Comparative Evaluation of Water Sorption in High-Strength Denture Base Resin Reinforced with 5% Silanized Titanium Dioxide Nanoparticles Using Microwave and Conventional Polymerization Methods: An In-vitro Study

Background: Water sorption is a critical determinant of the dimensional stability and long-term clinical performance of polymethyl methacrylate (PMMA) denture base resins. Absorbed water acts as a plasticizer within the polymer matrix, causing volumetric expansion and deterioration of mechanical properties. Titanium dioxide (TiO₂) nanoparticle reinforcement, particularly with silane surface treatment, has attracted considerable interest for improving the physical properties of PMMA. However, the combined influence of silanized TiO₂ incorporation and polymerization technique on water sorption in high-strength PMMA has not been comprehensively characterized. Aim: To evaluate and compare the water sorption behavior of high-strength PMMA denture base resin reinforced with 5% silanized TiO₂ nanoparticles when processed using conventional water bath and microwave polymerization techniques. Materials and Methods: Thirty standardized disc-shaped specimens (n = 15 per group) were fabricated in accordance with ADA Specification No. 12. Group A underwent conventional water bath polymerization (74°C/2 h + 100°C/1 h) and Group B underwent microwave polymerization (500 W/3 min). Water sorption was calculated gravimetrically after 7-day distilled water immersion at 37 ± 2°C and subsequent desiccation. Statistical analysis included the Shapiro–Wilk test, Levene’s test, and independent samples t-test (p < 0.05) with Cohen’s d effect size. Results: Group A demonstrated significantly lower mean water sorption (3.74 ± 2.33 µg/mm³) versus Group B (9.00 ± 5.52 µg/mm³; p = 0.002; Cohen’s d = 1.243). Conclusion: Conventional water bath polymerization conferred superior resistance to water sorption compared to microwave polymerization in TiO₂-reinforced high-strength PMMA. The polymerization technique remains a critical determinant of material behavior even when nanoparticle type and concentration are held constant.