California Dental Board Approved: Infection Control (2 Units)

Dental Unit Waterlines, Biofilm, and Water Quality


Dental Unit Waterlines and Biofilm

Studies have shown that colonies of microorganisms, or biofilms, can form on the inside of the small-bore plastic tubing that transports water within the dental unit to handpieces and air-water syringes. Once formed, a biofilm serves as a reservoir that may dramatically increase the number of free-floating microorganisms in water used for dental treatment.

Most organisms isolated from dental water systems originate from the public water supply and do not pose a high risk of disease for healthy persons. Although a few pathogenic organisms, such as Legionella spp. and Pseudomonas sp., have been found, adverse public health threats have not been documented.

Dental Unit Water Quality

Despite a lack of documented adverse health effects, using water of uncertain microbiological quality is inconsistent with infection control principles. Clearly, dental unit water quality (DUWQ) is a concern. Levels of contamination in water from untreated systems can exceed 1 million colony forming units per milliliter (mL) of water.

Untreated dental units cannot reliably produce water that meets drinking water standards (fewer than 500 CFU/mL of heterotrophic water bacteria). Even using source water containing <500 CFU/mL of bacteria (e.g., tap, distilled, or sterile water) in a self-contained system will not eliminate bacterial contamination in treatment water if biofilms in the water system are not controlled. Removal or inactivation of dental waterline biofilms requires use of chemical germicides.

Dental Water Quality

For routine dental treatment, meet regulatory standards for drinking water.*

* <500 CFU/mL of heterotrophic water bacteria.

For this reason, CDC recommends that water used for routine dental treatment meet regulatory standards for drinking water (fewer than 500 CFU/mL of heterotrophic water bacteria).

Available DUWL Technology

In recent years, commercial devices and procedures designed to improve the quality of water used in dental treatment have become widely available. Examples of methods shown to be effective include the following:

  • Self-contained water systems combined with intermittent or continuous chemical treatment.
  • In-line microfilters.
  • Combinations of these treatments.
  • Another alternative is to bypass the conventional dental water delivery system entirely and use either autoclavable or disposable pathways, such as sterile water delivery systems.

As with any dental equipment, always consult with the dental unit manufacturer for appropriate methods to maintain the recommended quality of dental water.

Monitoring Options

Monitoring of dental water quality may be performed using commercial self-contained test kits or commercial water-testing laboratories. In-office water-testing systems are available that work at room temperature using small paddles or plates of culture medium to reveal bacterial colonies after 72 or more hours.

Dentists should consult with the manufacturer of their dental unit or water delivery system to determine the best method for maintaining acceptable water quality (i.e., <500 CFU/mL) and the recommended frequency of monitoring.

Sterile Irrigating Solutions

During oral surgical procedures, microorganisms may enter the bloodstream and other normally sterile areas of the oral cavity (e.g., bone or subcutaneous tissue). For this reason, sterile solutions (e.g., sterile saline or sterile water) should be used as a coolant/irrigator when performing surgical procedures.

Because the tubing cannot be reliably sterilized, conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs. Sterile water delivery devices, such as sterile irrigating syringes, or bulb syringes should be used to deliver sterile water. Sterile water systems, such as those used with surgical handpieces, bypass the dental unit and use sterile disposable or autoclavable tubing.

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