Dental Unit Water Lines Contamination

Dental Unit Water Lines Contamination

The DUWL contamination is not just about microorganisms suspended in the water, the real problem lies in the presence of a reservoir that provides a constant and continuous source of bacteria, namely the bio-film. It consists of a microbial community that adheres to the inner surface of the dental waterline tubing. Most bio-films are heterogeneous in species composition and morphology, characteristics similar to those found in another bio-film with which dentists are more familiar with, dental plaque.
On average the bio-film is 30-50 microns thick and is enclosed in a polysaccharide layer known as the glycocalyx, which provides the bio-films with the property of resistance to some chemical agents. Bacteria derived from the incoming main water are intrinsically resistant to most biocides. These organisms become the primary source for continued contamination of the system. The mature bio-film eventually becomes populated with a wide variety of species of bacteria, fungi and amoebae. In addition growth within the confines of the bio-film enhances bacterial proliferation by binding and retaining a supply of nutrients which permits a higher level of metabolic activity whilst protecting bacterial population from biocide agents and flushing of the waterline.

Bio-film Formation

Bio-film formation is reversible in the early stages, as the adhesion to the surface is not strong. As occurs on tooth surface with pellicle formation preceding development of dental plaque, the inner surface of the tubing is first conditioned by absorbed macromolecules and low molecular weight hydrophilic molecules from the main water. This stage enhances the efficacy of bacterial adhesion. Initial colonisation and adhesion is by microorganisms that produce attachment structures (e.g. extracellular polymeric substances, fimbriae). Later adhesion events involve other species of bacteria that need prolonged exposure to a surface in order to attach firmly, adhesion and colonisation is achieved through the secretion of extracellular polysaccharides (EPS) and subsequent microbial multiplication, which is a time-dependent process.

As the water is continuously moving through the tubes of the working dental unit, how do the microorganisms find enough time to form bio-films? The answer lies in the properties of fluid dynamics and geometry of dental lines. A fluid in a tube moves in layers (laminar flow). At the centre of the lumen it travels fastest; the further away from this centre layer the slower the movement becomes as a result of friction. Water at the tubing walls is virtually stagnant allowing bacteria to adhere and colonise the internal surface, in addition the dental unit water lines represent an ideal place for bio-film formation because of the high surface-to-volume ratio in the tubing system. As the diameter of the water line decreases (as is the case for the micro bore tubing deployed in dental units) an increasingly larger surface area relative to volume becomes available for colonisation allowing the bacteria to be in contact with the water lines surface for a long time.

It is therefore essential that the water reservoir and supply lines are kept thoroughly clean and disinfected.


A dedicated decontamination agent developed exclusively for the routine cleaning of both the reservoir and water supply lines of integral systems used within the dental surgery. With a combined enzyme based detergent/disinfectant system it will rapidly remove bactericidal bio-film and render all treated internal surfaces thoroughly clean & disinfected.
Used as directed, a simple routine weekly service clean using Alkazyme-W will ensure ‘Clean Water in – Clean Water out’

For more information on Alkazyme-W please refer to products section.