Surface and microhardness alterations of denture materials following exposure to gastric juice

Abstract

Objective: To analyze the effects of exposure to simulated gastric juice on the mechanical properties and surface characteristics of resins used for partial and complete dentures. Material and Methods: Thirty discs of heat-polymerized, 3D-printed, and milled resins were fabricated and polished. Specimens were allocated into two groups according to the immersion medium: artificial saliva or simulated gastric juice. The degree of conversion of C=C bonds (DC) of heat-polymerized and 3D-printed resins was determined by Fourier-transform infrared spectroscopy. Surface characteristics were evaluated by surface roughness (Ra and Rz) and Knoop microhardness at baseline, 6 months and 1 year of exposure. Complementary scanning electron microscopy was performed. Roughness values were analyzed using the Friedman and Durbin–Conover tests, and microhardness by repeated-measures ANOVA and Tukey’s test (α = 0.05). Results: The degree of conversion was 85% for heat-polymerized resins and 65% for 3D-printed resins. At baseline, all materials exhibited relatively smooth surfaces with polishing marks. After exposure, surface morphology remained similar to the original, except for the heat-polymerized resin exposed to the acidic medium. Ra roughness was not affected by the immersion media (p = 0.449). However, time and material type significantly influenced microhardness (p = 0.002 and p < 0.001, respectively). Conclusion: Both immersion media reduced the microhardness of all resins. However, the extent of degradation caused by simulated gastric juice and artificial saliva was similar among heat-polymerized, milled, and 3D-printed resins.

KEYWORDS

CAD-CAM; Complete denture; Gastric juice; Mechanical tests; Printing three-dimensional.