Two different jobs, often confused
Dental infection control involves two problems that get discussed as though they were one. They are not, and the distinction matters when you are choosing a chemistry.
The first is surface disinfection — the operatory between patients, the chair, the light handles, the countertops. The second is dental unit waterline (DUWL) quality — the water that flows through your handpieces and air/water syringes. Both involve microbes. They are governed by different standards, and they are not solved by the same product.
This article covers what the published evidence supports for hypochlorous acid in each, and — just as importantly — where it does not apply.
What the CDC actually requires
For routine dental treatment, the CDC standard for dental unit water is ≤500 CFU/mL of heterotrophic water bacteria, the same threshold the EPA applies to drinking water. For surgical procedures, waterlines are not acceptable at all: CDC directs practices to "use sterile saline or sterile water as a coolant/irrigant when performing surgical procedures."
The reason waterlines are difficult is structural. CDC describes it plainly — waterlines "promote bacterial growth and development of biofilm due to the presence of long narrow-bore tubing, inconsistent flow rates, and the potential for retraction of oral fluids." Narrow tubing means a high surface-area-to-volume ratio. Water sitting still overnight means undisturbed biofilm growth. You are not fighting planktonic bacteria in a tank; you are fighting an established film on the inside of a 2 mm tube.
What the waterline studies show
Two studies are worth knowing.
Yoon and Lee (2016) tested a hypochlorous acid–based disinfectant in dental unit waterlines and reported it effective for waterline decontamination — the first substantial peer-reviewed look at HOCl in this specific application.
A 2025 study in BMC Chemistry went further, testing HOCl combined with silver nanoparticles in an end-of-day treatment cycle over seven weeks. The combination group reached 0 CFU/mL at all four sampling locations, with all groups hitting 100% compliance with the ≤500 CFU/mL standard by week five. Scanning electron microscopy showed biofilm "visibly disrupted post-disinfection," and confocal microscopy found a significantly lower proportion of live bacteria in the combination group (P < 0.05).
That second finding — biofilm disruption, not just planktonic kill — is the one that matters clinically. Anything can knock down free-floating bacteria in a water sample. Getting into the film is the hard part.
An important limit on what any of this means commercially
EcoloxTech HOCl-AS200 is registered with the EPA (Reg. No. 101112-1) as a disinfectant for hard, non-porous surfaces, and dental offices are named on the label as an approved use site — alongside hospitals, health clinics, doctors' offices, nursing homes and laboratories.
The label's pathogen table covers Staphylococcus aureus (ATCC 6538), MRSA (ATCC 33591), Pseudomonas aeruginosa, Salmonella enterica, Enterococcus faecium, Escherichia coli, Listeria monocytogenes and Streptococcus pyogenes. On the viral side it covers SARS-CoV-2, norovirus, influenza A (H1N1 and avian H3N2), RSV, rhinovirus, adenovirus, herpes simplex types 1 and 2, HIV-1, and duck hepatitis B virus as a surrogate for human hepatitis B. It also qualifies for EPA emerging viral pathogen claims across enveloped, large non-enveloped and small non-enveloped categories.
For a dental setting, the hepatitis B surrogate, HIV-1 and MRSA entries are the ones that matter, because those are the organisms your infection control protocol is written around.
That registration does not cover dental unit waterline treatment. Waterline treatment is a different use pattern with its own regulatory pathway. The research above describes what hypochlorous acid does as a chemistry in published studies; it is not a claim that any EcoloxTech product is approved for use in your waterlines, and it should not be read as one. If waterline treatment is your problem, ask any supplier — including us — for the specific registration covering that use.
Where the registration does apply is operatory surfaces, and there the requirement is specific: preclean the surface, spray from 6–8 inches, then keep it visibly wet for five minutes before allowing it to air dry. Not a wipe and walk away. Five minutes of dwell is what every entry in the pathogen table was tested at, and a surface that dries in ninety seconds has not been disinfected to label.
