Accelerated Chemical Aging Effects on Flexural Properties and Surface Wettability of Fumed Silica-Modified Additively Manufactured Denture Resins

This in vitro study evaluated the effects of accelerated chemical aging on the flexural properties and surface wettability of additively manufactured denture base and teeth specimens reinforced with fumed silica. Denture base specimens were prepared as an unfilled control and with 20 wt.% fumed silica using two nominal particle sizes (110 and 500 nm), whereas denture teeth ones were prepared as an unfilled control and with 10 and 20 wt.% fumed silica (100 nm). Specimens for rectangular flexural (64.0 × 10.0 × 3.3 mm; n = 5 per group) and wettability (50.0 × 50.0 × 3.3 mm; n = 3 per group) tests were fabricated using a digital light processing (DLP) 3D printer, post-processed, and then immersed at 37 °C in artificial saliva (pH 6.2), sodium bicarbonate solution (pH 9.1), or acetic acid solution (pH 3.3) for 2, 4, and 6 weeks for accelerated chemical aging. Flexural strength and modulus were determined using three-point bending, while static contact angle, contact-angle hysteresis, and optical microscopy were used to evaluate aging-induced surface changes. Incorporation of 20 wt.% fumed silica increased the initial flexural modulus and flexural strength of the denture specimens by approximately 80% and 27%, respectively. All materials exhibited time-dependent degradation during aging, with acidic conditions mainly resulted in the greatest reductions in flexural properties. Silica reinforcement improved stiffness retention in denture base resins and reduced aging-induced deterioration, although its effects on denture teeth resins depended on filler loading and aging medium. Changes in contact angle and contact-angle hysteresis were associated with changes in flexural properties, indicating that surface wettability characterization may serve as a complementary nondestructive approach for assessing aging-induced degradation and predicting the service life of 3D-printed dental materials.