title: Color stability, surface roughness and flexural strength of an acrylic resin submitted to simulated overnight immersion in denture cleansers.
abstract: This study evaluated color stability, surface roughness and flexural strength of acrylic resin specimens after immersion in alkaline peroxide and alkaline hypochlorite, simulating a period of one and a half year of use of overnight immersion. Sixty disc-shaped (16x4 mm) and 80 rectangular specimens (65x10x3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and distributed into 4 groups (n=20): C1: without immersion, C2: 8 h immersion in distilled water; AP: 8 h immersion in alkaline peroxide effervescent tablet; SH: 8 h immersion in 0.5% NaOCl solution. Properties were evaluated at baseline and after the immersion. Color data were also calculated according the National Bureau of Standards (NBS). Results were analyzed statistically by ANOVA and Tukey's HSD test (α=0.05). AP (2.34 ± 0.41) caused color alteration significantly higher than C2 (0.39 ± 0.30) and SH (1.73 ± 0.52). The mean ΔE values were classified as indicial for C2 (0.36 ± 0.29) and noticeable for AP (2.12 ± 0.39) and SH (1.59 ± 0.48). SH (0.0195 ± 0.0150) caused significantly higher ΔRa (p=0.000) than the C2 (0.0005 ± 0.0115) and PA (0.0005 ± 0.0157) groups. There was no statistically significant difference (p=0.063) among the solutions for flexural strength (C1: 105.43 ± 14.93, C2: 100.30 ± 12.43, PA: 97.61 ± 11.09, SH: 95.23 ± 10.18). In conclusion, overnight immersion in denture cleansing solutions simulating a year and a half of use did not alter the flexural strength of acrylic resin but caused noticeable color alterations, higher for alkaline peroxide. The 0.5% NaOCl solution caused increase in surface roughness.
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, USP - University of São Paulo, Ribeirão Preto, SP, Brazil. helenpar@forp.usp.br
authors.forename: Helena de Freitas Oliveira
authors.initials: Hde F
authors.lastname: Paranhos
authors.forename: Amanda
authors.initials: A
authors.lastname: Peracini
authors.forename: Marina Xavier
authors.initials: MX
authors.lastname: Pisani
authors.forename: Viviane de Cássia
authors.initials: Vde C
authors.lastname: Oliveira
authors.forename: Raphael Freitas
authors.initials: RF
authors.lastname: de Souza
authors.forename: Cláudia Helena
authors.initials: CH
authors.lastname: Silva-Lovato
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000468:Alkalies / Q000737:chemistry; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D003820:Denture Cleansers / Q000737:chemistry*; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D010545:Peroxides / Q000737:chemistry; D018583:Pliability; D012973:Sodium Hypochlorite / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D000468:Alkalies; D003764:Dental Materials; D003820:Denture Cleansers; D010545:Peroxides; C540407:corega tabs; C040291:Lucitone; D012973:Sodium Hypochlorite