Influence of postpolymerization methods and artificial aging procedures on the fracture resistance and flexural strength of a vat-polymerized interim dental material.

STATEMENT OF PROBLEM: The influence of postpolymerization methods and artificial aging procedures on the fracture resistance and flexural strength of additively manufactured interim polymers remains unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the conditions (dry and water- and glycerin-submerged) and time (25, 30, 35, 40, and 45 minutes) of postpolymerization methods with and without artificial aging procedures on the fracture resistance and flexural strength of an additively manufactured interim material. MATERIAL AND METHODS: Bar specimens (25×2×2 mm) were manufactured from an interim resin (NexDent C&B MFH N1) with a 3-dimensional printer (NexDent 5100) as per the manufacturer's recommendations. Three groups were created based on the postpolymerization condition: dry (D group) and submerged in a container with water (W group) or glycerin (G group) inside the ultraviolet polymerization machine (LC-3DPrint Box). Each group was divided into 5 subgroups (D1 to D5, W1 to W5, and G1 to G5) depending on the polymerizing time (25, 30, 35, 40, and 45 minutes) (n=20). Each subgroup was divided into nonaged and aged subgroups. The aged groups were treated in a mastication simulator. Fracture strength was measured on a universal testing machine. The flexural strength was calculated as per International Organization for Standardization (ISO) 10477-2018. The Kolmogorov-Smirnov test demonstrated that data were normally distributed. The 3-way ANOVA test was used to analyze the data (α=.05). RESULTS: A significant main effect was found on the fracture strength analysis for each of the 3 factors: postpolymerization condition (F[2, 449]=81.00, P<.001), treatment duration (F[4, 449]=2.84, P=.024), and aging procedure (F [1, 449] =7.62, P=.006). The only significant 2-way interaction was between postpolymerization condition and treatment duration (F[8, 449]=3.12, P=.002). Furthermore, a significant main effect was found on the flexural strength for each of the 3 factors including postpolymerization condition (F[2, 449]=82.55, P<.001), treatment duration (F[4, 449]=2.85, P=.024), and artificial aging procedure (F[1, 449]=6.72, P=.010). The only significant 2-way interaction was between postpolymerization condition and treatment duration (F[8, 449]=3.33, P=.001). Dry postconditions at 25 minutes and nonaged procedures obtained the significantly highest fracture resistance and flexural strength values. CONCLUSIONS: Postpolymerization conditions and duration time affected the fracture resistance and flexural strength of the additively manufactured interim material assessed. Artificial aging procedures significantly decreased the fracture resistance and flexural strength of the additively manufactured interim dental material.