Cross-contamination potential of saliva ejectors used in dentistry

It has been postulated that evacuation systems used in dentistry could be a source of cross-contamination between patients through backflow of bacteri a dislodged from the saliva ejector tubings. The bacterial microflora assoc iated with these systems was characterized using transmission electron micr oscopy (TEM) and microbiological cultures. The potential for backflow was i nvestigated by a study of pressure differentials in evacuation system tubin g and by the presence of bacteria in backflow samples. Evacuation lines wer e coated with microbial biofilms in which microcolonies of Gram-positive co cci and Gram-negative bacilli predominated, embedded in an extensive polysa ccharide matrix. Most bacteria were metabolically active. Occasionally, buc cal material such as collagen, fibrin and eukaryotic cell debris was observ ed. In other experiments, flow reversal was detected several times during s aliva ejector use though each of these events was brief (less than 0.1 s). Aspiration of saliva, or occlusion of the mouthpiece opening by the oral mu cosa, were the major factors leading to backflow episodes. Bacteria associa ted with backflow were found in almost 25% assays, with counts ranging from 1-300 cfu/occurrence. The majority of the bacteria isolated from biofilm o r backflow samples were staphylococci, micrococci and non-fermentive Gramne gative rods. Pathogens such as Pseudomonas aeruginosa and Staphylococcus au reus were also isolated from backflow fluids. No oral streptococci could be recovered from biofilms in the tubing beyond 15 min from the last saliva e jector use however, suggesting that these species did not survive in the bi ofilms. These data suggest, although without direct proof of cross-contamin ation, the possible existence of an infectious risk associated with oral ev acuation systems, as potential pathogens may be shed from tubing biofilms f ollowing backflow. Even if the risk of cross-contamination between patients is considered to be low, the necessity for regular disinfection of these s ystems must be stressed, since biofilms can serve as a reservoir for pathog ens or harbor potentially infectious material.