Most dental teams can tell you exactly when their last spore test was. Far fewer can tell you when they last tested the ultrasonic cleaner. That gap matters, because sterilization only works on instruments that are actually clean. Bioburden left behind in serrations, hinges and lumens can shield microorganisms from steam, and no biological indicator in the world will flag a cleaning failure that happened two steps earlier.

This guide covers what Canadian dental guidance says about ultrasonic cleaner testing, how the foil test and commercial cavitation indicators compare, and a simple routine your sterilization team can run every week.

Why ultrasonic cleaning is the step that gets missed

Ultrasonic units clean through cavitation: high-frequency sound waves create microscopic bubbles in the solution that implode against instrument surfaces and dislodge debris. The problem is that cavitation can weaken gradually as transducers age, and nothing about the unit looks or sounds different when it does. The tank still hums. The instruments still come out wet. Only a test tells you whether the energy is still there.

The Canadian Dental Association's Essentials guidance on infection prevention and control is direct on this point: instruments must be visibly clean before sterilization, and ultrasonic units need to be checked for performance using a commercial test or a foil test at least weekly, preferably each day they are used.

How often should you test a dental ultrasonic cleaner?

• Minimum: once a week, documented.
• Best practice: every day the unit is in use, ideally at the start of the day after fresh solution has been added and degassed.
• Always: after the unit has been serviced, moved, or had a failed result, and whenever the manufacturer's instructions for use (MIFU) call for it.

Your provincial regulator and your unit's manufacturer may set additional requirements, so check both and write the frequency into your office infection control manual.

Option 1: The foil test

The foil test is the traditional, low-cost way to check cavitation. Per the CDA guidance, it works like this:

1. Start with clean, fresh solution, filled to the level the manufacturer specifies.
2. Degas the solution for at least 10 minutes. Fresh solution holds dissolved air that interferes with cavitation.
3. Cut a piece of thin aluminum foil (10 to 25 μm) slightly shorter than the tank's length and slightly longer than its depth, and attach it to a dowel so it hangs vertically without touching the bottom.
4. Rest the dowel across the tank edges and run the unit for about one minute.
5. Remove the foil, let it dry, and look for a consistent pattern of pitting and perforations across the sheet.

The downside: foil results are subjective. Two team members can read the same sheet differently, the foil is awkward to file in a log, and it takes time that a busy sterilization area often doesn't have. Areas with little or no pitting point to dead zones in the tank, but deciding what counts as a pass is a judgment call.

Option 2: Commercial ultrasonic indicators

Commercial cavitation indicators replace the foil sheet with a chemical indicator that changes colour when it's exposed to enough ultrasonic energy. They take the guesswork out of reading results, they're quick enough to run daily, and the indicator itself can be attached to your log sheet as a record.

The Atlas Wash-U-Test Ultrasonic Indicator is built for exactly this. It's Health Canada registered, runs during a normal cleaning cycle, and gives a clear colour-change result, so anyone on the team can read it the same way. A pack of 50 covers roughly ten weeks of daily testing on a single unit.

If your clinic reprocesses instruments in a washer-disinfector instead of (or as well as) an ultrasonic, the CDA guidance calls for testing those machines with a commercial soil test daily. The Atlas Washer Test Indicator is compatible with major washer brands including Hydrim and Miele.

Solution matters as much as the machine

A perfectly working transducer won't clean well in exhausted or contaminated solution. A few rules worth posting beside the unit:

• Change the solution at least daily, or sooner if it's visibly soiled or cloudy. Clean and dry the tank before refilling.
• Use a solution made for dental ultrasonic units and dilute it exactly as directed. Over- and under-concentration both reduce performance. Pre-measured options like Mark3 Bioenzymatic Ultrasonic Cleaner Tablets remove the measuring step entirely, while Mark3 General Purpose Ultrasonic Solution (4L) is an economical multi-enzyme concentrate for higher-volume clinics.
• Degas every fresh batch before the first load and before testing.
• Rinse heavy soil off instruments first. Excess debris dulls cavitation for everything else in the tank.

Loading mistakes that undermine cleaning

• Overloading. CDA guidance notes that dental ultrasonic units are often bought too small for the office's volume. Instruments stacked on top of each other shadow one another from cavitation.
• Closed hinges. Open hinged instruments and keep them open through reprocessing.
• Mixing metals. Don't clean stainless steel alongside copper, aluminum or brass instruments; it causes corrosion and discolouration.
• Wrong materials. Rubber, chrome or chrome-plated items, plastic, wood, glass and cork shouldn't go in an ultrasonic unit.
• Skipping the rinse. Rinse instruments thoroughly after removing them, then dry with low-lint material. Don't air dry or use fans.

A weekly ultrasonic routine your team can follow

When	Task	Record
Start of each clinical day	Empty, clean and dry tank; add fresh solution; degas 10 minutes; run cavitation indicator	Date, unit, operator initials, result (attach indicator)
During the day	Replace solution if visibly soiled or cloudy	Time of change
Weekly (minimum)	Confirm at least one documented performance test per unit; review log for gaps	Reviewer sign-off
After any failed test	Take unit out of service; retest with fresh, degassed solution; contact service technician if it fails again; reclean affected instruments	Failure, action taken, retest result

Missing or incomplete logs are among the most common findings in infection control inspections. A test you ran but didn't record is, for audit purposes, a test you didn't run.

Where ultrasonic testing fits in your monitoring program

Think of reprocessing as a chain where every link gets verified:

1. Cleaning: ultrasonic or washer indicator
2. Air removal (pre-vacuum sterilizers): daily Bowie-Dick test
3. Each package: Type 5 chemical integrator
4. Sterilizer efficacy: biological indicator, with results in as little as 20 minutes using the Atlas Rapid Incubator

If you'd like a refresher on the later steps, see our posts on chemical vs. biological indicators and our sterilization compliance checklist.

Frequently asked questions

Can I use a foil test instead of a commercial indicator?

Yes. Canadian dental guidance accepts either a commercial test or a foil test. Many clinics move to commercial indicators because the results are easier to read consistently and file.

What does a failed ultrasonic test mean?

It means the unit may not be producing enough cavitation to clean instruments reliably. First rule out solution issues (old, under-diluted or not degassed), then retest. A repeat failure usually points to a transducer or generator problem that needs service.

Do I still need to test if instruments look clean?

Yes. Visual inspection catches gross soil but not thin biofilm or debris hidden in serrations and hinges. Testing confirms the process; inspection confirms the result. You need both.

Stock up on ultrasonic and reprocessing supplies

Penguin Express ships infection control and sterilization monitoring supplies to dental and allied health clinics across Canada. Browse ultrasonic indicators, ultrasonic cleaning solutions and the full Atlas sterilization monitoring line, or reach out to our team at orders@penguinhealthgroup.com for bulk pricing.

This article is general guidance. Always follow your equipment manufacturer's instructions for use and the standards set by your provincial regulatory authority.