Microbiological study of selected risk areas in dental technology laboratories

To investigate the microbiological status of certain risk areas in the dental technology laboratory, namely pumice slurry, impression agar and curing water baths.

Samples were inoculated onto selective and non-selective media. Resultant fungal and bacterial colonies were counted and identified to genus or species level.

Pumice slurry freshly made up using disinfectant was free from contamination, but colony counts approached 10(9) g-1 after 3 days' use. Impression agar was free from contamination, probably because of its method of preparation and maintenance, which appears to achieve sterility. Staphylococci were most commonly isolated from curing water baths (and from the air). Candida spp. and other yeasts were common in pumice slurry.

Personnel and managers should be aware of the potential cross-contamination hazards posed by the presence of a range of opportunist pathogens in dental technology laboratories.