Certain reports associate waterborne infections with dental water systems, and scientific evidence verifies the potential for transmission of waterborne infections and disease in hospital settings and in the community. Infection or colonization caused by Pseudomonas species and nontubercolous mycobacteria can occur among susceptible patients through direct contact with water or after exposure to residual waterborne contamination of inadequately reprocessed medical instruments. Nontuberculous mycobacteria can also be transmitted to patients from tap water aerosols. Healthcare associated transmission of pathogenic agents (eg, Legionella species) occurs primarily through inhalation of infectious aerosols generated from potable water source or through use of tap water in respiratory therapy equipment. Disease outbreaks in the community have also been reported from diverse environmental aerosol producing sources, including whirlpool spas, swimming pools and a grocery store mist machine. Although the majority of these outbreaks are associated with species of Legionella and Pseudomonas, the fungus Cladosporium has also been implicated.
Researchers have not demonstrated a measurable risk of adverse health effects among DHCP or patients from exposure to dental water. Certain studies determined DHCP had altered nasal flora or substantially greater titers of Legionella antibodies in comparisons with control populations; however, no cases of legionellosis were identified among exposed DHCP. Contaminated dental water might have been the source for localized Pseudomonas aeruginosa infections in two immunocompromised patients. Although transient carriage of P aeruginosa was observed in 78 healthy patients treated with contaminated dental treatment water, no illness was reported among the group. In this same study, a retrospective review of dental record also failed to identify infections.
Concentrations of bacterial endotoxin (< 1,000 endotoxin units/mL) from gram-negative water bacteria have been detected in water from colonized dental units. No standards exist in United States Pharmacopeia (USP) sterile water for irrigation is only 0.25 endotoxin units/mL. Although the consequences of acute and chronic exposure to aerosolized endotoxin in dental healthcare settings have not been investigated, endotoxin has been associated with exacerbation of asthma and onset of hypersensitivity pneumonitis in other occupational settings.