Effects of monomer contamination during post-rinsing in vat photopolymerization on dimensional stability

Accuracy is an important parameter of additively manufactured objects. The influence of post-processing on the objects, in particular the effects of monomer contamination in isopropanol used during the post-rinsing of parts produced by vat photopolymerisation, is therefore important. Forty test specimens were fabricated from standard dental resin and divided into four groups, each rinsed with isopropanol containing 0 wt%, 10 wt%, 20 wt% or 30 wt% resin contamination. Optical scans of the specimens were compared with the original design to assess dimensional deviations. The results showed no significant deviations at contamination levels up to 10 wt%. At 20 wt%, deviations were observed in small structures and inclined planes, while 30 wt% contamination resulted in significant deviations in all areas. Rinsing with 99.9% isopropanol consistently produced the highest accuracy. Resin build-up below 10 wt% did not affect dimensional stability, suggesting that isopropanol replacement is unnecessary at this level. However, a contamination level of 20 wt% can lead to deviations under certain conditions, and a contamination level of 30 wt% consistently affects accuracy. These findings highlight the importance of monitoring contamination levels to maintain the integrity of vat photopolymerisation workflows and suggest that isopropanol should be replaced at contamination levels approaching 30 wt%.