Abstract:
Autopolymerizing hard reline acrylic resins have not only have many advantages but also have disadvantages to patients. According to residual monomer (RM) content after polymerization, RM affect materials’ physical properties and also have harmful effects to soft tissue in oral cavity. Therefore, there are previous researches studied in reducing the RM content in acrylic resins such as water immersion in ultrasonic cleanser or immersion in ethanol solutions. The purpose of this study was to determine the appropriate concentration of ethanol under ultrasonic wave, affecting the reduction of RM content and maintain their flexural properties. Forty-eight specimens of Unifast Trad (UF) and forty-eight specimens of Kooliner (KL) were prepared according to their manufacturers’ instructions and divided randomly into eight groups (N=6): NC: Negative control; PC1 and PC2 (positive control); water immersion at 50°C 60 min and 55°C 10 min respectively; The others were immersed in ethanol solutions of 10, 20, 30, 40 and 50% with ultrasonic bath (40 kHz) at 55°C 5 min. RM were determined by HPLC following ISO 20795-1 (2013). Eighty specimens of UT and eighty specimens of KL were prepared according to their manufacturers’ instructions, and also divided into the same as the above eight groups to test 3-point flexural properties following ISO 20795-1 (2013)(N=10). Statistical analysis was performed using one-way ANOVA and Tukey HSD at p<0.05. Immersion UF in 40% ethanol solution under ultrasonic bath (40 kHz) at 55°C for 5 min and immersion KL in 10% ethanol solution under ultrasonic bath (40 kHz) at 55°C for 5 min are chosen to be a proper method to reduce RM effectively and maintain their flexural properties respectively.
