Methods: Therefore a hygiene concept was developed and its successful realization has been under constant surveillance over five years. At the beginning of the investigation all biofilms were removed. Afterwards the protocol was followed: consisting of flushing each tube twice a day for 2 min. while continuously adding disinfectant at lower concentration to the water. High concentrated disinfectants were used regularly in addition for intensive disinfection and technical services performed according to the manufacturerxs recommendations. Water samples were analyzed using established microbiological methods at regular intervals of at least every 6 months. The water was considered contaminated if more than 100 CFU/ml of microorganisms were counted. Furthermore the efficiency of different water disinfectants (Alpron, Alpro®, St. Georgen, Germany; Dentosept P/PL, Sirona, Bensheim, Germany; Oxygenal 6, KaVo, Biberach, Germany) used in four types of dental units (Sirodont 2, Sirona M1 and C1, Siemens/Sirona, Bensheim, Germany; ESTETICA® Sensus 1066, KaVo, Biberach, Germany) were compared. Statistics were carried out with the ANOVA- and the t-test.
Results: The initial biofilm-removal reduced the amount of microorganisms significantly and the water was able to be kept clean during the following years. No statistical differences were found between the different types of dental units or the various disinfectants. Nevertheless, the difference in the microbiological concentration between the student and the faculty units was highly significant. Yet it was impossible to avoid completely microbial contamination. Therefore regular microbiological analyses were necessary to ensure this result and to recognize a recontamination early. Sporadic contamination could be removed using concentrate disinfectants, but established biofilms needed a biofilm-remover.
Conclusion: Following a standardized protocol is mandatory in order to avoid contamination reliably.