Adopted by the American Dental Association Board of Trustees, April 24, 1996, and ADA Council on Scientific Affairs, April 21, 1996

The American Dental Association (ADA) has received a growing number of reports from dentists, as well as their constituent and component dental societies, of regulatory activity mandating the installation of backflow prevention devices in dental offices. Such activity has primarily arisen through state and local health and environmental departments as well as certain public water utilities.

The purpose advanced for this requirement centers on the supposed need to protect cross-connected water systems from potential aspiration of oral fluids through the high-speed dental handpiece, air/water syringe and cuspidor. Such aspiration, which has been hypothesized might occur during a sudden drop in water pressure (e.g., during a break in a water main), has apparently resulted in concern about bloodborne diseases (e.g., HIV, HBV) being transmitted via water systems cross connected to the dental unit.

It is important to note that the transmission of bloodborne disease has never been associated with the use of any type of water source. Viruses are unable to reproduce outside their living host and are, therefore, unable to multiply in water. If, in the unlikely event that backsiphonage did result in aspiration of oral fluids, the volume of fluid involved would be minuscule, and the dilution factor on entering the public water supply would be so great as to render any bloodborne viruses non-infectious.

The only dental unit attachments with possible cross-connections to water systems are the cuspidor, high-speed handpiece and air/water syringe. Today, most dental offices do not use cuspidors, and those currently manufactured include an air-gap which serves as an effective backflow preventer. The risk of backsiphonage from the high-speed handpiece or air/water syringe is virtually nonexistent because:

• neither device is intended nor designed to ever be immersed in oral fluids; and
• if water flow is disrupted for any reason, such as in the event of a backsiphonage, the dental worker would automatically discontinue use of the instrument and attempt to resolve the problem.

Additionally, the ADA is currently working with the scientific community and industry to develop technology that will allow dentists, in the provision of dental care, to provide water of a higher microbiological standard than drinking water. This technology will include the use of dental units with contained water systems (not connected to the public water supply). Such systems are already available in the marketplace, and technology to allow the retro-fitting of mains-connected dental units to contained water systems is also available.

The ADA agrees with the American Water Works Association that the installation of backflow prevention devices should be consistent with the degree of hazard. However, the ADA believes that in evaluating the degree of hazard, disciplined and systematic analyses of available information must be conducted before a balanced assessment of the degree of hazard can be attained. Because isolated pieces of information, such as that from the mass media, may distort the reality underlying a given risk, all information should be critically evaluated.

Although a theoretical possibility of contamination resulting from backflow from the dental unit exists, the ADA believes this risk to be nearly zero. While theoretical risks should always be analyzed, responsible risk management demands that they should be considered in light of any realistic benefit the public may receive from eliminating them and the cost to society, as well as to individuals, of any proposed action. In the case of dentistry, the social cost involves reduced access to dental care that results when increased overhead costs, including the cost of regulation, are passed to the patient in the form of higher fees for dental services.

In summary, the Association believes that regulatory intervention requiring the installation of testable backflow prevention devices in dental offices is unjustified because:

• the Centers for Disease Control and Prevention has not identified any evidence of a public health risk due to this theoretical phenomenon;
• bloodborne viruses cannot reproduce outside their living host and therefore, unlike bacteria and fungi, cannot multiply in water systems;
• the amount of fluid that could theoretically be aspirated is minuscule, and would be quickly diluted in the public water supply;
• most dental offices do not use cuspidors, and cuspidors currently manufactured include an air-gap;
• dental instruments with cross connections to water systems are neither designed nor intended to ever be immersed in patient fluids;
• if water flow is disrupted for any reason, such as in the event of a backsiphonage, the dental worker would automatically discontinue use of the instrument and attempt to resolve the problem;
• current trends within the dental profession are towards dental units with contained water systems (not connected to the public water system); and
• cost benefit analyses demonstrate that the expected returns (net increase in healthful life) from these safety requirements are negligible when weighed against the cost; much greater returns could be achieved by directing scarce resources elsewhere.

The ADA is aware of the importance of maintaining the quality of dental unit water as well as the quality of the public water system. The Association has already taken major steps in this direction by issuing a position paper setting a goal for dental unit water to be of a higher microbiological standard than drinking water. The ADA will continue to work with dental manufacturers and the scientific community to assure it achieves this goal.

November 1999

Page Updated: June 05, 2002