Dental Tribune International

Researchers use antibacterial nanoparticles to prolong dental restorations

OAK RIDGE, Tenn., U.S.: Researchers have been using neutron scattering to study how nanoparticles with antibacterial properties could be added to adhesive resins that are used by dentists to strengthen the bond between a tooth and its polymer composite filling. This would help reduce the number of dental restorations failing as a result of cracking and secondary caries.

“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,” said 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. “Also, tiny imperfections in the adhesive surface can lead to early-stage cracking that also contributes to the failure of restorations.”

The research team developed an experimental dental adhesive resin containing modified (nitrogen-doped) nanoscale titanium dioxide (N_TiO2) particles. They then studied samples of the adhesive resin using small-angle neutron scattering in Oak Ridge National Laboratory’s (ORNL’s) High Flux Isotope Reactor (HFIR) to determine the optimal shape, modifications and dispersion for the particles.

“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,” said co-author of the study Dr. Adam J. Rondinone, a senior staff scientist at ORNL’s Center for Nanophase Materials Sciences. “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,” he explained.

Early results show that the nanoparticles disperse well and are compatible with the commercially available adhesive resin that the scientists used in their test. Additionally, the new adhesive resin exhibits active on-demand antibacterial activity when irradiated with visible light, and passive on-contact antibacterial effects, even in a dark setting. This dual capability could enable a dentist to use light to improve the adhesive’s antimicrobial activity before filling the cavity. Afterward, the adhesive would serve as a long-term, contact-based antibacterial barrier.

The researchers are now planning to use neutron scattering to evaluate the potential bioactivity of the nanoparticles. “Studies have shown that nanoparticles can initiate the growth of crystalline structures and guide them to become chemically bound to teeth,” said Florez. “We plan to functionalize our N_TiO2 particles to produce crystals of hydroxyapatite, the primary component of dentin, which could promote the growth of the dentin layer to 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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