Bulletin of Dental Education

Researchers at OU COD Are Fighting Back Against Bacteria on Dental Restorations

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The University of Oklahoma College of Dentistry (OU COD) at the Health Sciences Center in Oklahoma City is on the forefront of discovering a secret weapon that helps fight the bacteria rapidly growing near the adhesive layer of a dental restoration. 

OUCOD’s Fernando Luis Esteban Florez, D.D.S., M.S., Ph.D., and Sharukh Khajotia, B.D.S., M.S., Ph.D., started this journey together in 2012 when Dr. Esteban Florez was first hired as a postdoc at the OU COD. Dr. Khajotia’s research in dental biomaterials, advanced surface analysis and materials properties testing and Dr. Esteban Florez’s background in lasers in dentistry, biophotonics and materials sciences sparked a conversation that led to the question: What if adhesive resins used in restorative dentistry could not only bond a filling to the tooth, but also be antibacterial to fight against bacteria that are constantly trying to attack the tooth? The solution they proposed for that problem was the utilization of nitrogen-doped titanium dioxide nanoparticles (N_TiO2). 

By definition, a nanoparticle must have all dimensions smaller than 100 nanometers. “A nanoparticle can be 750 times smaller than the thickness of a human hair,” Dr. Khajotia says. “The properties of many conventional materials are changed when formed from nanoparticles because they have a great surface-to-volume ratio when compared to larger particles.” Their initial plan was based on the incorporation of N_TiO2 from a manufacturer into a commercial adhesive resin. However, that approach resulted in higher levels of bacterial attachment and biofilm growth. 

Drs. Esteban Florez and Khajotia went back to the drawing board and determined they needed to synthesize higher-quality nanoparticles and make them functional within dental polymers. Toward this end, they established a collaboration with Adam Rondinone, Ph.D., a scientist from the Center for Nanophase and Materials Sciences (CNMS) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN.

This multidisciplinary team started to fabricate N_TiO2 using robust synthesis processes based on solvothermal reactions. Unlike other adhesive resins, the materials developed display antibacterial properties that are enhanced by on-demand light irradiation. 

The research is promising, and the team is hopeful that it will one day be translated into practice. For now, it has led to other in vitro findings, such as the nanoparticles’ ability to precipitate crystals containing high concentrations of phosphorous and calcium from saliva-like solutions.

The team investigated the nanoparticles using cutting-edge scientific technologies available at ORNL, including time-of-flight secondary ion spectrometry (ToF-SIMS), small-angle x-ray spectroscopy (SAXS), small-angle neutron scattering (SANS) and advanced microscopies. “Using neutron scattering, we can understand how well the nanoparticles are dispersed, how they are impacting polymer chains, and what types of interfaces are being established between the polymer and nanoparticles,” Dr. Florez says. 

Today, the research team holds two patents, one for the development of adhesive resins containing either doped or co-doped TiO2 nanoparticles, and the other for the nanoparticles’ surface modification. Current research is ongoing into functionalizing the nanoparticles in areas other than dentistry, including antibacterial coatings for the control of cross-contamination in hospitals. 

Courtesy of Caroline Rykard, Media Relations Specialist, OU Medicine | Marketing

Published on Oct. 9, 2019

 

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