Izabela Kruszelnicka

Is water in dental units microbiologically safe

BACKGROUND Water supplied to the dental units must be of sufficient quality. The article presents the results of the microbiological analysis of cold municipal water which flows into a patients disposable mouthwash cup, and demineralized water which flows through a waterline into the tool panel of a dental unit from the tank placed in the water group. MATERIAL AND METHODS In order to assess the degree of purity (impurities) of water used in dental units, 2 series of microbiological tests were carried out in 6 dental surgeries from April to June, 2013. The water samples for microbiological testing were collected into sterile microbiological bottles in accordance with the current methodology. The water for the tests was collected from a sterile cup-filling tap (municipal water) and from an air/water syringe (demineralized water). The bacteria were cultured according to the Polish Standards - PN-EN ISO 6222, PN-EN ISO 9308-1, and PN-EN ISO 16266. RESULTS In the tested samples of water numerous psychrophilic bacteria (max 29 100 CFU/ml) and mesophilic bacteria (max 24 700 CFU/ml), including single coliforms, were found. CONCLUSIONS The results show that water delivered to a dental unit should be periodically tested bacteriologically and in terms of physical and chemical properties. Water systems of dental units should also be periodically disinfected to eliminate bacteria and biofilm.

The Variability of the Concentration of Bioaerosols Above the Chambers of Biological Wastewater Treatment

Abstract The article presents the results of research over microorganisms (psychrophilic and mesophilic bacteria and microscopic fungi) found in wastewater in denitrification and nitrification chambers and specifies the proportion of these microorganisms in bioaerosol at various levels above wastewater level (20, 50 and 100 cm). In the denitrification chamber (anoxic) in 1 cm3 of sewage there were on average 30.35 · 106 CFU of mesophilic bacteria, 72.88 · 106 CFU of psychrophilic bacteria, and 37.3 · 105 CFU of microscopic fungi. In the nitrification chamber, where the oxygen concentration ranged from 0.37 to 2.32 mg O2·dm−3 of wastewater, the number of microorganisms was lower. In 1 cm3 of wastewater there were on average 20.2 · 106 CFU of mesophilic bacteria, 51.76 · 106 CFU of psychrophilic bacteria, and 15.22 · 105 CFU of microscopic fungi. In sewage bioaerosols above these chambers, higher numbers of psychrophilic bacteria than mesophilic ones and microscopic fungi were reported. At the same time differences in the number of microorganisms at different heights above the surface of wastewater could be observed in bioaerosol, as well as between the chambers of the bioreactor. It was found that most frequently the amount of microorganisms decreased with height. The percentage emission ratio (ER) of microorganisms in bioaerosols coming from wastewater accounted for only a fraction of a percent and ranged from 1.13 · 10−8 % (microscopic fungi over the denitrification chamber) to 24.53 · 10−9 % (psychrophilic bacteria over the denitrification chamber). It was found that the process of mixing, aeration of wastewater, have an effect on the emission of microorganisms.