EFFECT OF WATER SOFTENING AND HEATING ON MICROBIAL-CONTAMINATION OF DENTAL UNIT SYSTEMS

This study regards the quality of the water used in 4 types of dental units making use of softened and heated water, softened but non-heated water, non-softened but heated water and non-softened and non-heated water The samples were taken from the incoming tap water, from oral ri nsing cup, the air-water syringe and the ultrasound descaling handpiec e. The results showed how the water underwent a notable growth in bact eria during its passage within the circuits of the units, reaching het erotrophic total counts greately exceeding the guidelines set down by Italian laws regarding drinking water. While the influence of softenin g was evident, the bacteria in the samples taken from descaling handpi ece, where there is more stagnation, found excellent growing condition s also at high temperatures. In the softened and heated waters a notab le growth of Pseudomonas aeruginosa was found and it is likely that th is was encouraged by the combined effect of the softening and heating. As far as the origin of the contamination is concerned, the bacteria present in the water systems seem to have come from the incoming water .