Effect of additive manufacturing process and storage condition on the dimensional accuracy and stability of 3D-printed dental casts

Statement of problem. Additively manufactured dental casts are gaining popularity as the digital workflow is adopted in dentistry. However, studies on their dimensional accuracy and stability under different storage conditions in the dental laboratory are lacking. Purpose. The purpose of this in vitro study was to compare the effects of different additive manufacturing processes and storage conditions on the dimensional accuracy and stability of 3D-printed dental casts.Material and methods. A completely dentate maxillary typodont model was digitized 10 times with a dental laboratory laser scanner, and the standard tessellation language (STL) files were used to manufacture 3D-printed diagnostic casts with the digital light projection (DLP) 3D printer (Asiga MAX) and material jetting (MJ) 3D printer (ProJet 3510 DPPro). Twenty DLP-printed and 20 MJ-printed diagnostic casts were digitized within 24 hours of production. Subsequently, all 3D-printed diagnostic casts were stored for 3 months, either in closed laboratory boxes or in dental laboratory open-face plastic containers with direct exposure to full-spectrum balanced light. After 3-month storage, all 40 3D-printed casts were digitized again. All scanned files were compared with the corresponding STL files in a surface -matching software program. The dimensional accuracy was measured and compared by the root mean square (RMS, in gm). Repeated measures analysis of variance (ANOVA) was used to compare RMS values among the variables, and the Tukey honestly significant difference (HSD) test was used for post hoc multiple comparisons (a=.05).Results. The casts produced from the DLP 3D printer had a significantly higher mean +/- standard deviation RMS of 153.7 +/- 25.4 gm than those produced with the MJ 3D printer with RMS of 134.1 +/- 16.0 gm (P<.001). The storage condition (box storage versus light exposure) did not affect the accuracy of the DLP-printed casts (P=.615) or the MJ-printed casts (P=.999). When comparing all 3D-printed casts after 3-month storage, group DLP-3M-Lit had the highest mean +/- standard deviation RMS of 163.0 +/- 26.5 gm, and group MJ-3M-Box had the lowest RMS of 132.8 +/- 16.9 gm. The DLP-printed casts stored under light exposure were significantly less accurate than the MJ-printed casts stored in the box (P=.048). DLP-printed casts stored under light exposure showed significant surface color change under visual inspection.Conclusions. The MJ 3D printer produced more accurate 3D-printed dental casts than the DLP 3D printer. After 3-month storage, the DLP-printed casts stored under light exposure were the least accurate, and the MJ-printed casts stored without light exposure were the most accurate. The surface color change of DLP-printed casts stored under light exposure after 3-month storage was evident. (J Prosthet Dent 2022;128:1041-6)

Automated summary

This study compares the effects of different additive manufacturing processes and storage conditions on the dimensional accuracy and stability of 3D-printed dental casts. The results show that the MJ 3D printer produces more accurate casts compared to the DLP 3D printer. After a 3-month storage period, the DLP-printed casts exposed to light show the least accuracy, while the MJ-printed casts stored in a box exhibit the highest accuracy.