Effect of the physical properties of acrylic resin of overnight immersion in sodium hypochlorite solution.
OBJECTIVE
This study evaluated colour stability, surface roughness and flexural strength of microwave-polymerised acrylic resin after overnight immersion in sodium hypochlorite, simulating 180 days use.


METHODS
Forty disc-shaped (15 mm x 4 mm) and 40 rectangular specimens (65 mm x 10 mm x 3 mm) were prepared from microwave-polymerised acrylic resin. The specimens were immersed in 0.5, 1% sodium hypochlorite, Clorox/Calgon and distilled water. Colour measurements (ΔE) were determined by a portable colorimeter. A surface analyser was used to measure roughness (μm). The flexural strength (MPa) was measured using a three-point bending test in a universal testing machine. Data were evaluated by one-way anova, followed by Student-Newman-Keuls test (α = 0.05).


RESULTS
Statistical analysis found significantly higher colour changes (SNK, p < 0.001) for the 1% sodium hypochlorite, but mean ΔE value quantified by National Bureau of Standards was classified as slight. When comparing the surface roughness, no statistical significance was found among the solutions (anova, p = 0.637). The 1% sodium hypochlorite presented significantly lower flexural strength compared with the control group (SNK, p = 0.034).


CONCLUSIONS
It was concluded that immersion in 1% sodium hypochlorite solutions for 8 h does influence the colour stability and flexural strength of microwave-polymerised acrylic resin, during the simulated period of 180 days.
Davi
Letícia Resende
LR
Department of Dental Materials and Prosthodontics, Ribeirão Preto School of Dentistry, University of São Paulo, Ribeirão Preto, Brazil. leticiadavi@hotmail.com
Peracini
Amanda
A
Ribeiro
Nathália de Queiroz
Nde Q
Soares
Rafael Bellini
RB
da Silva
Cláudia Helena Lovato
CH
Paranhos
Helena de Freitas Oliveira
Hde F
de Souza
Raphael Freitas
RF
D000180:Acrylic Resins / Q000737:chemistry*; D055598:Chemical Phenomena; D003116:Color; D003124:Colorimetry; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003902:Detergents / Q000737:chemistry; D004202:Disinfectants / Q000737:chemistry*; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008872:Microwaves; D010710:Phosphates / Q000737:chemistry; D018583:Pliability; D058105:Polymerization; D012973:Sodium Hypochlorite / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
D000180:Acrylic Resins; D003764:Dental Materials; D003902:Detergents; D004202:Disinfectants; D010710:Phosphates; D012973:Sodium Hypochlorite; C009285:sodium polymetaphosphate