Tooth cavities are usually closed with plastic fillings. However, the initially soft plastic shrinks as it hardens. The tension can cause gaps to appear between the tooth and the filling, encouraging more caries to form. For the first time, researchers have simulated this process.
The patient's hands are clasped firmly around the armrests as the dentist drills away the caries-stricken sections of the tooth. Once the drilling is over, most toothache sufferers can begin to relax. All the doctor now has to do is to slightly etch the cavity, apply an adhesive film, and fill it with a special type of plastic.
The plastic is soft at first, so that the doctor can easily press it into the cavity. It only solidifies afterwards under the light of a small lamp. However, the material tends to shrink slightly as it hardens, occasionally producing tension that can cause tiny gaps to form between the plastic filling and the tooth. Bits of food can get caught in these gaps and lead to more caries. Manufacturers of filling materials therefore offer a variety of plastics to choose from. But which filling is best suited to which shape of cavity? This is where dentists have to draw on their experience.
"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," says Dr.-Ing. Christof Koplin, research assistant at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg. Measurements do not help either, as tension can only be measured selectively. Its precise course of development has never yet been observed.
A new method of simulation now enables tension in dental fillings to be accurately predicted, helping doctors to choose the least tension-prone plastic for each shape of cavity. Dentists can now draw on the results of the IWM to select the best material, and manufacturers can use the simulations to optimize their products.
"We theoretically subdivide the dental filling into thousands of small parcels and calculate how each element affects its neighbor. Experimental parameters are incorporated in the individual elements. We started our laboratory tests by using a standard geometry to find out how each material reacts to the stresses that occur when the volume shrinks, and how the flow capability of the material changes as it hardens," explains Koplin. The IWM researchers have now successfully simulated the development of tension in dental fillings for various cavity shapes and materials, and more will follow.
Source: Fraunhofer-Gesellschaft
Related stories:
Plastic surgeons warn of malnutrition in body contouring patients
Identifying malnutrition before surgery in massive weight loss patients seeking body contouring will significantly decrease surgical complications, accelerate wound healing, improve scar quality and boost patient energy levels, according to a study in the December issue of Plastic and Reconstructive Surgery, the official medical journal of the American Society of Plastic Surgeons (ASPS). Optimizing nutrition with the addition of supplements, such as powder drinks and multi-vitamin tablets formulated for massive weight loss patients, is vital to successful body contouring surgery, the study reveals.
Physicists Explain Why Liquid Optical Fibers Don't Collapse
(PhysOrg.com) -- For several years, physicists have known that liquid columns can be used to guide light. By trapping a light beam, a liquid column can act like an optical fiber, but with a liquid sheathing instead of glass or plastic.
Terahertz laser source at room temperature
“There is a growing interest in utilizing terahertz radiation, or T-rays, for a variety of applications,” Mikhail Belkin, a scientist at Harvard University, tells
PhysOrg.com. “The terahertz region is a part of the electromagnetic spectrum that lies between the radio waves and infrared/visible light.”
Saltwater sleuths: Seeking clues to help determine the ages of fish and shellfish populations
Fishery biologist Sandy Sutherland looks through the lens of the microscope at tiny sections of fish earbones, known as otoliths, each showing annual bands of growth. She carefully counts the bands to determine the age of the fish, then moves on to the next sample. Known as an age reader, Sutherland is one of a small team at NOAA’s Northeast Fisheries Science Center (NEFSC) whose aging work is critical to stock assessments needed to manage the nation’s fishery resources in the Northwest Atlantic Ocean.
Carbon nanotubes that look like asbestos, behave like asbestos
A major study published today in
Nature Nanotechnology suggests some forms of carbon nanotubes – a poster child for the “nanotechnology revolution” – could be as harmful as asbestos if inhaled in sufficient quantities.
Study finds technique for nasal obstruction helps patients breathe easier
Z-plasty, a minimally invasive surgical technique to treat internal nasal valve collapse, showed significant improvement in relieving nasal obstruction with less recovery time compared to more traditional open rhinoplasty, according to a research study by Rush University Medical Center. The study findings are published in the May 21 issue of the
Archives of Facial Plastic Surgery.
Melting defects could lead to smaller, more powerful microchips
As microchips shrink, even tiny defects in the lines, dots and other shapes etched on them become major barriers to performance. Princeton engineers have now found a way to literally melt away such defects, using a process that could dramatically improve chip quality without increasing fabrication cost.
Plastic bags killing Queensland’s turtles
A group of University of Queensland researchers are urging Queenslanders to avoid littering the state's marine environment during the upcoming Easter holiday weekend.
