Prescription Bleaching Agent Damages Dental-Fillings Material

BUFFALO, N.Y. -- Dental bleaching agents can damage some tooth fillings, leaving the tooth surface potentially more susceptible to staining and plaque formation, a study by researchers at the University at Buffalo School of Dental Medicine has found.

Results of the research were presented Sunday, March 12, at the American Association of Dental Research meeting in San Antonio, Texas.

The study looked particularly at the effect of a carbamide peroxide bleaching agent on glass ionomer resins, a family of newer materials becoming popular with dentists for filling cavities in teeth. Carbamide peroxide bleaching agents are available only by prescription, and are not to be confused with over-the-counter teeth whiteners.

Gerard Wieczkowski, D.D.S., UB associate professor of restorative dentistry and lead author on the study, said there has been a substantial increase in interest in dental bleaching. When the bleaching agents are applied, dental restorations, or fillings, are exposed along with the natural teeth.

"The resin-based materials have the advantage of containing fluoride, but they also contain many other chemical compounds present as filler particles," Wieczkowski said. "Nobody knows the effect of bleaching on this group of restorative materials."

To test the effect, the researchers prepared simulated dental fillings in molds, using five commercially available resin-based materials. After allowing the samples to cure, they bathed them in the bleaching agent eight hours a day for 14 days. The researchers analyzed the restoration surface before and after bleaching.

Results showed that three of the five brands experienced substantial erosion.

"The bleaching agents caused physical changes on the surface of the restoration," Wieczkowski said. "We think the agent might be washing out the resins, exposing the filler particles. These roughened surfaces might leave the tooth more susceptible to staining, and to the accumulation of plaque. Increased plaque could lead to damage of the gingival tissue."

He cautioned that these laboratory studies need to be followed up with clinical studies to substantiate the findings.

Patients are instructed to go back to their dentists to have their bleaching monitored, but many do not, Wieczkowski said. "They can use these bleaching agents as frequently as they want at home, but they may not know that, in a sense, they are making the problem they are trying to solve worse."

He noted, however, that carbamide peroxide bleaching agents must be prescribed, and that dentists probably would not prescribe them for patients who have a lot of front-surface fillings.

Members of the research team in addition to Wieczkowski were Xin Yi Yu, D.D.S.; Robert B. Joynt, D.D.S., and Elaine L. Davis, Ph.D, all of the UB Department of Restorative Dentistry.