Legionnaires' disease isn't something you hear about every day-but when it shows up in a dental office, it’s not a minor issue. It’s a serious, sometimes deadly, lung infection caused by Legionella bacteria. And yes, it can come from the very water you use to rinse your mouth during a dental cleaning.
How Legionella Gets Into Dental Water Lines
Dental chairs use water to cool tools, rinse debris, and flush suction lines. That water doesn’t always come from the building’s main supply. Many clinics use independent water delivery systems-small tanks or bottles that feed water directly to the handpieces. These systems are often not connected to the building’s hot water heater or municipal water treatment.
Legionella thrives in warm, stagnant water between 20°C and 45°C. Dental water lines, especially if they’re not flushed daily or cleaned regularly, become perfect breeding grounds. Biofilm-a slimy layer of bacteria and microbes-builds up inside the narrow tubes. Once it’s there, it’s hard to remove without proper maintenance.
In 2023, a CDC report linked an outbreak of Legionnaires’ disease in Ohio to a dental clinic where water lines hadn’t been treated for over a year. Five patients were infected; two required intensive care. The source? Water from the dental unit’s reservoir.
Why Dental Clinics Are at Higher Risk
Unlike hospitals, dental offices aren’t always subject to strict water safety regulations. In Australia, the National Health and Medical Research Council (NHMRC) recommends water quality standards for dental units, but enforcement varies by state. Many clinics assume their water is safe because it comes from a tap. It’s not that simple.
Here’s what most people don’t realize: when you sit in the dental chair and the dentist turns on the spray, you’re inhaling tiny water droplets-called aerosols. If those droplets contain Legionella, you’re at risk. People with weakened immune systems, smokers, or those over 50 are especially vulnerable.
Even if you’re healthy, repeated exposure over time increases your risk. And because symptoms of Legionnaires’ disease-fever, cough, shortness of breath, muscle aches-look like the flu, it’s often misdiagnosed. By the time it’s correctly identified, it’s too late for simple treatment.
What Dental Clinics Should Be Doing
There are five proven steps every dental clinic should follow to keep water safe:
- Flush lines daily-at least two minutes before the first patient arrives and after each patient. Use both water and air to clear the lines.
- Use filtered or treated water-install in-line filters certified to remove Legionella. Some clinics use sterile water for procedures like surgery.
- Install water treatment systems-chemical treatments like chlorine dioxide or hydrogen peroxide can kill biofilm. UV light systems are also effective and chemical-free.
- Test water regularly-send samples to a lab every 3-6 months. The goal? Less than 100 CFU/mL of Legionella. Anything above that is unsafe.
- Train staff-every hygienist and assistant should know how to flush lines, recognize warning signs, and report issues.
Some clinics in Perth have started using bottled sterile water for all procedures. It’s more expensive, but it eliminates the risk entirely. Others use automated flushing systems that trigger after each patient. These aren’t luxuries-they’re basic safety measures.
What Patients Should Ask
You don’t need to be an expert to protect yourself. Before your next appointment, ask your dentist:
- Do you test your water for Legionella?
- How often do you flush the lines?
- Do you use treated or sterile water?
If they look confused or say, “We just use the tap,” that’s a red flag. Legally, clinics in Australia aren’t required to disclose this-but ethically, they should. If you’re immunocompromised, diabetic, or over 60, this question could save your life.
One patient in Melbourne, 68, developed Legionnaires’ disease after a routine cleaning. He didn’t realize the connection until his doctor found Legionella in his lung fluid. The clinic had never tested their water. He spent six weeks in hospital. His recovery took months.
What Happens If It’s Not Addressed?
Legionnaires’ disease kills 10-15% of people who get it. For those over 70, the death rate jumps to nearly 30%. Even survivors often face long-term complications-chronic fatigue, nerve damage, memory loss.
Legionella outbreaks in healthcare settings are rising. In 2024, Australia recorded 12 cases linked to dental clinics-up from 3 in 2020. Most were avoidable. The bacteria didn’t magically appear. It grew because no one checked.
Regulators are starting to act. Western Australia now requires dental clinics to submit annual water safety plans. Other states are considering similar rules. But until then, the responsibility falls on the clinic-and the patient.
Real Solutions, Not Just Theory
Some clinics use simple, low-cost fixes. A $200 inline filter can reduce Legionella by 99%. A $500 UV system lasts years and needs no chemicals. Automated flushers cost around $1,000 but pay for themselves in reduced liability and patient trust.
One Perth dental practice installed a UV system and started publishing their water test results on their website. Patient satisfaction scores jumped 40%. People started referring friends-not because they had the nicest chairs, but because they felt safe.
Legionella isn’t a conspiracy. It’s biology. It’s water. It’s neglect. And it’s preventable.
Final Thought: Safety Isn’t Optional
Water is essential in dentistry. But it shouldn’t be a hidden danger. Whether you’re a patient, a dentist, or a clinic owner, ignoring water safety is gambling with lives. You wouldn’t skip sterilizing your tools. Don’t skip sterilizing your water.
Legionnaires’ disease is rare-but it’s not rare because it’s impossible to prevent. It’s rare because most clinics don’t know how.
Can Legionnaires' disease be caught from a dental filling?
No, you can’t catch Legionnaires’ disease from a filling itself. The risk comes from breathing in water aerosols from dental tools like high-speed drills or ultrasonic scalers. These tools mix water and air, creating mist that can carry bacteria. The filling material is sterile and not a source of infection.
Is tap water safe for dental procedures?
Not necessarily. Tap water in Australia meets drinking standards, but dental equipment can introduce contamination. Water sitting in lines for hours can grow biofilm and Legionella. Even if the source is clean, the delivery system isn’t. That’s why clinics need dedicated water treatment-tap water alone isn’t enough.
How often should dental water lines be tested?
At least every three to six months. If a clinic uses chemical treatment or UV systems, testing every six months is acceptable. If they use untreated reservoirs or haven’t upgraded their system, monthly testing is recommended. Any reading above 100 colony-forming units per milliliter (CFU/mL) means immediate action is needed.
Are children at risk from Legionella in dental clinics?
Children are much less likely to develop Legionnaires’ disease. Their immune systems are usually strong enough to fight off the bacteria. But if a child has a chronic lung condition, is on immunosuppressive drugs, or was born prematurely, they should be considered at higher risk. Parents of high-risk children should ask about water safety before appointments.
What should I do if I think I got Legionnaires' disease from a dental visit?
See your doctor immediately and mention your recent dental visit. Tell them you suspect Legionella exposure. A urine test or sputum culture can confirm it. Report the incident to your local health department-they track outbreaks and can investigate the clinic. Don’t wait. Early antibiotics like azithromycin or levofloxacin can prevent serious complications.