Biofilm reduction and staining potential of a 0.05% chlorhexidine rinse containing essential oils.

OBJECTIVES: To assess the biofilm reduction and discolouration potential of a new 0.05% chlorhexidine (CHX) digluconate solution, containing additional essential oil and alcohol components, compared with that of standard control CHX solutions (0.05% and 0.2% CHX). METHODS: The potential to reduce total viable counts of growing mixed microbial populations was examined using the Zurich biofilm model. Biofilms were created on sterile pellicle-coated hydroxyapatite discs and exposed to test substances at different time points. After 64.5 h, mean colony-forming units and SDs were determined. Colour change measurements using light reflection analysis were carried out on saliva preconditioned bovine dentin and enamel samples, as well as on composite and glass ceramic restorative materials, after successive immersions in a standardized tea brew and the CHX solutions. RESULTS: The test solution was able to reduce biofilm formation by 3 log steps compared with a negative (water) control. This was significantly less effective than the standard control CHX solutions, which reduced viable counts by 6 log steps. Both the test and control solutions exhibited staining on all surfaces. Staining was most pronounced on dentin, followed by enamel and to a significantly lesser degree on the restorative materials. Furthermore, the staining caused by the test solution on these restorative materials was generally lower than that caused by the control solutions. CONCLUSIONS: The test solution exhibited an antimicrobial activity. The composition, however, seems to hamper its effectiveness. Accordingly, it produced statistically significant, although by trend less, staining on restorative materials.

Stainless steel sponge: a novel carrier for the immobilisation of the white-rot fungus Trametes hirsuta for decolourization of textile dyes.

Alginate beads, polyurethane foam, nylon sponge and stainless steel sponge were tested as carrier materials for the white-rot fungus Trametes hirsuta for laccase production under submerged fermentation conditions. Stainless steel sponge was the best carrier material leading to the highest laccase activities of up to 800 U/l after 8 days of cultivation. These values are higher than those reported to date operating with inert supports and without inducer addition. In a 1-l bioreactor containing T. hirsuta immobilised on stainless steel sponge laccase activities of about 2200 U/l were obtained when the culture medium was supplemented with 1 mM copper sulphate. There were no operational problems with this system during culturing time. The textile dye Indigo Carmine was almost totally degraded in 3 days by T. hirsuta grown in this bioreactor, while Lanaset Marine was degraded in two successive batches, reaching in the first batch a decolourization percentage of about 82% in 15 h and in the second one by 71% in 28 h. Results obtained after inhibition of growth of T. hirsuta by antibiotics indicated that dye decolourization could not exclusively be attributed to laccase activity.