Ozone Efficacy in the Treatment of Dental Unit Water Lines.

H AL SHORMAN*1 , L ABU-NABA'A1 , W COULTER2 , E LYNCH1 . 1Restorative, 2 Microbiology Dept, School of dentistry, Queen's University Belfast, NI

Ozone (O3) has been used for purification of water due to its efficiency and lack of side effects.

Objectives: This study aimed at testing the efficacy of ozone to control the contamination of dental unit water lines (DUWL) at two proposed regimens. Methods: Two dental units with existing biofilms were treated with O3 and subjected to microbiological assessment. The O3 device used was the HealOzone unit (CurOzone USA). It was connected to the dental unit water bottles using a quick release coupling. Control water samples were collected before treatment. O3 was applied for 1 minute to the water bottle in the first unit and for 3 minutes in the second unit. The lines were subsequently flushed with ozonated water for 2 minutes, after which water was immediately sampled via the highspeed handpeice into sterile containers. This was repeated daily every morning for 4 days (Tue.-Fri.) and after the weekend, on day 7. All the samples were cultured on nutrient agar plates and incubated at 35°C for 3 days after which bacterial counting was carried out.

Results: In the first unit the base line bacterial count was 7*104 CFU/ml. After O3 treatment the bacterial count was 1.2*105 , 2.4*103 , 1*103 , 80, 500 CFU/ml after the first, second, third, fourth and seventh daily application respectively. In the second unit, the baseline bacterial count was 5.2*103 CFU/ml. It showed a reduction to 300 CFU/ml after the first O3 application and then to 0 CFU/ml after the second application onwards. The bacterial count of samples from this unit remained 0 CFU/ml for 5 weeks afterwards.

Conclusions: The results suggest that O3 delivered in this way can play an important role in controlling the problem of contamination of DUWL. Application of O3 for 3 minutes is more effective than 1 minute.