTM F-394), polished surface. The results obtained clearly show the difficulty in performing flexural strength testing of a bioceramic Material. By using the ball-on-disc method the defect size was reduced and thus the resulting flexural strength higher. The strength of DoxaDent tested in the ball-on-disc method is close to the theoretical strength based on the microstructure of the Material (maximum grain size of 15 mu m). The composite Material and the phosphate cement were rather insensitive to the test method whereas the glass ionomer cement also showed sensitivity towards the test method. Based on fracture mechanics the flexural strength of bioceramic Materials is discussed. A modified biaxial test method for evaluation of strength of Dental Materials in a close to real-life component is proposed.
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microleakage of a Dental Restorative Material based on biominerals
Advances in Bioceramics and Biocomposites: Ceramic Engineering and Science Proceedings Volume 26 Number 6, 2005Co-Authors: Håkan Engqvist, Jesper Loof, Emil Abrahamsson, Leif HermanssonAbstract:Since the introduction of the resin composites on the market marginal leakage causing secondary caries has been one of the major clinical topics. As the composites shrink during hardening they tend to develop a gap between the filling and the tooth, where bacteria can enter. This can be overcome by using bonding techniques, but bonding does not give complete success. An alternative to use shrinking composites could be the use of fully ceramic filling Material based on biominerals that harden via a acid base reaction with water. The biomineral technology based on Ca-aluminate has been proven to yield a bond to living tissue and as such the filling Material would naturally avoid marginal leakage without the use of any pre-treatment or extra bonding systems. In this paper the influence of thermo cycling on the marginal leakage of a Restorative Material based on biominerals is evaluated and compared to that of a resin composite.
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Early-age deformation, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on calcium aluminate cement
Cement and Concrete Research, 2004Co-Authors: Lars Kraft, Håkan Engqvist, Leif HermanssonAbstract:Abstract Dimensional changes during the first hour of hydration for small specimens of a Dental Material based on calcium aluminate cement (CAC) was examined. The study was conducted on specimens prepared in two different ways. First, intact tablets (three pieces per test) dipped in water were measured. Second, compacted specimens from four tablets were measured after 10 min of hydration. The dimensional changes were studied in both wet and dry conditions at 37 °C and in a dry condition at 25 °C. In the wet environment at 37 °C no dimensional change of the samples was observed. At normal room humidity (RH 55%) at both temperatures, shrinkage of 0.35–0.40% was observed. For comparison to the early-age drying shrinkage, a study of the drying shrinkage in mature Material, hydrated for 50 and 100 days, respectively, was conducted. Furthermore the thermal expansion coefficient was determined and found to be close to that of tooth substance.
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Early-age dimensional changes, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on Calcium aluminate
2004Co-Authors: Lars Kraft, Håkan Engqvist, Leif HermanssonAbstract:Early-age dimensional changes, drying shrinkage and thermal dilation in a new type of Dental Restorative Material based on Calcium aluminate
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scratch testing of a Dental Restorative Material based on calcium aluminate
28 th International Cocoa Beach Conference and Exposition on Advanced Ceramics & Composites, 2004Co-Authors: Anna Pallas, Håkan Engqvist, S Jacobsson, Leif HermanssonAbstract:To study the basic abrasive wear mechanisms of a new bioceramic Dental Restorative Material scratch testing has been conducted. The Material is a chemically bonded bioceramic with calcium aluminate as binder. It is intended to be used in small and medium sized posterior class I, II and V fillings. A spherical diamond tip scratched the surface under increasing load from 0 to 50 N. The scratch hardness was measured and the wear mechanisms were classified according to the scale suggested by Powers. For comparison a glass-ionomer cement and a polymer composite were also tested. The scratched surfaces were studied with light optical microscopy and scanning electron microcopy. The bioceramic Material had a lower scratch hardness than that of the composite but higher than that of the glass-ionomer. Regarding the wear mechanisms, the bioceramic Material showed a plastic deformation up to about 15 N and above cracking and flaking began. The composite Material did not enter into a more severe wear until 35 N. The glass-ionomer cement was more unreliable and some samples broke completely already at low loads or showed extensive cracking.
Christopher N. Bowman - One of the best experts on this subject based on the ideXlab platform.
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Investigation of thiol-ene and thiol-ene–methacrylate based resins as Dental Restorative Materials
Dental Materials, 2009Co-Authors: Neil B. Cramer, Jacquelyn A. Carioscia, Charles L. Couch, Kathleen M. Schreck, Jordan E. Boulden, Jeffrey W. Stansbury, Christopher N. BowmanAbstract:Abstract Objectives The objective of this work was to evaluate thiol-norbornene and thiol-ene–methacrylate systems as the resin phase of Dental Restorative Materials and demonstrate their superior performance as compared to dimethacrylate Materials. Methods Polymerization kinetics and overall functional group conversions were determined by Fourier transform infrared spectroscopy (FTIR). Flexural strength and modulus were determined with a 3-point flexural test. Polymerization-induced shrinkage stress was measured with a tensometer. Results Thiol-ene polymer systems were demonstrated to exhibit advantageous properties for Dental Restorative Materials in regards to rapid curing kinetics, high conversion, and low shrinkage and stress. However, both the thiol-norbornene and thiol-allyl ether systems studied here exhibit significant reductions in flexural strength and modulus relative to BisGMA/TEGDMA. By utilizing the thiol-ene component as the reactive diluent in dimethacrylate systems, high flexural modulus and strength are achieved while dramatically reducing the polymerization shrinkage stress. The methacrylate–thiol-allyl ether and methacrylate–thiol-norbornene systems both exhibited equivalent flexural modulus (2.1 ± 0.1 GPa) and slightly reduced flexural strength (95 ± 1 and 101 ± 3 MPa, respectively) relative to BisGMA/TEGDMA (flexural modulus; 2.2 + 0.1 GPa and flexural strength; 112 ± 3 MPa). Both the methacrylate–thiol-allyl ether and methacrylate–thiol-norbornene systems exhibited dramatic reductions in shrinkage stress (1.1 ± 0.1 and 1.1 ± 0.2 MPa, respectively) relative to BisGMA/TEGDMA (2.6 ± 0.2 MPa). Significance The improved polymerization kinetics and overall functional group conversion, coupled with reductions in shrinkage stress while maintaining equivalent flexural modulus, result in a superior overall Dental Restorative Material as compared to traditional bulk dimethacrylate resins.
