Influence of Different Postpolymerization Strategies and Artificial Aging on Hardness of 3D-Printed Resin Materials: An In Vitro Study
Marcel Reymus, Bogna Stawarczyk
Abstract
Marcel Reymus, Dr Med Dent/Bogna Stawarczyk, Prof Dr Rer Biol Hum, Dipl-Ing (FH), MSc: Purpose: To investigate the influence of different postpolymerization strategies and artificial aging periods on the Martens hardness parameters of 3D-printed resin materials indicated for temporary use. Materials and Methods: Disks made of four 3D-printed resin materials (n = 30 each) were additively manufactured and postpolymerized with three different postpolymerization devices (n = 10 specimens of each material per device). Disks cut from a prefabricated milling material served as a control. The Martens parameters (ie, Martens hardness [HM] and indentation modulus [E<sub>IT</sub>]) were measured initially and after 14- and 28-day storage periods in 37°C distilled water. The data were statistically analyzed using univariate analysis, Kolmogorov Smirnov test, and nonparametric tests, including Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests (α = .05). Results: The highest impact on the Martens parameters was exerted by material (HM: η<sub>P</sub><sup>2</sup> = 0.957, E<sub>IT</sub>: η<sub>p</sub><sup>2</sup> = 0.967, P < .001), followed by postpolymerization device (HM: η<sub>P</sub><sup>2</sup> = 0.557, E<sub>IT</sub>: η<sub>P</sub><sup>2</sup> = 0.496, P < .001) and duration of water storage (HM: η<sub>P</sub><sup>2</sup>= 0.068, E<sub>IT</sub>: η<sub>P</sub><sup>2</sup>= 0.038, P < .001). The values for HM ranged between 108 and 282 N/mm<sup>2</sup>, and for E<sub>IT</sub> between 2.89 and 7.73 kN/mm<sup>2</sup>. The materials 3Delta Etemp and Temp PRINT showed the highest HM and E<sub>IT</sub> values regardless of the postpolymerization device and water storage duration (P < .001). In contrast, NextDent C&B, followed by Freeprint Temp, showed the lowest HM and E<sub>IT</sub> values (P < .001). The milled control group Telio CAD ranged between the two lower groups. Conclusion: Postpolymerization strategy has a high impact on the mechanical properties of 3D-printed resin materials. Materials with a higher filler content showed better results regarding the Martens parameters. Such materials might be an alternative to conventional materials for the milling procedure.