KDA Today

KDA Today

For Immediate Release

Date: Dec 20th, 2016
Contact: Dr. Beverly A. Largent
Phone: 800-292-1855
Email: info@kyda.org

Whats in Your Water?!

What’s in your water?! The Culligan Man (1) may not be the only one asking this question. In late September, it was reported that 24 children who had received pulpotomies on primary teeth at Children’s Dental Clinic of Anaheim (California) developed infections that have been traced to the dental waterlines in the clinic. One child had three permanent teeth, one primary tooth and part of her jaw bone removed. The infections were caused by Mycobacterium abscessus, which is treated surgically due to antibiotic resistance. In 2015, this rare infection caused hospitalization of 20 children with suspected or confirmed infections in Georgia. (2)

Care for dental waterlines is difficult due to the formation of biofilm in the water lines. “The term ‘biofilm’ refers to the development of microbial communities on submerged surfaces in aqueous environments. The growth of biofilm is considered to be a result of complex processes involving transport of organic and inorganic molecules and microbial cells to the surface, adsorption of molecules to the surface (formation of the conditioning layer) and initial attachment of microbial cells, followed by their irreversible adhesion, facilitated by production of extracellular polymeric substances often referred to as glycocalyx or slime.” (3) Biofilm is present in community water pipes, and its formation and accumulation is dependent on several factors including the roughness of the pipe wall, the water temperature and pH. Control of the biofilm in the drinking water is obtained by chlorination at different levels, flushing the system with high velocity flow, and in extreme cases scouring with mechanical devices. (4)

“Biofilm provides microbial cells with: 1.) easier exchange of genetic material; 2.) easier accumulation of nutritive substances from the water phase; 3.) protection against an excess of nutritive substances and against drying. Biofilm bacteria are substantially resistant to surfactants, biocides and antibiotics.” (3) Biofilm formation in dental waterlines has been known for nearly 40 years. The ADA first issued a statement on dental waterlines in 1995, calling for improved design in dental equipment. The source for dental water line biofilm is the municipal water used in the system and suck back of patient saliva when anti-retraction valves are not used. The slime, composed of colonies of bacteria, fungi and protozoa, forms on the inner surface of the waterlines, thickens, and traps more free floating microorganisms from the water source. Pieces of the biofilm can dislodge, and pass out of the waterlines through the handpiece or the water syringe, causing potential problems for the patient or the dental health care worker. (3)

Appropriate waterline treatment can be confusing for the dental practitioner, as many recommendations seem contradictory. For example, some sources recommend filtration, while others say that it has no effect on the biofilm. New waterlines would seem to be the obvious solution, but biofilm has been shown to form in new lines from 0-120 days. (3) Separate water reservoirs for dental waterlines do not offer freedom from biofilm formation even with sterile or distilled water, although they do avoid interruptions in care during “boil water” notices. Flushing of the waterlines at the beginning of the day, recommended by the CDC in 1993, has been proven to be ineffective in reducing the biofilm or consistently improving the quality of the water used during dental treatment.

The current recommendations from the ADA for dental waterline maintenance is from the Council on Scientific Affairs, and seeks to balance the cost in light of the expected benefit, based on sound science. The guideline is for non-surgical dental procedures. There are separate Centers for Disease Control guidelines for surgical irrigation which were last updated in 2003. The CDC recommends that “sterile solutions such as sterile saline or sterile water should be used as a coolant/irrigation in the performance of oral surgical procedures. Oral surgical procedures involve the incision, excision, or reflection of tissue that exposes the normally sterile areas of the oral cavity including biopsy, periodontal surgery, apical surgery, implant surgery, and surgical extractions of teeth (removal of erupted or non-erupted tooth requiring elevation of mucoperiosteal flap). Conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs because the water-bearing pathway cannot be reliably sterilized. Delivery devices (e.g., bulb syringe or sterile, single-use disposable products) should be used to deliver sterile water. Oral surgery and implant handpieces, as well as ultrasonic scalers, are commercially available that bypass the dental unit to deliver sterile water or other solutions by using single-use disposable or sterilizable tubing.” (5)

Dental unit water should meet the same standards as drinking water. The drinking water quality is established by the Environmental Protection Agency, the American Public Health Association, and the American Water Works Association. The standard dictates that safe drinking water may not exceed 500 Colony Forming Units per milliliter (CFU/mL) of heterotrophic bacteria. Heterotrophic bacteria is defined as bacteria that require a carbon source to grow. These bacteria are not necessarily harmful, and are found in every type of water. They are measured by the heterotrophic plate count and are used as an indication of the amount of residual disinfectant present in a water supply. (6) “Sudden increases in HPC above levels typically seen may indicate a change in the quality of raw water, or that bacterial regrowth has occurred in the distribution system or plumbing.” (7)

The ADA recommends identifying the source of water for the dental unit, which in most cases is a municipal water supply. Options for controlling water quality include installation of a point-of-use filter between the dental instrument and waterline tubing, retrofitting the dental unit so that the water is supplied by a self- contained water system for easy delivery of chemical treatments, or installing a system that allows delivery of cleaning agents at the junction box. In association with the manufacturer of the dental unit, products can be identified that are compatible with the dental unit and fit the needs of the practitioner. There is a listing of the products available to the practitioner at ADA.org under the heading of Dental Unit Waterlines.

Strict adherence to maintenance protocols is required to maintain the quality of dental unit water. Each office should develop a schedule for waterline maintenance depending on the recommended treatment methods, and assign the duty to a specific person.

Water quality can only be determined with testing. There are many products available to the practitioner for testing water quality in the office. There are also labs that provide the service. ADA.org has a listing of products and laboratories that meet testing requirements. There are varied recommendations on how often the water should be tested. Some sources recommend one time a week, while others endorse a quarterly routine.

While there is not a public health problem with dental unit waterlines, there is scientific evidence that dental waterlines left untreated can have water that is not considered safe to drink. The presence of biofilm in the dental waterlines can put immunocompromised and older patients at risk. Protection of the patient, and the ability to provide the highest quality dental services require attention to dental unit water.

References:
1. (2015). Retrieved from http://www.culligan.com/
2. Ross, Erin (2016, September 30). Infection Outbreak Shines Light on Water Risks at Dental Offices. KQED News. Retrieved from https://ww2.kqed.org/
3. Szymanska, J. (2003). Biofilm and Dental Unit Waterlines. Ann Agric Environ Med 2003, 10, 151-157. Retrieved from https://www.ncbi.nlm.nih.gov/
4. Reiff, F. (1996, Fall) Biofilm in Water. Drinking Water & Health Newsletter. Retrieved from http://www.waterandhealth.org/
5. Recommendations from the Guidelines for Infection Control in Dental Health-Care Settings. (2003). Retrieved from http://www.cdc.gov/
6. Dental Unit Waterlines. (Updated August, 2016). Retrieved from http://www.ada.org/en/member-center/oral-health-topics/dental-unit-waterlines
7. Gandham, L. Heterotrophic Plate Count: What is HPC and when is the right time to use it? [Web log post]. Retrieved from http://www.moldbacteriaconsulting.com/bacteria/heterotrophic-plate-count-what-is-hpc-and-when-is-the-right-time-to-use-it.html

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