Dental Waterline Testing – A Crash Course in Commonly Accepted Methods
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So, you’ve done your due diligence and implemented your waterline disinfection measures. You’ve become familiar with terms like biofilm, shock, or residual disinfectant, and you’re probably feeling pretty good about your dental unit waterlines (DUWL). Don’t get me wrong, you should be. But you might be missing the final step in the equation-bacteria testing. A bacteria test is the only way to truly know what the “bacterial load” is on your waterlines. It’s also the only way to know for sure that your infection control protocols are effective.
Artist rendering. Bacteria suck and never look this cool in real life.
HPC Testing - Assessments You Will Literally Count On
Now that you’re ready to test, it’s important to know what you’re testing for and how to get a proper assessment. The American Dental Association accepted standard for bacterial load in a dental waterline is ≤500 CFU/ml HPC purity. If you don't know what HPC stands for I highly recommend you go back through our previous posts and get up to speed. HPC stands for Heterotrophic Plate Count, and it’s the standard metric by which we quantify the relevant bacterial content in a test sample. Though there are many different types and classifications of bacteria, carbon sourced HPC is what we are concerned with when it comes to dental lines.
Row Your Understanding, Then Your Samples
Bacteria testing as it relates to dental waterlines is a tricky business. Getting an HPC assessment can be relatively easy while at the same time being very difficult to quantify with absolute confidence. For lack of a better way to say it: take this with a grain of salt.
Bacteria are virtually impossible to eliminate completely and, for that reason, most test samples will contain some that can be grown in a test. As a dental health professional, your primary concern should be capturing an assessment of the bacterial load that your patients may be exposed to, hence the significance of the test method. Depending on your demand for relative accuracy, there are a few different test methods regularly employed in the dental setting.
Not All Methods are Created Equal
Bacteria Got You Feeling Dead in the Water? Grab Your Paddle and Get Moving
Lab Testing - Know Your Methods
There are two common test methods used by 3rd party labs: SimPlate HPC and R2a Agar Plating. Both tests will give you a valid HPC count, but there may be some test related factors in play. In the interest of not getting too technical, let’s simplify it to the basics. SimPlate HPC tests are incubated at a higher temperature for a shorter time which captures less bacteria in total but favors strains that are more likely to grow at body temperature. Compare that with the R2a Agar Spread Plate method which incubates at a lower temperature for a longer duration, capturing a more comprehensive spectrum of pathogens in the process.
So which one is best? That would depend. If you are looking at a realistic threat level of infectious pathogens to patients, SimPlate HPC gives you that assessment. If you are looking for your worst-case scenario and broad spectrum exposure, the R2a Agar Spread Plate method gives you the comprehensive perspective.
Regardless which method you choose, the importance of testing as part of the overall infection control protocol cannot be overstated. It is the only way to truly know what’s in your lines. Without it, you’re just guessing. Interpreting your results can be tricky. If you have questions about your water test results, you should contact your waterline disinfection manufacturer. Sterisil customers have the complete backing of Sterisil Technical Support (719.622.7200) and their Dental Water Compliance Specialist. Since waterlines are our sole focus, we can work with you and your team should you have questions about your test results.
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