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Thiol-ene oligomers as Dental Restorative Materials.
Dental materials : official publication of the Academy of Dental Materials, 2005Co-Authors: Jacquelyn A. Carioscia, Jeffrey W. Stanbury, Christopher N. BowmanAbstract:Summary Objective The aim of this work was to prereact thiol-ene monomers to create reactive thiol or vinyl (ene)-functionalized oligomers, and to investigate the use of these Materials as novel Dental Restorative Material. Investigation has focused on the application of oligomeric thiol-ene Materials as Dental Restorative resins with lower polymerization shrinkage and polymerization stress as compared to monomeric thiol-ene systems and particularly with respect to current dimethacrylate-based systems. Methods Reactive thiol-functionalized oligomers were created via photopolymerization using triallyl-1,3,5-triazine-2,4,6-trione (TATATO), trimethylolpropane tris(3-mercaptopropionate) (trithiol) and pentaerythritol tetramercaptopropionate (tetrathiol). Kinetic and mechanical investigation of Bis-GMA/TEGDMA, and oligomeric and monomeric thiol-ene systems were conducted. More specifically, polymerization shrinkage and stress, polymerization kinetics, glass transition temperature, flexural strength and flexural modulus were evaluated. Results Upon evaluation, the polymerization stress of oligomeric thiol-ene systems was dramatically reduced by as much as 33% when compared with the stress exhibited by monomeric thiol-ene systems and as much as a 92% reduction in stress relative to the current dimethacrylate-based Dental Restorative Materials. Furthermore, the flexural strength and modulus of the monomeric and oligomeric thiol-ene resins were not significantly different. Significance Oligomeric thiol-ene systems offer potential as alternative Dental Restorative resins due to the significant reduction in polymerization shrinkage and stress while retaining the mechanical properties of monomer-based thiol-ene resins.
Marju Vakiparta - One of the best experts on this subject based on the ideXlab platform.
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release of silica calcium phosphorus and fluoride from glass ionomer cement containing bioactive glass
Journal of Biomaterials Applications, 2004Co-Authors: Helena Yliurpo, Timo Narhi, Pekka K. Vallittu, Aripekka Forsback, Marju VakipartaAbstract:The aim of this study was to examine the release of silica (Si), calcium (Ca), phosphorous (P), and fluoride (F) from conventional glass ionomer cement (GI) and resin-modified glass ionomer cement (LCGI), containing different quantities of bioactive glass (BAG). Further aim was to evaluate in vitro biomineralization of dentine. The release of Si increased with the increasing immersion time from the specimens containing BAG, whereas the amount of Ca and P decreased indicating in vitro bioactivity of the Materials. LCGI with 30wt% of BAG showed highest bioactivity. It also showed CaP-like precipitation on both the surface of the test specimens and on the dentin discs immersed with the Material. Within the limitations of this study, it can be concluded that a Dental Restorative Material consisting of glass ionomer cements and BAG is bioactive and initiates biomineralization on dentin surface in vitro.
Alessandra Nara De Souza Rastelli - One of the best experts on this subject based on the ideXlab platform.
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titanium dioxide and modified titanium dioxide by silver nanoparticles as an anti biofilm filler content for composite resins
Dental Materials, 2019Co-Authors: Hercules Bezerra Dias, Maria Ines Basso Bernardi, Tais Maria Bauab, A C Hernandes, Alessandra Nara De Souza RastelliAbstract:Abstract Objective The aim of this study was to evaluate the antibacterial activity of a composite resin modified by TiO 2 and TiO 2 /Ag nanoparticles and their influence over different properties. Methods TiO 2 and TiO 2 /Ag NPs were synthesized by polymeric precursor and microwave-assisted hydrothermal methods and then, characterized by different techniques. Direct contact test was performed using Filtek™ Z350XT blended with 0.5; 1 and 2% (wt.) of NPs against Streptococcus mutans to determine the best concentration to the other tests. After that, the modified composite resin was tested against S. mutans 7-day biofilm (CFU/mL). Also, compressive and diametral tensile strength (n = 40), degree of conversion (n = 25) and surface roughness (n = 50) was performed. The data were analyzed by ANOVA and Tukey’s test for multiple comparison at 5% significance level. Results The direct contact test demonstrates that by increasing the nanoparticle content, the bacterial growth is significantly reduceed (p 2 /Ag NPs significantly decreased (p S. mutans on the composite resin surface compared to the control Group. The TiO 2 NPs treated with an organosilane increased compressive strength of composite resin (p 0.05) and the surface roughness increased with the NPs (p 2 by polymeric precursor Group (p > 0.05). Significance The development of an antibacterial Dental Restorative Material that hinder S. mutans biofilm without sacrificing the mechanical and physical properties is desirable in Dental Material science.