One further label condition worth knowing: the product must carry at least 149 ppm available chlorine. On-site generation is convenient, but solution that has sat too long should be verified with a chlorine test kit rather than assumed.
Why the pH matters more than the concentration
Free chlorine exists in water as two species in equilibrium: hypochlorous acid (HOCl) and hypochlorite ion (OCl⁻). The proportion is set by pH, and the two are not equally effective. HOCl is uncharged and penetrates the bacterial cell wall readily; OCl⁻ carries a negative charge and is repelled by it.
Between pH 5 and 6.5, over 95% of free chlorine exists as HOCl. Above pH 6.5, the equilibrium shifts toward OCl⁻ and effectiveness drops. Below pH 5, chlorine gas begins to come out of solution — undesirable for different reasons.
The practical consequence shows up in direct comparisons. In one study, slightly acidic electrolyzed water at just 0.5 mg/L free chlorine, pH 5.5–5.8, one minute contact achieved >4.49 log₁₀ reduction of E. coli and >4.38 log₁₀ of P. aeruginosa. Sodium hypochlorite at the same 0.5 mg/L managed 1.28 and 2.31 log₁₀ respectively. Same chlorine, roughly three log units of difference, attributable to pH.
This is the substance behind the "more effective than bleach" claim you will see repeated across the industry. It is real, it is measurable, and it is about speciation — not about hypochlorous acid being a different or more exotic molecule.
The oral rinse question
Practices sometimes ask about hypochlorite as a pre-procedural rinse. The clinical literature here is on sodium hypochlorite, not on HOCl products, and it is early.
Galvan et al. (2014) ran a randomised, single-blind trial at USC's Ostrow School of Dentistry: 30 periodontitis patients, 0.25% sodium hypochlorite versus water, twice weekly for 30 seconds, over three months. Only 12 completed. Among those who did, plaque-free lingual surfaces increased 195% versus 30% in controls (p = 0.042), and bleeding-free teeth increased 421% versus 29% (p = 0.012). No significant change in probing depth or recession. Adverse effects were limited to complaints about taste.
Encouraging, and worth watching. But 12 completers is a pilot, not an evidence base — and to be explicit: this is not an approved use of any EcoloxTech product. We make generators for surface disinfection and process water. Nothing in our range is registered, cleared or intended for use in the mouth.
Where this leaves a practice
If your problem is operatory turnover, hypochlorous acid at label concentration is a registered disinfectant with a broad organism list, no fumes to ventilate, and no PPE burden beyond normal practice — with the caveat that five minutes of wet contact time is not optional.
If your problem is waterlines, the chemistry has genuine published support, but you need a product registered for that use, and you need to be monitoring against the ≤500 CFU/mL standard rather than assuming.
If your problem is instrument reprocessing, neither of these is your answer — that is high-level disinfection or sterilisation territory, and we cover the comparison with glutaraldehyde and the contact-time data against S. aureus separately.
References
- Centers for Disease Control and Prevention. Dental Unit Water Quality. Dental Infection Prevention and Control.
- Yoon HY, Lee SY. Dental unit waterlines disinfection using hypochlorous acid-based disinfectant. PubMed 27563184.
- In vitro evaluation of hypochlorous acid-silver nanoparticle waterline disinfectant for dental unit waterline disinfection. BMC Chemistry, 2025.
- Electrolysed water (hypochlorous acid) generation and efficacy against food-borne pathogens. Sustainable Food Technology, Royal Society of Chemistry, 2023.
- Effectiveness of slightly acidic electrolyzed water on bacteria reduction: in vitro and spray evaluation. PeerJ, 2020.
- Galvan M, et al. Periodontal effects of 0.25% sodium hypochlorite twice-weekly oral rinse. A pilot study. PubMed 24329929.
- US EPA. Stamped Product Label, HOCL-AS200, EPA Reg. No. 101112-1, accepted 10 December 2025 (label version 3).