Infection control in dentistry: Microbial contamination of dental unit water and aerosols

The dental clinic is a potential site for the transmission of pathogenic microorganisms between patients and dental health care workers (DHCW), originating from the oral cavity and of dental unit waterlines (DUWL). There is a risk of transmission of pathogens due to the exposure to aerosols and spats, generated during dental treatment of infectious patients, which are dispersed in the environment.
The air and surfaces within 80cm from the patient’s oral cavity are substantially contaminated by microorganisms from water and human origin. These microorganisms are in low numbers also found up to 2 meters from the head of the patient.
Biofilms in the DUWL contribute to the microbial contamination of the effluent water from the dental unit. If these biofilms are treated with high concentrations of hydrogen peroxide or chlorine followed by a low dose of the same chemical disinfectants, these DUWL-biofilms can be controlled successfully. Prolonged exposure to chemicals may result in a shift of the microbial composition of DUWL biofilms leading to a selection of microbes which could lead to potentially pathogenic alterations of the composition in time.
Airborne pathogens pose a risk for DHCW, which varies from very low to almost 100%, depending on the characteristics of the microorganism, the level of air-ventilation in the treatment room and the level of personal protection (mainly respiratory protection).
This thesis reports on the risk of pathogen transmission in the dental clinic. The risk of infection for DHCW can be reduced by strict application of hygiene and infection control protocols.