Case Review: How a Multi-Chair Dental Clinic Recovered from a Failed Sterilization Audit
A positive biological indicator during an infection control audit does not have to sink a clinic's week. This de-identified case review follows an Ontario multi-chair dental practice from a failed sterilization audit to a cleared re-inspection. If your office gets that call, here is the route they used.
The audit finding: a positive spore test
The practice, a seven-chair clinic near Toronto, ran three tabletop steam sterilizers and spore-tested each unit weekly — short of what the RCDSO expects, which is a BI on each day a sterilizer is used. Trouble started when the biological indicator (BI) from Friday's final load on unit #2 came back positive for Geobacillus stearothermophilus.
Blaming the test came first: the hygienist suspected a faulty incubator, the manager wondered about expired vials. The auditor steered the conversation somewhere more useful — what went through that chamber, and could every item be accounted for?
Reconstructing the failed load
This clinic kept a written load log, and that habit made the recovery possible. Without it, the team would have recalled a full week of instruments instead of one afternoon.
The log showed 14 wrapped cassettes and 22 pouches in a sterilizer validated for about 12 wrapped cassettes per cycle. The operator, a recent hire, loaded the chamber as a busier downtown office had taught her: cassettes on edge, pouches stacked flat in layers, paper facing paper.
On paper, the cycle looked clean: 121°C for 30 minutes at the built-in probe, indicator tape changed colour on every pack. But chemical indicators only confirm that steam reached the package; they say nothing about whether the load was sterilized. Only a biological indicator can answer that, by challenging the cycle with living spores.
Root causes: three compounding errors
The sterilizer's technician ran a diagnostic series and found three issues that worked together to defeat that load:
- Overloading. More wrapped items than the manufacturer's validated capacity, so steam could not circulate.
- Flat-stacked pouches. Pouches lying flat trap air between layers; they should stand on edge, never plastic-to-paper.
- A clogged drain filter. Paper-fibre buildup slowed air removal and left a cold zone where Friday's BI sat.
None of this appeared on the printout. The sterilizer reached temperature at its probe while the load did not — the exact gap a spore test exposes.
The corrective plan
The owner treated the fix as four commitments:
- Load limits posted on every unit. Each sterilizer carries a card stating its validated maximum, and nobody exceeds it.
- Retraining on loading. Pouches stand on edge in baskets, cassettes in a single layer, drain filter cleaned weekly.
- Stronger biological monitoring. The practice switched to CliniEco 24-hour rapid-readout biological indicators and now runs a BI in the first load of every operating day — which is what the RCDSO requires in Ontario.
- Standardized packaging. Wrapped sets go into CliniEco Class 4 dual-indicator pouches, each marked with CliniEco autoclave indicator tape.
The re-test: three consecutive clean cycles
Two weeks later, the clinic ran its recovery protocol: three full loads, each challenged with a biological indicator placed bottom front beside the drain. All three came back negative, and the follow-up audit cleared the sterilizer. The incident is now a training case in the office's infection control manual.
What other Ontario clinics should take from this case
The practice did three things right even while failing: it logged every load, used biological indicators, and treated the positive result as a process problem. Those habits turned a potential shutdown into a contained fix.
For clinics running tape-only monitoring, this case argues for upgrading. Daily spore testing is the requirement in Ontario; it is also the margin that keeps a small mistake from reaching a patient. When a BI does come back positive, honest load logs and a clear retrace-and-retest protocol turn an audit scare into a manageable fix.
Frequently Asked Questions
How often does the RCDSO require biological monitoring for dental sterilizers?
In Ontario, the RCDSO requires a biological indicator on each day a sterilizer is used. The weekly baseline is the CDC / AAMI ST79 standard in most US states; going beyond the requirement is never a compliance problem, only a resource question. A 25-pack of CliniEco 24-hour rapid-readout biological indicators covers about one month of daily testing in a single-sterilizer Ontario clinic.
What should you do the moment a spore test comes back positive?
Stop using that sterilizer immediately and quarantine everything processed since the last negative result. Pull the load log, identify the items and patients involved, and document each step. After fixing the suspected cause (overload, loading errors, maintenance), run three consecutive full cycles with negative BIs before returning the unit to service, per ANSI/AAMI ST79. Vacuum-cycle sterilizers should also get a Bowie-Dick test.
Do chemical indicator pouches or autoclave tape prove that sterilization worked?
No. Chemical indicators, whether Class 1 tape, Class 4 dual-indicator pouches, or internal strips, only confirm that a package was exposed to steam; they cannot confirm that spores were killed. That is the job of a biological indicator, which is why ISO 11138-3 sets strict requirements for the spores used. Think of the chemical indicator as the warning light and the BI as the crash test.
What causes a sterilizer to fail a spore test when the temperature display looks correct?
The probe reads the chamber, not the load. Overloading, flat-stacked pouches, a clogged drain filter, or items touching the walls create cold spots that never show on the printout — the same errors behind this case. ANSI/AAMI ST79 load-configuration guidance is a good start for rewriting your protocols, and fresh CliniEco biological indicators keep retest results trustworthy.
Related reading: browse the dental compliance hub for more clinic-ready sterilization guides.
read our dental sterilization monitoring compliance pillar for RCDSO rules.
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