New material for stronger, non-toxic dental fillings

Graphene oxide could be used to make non-toxic, super strong dental fillings that do not corrode, researchers have found.
Fillings are typically made of a mixture of metals, such as copper, mercury, silver and tin, or composites of powdered glass and ceramic. Typical metal fillings can corrode and composite fillings are not very strong.
Graphene on the other hand is 200 times stronger than steel and does not corrode, making it a prime new candidate for dental fillings, the researchers said.
"The idea of the project was to add graphene into dental materials, in order to increase their resistance to corrosion as well as to improve their mechanical properties," said Stela Pruneanu, from the National Institute for Research and Development of Isotopic and Molecular Technologies in Romania.

"There is contradictory information regarding the cytotoxicity of graphene, so we first wanted to determine how toxic it is for teeth," Pruneanu said.
Graphene comes in different forms, including graphene oxide, nitrogen-doped graphene and thermally reduced graphene oxide.

The researchers tested how toxic these different types of graphene are in vitro for stem cells found in teeth.
Thermally reduced graphene oxide was highly toxic, making it inappropriate as a dental filling material. Nitrogen-doped graphene caused membrane damage at high doses (20 and 40 microgrammes per millilitre).
However, it was shown to have antioxidant properties, so it could be useful if covered in a protective layer. Graphene oxide was least toxic to cells, making it an ideal candidate.

"The results were very interesting and proved that graphene is appropriate for use in dental materials," said Gabriela Adriana Filip, Associate Professor at Iuliu Hatieganu University of Medicine and Pharmacy in Romania.
"We believe that this research will bring new knowledge about the cytotoxic properties of graphene-based materials and their potential applications in dental materials," Filip said.
The next step for this research is for the team to make dental materials with graphene oxide and test how compatible they are with teeth, and how toxic they are to cells.
The study was published in the journal Colloids and Surfaces B: Biointerfaces.