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Impact of different post-polymerization protocols on the material properties of three printed dental resins
Sophie Gekle1, Felicitas Mayinger1, Ursula Kreitmair2
1Department of Prosthetic Dentistry, University Hospital, LMU Munich, Goethestraße 70, 80336, Munich, Germany.
Objectives:
To investigate the influence of different post-polymerization protocols (PP) on polymerization depth and resultant degree of conversion (DC), Martens hardness (HM), flexural strength (FS) and elastic modulus (EM) of 3D-printed specimens with and without aging regimes.
Methods:
Specimens of a specific geometry (N = 720) were 3D printed from two resins for permanent applications (VAR=Varseo Smile Crownplus, BEGO Medical; CRO= Crowntec, Saremco Dental), and one resin for temporary applications (FRE=Freeprint temp, Detax). They underwent five PP's, divided into three LED-groups (PP 1: 385 nm, 76 mW/cm2, 180 s; PP 2: 400 nm, 77 mW/cm2, 180 s; PP 3: 460 nm, 49 mW/cm2, 180 s) and two flash curing groups (PP 4: 37 mW/cm2, ten flashes per second, pulse duration 100 μs, curing period 2000 flashes/200 ms; PP 5: 90 mW/cm2, ten flashes per second, pulse duration 100 μs, curing period 2000 flashes/200 ms). DC, HM, FS and EM were tested initially and after thermal cycling (10.000x, 5/55 °C) and within three different depths (0 mm, 2 mm, 4 mm). Data were analyzed with Kolmogorov-Smirnov, Kruskal-Wallis, Mann-Whitney-U test, Wilcoxon signed-rank test and Spearman's correlation (p < 0.05).
Results:
PP 5 consistently showed high values for both aging regimes, while PP 3 presented the lowest results. Artificial aging increased the properties for most groups, some decreased. For DC 25/30 PP-groups and HM 27/30 PP-groups showed higher values for 0 mm depths in comparison with 2 mm and 4 mm depths.
Significance:
Post-polymerization enhances the properties of the tested specimens intended for fixed dental prostheses (FDPs). PP 5 is recommended because it consistently resulted in highest DC, HM, FS, and EM across most groups, especially when combined with depths of 0 mm for DC and HM. Depths of 2 mm and 4 mm mostly resulted in lower values. Among LED groups, wavelengths of 385 nm and 400 nm are recommended for all materials, while wavelength of 460 nm seems not advisable.
