A biofilm is a well organized, cooperating community of microorganisms.5,6 The slime layer that forms on rocks in streams is a classic example of a biofilm (Figure 3a). So is the plaque that forms in the oral cavity. Biofilms are everywhere in nature. They form under fluid conditions. It is estimated over 95 percent of bacteria existing in nature are in biofilms.6 Sometimes biofilms are seen as positive, such as their use for detoxification of waste water and sewage. Humans have a symbiotic relationship with their microbiome. Our resident microorganisms can provide benefits. More often biofilms provide a challenge for humans.3,6

The slime layer that forms in dental unit water lines is an example familiar to most dental professionals. Biofilms can also be found lining oil pipelines, fish tanks, indwelling catheters, internal implants, contact lenses, and prosthetic devices (Figure 3b). Biofilms are responsible for the majority of infections in humans.6,7 Occasionally biofilms are deadly. Legionnaire's disease that killed 29 persons in Philadelphia in 1976 was ultimately traced to bacteria in the biofilm of the air conditioning system. Millions of dollars are spent each year working to control these biofilms.3,8

Figure 3a. Formation of biofilm on rock surface.
Image: Formation of biofilm on rock surface.
Figure 3b. Biofilm found on dental equipment.
Image: Biofilm found on dental equipment.