# Impact of curing temperature on accuracy and physical properties of additively manufactured FDPs and bar specimens

## TL;DR

This study examines how different curing temperatures affect the strength and accuracy of 3D-printed dental prostheses and bar specimens.

## Contribution

The study provides new insights into the optimal post-processing temperature for additive manufacturing in dental prosthetics.

## Key findings

- Additively manufactured bar specimens showed higher flexural strength than subtractively made ones.
- Additively manufactured dental bridges had lower fracture strength compared to subtractively made bridges.
- Curing at 40°C for 40 minutes was sufficient for optimal mechanical properties without needing higher temperatures.

## Abstract

Additive manufacturing based on photopolymer resins requires additional light curing during postprocessing to achieve the final mechanical properties. The present in-vitro study aimed to evaluate the impact of the curing temperature during postprocessing on the fracture resistance and accuracy of both additively manufactured four-unit fixed dental prostheses (FDPs) and bar-shaped, ISO-conform specimens. All samples were fabricated by either additive manufacturing using two different light-curing resins or subtractive manufacturing using polymethyl methacrylate. Three different curing temperatures were evaluated (40 °C, 60 °C, 80 °C). All bars (n = 136) were subjected to a three-point bending test after 68 of them had been stored in water for 24 h. All bridges (n = 90) were analyzed for dimensional accuracy and afterwards subjected to static loading until fracture. Additively manufactured bar-shaped specimens exhibited significantly higher flexural strength compared to the subtractively manufactured counterparts. In contrast, all but one group (p = 0.082) of the additively manufactured four-unit FDPs demonstrated significantly lower fracture strength than the subtractively manufactured bridges (p < 0.024). Post-curing temperature had no significant effect on accuracy for the temporary resin (p > 0.469), whereas the permanent resin showed significant differences for some regions of interest and temperature combinations. For the recommended curing duration of 40 min, the lowest tested curing temperature of 40 °C already resulted in a sufficient degree of cure and mechanical properties with no general benefit to higher curing temperatures, indicating their use to be unnecessary.

The online version contains supplementary material available at 10.1038/s41598-025-28886-7.