Bioactive Glass Reduces Decay in Tooth Cavity Fillings

23 December 2015. An engineering group at Oregon State University adapted a type of glass material that in lab models slows the decay in teeth with composite cavity fillings. The team led by materials engineering professor Jamie Kruzic published its findings in the January 2016 issue of the journal Dental Materials.

Kruzic, with colleagues from the university’s dental school and Midwestern University in Arizona, are seeking a technology to improve the performance and longevity of composite cavity fillings. The authors cite data from NIH showing Americans receive more than 122 million composite fillings a year, but these fillings face failure rates as high as 15 percent and have an average lifetime of only 6 years.

“New tooth decay often begins at the interface of a filling and the tooth,” says Kruzic in a university statement, “and is called secondary tooth decay. The tooth is literally being eroded and demineralized at that interface.”

The Oregon State team investigated the potential of a material called bioactive glass, made with silicon, calcium, and phosphorus compounds. Like window glass, bioactive glass is hard and stiff, but because of its chemistry, releases calcium and phosphate ions toxic to bacteria, which also help neutralize the lactic acid that builds up when decay begins around the fillings. Bioactive glass is already used for bone healing, and could replace the inert crushed glass material now added to composite fillings.

The lab prepared a bioreactor that simulates activity in a human mouth, where they tested human molar material filled with typical composite fillings. The molars were made with tiny gaps between the composite and tooth, like those that develop in real fillings, and biofilms of tooth bacteria were grown on their surfaces. Some of the fillings had bioactive glass added to the composite, about 15 percent by weight, while a comparison group had composite fillings alone.

After 2 weeks, the researchers measured the depth of bacterial penetration from the biofilms, and found the molars with bioactive glass had on average 61 percent less bacterial growth than the molars without bioactive glass, a large enough difference to be statistically reliable. In many molars without bioactive glass, bacteria penetrated clear to the bottom of the cavities.

“The bacteria in the mouth that help cause cavities don’t seem to like this type of glass,” notes Kruzic, “and are less likely to colonize on fillings that incorporate it. This could have a significant impact on the future of dentistry.”

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