University of Texas at Dallas researchers have developed a technology that enables same-day, 3D-printed dental restorations made of zirconia, the gold-standard material for permanent dental work.
The team is working to make the technology, which could be used for crowns, bridges, veneers and other restorations, commercially available with support from the National Science Foundation (NSF).
Dental crowns are caps that are placed over damaged or decaying teeth. They also can serve as supports in a dental bridge, which replaces a missing tooth. 3D-printed restorations have emerged as an option that offers better customization and color-matching, as well as a more efficient manufacturing process that could reduce cost and waste. Currently available same-day, 3D-printed crowns, however, are made of ceramic resins that are not as strong as zirconia.
And while same-day zirconia crowns are also available, they are not 3D-printed; rather, they are milled, a process that involves carving the crown from a block of zirconia. These zirconia restorations face challenges and limitations in design complexity and risks for micro-cracking during milling or sintering.
The UT Dallas researchers and their collaborators have solved a challenge in producing 3D-printed zirconia restorations by significantly reducing the time involved in processing a zirconia restoration after it is 3D-printed. The researchers explain their approach in the September print edition of the journal Ceramics International. The method will require clinical validation and regulatory approval before it becomes commercially available.
After a zirconia crown is 3D-printed, it must undergo two key steps: debinding and sintering. In the debinding stage, heat is applied gradually to burn off the resin that held the zirconia particles in place during printing. This process can take from 20 to 100 hours. Once the resin is removed, the crown undergoes sintering – a high-temperature firing process similar to baking clay in a kiln – which fuses the zirconia particles together into a dense, hardened solid.
“Debinding has been the bottleneck in the process,” said Minary, corresponding author of the article. “It must be done very slowly. If you speed it up, the polymer being burned off turns into gas, and if that gas cannot escape, the crown may crack or fracture. A debinding time of 20 to 100 hours is not practical for same-day dental service. As a result, 3D-printed permanent zirconia restorations are not yet commercially available.”