When dentists find cavities, they hollow out the decayed part of the tooth and replace it with synthetic materials such as amalgam (silver fillings) or tooth-colored composites. Amalgam's silver-gray color can be unsightly, however, and composite materials can shrink, leaving teeth vulnerable to more decay. Researchers at The University of Texas Health Science Center at San Antonio (UTHSCSA) are developing new filling materials they believe will prevent these problems and better protect teeth.
One of these new materials already exists in our mouths. A research team is investigating ways to stimulate the body's own defense mechanisms. "Over time the tooth will naturally produce tertiary dentin to keep bacteria from leaking into the pulp," said Mary MacDougall, Ph.D., UTHSCSA cell biologist and professor in the department of pediatric dentistry.
Teeth produce tertiary dentin as a self-healing process, but when a patient gets a cavity filled, the dentist's high-speed drill hinders the natural process. Dr. MacDougall and her colleagues are investigating a system through which cytokines, proteins that stimulate dentin-forming cells, are applied to the floor of the cavity.
"The cytokines are delivered in a "carrier" solution that helps preserve cytokine activity and facilitates their movement into the dentin to efficiently stimulate tertiary dentin formation," Dr. MacDougall said. "Stimulating this natural repair mechanism is a first step toward eventually being able to restore a cavity with natural mineral instead of a synthetic material."
A more immediate solution to the leakage problem is a replacement for current synthetic filling materials. "Tooth-colored 'composites' are soft, moldable materials that are photo-cured to become hard and permanent after a dentist fills a cavity," said H. Ralph Rawls, Ph.D., professor of biomaterials in the department of restorative dentistry. "Unfortunately, these materials shrink and put stress on the bonded surfaces. Over time, these weakened areas may form a gap, allowing bacteria to leak into the tooth's pulp and possibly cause a painful infection. Eventually, a patient could need a root canal."
Liquid crystal resins are an option the researchers are exploring to overcome the shrinkage problem. These materials shrink 25 percent to 50 percent less than current materials, substantially reducing the chance for leakage and decay.
The work by Drs. MacDougall and Rawls is a collaboration between UTHSCSA and the Southwest Research Institute (SwRI). The research team includes UTHSCSA's Drs. Barry Norling and Neera Satsangi in the department of restorative dentistry and Drs. Ed Boland and David Carnes in the department of periodontics, as well as SwRI's Drs. Joe McDonough, Dan Nicolella and Steve Wellinghoff. A $5.9 million grant from the National Institute of Dental and Craniofacial Research funds the project and was recently renewed for five years.