Nanotechnology has the potential to produce restorations that are stronger than today’s resin-based composite restorations and more effective in preventing secondary caries, according to a study published in the April issue of Journal of Dental Research.
Scientists at the American Dental Association Foundation’s Paffenbarger Research Center, Gaithersburg, Md., a joint research program at the National Institute of Standards and Technology, developed a technique that solves a problem with standard resin-based composite restorations. Such restorations are made by mixing the pure liquid resin with a powder that contains coloring, reinforcement and other materials, packing the resulting paste into the cavity and polymerizing the paste.
The problem arises from an additive that is included in the powder to provide a steady release of calcium and phosphate ions. These ions are essential to the long-term success of the restoration, because they not only strengthen the crystal structure of the tooth itself but also buffer it against the caries-causing acid produced by bacteria in the mouth. However, the available ion-releasing compounds are structurally quite weak, to the point at which they weaken the restoration as a whole.
To get around this conundrum, the researchers devised a spray-drying technique that yields particles of several such compounds—one of which is di-calcium phosphate anhydrous (DCPA)—that are about 50 nanometers across, or 20 times smaller than the 1-micrometer particles in a conventional DCPA powder. Because these nanoscale particles have a much higher surface-to-volume ratio, they are much more effective in releasing ions, which means that much less of the material is required to produce the same effect. This, in turn, leaves more room in the resin for reinforcing fibers that strengthen the restoration.
The researchers also developed nanoscale silica-fused fibers that produce a resin-based composite nearly twice as strong as the currently available resin-based composite materials.
This study was supported by the National Institute of Dental and Craniofacial Research, the National Institute of Standards and Technology and the American Dental Association Foundation.
