Water Sorption and Water Solubility of Digitally Fabricated Denture Base Materials

(1) Background: Digitally fabricated denture base materials are increasingly used in everyday clinical practice, but scientific data on their properties is limited, especially regarding water sorption and water solubility. Water absorbed in denture base material penetrates between the polymer chains, acts as a plasticiser, and negatively affects mechanical properties. Residual monomers and other chemicals not chemically bonded in the polymer matrix can dissolve in water and may cause biological consequences such as irritation and inflammation of the oral mucosa or even allergic reactions. This can also have a deteriorating effect on the materials. Therefore, the aim of this study was to investigate the water sorption and water solubility of digitally fabricated denture base materials. (2) Methods: Six denture base materials were used in this investigation: three subtractively manufactured materials, two additively manufactured materials, and one heat-cured poly(methyl methacrylate) material as a control group. The investigation was carried out according to ISO 20795-1:2013. (3) Results: Water sorption for the control group was 28.02 µg/mm3, while all digitally fabricated denture base materials showed statistically significantly lower values, ranging between 20.42 and 23.54 µg/mm3, with a statistical difference observed within the subtractively manufactured group. All materials had water sorption values below the upper limit of 32 µg/mm3 specified in ISO 20795-1:2013. Water solubility for subtractively manufactured materials ranged between 0.04 and 0.40 µg/mm3, with values both higher and lower than the control group, but with no statistical difference. Water solubility for additively manufactured materials was 3.01 and 3.22 µg/mm3, which was statistically significantly higher than the control group, and these results exceeded the upper limit of 1.6 µg/mm3 specified in ISO 20795-1:2013. (4) Conclusions: Digitally fabricated denture base materials showed improved water sorption compared to the heat-cured material, while water solubility for subtractively manufactured materials was similar to the heat-cured material and poorer for additively manufactured denture base materials, with results that did not meet the minimum requirements set by ISO 20795-1:2013.