Additively manufactured water-washable resin dies cleaned with nonhazardous solutions: Can dimensional and positional...

The purpose of this in vitro study was to evaluate the dimensional and positional trueness of additively manufactured (AM) removable dies in water-washable (WW) resins and cleaned using different post-processing solutions (98% isopropyl alcohol [IPA], methyl ether solvent [MES], and water). These were also compared to removable dies fabricated with a non-WW dental cast resin.

The scan file of a typodont model with a prepared first right mandibular molar was used to design a master removable die and its corresponding hollow partial arch cast. Ninety removable dies (N = 45) and 6 hollow casts (N = 3) were fabricated from these designs in 2 WW dental cast resins (EPAX water-washable dental model resin, WW1, and Phrozen water-washable dental model resin, WW2). The fabricated specimens were divided into three groups and cleaned with IPA, MES, or water (n = 15 per removable die, n = 1 per hollow cast). The same design files were used to fabricate 15 dies and 1 hollow cast in a non-WW dental cast resin (KeyModel Ultra resin-ivory, NWW), cleaned with IPA, and served as the control group. All removable dies were digitized for dimensional trueness analysis and for fit analysis when seated in their respective casts. The master designs and scans were imported into a metrology-grade analysis software program (Geomagic Control X) to assess dimensional deviations of different regions (crown, root, root base, and overall) using the root mean square method. The positional deviations of seated dies were analyzed by calculating the crown region surface deviations and point-based deviations. The comparisons among WW dies were performed with either three-way (dimensional deviations) or two-way (positional deviations) analysis of variance (ANOVA) and Bonferroni-corrected post hoc tests, while one-way ANOVA and Dunnett tests were used for comparison with NWW dies (α = 0.05).

WW1-IPA and WW1-water dies had the highest dimensional deviations (p < 0.001). In addition, the crown region of the dies had the lowest and the root base region had the highest dimensional deviations (p < 0.001). WW1-IPA, WW1-water, and WW2-MES dies had the lowest crown region surface deviations, whereas WW1-IPA and WW2-MES dies also mostly had the highest point-based deviations (p ≤ 0.036). NWW dies had higher crown region deviations than WW2-IPA and WW2-water dies, lower overall deviations than WW1-IPA and WW1-water dies, and mostly lower root and root base deviations than WW dies (p ≤ 0.038). The positional deviations of NWW dies were mostly lower than WW dies (p ≤ 0.009).

Dimensional deviation differences among WW dies were small. Their trueness was similar to NWW dies, except for the root and root base regions. Among the tested materials, only WW1-water and NWW dies achieved positional trueness within reported clinical thresholds, whereas the other water-washable dies demonstrated higher deviations, potentially limiting their suitability for precise prosthetic applications.