New research: Resin materials for 3D-printing and milling of indirect restorations

NIOM researchers have evaluated two liquid resins and a milled material for chemical release in an artificial saliva model.

“Our results show that even materials intended for the same use can release surprisingly different substances into the oral environment,” says NIOM scientist Mina Aker Sagen.

What is this about?

The study carried out at the Nordic Institute of Dental Materials (NIOM) focuses on how resin-based dental materials behave chemically when used for indirect restorations such as temporary crowns or bridges. Two liquid resins designed for 3D-printing and one milled resin material were tested for their release of monomers and other chemicals into an artificial saliva environment.

What did the researchers find out?

Specimens were immersed in artificial saliva at 37 °C, and analyses were conducted at 1 hour, 24 hours, 1 week and 3 months.
The team used targeted methods (LC-MS/MS) to quantify known methacrylate monomers and photoinitiators, and untargeted methods (UHPLC-HRMS) to detect other unknown substances.

They confirmed that the SDS-listed methacrylate BisEMA was present in both liquid resins, and discovered that one resin also contained an undisclosed UDMA monomer.

They found that one resin released significantly higher concentrations of chemicals at all time points compared with the other 3D-print resin print and the milled material.

Key results

• The majority of residual methacrylate monomers from the 3D-print resins leached out within the first 24 hours.
  
  However, the untargeted analysis revealed that many other compounds (at least 67 putative substances) continued to leach over longer periods (up to three months), especially from the higher-releasing resin.
• The stark difference in chemical release between materials highlights that simply knowing the monomer composition is not sufficient; broader chemical assessment is crucial for evaluating biocompatibility.
• For clinical practice and dental laboratories, the findings suggest that selection of resin material and the manufacturing route (3D-print vs. milling) may have important implications for patient exposure and long-term stability of restorations.