No one can see sterility. Instruments that went through a failed cycle look exactly like instruments that went through a good one. That is why dental infection control relies on three layers of monitoring, each catching different failures, and on records that tie every package back to the cycle that processed it. When something does go wrong, those records decide whether you recall one load or three weeks of instruments.
This guide covers the monitoring equipment and supplies (indicators, test packs, incubators, and mail-in services), the routine, the failed spore test protocol, and record keeping. It pairs with our autoclave guide.
Key takeaways
- The CDC calls for three kinds of monitoring: mechanical (every cycle), chemical (an internal indicator in every package, plus an external one if the internal one is not visible), and biological (a spore test at least weekly).
- Spore test every load that contains an implantable device, and use a matching control from the same lot as the test indicator.
- Chemical indicators come in six ISO types. Internal indicators should be multiparameter types, and every indicator must be labeled for your sterilization method and cycle.
- After a positive spore test: take the sterilizer out of service, review procedures, retest immediately, and recall implantable items. A second positive keeps the unit out of service until it is repaired and passes three consecutive fully loaded test cycles.
- Keep mechanical, chemical, and biological records as long as your state requires; retention rules vary by state.
What monitoring does and how it works
The CDC's sterilization monitoring best practices describe a combination of three methods:
- Mechanical monitoring: checking the sterilizer's gauges, display, or printout to confirm that pressure, temperature, and exposure time reached the manufacturer's levels. Done for every load. It tells you the machine thinks the cycle was correct.
- Chemical monitoring: indicators that change color when exposed to sterilizing conditions. An internal indicator goes in every package; an external indicator is used when the internal one cannot be seen from outside. It tells you conditions reached the inside of that package. Results are immediate.
- Biological monitoring: spore tests that challenge the process with highly resistant bacterial spores (for steam, Geobacillus stearothermophilus). If the spores are killed, the cycle was lethal. It is the most direct test of sterilization but takes time to read.
Parts and supplies you should know
- Cycle printout or data log: the mechanical record. Newer sterilizers store cycle history internally or send it to software.
- External indicators: indicator tape and the ink on pouches, which show a package has been processed.
- Internal indicators: strips or cards placed inside packages and cassettes.
- Air removal test packs: Bowie-Dick style tests for pre-vacuum sterilizers.
- Biological indicators (BIs): self-contained vials for in-office incubation, or spore strips in envelopes for mail-in services.
- Process challenge devices: test packs or holders that put the BI in a defined, challenging position.
- Incubator or auto-reader: for in-office BIs; auto-readers detect results by fluorescence or color change.
- Logbook or software: where it all comes together.
Chemical indicator types, explained
Chemical indicators are classified in ISO 11140-1 into six types. Older CDC and industry documents talk about five "classes"; you will see both words.
| Type | What it responds to | Typical use in a dental office |
|---|---|---|
| Type 1: process indicator | Exposure to the process; distinguishes processed from unprocessed items | Autoclave tape, pouch ink. External use only; not proof of sterilization conditions |
| Type 2: specific test indicator | Used in specific test procedures | Bowie-Dick and similar air removal tests for pre-vacuum sterilizers |
| Type 3: single-variable indicator | One critical variable, such as temperature | Rarely the right choice for internal use |
| Type 4: multi-variable indicator | Two or more critical variables | Internal indicator in packages and cassettes |
| Type 5: integrating indicator | All critical variables, with performance correlated to a biological indicator | Internal indicator; common in cassettes and implant or surgical packs |
| Type 6: emulating indicator | All critical variables for a specific cycle | Internal indicator matched to a defined cycle |
The CDC notes that multiparameter internal indicators, which respond to two or more parameters such as time and temperature, give more information than single-parameter ones. In practice that means Type 4, 5, or 6 inside packages. Whatever you choose, it must be labeled for your method (steam, dry heat, or chemical vapor) and your cycle parameters. Midmark's sterilizer manual, for example, specifies FDA-cleared chemical indicators labeled for the cycle parameters in use. A chemical indicator that has not fully changed means the package cannot be used.
