Are bio-based resins suitable alternatives for additively manufactured removable dies? An in vitro study on dimensional and positional trueness and stability.

Purpose: This study aimed to compare the dimensional and positional deviations of additively manufactured removable dies fabricated using two bio-based resins and one conventional dental cast resin, while also evaluating these outcomes over a 4-week period.

Materials and methods: A right mandibular first molar preparation on a typodont was scanned to digitally design removable dies and hollow partial arch casts. Based on a priori power analysis, a total of 30 dies (n = 10) and three hollow casts (n = 1) were fabricated using additive manufacturing (AM) from three different dental cast resins: DentaMODEL (DM), FotoDent bio-based model (CB), and soy-based resin (SB). The dies and their seated positions in casts were digitized 1 day (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), and 4 weeks (T4) after fabrication. Dies' dimensional deviations (crown, root, base of the root, and overall) and positional deviations in casts (crown region surface and point-based) at T0 were defined as trueness, while deviations measured over 4 weeks (T0-T4) were defined as stability. The deviations measured at T0 were analyzed either using a generalized linear model (dimensional deviations) or one-way analysis of variance (crown region and point-based deviations). The deviations measured over the 4-week period were analyzed with generalized linear model analysis and Bonferroni-corrected post hoc tests (α = 0.05).

Results: CB dies mostly had the lowest and SB dies mostly had the highest dimensional deviations (p ≤ 0.001). The crown region had the lowest dimensional deviations, while the dimensional deviations measured at T3 were higher than those at T2 and T4 (p ≤ 0.003). SB dies had the highest and CB dies had the lowest positional deviations, while crown region deviations were lower at T0 and T1 than at T4, and point-based deviations were lower at T0 than at T4 (p ≤ 0.049).

Conclusions: CB dies mostly had better dimensional and positional trueness and stability over 4 weeks. The changes in tested outcomes for all dies over time were small.