Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New research into materials for tooth fillings

10.03.2015

Tooth decay is a serious health problem and it is often necessary to repair cavities. Today they often use a composite filling material made of acrylate compounds, as it resembles the colour of the teeth and is reasonably strong so it can handle the rigors of the powerful chewing movements. But composite filling materials have some disadvantages and now researchers are working on an interdisciplinary collaboration between physicists and dentists to develop a material comprised of glass ionomer cement. The results are published in the scientific journal, Scientific Reports.

Amalgam, also called silver amalgam filling, is a reasonably strong material, but the disadvantage of silver amalgam is that they contain mercury, which can poison the environment. So they have mostly moved away from silver amalgam.


On the left are X-rays of teeth with fillings of glass ionomer cement. The images show how porous the cement is. On the right are images of the same teeth using neutron scattering. Here you can see if the pores are filled with liquid.

(Credit: Benetti, A.R.et al., DOI:10.1038/srep08972 (2015)

Today, composites are usually used, but one of the drawbacks of many composites is that the fillings need to be replaced more frequently in patients that have a tendency to get many cavities. Another drawback is that composite materials require the use of an adhesive to bond the filling to the tooth and this makes the filling process more vulnerable. An interdisciplinary team of researchers decided therefore to develop a new alternative mercury-free material. The choice fell on glass ionomer cement.

"Glass ionomer cement has the advantage that it does not need an intermediate layer of adhesive to bond to the tooth and it also has the interesting property in that it releases fluoride, which of course help to prevent cavities (caries).

The material also has good biological properties, while it is almost as strong. Our research therefore focuses on understanding the connection between the microstructure of the material and its strength in order to improve its properties," explains Ana Benetti, dentist and researcher at the Odontological Institute at the University of Copenhagen.

Glass ionomer cement also has the property that when pulverised, it can be mixed with a liquid by hand without the use of special equipment and the material does not need to be illuminated with a lamp to harden (this is necessary for composite materials). This is a great advantage in remote areas without electricity like in Africa, China or South America.

Different mixing methods

The researchers studied two kinds of glass ionomer cement. The cement itself is the same, but a mix of acids was blended into one them. They used two different kinds of liquids to mix the cement powder up, either ordinary water or water mixed with an acidic mixture. The question now was whether it was best to mix the acid up with the cement powder or with the water?

They now carried out a series of experiments where they not only studied the cement, but also studied them as fillings inserted into teeth, i.e. teeth that had been pulled out and were no longer sitting in anyone's mouth.

"First, we took X-rays of the teeth with the cement fillings. They show the structure of the material. Glass ionomer cement is porous and you can get an accurate image in 3D, which shows the microstructure," explains Heloisa Bordallo, associate professor and materials researcher at the Niels Bohr Institute at the University of Copenhagen.

Heloisa Bordallo explains that it is ok for the material to be porous, but it is not ok for there to be liquid in the pores as it can make it easier for the fillings to break. So the next thing they did was take pictures with neutron scattering. Neutrons are good at showing where there are hydrogen atoms, which are found in all liquids.

Studies complement each other

Both the X-ray and neutron experiments were carried out at the Helmholtz-Zentrum facilities in Berlin in collaboration with Markus Strobl, a materials researcher at the European Spallation Source, ESS and affiliated professor at the Niels Bohr Institute at the University of Copenhagen.

By comparing the X-rays with the neutron images, they could now see whether the pores were dry or filled with liquid. It is not just the number of pores that determine the strength of a material. The strength or weakness lies in how the liquid moves around or attaches to the material itself. So the researchers repeated the experiments at research facilities in England and France over the course of many days in order to follow the chemical reactions that took place during the hardening.

"Experiments showed that the combination where the acid is mixed up in the cement, so you only have to add water to the cement powder is the weakest material. You get the strongest material by having cement powder mixed with water that has had acid added to it. So it is better to have the acid in the water - it helps to bind the liquid faster and stronger to the cement and there is less water in the pores," explains Heloisa Bordallo.

There is still too much loose liquid in the pores, so now the research is continuing with new mixtures where they will try adding natural minerals to the cement.

###

Article: http://nature.com/articles/doi:10.1038/srep08972

Contact:

Heloisa Bordallo, associate professor and materials researcher at the Niels Bohr Institute at the University of Copenhagen, +45 2130-8829, bordallo@nbi.ku.dk

Ana Benetti, dentist and researcher at the Faculty of Health and Medical Sciences at the University of Copenhagen, +45 3532-6860, arbe@sund.ku.dk

Markus Strobl, materials researcher and affiliated professor at the Niels Bohr Institute at the University of Copenhagen, +46 46 888-3068, markus.strobl@esss.se

Media Contact

Gertie Skaarup
skaarup@nbi.dk
45-28-75-06-20

http://www.nbi.ku.dk/english/press_and_media/

Gertie Skaarup | EurekAlert!

Further reports about: X-rays acid composite materials glass liquids materials pores porous powder teeth

More articles from Materials Sciences:

nachricht Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University

nachricht 3D-Printing: Support structures to prevent vibrations in post-processing of thin-walled parts
12.07.2018 | Fraunhofer-Institut für Produktionstechnologie IPT

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>