Comparative effects on acrylic resin properties of short- and long-term immersion in alkaline peroxide solution.

Purpose: To evaluate the color stability (ΔE), surface roughness (ΔRa), and flexural strength of denture base acrylic resin after short (20 minutes) and long-term (8 hours) immersions simulating a period of 5 years of use.
Methods: 120 disk-shaped (16 mm x 4 mm) and 120 rectangular (65 mm x 10 mm x 3.3 mm) specimens were prepared (Lucitone 550) and distributed into three groups (n=20): distilled water (Control); Corega Tabs (CT) and Polident (Po), for immersions of 20 minutes and 8 hours. ΔE were determined by a colorimeter, ΔRa by a profilometer and the flexural strength by a universal testing machine. Data were evaluated by two-way ANOVA followed by Tukey's test and Bonferroni correction (α= 0.05).
Results: Short-term immersions for 20 minutes resulted in significant differences in ΔE, as CT values (1.46 ± 1.41) were higher than Po (0.55 ± 0.25) and Control (0.47 ± 0.21). Specimens immersed for 8 hours showed more extensive alterations overall than the control (ΔE [Po: 7.27 ± 0.53; CT: 5.58 ± 0.49; Control: 1.26 ± 0.23]; 916;Ra [Po: 0.16 ± 0.08; CT: 0.12 ± 0.11; Control: 0.07 ± 0.06]; flexural strength [Po: 42.99 ± 9.34; CT: 63.96 ± 12.98; Control: 64.59 ± 12.87]). The tested alkaline peroxide-based solutions promoted significant alteration on acrylic resin properties after overnight immersion. Therefore, short-term immersions seem to be more suitable for daily denture hygiene.
Clinical Significance: Alkaline peroxides were able to alter color stability, surface roughness and flexural strength of acrylic resin after overnight immersions, in a 5-year-simulated period of use.
Competing Interests: The authors declared no conflict of interest. Financial support: Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP (grants no.2010/51543-6 and 2011/22898-3).
(Copyright©American Journal of Dentistry.)