[Hygiene problems in dental practice with special attention to dental units].

Within a scope of an investigation concerning hygiene-problems in dental practice a longitudinal study was carried out in 20 dental offices with 53 units. In order to guarantee equal experimental conditions and to eliminate variations caused by changing water flow during the day, we took the samples before office hours alternating mondays, tuesdays and wednesdays. Those samples gathered from all handpieces (n = 530) and the drinking water faucets (n = 200) were examined according to the "Trinkwasser-Verordnung" (1986), diagnostics were supplemented concerning special groups of bacteria (see also Table 1). Analyses of copper, zinc and iron were done once during the study. Selecting certain sampling spots (see also Table 2) the surface contamination of the units and the surroundings was examined using the "Rodac"-method (n = 4800). The results of the study may be summarized as follows: The investigation concerning the surface contamination showed under qualitative and quantitative aspects (see also Fig. 10) constant contaminations on the patients' head- and armrests, the operating lamp, cuspidor-bowl and hand-wash-basin. In samples taken from the water system of dental units potentially pathogenic bacteria were isolated in 71%, in first place Ps. aeruginosa, followed by Ps. acidovorans and other species of this group. Legionella species occurred sporadically in the units and potable water of 8 offices. On the base of the total germ count (22 degrees C and 37 degrees C) the diagnosis "drinking-water quality" was possible only in 31%. The longitudinal investigation showed, that the contamination of the water system follows different progressive forms regarding extent and quality (see also Fig. 7). Relating to these results in the first step the development of a theoretical model concerning the different influencing factors (quality of water tubes and other devices, variation of temperature, quality of potable water and the effect of ionic exchangers, indirect contamination by patients and dental staff, nature of dental treatment, utilization frequency of the direct handpieces) appears to be necessary. Thus the contamination has to be understood as a developing process determined by specific promotors and catalyzers; in the second step the evaluation of adequate bactericidal and virucidal decontamination procedures fitting into the daily practical needs of dental offices should follow.