In pursuit of the perfect fit
Germany: Researchers from the Fraunhofer Institute for Mechanics of Materials (IWM) in Freiburg have discovered a way to simulate the tension created by shrinkage after curing of filling material in dental restorations. Research assistant, Dr Christof Koplin explains: “Until now, it has not been possible to establish a theoretical model of the hardening process. The tension occurring in the material always depends on the shape of the cavity, and can vary widely by a factor of up to ten, particularly at the edges.”
According to Dr Koplin, the two main challenges of the study were to find a combined model that integrates all the important influences (11 model parameter had to be estimated) and to find an experimental methodology that can be used to characterize a process that is completed in three minutes and the related material changes from a paste-like sticky behaviour to a stiff form and consistency. “Our solution is based on the experiences of many and the detailed documentation by individuals in dental research, polymer science, material science and numerical methodology,” he explains.
With this method, dentists can now draw on the results of the IWM to select the best material which will create the least amount of tension for each cavity shape. At the same time, manufacturers can use the simulations to optimize their products. Koplin feels this methodology will be of great benefit to dentists. “When doing a restoration a dentist has to tailor his process to each individual patient and select his tools from an arsenal of different materials and devices. Dentists may have experience with several materials but there are always more to choose from. Anything that will help them select the right material in the shortest amount of time is a valuable asset to any practice,” he says.
In the near future, Koplin and his team will test various filling materials that are commercially available. It is hoped that manufacturers will publish their results of this unbiased method as an aid to dentists. “The results between filling materials are sometimes surprisingly similar but differences occur in the maximal internal stress with a factor >2 for state-of-the-art composites,” he says.
Moving forward, the team aims to further explore the underlying and distributed stress in fillings as a starting point to understand degradation and how it can be deal with. “The great field of adhesive research is based on the challenge of adhesive strength overcoming internal and loading stresses despite of chemical and biological attack,” he concludes.
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USA: The methods used to assess the outcomes of remineralization of dentin were critically evaluated by Professor Grayson Marshall, President-elect of the American Association for Dental Research. Currently, the most used assessment methods fall either into quantitative analysis of the mineral content of the remineralized structures or dry measurements of their mechanical properties.
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Germany: Researchers from the Fraunhofer Institute for Mechanics of Materials (IWM) in Freiburg have discovered a way to simulate the tension created by shrinkage after curing of filling material in dental restorations. Research assistant, Dr Christof Koplin explains: “Until now, it has not been possible to establish a theoretical model of the hardening process. The tension occurring in the material always depends on the shape of the cavity, and can vary widely by a factor of up to ten, particularly at the edges.”
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Following the success of the Minimum Intervention Symposium at the 2007 FDI Congress in Dubai, GC’s most recent session took the concept to a new level in the general dental practice. Hosted in Stockholm, Sweden, at the FDI’s 2008 Congress, the symposium aimed to equip practitioners with a clear strategy for implementing the MI approach in daily routines.
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Dr Elmar Reich serves on the FDI Education Committee, has a dental practice in Biberach, Germany, and is the scientific coordinator of the GC MI Advisory Board. He opened his dental practice in 2004 with a clear goal of practising according to the Minimum Intervention philosophy. We asked him a few questions about how he achieves this goal.
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CAM (computer-aided manufacturing) and CAD (computer-aided design)/CAM systems facilitate the use of zirconia substructure materials for all-ceramic fixed partial dentures. An in vitro study, led by Dr Florian Beuer from the Department of Prosthodontics at Ludwig-Maximillians University in Munich, Germany, compared the precision of fit of frameworks milled from semi-sintered zirconia blocks that were designed and machined with two CAD/CAM and one CAM system. Results showed that CAD/CAM systems were more precise than the CAM system. Dr Beuer told Dental Learning Hub more about the study.
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Trauma to anterior teeth in children could become a long-term problem to dental health. To a large extent, the management actions of the dentists involved determine the clinical outcome and these actions are related to their levels of knowledge. A recent study investigated dentists' management of traumatic injuries to maxillary permanent incisors in children in Victoria, Austalia. Overall, the respondents to the survey demonstrated only a moderate level of knowledge. Dr Thai Yeng explained the significance of the research and how the knowledge gap can be addressed.
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Research conducted at Universidade Federal de Pernambuco in Recife, Brazil analysed the images sites of fracture initiation and slow crack propagation in a fiber reinforced composite using optical coherence tomography (OCT). Drs Ana Braz and Anderson Gomes from the university’s Graduate Programme in Odontology, concluded that OCT images provide a superior insight into crack propagation, which cannot be seen by the naked eye. By using OCT the possibility of analyzing fracture propagation both thoroughly and quantitatively opens up possibilities for further quantitative studies. They told Dental Learning Hub about the study.
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