Effect of Ozone on Biofilms in Dental Unit Waterlines
AL SHORMAN H1*, COULTER WA2, ABU-NBA’A L1, LYNCH E1. 1Restorativ e Dentistry, 2Microbiology, School of Dentistry, Queen’s University Belfast, NI
Ozone (O3) has been investigated for the treatment of DUWLs contamination due to its strong oxidative ability that enables it to kill all types of microorganisms.
Objectives: the aim of this study was to evaluate the efficacy of O3 to control the problem of DUWLs contamination and remove the biofilms from inside these lines
Methods: Two different treatm ent protocols were used. In the first protocol, three dental units with existing biofilms were treated with O3 for 1, 2 and 3 minutes respectively. The lines were subsequently flush ed with ozo nated water for 2 minutes, after which water was immediately sampled via the high-speed handpeice into sterile containers. Control water samples were collected b e fore treatment. This was repeated daily every morning for 7 days. Samples were cultured on nutrient agar plates and incubated at 35°C for 3 days after which bacterial counting was carried out. In the second protocol, a fourth dental unit was treated similarly with Ozone for 15 minutes. The line was then flushed for 15 minutes and tube samples were cut for immunoflourescence study at baseline, 5, 10 and 15 minutes. 3-4 sections of each sample were made. The imunoflourescence stain used was propedium iodide (PI).
Results: The baseline bacterial count was 2.9*104, 9*104 and 2.7*104 CFU/ml in the 1st, 2nd and 3rd units respectively. After the last O3 application, the bacterial count became 2*105, 0 and 0 CFU/ ml in the 1st, 2nd and 3rd units respectively. In the fourth unit, the biofilm was clearly evident in the baseline samples. It showed marked reduction after 5 minutes of flushing and was absent in the other samples.
Conclusions: The results suggest that O3 is capable o f reducing the bacterial count in D U W Ls to acceptable levels using this method. O3 was also able to reduce and then remove the biofilm from inside the DUW Ls.