Bacterial aerosols in dental practice - a potential hospital infection problem?

Aerosols containing microbes from the oral cavity of the patient are created when using modern high-speed rotating instruments in restorative dentistry. How far these aerosols spread and what level of contamination they cause in the dental surgery has become a growing concern as the number of patients with oro-nasal meticillin-resistant Staphylococcus aureus colonization has increased. The present study aimed to determine how far airborne bacteria spread during dental treatment, and the level of contamination. Fall out samples were collected on blood agar plates placed in six different sectors, 0.5-2m from the patient. Restorative dentistry fallout samples (N=72) were collected from rooms (N=6) where high-speed rotating instruments were used, and control samples (N=24) were collected from rooms (N=4) used for periodontal and orthodontic treatment where rotating and ultrasonic instruments were not used. The collection times were 1.5 and 3 h. In addition, samples were taken from facial masks of personnel and from surfaces in the rooms before and after disinfection. After 48 h of incubation at 37 degrees C, colonies were counted and classified by Gram stain. The results showed significant contamination of the room at all distances sampled when high-speed instruments were used (mean 970 colony-forming units/m2/h). The bacterial density was found to be higher in the more remote sampling points. Gram-positive cocci, namely viridans streptococci and staphylococci, were the most common findings. The area that becomes contaminated during dental procedures is far larger than previously thought and practically encompasses the whole room. These results emphasize the need for developing new means for preventing microbial aerosols in dentistry and protection of all items stored temporarily on work surfaces. This is especially important when treating generally ill or immunocompromised patients at dental surgeries in hospital environments.