by Jingrong Wang, Anna Miyayasu, Maiko Iwaki, Roubing Ha, Manabu Kanazawa 1 Digital Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University 2 Advanced biomaterials, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University
The deformation due to internal stress during post-curing could negatively affect the accuracy of 3D printed castable resin patterns for frameworks of removable partial dentures (RPD). This study aimed to verify the accuracy of 3D printed castable resin patterns for RPD frameworks fabricated by the vacuum-sealed method in order to establish a method of fabricating accurate frameworks with less deformation of the 3D printed castable resin patterns.
One master simplified cast simulating the maxillary palate was scanned (E3 scanner, 3 Shape A/S), and a framework of a simplified major connector was designed by CAD software (Dental System, 3Shape A/S). Fifty-four specimens of castable resin patterns (Dima Print Cast emerald, Kulzer) were printed by the 3D printer (cara Print 4.0, Kulzer GmbH.). Printed specimens were rinsed with 99% Isopropyl alcohol (IPA) in the ultrasonic cleaning machine. Different procedures after printing were applied for each group. The specimens of the control group (CON group) were post-cured with supportive structures. The specimens of the vacuum-sealed (VS group) were post-cured (cara Print LEDcure, Kulzer GmbH.) after vacuum-sealed (S-WAVE Vacuum Sealer, Shofu) with working cast. And the specimens of the heat-treated group (VSH group) were vacuum-sealed with working cast, heat-treated in water at 90℃ for 5 minutes, and then post-cured. The specimens of each group were scanned immediately (Im), 1 hour later (1h) and 3 hours later (3h). The sealing packs were opened just before scanning. Six specimens in each group (VS-Im, VS-1h, VS-3h, VSH-Im, VSH-1h, VSH-3h, CON-Im, CON-1h and CON-3h) were analyzed. The root mean square (RMS) was calculated by superimposing the specimen’s STL file and the original STL file to evaluate the trueness (Artec Studio 12 Professional, Artec). To compare the differences between the groups, the one-way ANOVA and Tukey test were performed (α=0.05).
The RMS values of CON-Im and VSH-Im were significantly smaller than VS-Im (P<0.05). VSH-1h has the smallest value compared with CON-1h and VS-1h (P<0.05). CON-3h and VSH-3h were significantly smaller than VS-3h (P<0.05).
This study indicated that post-curing and heat-treatment with the vacuum-sealed method could reduce the deformation of 3D printed castable resin patterns. Heat-treatment suggested to be necessary for the vacuum-sealed method.
