Trueness and stability of additively manufactured removable dies: An in vitro study on plant-based resins and alcohol-free cleaning solutions

STATEMENT OF PROBLEM: Recent advances in dental additive manufacturing have introduced plant-based resins for casts and alcohol-free cleaning solutions; however, their suitability for producing dimensionally accurate and stable removable dies remains unclear. PURPOSE: The purpose of this in vitro study was to assess the dimensional and positional deviations and 4-week stability of additively manufactured removable dies made from 2 plant-based and 1 dental cast resins, cleaned with methyl ether solvent (MES), isopropyl alcohol (IPA), or a water-based solution (WBS). MATERIAL AND METHODS: A typodont with a prepared right first mandibular molar was digitized to design removable dies and hollow partial arch casts. Fifty-four dies (N=18) and 9 casts (N=3) were fabricated from 3 resins: Soy-Based Resin (EX), FotoDent biobased model (FD), and KeyModel Ultra Ivory (KM). Specimens were divided into 3 subgroups by cleaning solution; MES, IPA, and a WBS (n=6 dies, n=1 cast). Dies and their corresponding seated casts were digitized at 1 day (T0) and at 1-week intervals up to 4 weeks (T1-T4) after fabrication. Trueness was assessed from the surface deviations of die regions (crown, root, and root base) and positional deviations within casts at T0, while T0-T4 deviations evaluated stability. T0 deviations were assessed with a generalized linear model, while those over time were evaluated with linear mixed-effects models (α=.05). RESULTS: Resin type-cleaning solution interaction influenced the dimensional and positional deviations at T0 (P≤.049). In addition, crown region deviations were influenced by resin type-cleaning solution and resin type-time point interactions, whereas other surface and positional deviations were affected by interactions among all main factors (P≤.005). FD dies and MES-cleaned dies mostly had lower surface deviations, while IPA-cleaned FD dies had the lowest positional deviations (P≤.040). CONCLUSIONS: FD resin dies generally showed higher dimensional trueness and stability, while MES-cleaning also increased the dimensional trueness and stability of tested dies. IPA-cleaned FD dies exhibited the highest positional trueness and stability. The effect of the time point on deviations was minimal and likely clinically negligible.