Fillings can stop caries in the short term. But there are long-term risks as pathogenic bacteria colonies form at the junction of the filling material and dentin—and that’s just the beginning of potential problems. Researchers at the National University of Science and Technology Moscow Institute of Steel and Alloys State Technological University (NUST MISiS) have developed materials that work as antibiotics without side effects, eliminating these possible failures.
The researchers have synthesized liquid colloidal systems, which are ultrathin suspensions that do not precipitate, consisting of high-energy oxide nanoparticles of iron, zinc, titanium, and other metals ranging from one to 3 Nm. Despite their ultra-low concentration in disperse systems (no more than 0.1 mg per liter of water), they have a long bactericidal effect on the microflora responsible for the development of caries.
These nano-additives can give dental materials used in the preparation and placement of fillings prolonged antiseptic properties, preventing the appearance and reproduction of pathogenic microbes that cause caries, the researchers said. The presence of colloidal metal particles and metal oxides in such materials also improves their adhesion with the tooth and significantly reduces the shrinkage of the filling upon curing, further extending the lifespan of the filling.
Plus, the researchers add, these materials address the need to find fundamentally new drugs with high antibacterial activity to reduce the resistance of pathogenic micro-organisms to natural and medicinal antibiotics, a growing problem that threatens thousands of lives around the world.
“We assume that the mechanism of microbial cell destruction under the effect of colloidal nanosystems, created by us, resembles the effect of antibacterial enzymes of the hydrolase class, which destroy the bacterial walls through hydrolysis. Such enzymes in relatively high concentrations are contained in the places of body contact with the environment: saliva, mucus from the nasopharyngeal cavity and gastrointestinal tract, human milk,” said Georgii Frolov, head of the scientific group and associate professor in the physical chemistry department.
“Their action leads to the process of lysis (destruction of cells into fragments) and the death of the pathogenic cell. Apparently, nanoparticles of metal oxides act as a catalyst for hydrolases, which eventually leads to the destruction of peptide and glycosidic bonds of cell walls and membranes. Under their action, the mechanism of ‘self-destruction’ of pathogenic bacteria starts. At present, the composition is used at the dental department of Kirov State Medical Academy,” said Frolov.
While these nanoparticles inhibit the development of pathogenic micro-organisms, in most cases they do not inhibit the vitals of natural flora or affect the cells of body tissues, the researchers said. Via material received, the researchers solved the problem of the “spending” of antibacterial composition, which reacts chemically and is actually spent, alongside being impossible to add to a filled tooth. The new composition has an everlasting effect once the filling goes on the tooth, which is a major advantage, the researchers said.
“The research results of the NUST MISiS scientists is in fact a technological revolution in dentistry, as it represents dental composites of the new, sixth generation. At the edge of the phase separation, this material creates a bactericidal effect limitless in time and improves the adhesion of the filling with the tooth tissue by more than 40%,” said Yakov Karasenkov, PhD, project participant and head physician of the school’s clinic.
“The antibacterial additive can be used not only in the composition of the filling, but also in the adhesive, in composites, etching materials, interlayers, implants, and in the compounds for sealing dental fissures. In all formats, it creates a surface and volume antibacterial effect in the operated areas and ultimately prolongs the life of the fillings and implants. Our clinic has successfully used the drug since September 2016,” said Karasenkov.