Effect of preservation on the mechanical properties of 3D printing resins for occlusal splints

This study aims to evaluate the mechanical properties of 3D printing resins for occlusal splints (OS) under different preservation conditions based on sleep duration. The study factors (n = 10) included material types: PriZma 3D Bio Splint (PZ), Cosmos Splint (CS), NightGuard Firm (NGF), and self-polymerizing acrylic resin (control group - CG); preservation: artificial saliva (S), natural water (W), 0.12% chlorhexidine (C), and Corega tabs (CTs); and evaluation times: T0 (24 h after fabrication) and 30 d after exposure. Further, the surface roughness (Ra), Knoop microhardness (KH), three-point flexural strength (FS), and flexural modulus (FM) were analyzed. In terms of the time and material, Tukey's test revealed no significant differences in Ra between the groups at 24 h. After 30 d, PZ showed significantly lower values than the other groups (p < 0.05). For the KH, NGF was significantly higher than that in all groups at 24 h (p < 0.05); after 30 d, the NGF decreased in W and C (p < 0.05), and the NGF and PZ exhibited elevated values in S and CT, respectively. The Kruskal-Wallis test and multiple comparisons showed that the PZ had a higher value at 24 h (p < 0.05). Post 30 d, all 3D-printing resins increased values in CT and S (p < 0.05), and the PZ decreased in the C and W (P < 0.05). Finally, the FM increased under all conditions. The preservation of S and CT partially enhanced the mechanical properties of the OS.