The Fracture Strength of Acrylic Palatal Prostheses After Microwave and Chlorhexidine Disinfection: A Comparative In Vitro Study

Background/Objectives: Disinfection of removable prostheses is essential for controlling oral infections, yet the methods employed may compromise the mechanical reliability of denture base materials. This study evaluated the effect of microwave irradiation and immersion in 0.2% chlorhexidine solution on the fracture strength of three commonly used acrylic denture bases. Methods: Forty-five standardised maxillary palatal denture bases were fabricated from cross-linked conventional, high-impact, and light-cured acrylic resins. The specimens were divided equally into three treatment groups: water storage (control), immersion in 0.2% chlorhexidine solution for 30 min twice weekly, and microwave disinfection at 650 W for three minutes, each continued for four weeks. Fracture strength was determined by using the Universal testing machine. The data were analysed with one-way ANOVA followed by Bonferroni post hoc testing. Results: Cross-linked and high-impact acrylic resins exhibited significantly greater fracture strength than light-cured acrylics (p < 0.001). The overall ANOVA showed no statistically significant differences among disinfection methods (p = 0.069); however, post hoc comparisons revealed significant reductions in fracture strength within specific material groups following microwave disinfection. This effect was most pronounced in the light-cured group, whereas immersion in chlorhexidine produced no significant changes. Notably, the fracture strength of all groups remained above clinically acceptable thresholds. Conclusions: Microwave disinfection negatively influences the mechanical integrity of acrylic denture bases, particularly those fabricated from light-cured resins. In contrast, immersion in 0.2% chlorhexidine preserves fracture strength, supporting its use as a safe and effective protocol for routine disinfection in dental practice.