In situ study of the effect of endogenous and exogenous agents on color stability, hardness, and surface roughness of an elastomer for facial prostheses.

PURPOSE: To evaluate in situ the influence of sweat, oil, sunscreen, and disinfectant solution on the color stability, hardness, and roughness of elastomer for facial prostheses. MATERIALS AND METHODS: Standardized and intrinsically pigmented specimens remained in contact with human skin from the same person for 30 days, considering exposures (n = 36 per group), absent of exposition (Control, C); sweat and oiliness contact (SO); sweat and oiliness associated with sunscreen (SOS); 0.12% chlorhexidine digluconate immersion (CD0.12%); and all agents exposed (SOSCD). The main variables were color change (CIELab and National Standard Bureau system, NBS), Shore A hardness, and surface roughness, measured at baseline and 30 days. Qualitative analyses were performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The data were analyzed by Kruskal-Wallis tests (color) and two-way ANOVA (hardness and roughness) with Sidak post-test (α = 0.05). RESULTS: CD0.12% (1.54 ± 0.49) and SOSCD (2.10 ± 1.03) had similar effects and caused the smallest color changes, considered mild and noticeable (NBS), respectively. SOS promoted the greatest color change (6.99 ± 1.43, NBS: large) and hardness (17.97 ± 0.56); SOS promoted intermediate roughness (3.48 ± 1.05) between SOSCD (2.25 ± 0.53), and two similar groups: C (4.46 ± 0.95), and CD0.12% (4.39 ± 1.26). The qualitative analysis showed an irregular, dense, dry, and whitish layer on the surface of the specimens exposed to sunscreen, which was reduced when in contact with 0.12% chlorhexidine digluconate. CONCLUSIONS: Endogenous and exogenous factors are capable of altering elastomer properties. The 0.12% chlorhexidine digluconate minimized the changes caused by sweat, oil, and sunscreen.

Antimicrobial effect and cytotoxic activity of vinegar-hydrogen peroxide mixture: A possible alternative for denture disinfection.

STATEMENT OF PROBLEM: Soaking dentures in vinegar or hydrogen peroxide does not seem to remove the microorganisms involved with prosthetic stomatitis efficiently. A mixture of these 2 substances may be effective, but studies are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the antimicrobial effect and cytotoxic activity of vinegar-hydrogen peroxide mixtures against Candida albicans and Staphylococcus aureus. MATERIAL AND METHODS: For antimicrobial tests, planktonic cells and biofilms of C. albicans and S. aureus cultured on acrylic resin disks were exposed to 0.5% sodium hypochlorite; 0.2% peracetic acid; vinegar-hydrogen peroxide mixtures at concentration ratios 1:1, 1:3, and 3:1; vinegar-water mixtures at concentration ratios 1:1, 1:3, and 3:1; and hydrogen peroxide-water mixtures at concentration ratios 1:1, 1:3, and 3:1. Antimicrobial activity was evaluated by counting viable colony-forming units after disinfection. For cytotoxicity tests, the 1:1 vinegar-hydrogen peroxide mixture was serially diluted (10-1 to 10-4) and allowed to be in direct contact with HaCaT keratinocytes for 24 hours. Cytotoxicity was quantitatively and qualitatively determined by counting the number of viable cells and analyzing morphological cell changes. RESULTS: All vinegar-hydrogen peroxide mixtures, sodium hypochlorite, and peracetic acid efficiently eliminated C. albicans and S. aureus (P<.05), whereas vinegar and hydrogen peroxide solutions used separately were not as efficient as the experimental mixtures. The 10-3 and 10-4 dilutions of vinegar-hydrogen peroxide solutions were considered noncytotoxic, whereas dilutions below 10-2 were strongly cytotoxic, comparable with the 10-2 dilution of 0.2% peracetic acid. CONCLUSIONS: The vinegar-hydrogen peroxide mixture effectively eliminated C. albicans and S. aureus from acrylic resin. Dilutions equal or below 10-2 of this mixture presented strong cytotoxic effects.