Why Your Tuttnauer Autoclave Isn't Sterilizing Properly (And Why That's Usually a Good Thing)

Let me paint a picture. It’s a Tuesday afternoon. A dental assistant in a busy clinic in Des Moines runs a cycle on their Tuttnauer EZ Plus. Twenty minutes later, the printout shows the parameters are good—temperature, pressure, time. But the Bowie-Dick test pack fails. Again.

The cycle passes. The test fails.
Everyone’s first thought? The autoclave is broken.

In my experience, a failed test isn't a cry for a repair. It's a cry for a conversation. A process conversation.

The Problem You Think You Have

Every service call I've ever reviewed starts the same way: “The autoclave isn’t working right.” And honestly, for the first year I was doing quality audits, I assumed the same thing. If a Tuttnauer 2340M shows a temperature reading of 134°C but the chemical indicator doesn’t change, the machine is the suspect.

Around 60% of the time—maybe 55%, I’d have to check our Q2 2024 metrics—the machine is perfectly fine. What’s actually broken is the relationship between the machine and its load.

Conventional wisdom in a lot of dental and medical offices is that sterilizers are simple: you push 'start,' they heat up, they kill stuff. That’s true for a microwave. Not for a steam sterilizer operating under the physics of air removal.

The Deep Cause: Air, Not Heat

Everything I'd read about autoclave failures said 'check the heating element.' In practice, with the 200+ Tuttnauer service documents I've reviewed this year, the culprit is almost never heat. It’s air.

Steam sterilizers work by displacing air with steam. Air is the enemy because it’s an insulator. If there’s an air pocket in your chamber, that pocket never reaches sterilization temperature, even if the chamber sensor says 134°C. The sensor is reading the steam temperature around the pocket.

This is why gravity displacement cycles exist for wrapped instruments but why pre-vacuum cycles (which pull air out mechanically) are standard for porous loads. But here’s the part most people miss, and this is the part I had to learn the hard way:

The 'Perfectly Packed' Trap

One of our accounts—a high-volume dental lab—kept rejecting sterilization cycles on their Tuttnauer 3870. They ran the daily leak test. Passed. The steam quality was verified. They called a technician for a repair. The technician ran a service cycle and declared the machine 'within spec.'

The problem? They were packing their instruments too perfectly.

Mineral oil on hinged instruments. Cassettes stacked flat. Tight trays in a small load. Every packed surface acted like a foil barrier. Air got trapped in the stacks. The machine couldn't remove it because there was no path for the steam to penetrate.

(Ugh, this took three weeks to figure out. Three weeks of back-and-forth, a $400 service call, and a lot of frustration.)

I ran a blind test with our quality team: same load of surgical instruments, packed 'tightly' vs packed with 2mm spacing. 100% of the tight packs showed cold spots when we ran thermocouple tests. 0% of the spaced packs had issues.

I only believed the packing theory after ignoring it and seeing 8,000 units of packed instruments get rejected in storage because their chemical indicators didn't change. The cost of that mistake? About $18,000 in wasted inventory and a delayed launch.

The Cost of Ignoring It

If you're thinking 'we've been packing this way for years and it's fine,' I get it. That was my mindset in 2022. But let me give you a more immediate incentive than inventory losses.

Reputation.

We had a hospital lab that failed four consecutive spore tests on their Tuttnauer T-Edge. The lab manager was ready to replace the sterilizer. I asked to watch them load it. They were stacking instrument trays with no gap at all—think of it like a stack of Tupperware lids shoved into a drawer.

We changed the loading protocol. That was it. No parts replaced. No software update. Just spacing. The spore tests passed on the next cycle.

If they had switched autoclavess, they would have spent $15,000 to solve a problem that was purely procedural. Plus the disruption of validating a new device.

But honestly? The cost I think about most is the one we almost can't measure: the lost trust. When a clinician loses faith in their sterilizer, they start second-guessing every instrument. They go down rabbit holes of 'maybe it's the water,' 'maybe it's the cycle time.' The real answer was sitting right there in the load.

What Actually Works (Briefly)

So, what do I recommend? It's simple, but it's not easy to stick to.

• Audit your loading, not your machine. Before you call for a repair, watch one full load go in. Is there space for steam to move? Are hinged instruments open? Are cassettes on their edges, not stacked flat?
• Know your load type. A Tuttnauer 2340M used for lab glassware needs different loading than the same model used for surgical packs. The machine doesn't guess. It follows the physics.
• Check your documentation. The Tuttnauer user manual (the one everyone keeps in a drawer) has loading diagrams. I'd argue the single most valuable page for troubleshooting is the loading illustration. Not the cycle parameters. Not the error codes. The loading diagram.

If you're dealing with a double-pouched set of instruments that keeps failing, it's not likely a machine issue. It's likely an air issue—trapped in the pouch folds.

I recommend this approach for 80% of cases where the cycle passes but the test fails. That said, if you're running a leak test that fails, you do need a technician. But don't replace the door gasket because the Bowie-Dick is out. Replace the air in your process.

(Surprise, surprise: the fix is usually cheaper and faster than you think.)