[The Chemiklaven 7000/8000 on the test bench].

Sterilization of metal instruments in Chemiclaves is undoubtedly the most protective mode of sterilization, because corrosion and formation of spots is minimal. In the past sterilization with Chemiclaves was criticised, because of the emission of formaldehyde by older models and the questionable efficacy of formaldehyde sterilization for wrapped instruments. In the present investigation the capability of the newest Chemiclaves (7000/8000) to sterilize dental instruments was investigated. To monitor sterilization efficacy filter paper strips loaded with spores of Bacillus stearothermophilus or dental instruments directly contaminated with these spores were used as biological indicators. The performance of the Chemiclaves was assessed with and without a full load of instruments; after running half of the program cycle, the spore strips in the chamber being either unpacked or packed into paper bags. In addition it was investigated, whether it was feasible to use a formaldehyde free sterilization solution (Steri-Vap) with these sterilizers. The daily performance of the Chemiclaves in a dental practice and the emission of formaldehyde were tested in a room < 10 m3, in which both apparatus were operated at the same time. The Chemiclaves 7000/8000 sterilized reliably under the set test condition, however, the formaldehyde-free sterilization solution did not lead to an acceptable efficacy of sterilization. The new Chemiclaves efficiently adsorbed formaldehyde vapours. Harvey sterilizers require a meticulous observation of the producer's instruction, because in comparison to saturated steam the chemical vapours have a lower heat capacity. The Chemiclaves 7000/8000 are recommended for the sterilization of well cleaned, dry instruments wrapped in original MDT paper bags.