3D printers outperform milling machines in crown production

Japan: A study result showed that 3D printers performed better than conventional milling machines in crown production.

A research team from the Department of Dental Materials Engineering at the Graduate School of Dentistry, Tohoku University, Japan, revealed this as a result of comparative analysis of the dimensional accuracy of composite resin crowns made with 3D printers or milling machines.

The research paper ‘Comparison of the accuracy of resin-composite crowns fabricated by three-dimensional printing and milling methods’ was published in the recent issue of Dental Materials Journal (IF 2.102).

According to the study results, crowns produced by 3D printer digital light processing (DLP) showed consistent accuracy with the original data set compared to milling machines, and had lower peripheral discrepancy. In addition, the 3D printer showed a higher level of accuracy regardless of the shape of the abutment.

On the other hand, the crown produced by a milling machine had a large dimensional deviation from the original data set – negative deviation and grooves were produced when correcting with an offset on the inner surface. The team observed in the milled parts “a definite internal groove,” which they attributed to the crowns’ brittle base material.

The milling machine also showed that the accuracy was greatly influenced by the material properties. Fragile materials such as ceramics and polymer impregnated ceramics also tended to break or become rough during processing. This could potentially lead to poor quality results.

 “Although CAD/CAM-fabricated milling crowns have proven to be a popular alternative to traditional metal restorations in recent years, advances in 3D printers offer dentists a higher level of accuracy at a lower cost than before,” said the research team.

“It shows that we can provide a much better product.”

The test specimens were produced from a 3D scan of an abutment tooth model. They were then milled from a hybrid resin-composite block and 3D printed using an Asiga Max system, respectively. Each of these prototypes were compared to their original design models via an industrial 3D digitizer, which gathered the data needed to help identify any deviations.