Influence of resin type and postprocessing cleaning solution on the accuracy of additively manufactured hard occlusal devices

To evaluate how hard occlusal device resins and postprocessing cleaning solutions affect the fabrication accuracy (trueness and precision) of additively manufactured (AM) hard occlusal devices. Two AM hard occlusal device resins (KeySplint Hard [KSH] and FreePrint Splint 2.0 [FPS]) were used to fabricate Michigan-type maxillary occlusal devices, which were subsequently cleaned using isopropyl alcohol, a methyl ether solvent, or a water-based solution (n = 9 per resin-solution combination). Each device was digitized with an intraoral scanner, and deviations from the reference design file (trueness) were quantified using the root mean square method. Precision was assessed as within-group dispersion based on the absolute deviations from the subgroup median. Trueness data were analyzed using a generalized linear model with Bonferroni-corrected post hoc tests, whereas precision data were analyzed using factorial Levene-type tests based on the Brown-Forsythe modification (α = 0.05). Resin type significantly affected the trueness and precision of tested occlusal devices (P ≤ 0.045), whereas cleaning solutions (P ≥ 0.273) or the interaction between these factors (P ≥ 0.196) did not. KSH devices had lower deviations and within-group dispersion than FPS devices for both outcomes (P ≤ 0.045). Regardless of the cleaning solution used, Michigan-type hard occlusal devices fabricated by using the KSH resin demonstrated greater accuracy than those fabricated from the FPS resin. Under the present experimental conditions, Michigan-type occlusal devices fabricated from KSH resin demonstrated greater fabrication accuracy. For both tested resins, cleaning with the methyl ether-based solvent or water-based solution did not result in a significant difference in fabrication accuracy compared with isopropyl alcohol. However, the clinical implications of these deviations for intraoral fit, retention, and clinical adjustment requirements warrant further investigation.