An average person uses their teeth for more than 600,000 "chews" a year. Prolonging the life of composite tooth fillings could be an important step forward since more than 122 million composite tooth restorations are made in the United States every year, the researchers at Oregon State University state in a new study published in the journal Dental Materials. Bioactive glass, which looks like powdered glass, is called "bioactive" because the body notices it is there and can react to it, as opposed to other biomedical products that are inert. Bioactive glass is very hard and stiff, and it can replace some of the inert glass fillers that are currently mixed with polymers to make modern composite tooth fillings.
The new research, which has been supported by the National Institutes of Health, states that the depth of bacterial penetration into the interface with bioactive glass-containing fillings was significantly smaller than for composites lacking the glass. "Bioactive glass has been used in some types of bone healing for decades," said Jamie Kruzic, a professor and expert in advanced structural and biomaterials in the OSU College of Engineering. "This type of glass is only beginning to see use in dentistry, and our research shows it may be very promising for tooth fillings." Some studies suggest the average lifetime of a posterior dental composite is only six years. "Almost all fillings will eventually fail," Kruzic said. "New tooth decay often begins at the interface of a filling and the tooth, and is called secondary tooth decay. The tooth is literally being eroded and demineralized at that interface."
Fillings made with bioactive glass should slow secondary tooth decay, and also provide some minerals that could help replace those being lost, researchers say. The combination of these two forces should result in a tooth filling that works just as well, but lasts longer. To test the idea, the team used recently extracted human molars to make samples that simulated the human mouth. Composite fillings containing 15 percent bioactive glass were placed in some samples, and non-bioactive composite fillings were placed in others. Microscopic gaps were allowed to form around the fillings, before tooth-decaying bacteria were added.
The results showed that in the samples with bioactive glass fillings, there was a significant reduction (61 percent) in bacterial penetration into the gaps, reducing their ability to attack the fillings. In the other samples however, with no bioactive glass, there was 100 per cent penetration. "The bacteria in the mouth that help cause cavities don't seem to like this type of glass and are less likely to colonize on fillings that incorporate it. This could have a significant impact on the future of dentistry," Kruzic said. Bioactive glass has this antimicrobial effect partly thanks to ions such as calcium and phosphate, which have a toxic effect on bacteria. If the findings by Kruzic and his team can be confirmed by clinical research, Kruzic believes bioactive glass could be easily incorporated into existing formulations for composite tooth fillings to help prevent decay and promote dental health.
Bioactive glass holds promise of longer lasting tooth fillings
