Use of antibacterial nanoparticles to prolong the life of dental restorations

According to the lead author of the study Dr. Fernando Luis Esteban Florez, an assistant professor at the University of Oklahoma Health Sciences Center, Oklahoma City, U.S. “The adhesive layer applied by a dentist prior to filling a cavity is fundamental to the success of the restoration, because the polymer materials used in fillings can promote the growth of biofilms.” On restoration failures, he said “Tiny imperfections in the adhesive surface can lead to early-stage cracking that also contributes to the failure of restorations.”

The Oklahoma researchers developed an experimental dental adhesive resin made up of modified (nitrogen-doped) nanoscale titanium dioxide (N_TiO2) particles. In order to determine the optimal shape, modifications and dispersion for the particles, they subjected the adhesive resin samples to small-angle neutron scattering in Oak Ridge National Laboratory’s (ORNL’s) High Flux Isotope Reactor (HFIR).

Dr. Adam J. Rondinone, a senior staff scientist at ORNL’s Center for Nanophase Materials Sciences and a co-author of the study said “In creating the adhesive resin, we modified the surface of the N_TiO2 nanoparticles with silanes and proteins to improve both the function of the nanoparticles within the polymer matrix and the ability of these materials to establish covalent bonds to a tooth’s naturally occurring proteins.” 

Early results were encouraging as they showed good dispersion of nanoparticles and their compatibility with the adhesive resins tested. About the choice of instrument, Dr. Rondinone said “The benefit of using the Bio-SANS beamline instrument at HFIR is that the neutrons can tell us how the proteins bond to the N_TiO2 and how the particles disperse.”

In addition, the new adhesive resin demonstrates dual antibacterial potential: active antibacterial activity when irradiated with visible light, and passive on-contact antibacterial activity, even in a dark setting. This dual potential could be used by a dentist, who would first use light to improve the antimicrobial activity of  the adhesive, before filling the cavity. Later, the adhesive would exhibit its passive on- contact antibacterial property in the long run. 

The next step is to study the potential bioactivity of the nanoparticles using neutron scattering. Dr. Florez says “Studies have shown that nanoparticles can initiate the growth of crystalline structures and guide them to become chemically bound to teeth.”  The research team plans to functionalize the N_TiO2 particles to produce hydroxyapatite crystals, the main constituent of dentin, which could promote the growth of the dentin layer and minimize gaps at the adhesive interface.

The study, titled “Antibacterial dental adhesive resins containing nitrogen-doped titanium dioxide nanoparticles,” was published on Dec. 1, 2018, in Materials Science and Engineering C: Materials for Biological Applications.

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