OU College of Dentistry Researchers Are Fighting Back Against Bacteria on Dental Restorations

Most people don’t look forward to going to the dentist, especially when continually replacing fillings and crowns. What if there were a secret weapon fighting the bacteria that causes dental restorations to fail?

Fernando Luis Esteban Florez, D.D.S., M.S., Ph.D., and Sharukh Khajotia, B.D.S., M.S., Ph.D., two researchers at the University of Oklahoma College of Dentistry, are on the forefront of developing that secret weapon.

The traditional procedure used to place composite fillings involves several steps, but before the placement, an adhesive resin must be applied to bond the tooth to the filling. The disadvantage is that cavities can recur over time as a result of biofilm—a pool of various bacteria—seeping into micro cracks of a restoration. Because of this common problem, Esteban Florez and Khajotia asked themselves: What if the adhesive resins used in restorative dentistry could not only bond a filling to the tooth, but also could fight against bacteria that attack it?

The solution they proposed was the utilization of nitrogen-doped titanium dioxide nanoparticles.

“A nanoparticle can be 750 times smaller than the thickness of a human hair,” Khajotia said. “The properties of many conventional materials change when formed from nanoparticles because they have a great surface-to-volume ratio compared to larger particles.”

Esteban Florez and Khajotia determined they needed to construct higher-quality nanoparticles and make them functional within dental polymers to create the adhesive resin. Toward this end, they established a collaboration with Adam Rondinone, Ph.D., a scientist from the Center for Nanophase and Materials Sciences at Oak Ridge National Laboratory in Oak Ridge, Tennessee.

This multidisciplinary team started to fabricate nitrogen-doped titanium dioxide nanoparticles using robust synthesis processes based on the production of chemical compounds, known as solvothermal reactions. Unlike other adhesive resins, the materials developed display antibacterial properties, which are enhanced by on-demand light irradiation.

The research is promising, and the team is hopeful about its translation into practice. For now, it has led to other findings, such as the nanoparticles’ ability to produce crystals containing high concentrations of phosphorous and calcium from saliva-like solutions.

The team investigated the nanoparticles using cutting-edge scientific technologies available at Oak Ridge, including time-of-flight secondary ion spectrometry, small-angle x-ray spectroscopy, small-angle neutron scattering and advanced microscopies.

“Using neutron scattering, we can understand how well the nanoparticles are dispersed, how they impact polymer chains, and what types of interfaces are established between the polymer and nanoparticles,” Esteban Florez said.

Today, the research team holds two patents. Current research is ongoing into functionalizing the nanoparticles in areas other than dentistry, including antibacterial coatings for the control of cross-contamination in hospitals.