In vitro evaluation of sodium hypochlorite and effervescent tablets actionregarding color alteration of heat and microwave-polymerized acrylic resins
The aim of this study was to evaluate color alteration of heat-polymerized acrylic resins (conventional and microwave-polymerized), after immersion in chemicals solutions of denture cleansers for different periods of time. Wax patterns were obtained (15 mm in diameter and 4 mm thickness) from a teflon matrix and were invested in metallic or microwavable flasks. The wax had been eliminated and the resins were mixed, packed and polymerized according to the manufacturers instructions. Two hundred specimens were made, 100 specimens of each commercial resin Lucitone 550 (L) e Onda Cryl (OC), which were immersed in the solutions: A)Distilled water-3 min.; B)Bony Plus-3 min.; C)Distilled water-5 min.; D)Corega Tabs-5 min.; E) Distilled water -20 min.; F) 0,5% Sodium Hypochlorite-20 min.; G) 1% Sodium Hypochlorite-20 min.; H)Distilled water-8 hours; I)0,5% Sodium Hypochlorite-8 hours; J)1% Sodium Hypochlorite -8 hours. Color alteration was assessed by a spectrocolorimeter (Color Guide 45/0 (BYKGardner) before and after 180 days simulation. The results were analyzed statistically by a two-way analysis of variance (ANOVA), and Student Newman-Keuls test, with significance level of 0.05. To relate the color differences to a clinical environment, the data were quantified by National Bureau of Standards (NBS) units. The results showed that the resin Lucitone 550 (ΔE=0,47±0,18) was more stable than the resin Onda-Cryl (ΔE=0,53±0,31). For both resins, the tablets, the hypochlorite by 20 minutes (0,5% e 1%) and by 8 hours (0,5%) did not produce higher alterations than the respective controls (L-A: 0,27 ±0,10; L-B: 0,44±0,21; L-C: 0,48±0,21; L-D: 0,46±0,13; L-E: 0,29±0,07; L-F: 0,37±0,08; L-G: 0,47±0,10; L-H: 0,61±0,11; L-I: 0,55±0,10; OC-A: 0,22±0,08; OC-B: 0,43±0,32; OC-C: 0,65±0,35; OC-D: 0,41±0,11; OC-E: 0,31±0,11; OC-F: 0,29±0,07; OC-G: 0,37 ±0,11; OC-H: 0,78±0,10; OC-I: 0,79±0,08). The 1% hypochlorite solutions (L-J: 0,74±0,09; OC-J: 1,06 ±0,13) produced higher alterations than the respective controls. The solutions employed by 8 hours (water and 0,5% and 1% hipochlorite) produced alterations classified as slight, according to the NBS system. The findings of this study showed that the effervescent tablets, used according to the manufacturer´s instructions, and the sodium hypochlorite (0,5% and 1%) used by 20 minutes presented lower values of color alterations in acrylic resins after a period of 180 days simulation. Higher mean averages were obtained when a period of 8 hours was simulated.
Advisor:Helena de Freitas Oliveira Paranhos; Celio Jesus do Prado; Raphael Freitas de Souza; Helena de Freitas Oliveira Paranhos
School:Universidade de São Paulo
Source Type:Master's Thesis
Keywords:Acrylic Resins Denture Cleansers Complete
Date of Publication:07/10/2008