Microbial contamination of dental units treated with different disinfectant solutions

Objectives: The aim of the present study was to evaluate the microbial contamination of general and surgical dental units after cleaning with different disinfectant solutions. Methods: A total of 8 dental units predominantly used for (A) general or (B) surgical treatment procedures were disinfected for 9 months with one of three different commercially available solutions: Alpron® [AL] (Alpro Dental Produkte GmbH, St. Georgen, Germany); Oxygenal® [OX] (KaVo, Biberach, Germany) or Chlordioxide [CD]. The disinfectant group was changed every 3 months. For testing the microbial contamination, water samples were taken from the conduit of each unit every week. The following microbial standard parameters were evaluated: amount of colony forming units (CFU) in 100 ml after 3-day cultivation at 22° and 36° C (threshold was defined at 100 CFU / 100ml), CFU in 100 ml after 7-day cultivation at 22° C, quantity of moulds after 3-day cultivation at 22° and 36° C. Additional tests were performed in order to detect Legionellae and Pseudomonas aeroginosa contamination in 1 ml of each sample. Results: In (A), only a small number of specimen transgressing the threshold of 100 CFU / 100 ml and neither Legionellae, nor Pseudomonas aeroginosa could be observed during the entire study period. No statistically significant difference was found according to the different cleaning techniques (p>0,05, Mann-Whitney-U-Test) In (B), significantly more bacterial contamination could be observed than in (A). Amount of CFU was significantly lower in [AL] and [OX] than in [CD]. Nevertheless, [AL] showed more CFU of Legionellae than [OX] and [CD] (p<0,05, Mann-Whitney-U-Test, respectively). Conclusion: Within the limits of the present study, it was concluded that (I) the risk for microbial contamination of dental units used predominantly for surgical procedures is higher than for general units. (II) In surgical units, [AL] and [OX] provides a better bacterial decontamination than [CD].