Which biological monitoring setup does your practice need?
| Option | How it works | Pros | Cons |
|---|---|---|---|
| Mail-in service | Staff process spore strips in a load, then mail them with an unprocessed control to a lab that incubates and reports | Third-party documentation; reminders and reports; no incubator to maintain | Results take days, so a failure is discovered after more loads have been used; mail delays |
| In-office self-contained BIs | Staff process a vial, activate it with a control from the same lot, and incubate in an office incubator or auto-reader | Much faster results; immediate retesting; easier to hold implant loads for results | Incubator purchase and upkeep; staff must follow the protocol exactly; office keeps its own records |
| Hybrid | Routine weekly mail-in plus in-office BIs for implant loads and retests | Documentation plus speed when it matters | Two systems to manage |
Decision guide
- Implant and surgical practices: the CDC calls for a BI with every load containing implantable devices, and those items should be held until results are known where possible. Rapid-readout in-office systems make that practical.
- General practices with one or two sterilizers: mail-in service is simple and provides outside records; add an in-office incubator if you want same-week retests after a failure.
- Multiple sterilizers: every sterilizer gets its own weekly test, including cassette units and backups in regular use. The CDC does not have a separate rule for part-time sterilizers.
- Check your state: some state rules specify spore test frequency, the type of service, or record retention.
How to use it: daily and weekly operation
These steps are generic. Follow the indicator manufacturer's instructions, your sterilizer's IFU, and your state's rules.
Every load
- Place a correct-type internal chemical indicator in every package or cassette, in the area steam reaches last (usually the center).
- Label each package with the sterilizer, load or cycle number, and date.
- After the cycle, confirm the mechanical readout met the cycle parameters. Initial and file the printout or save the log.
- Check external indicators before storage and internal indicators when the package is opened at chairside. Any failure: do not use, reprocess, and log it.
Daily, for pre-vacuum sterilizers
- Run the air removal test the manufacturer requires (for example, a Bowie-Dick or vacuum test) in an empty chamber before the first load, and record the result.
Weekly spore test
- Pick a consistent day, often the first load of the week, and record which sterilizer is being tested.
- Place the BI where the indicator instructions direct, typically inside a package or process challenge device in the most challenging spot of a representative, normally loaded chamber.
- Run the cycle you use most for patient instruments (or the one the indicator instructions specify).
- After the cycle, let the BI cool as directed. For in-office systems, activate and incubate it alongside an unprocessed control from the same lot. For mail-in, package the processed strip and the control and ship them promptly.
- Read and record results. The control must grow (positive) for the test to be valid; the processed BI should show no growth.
- Also test after installation, relocation, or major repair before returning a sterilizer to patient use, following the manufacturer's instructions.
What to do after a failed spore test
Write this protocol down before you need it. The CDC's dental FAQ lays out the steps for a positive spore test when mechanical and chemical indicators looked normal:
- Remove the sterilizer from service. Use a backup unit if you have one.
- Review procedures: loading, packaging, cycle selection, indicator placement, and whether the correct BI and control were used.
- Quarantine or recall implantable items processed since the last negative test. Non-implantable items do not require recall after a single positive result unless the sterilizer is found to be malfunctioning.
- Repeat the spore test immediately in the same cycle.
- If the repeat is negative and procedures were correct, return the sterilizer to service.
- If the repeat is positive, keep the sterilizer out of service until it has been inspected or repaired and then rechallenged with spore tests in three consecutive, fully loaded chamber cycles.
- Recall suspect loads where possible, then rewrap and resterilize them. Your load numbers and records tell you which packages came from which cycles.
- Document everything: the failure, the review, retest results, repairs, recalls, and who did what.
The expensive mistake is not knowing which loads to recall. If packages are not labeled with sterilizer and load numbers, or if cycle records are incomplete, the only safe answer after a confirmed failure may be to reprocess everything back to the last negative test. Labeling every package costs seconds.
Your state may add its own requirements for failures and documentation. Confirm with your state dental board, and if a confirmed failure raises questions about patient notification, involve your professional liability carrier and a dental-specific attorney.
Record keeping
The CDC says to keep mechanical, chemical, and biological monitoring records long enough to comply with state and local regulations, along with equipment maintenance records. Because retention periods vary by state, check your board's rules and keep records at least that long. A practical record set:
| Record | What to capture |
|---|---|
| Cycle log | Date, sterilizer, load number, cycle type, time, temperature, pressure, operator initials, pass or fail |
| Load contents | Cassette or kit IDs, or a general description; implant loads flagged |
| Chemical indicator failures | Package, load, action taken |
| Air removal tests | Date, sterilizer, result, operator |
| Spore tests | Date, sterilizer, BI lot, control result, test result, reader or lab report |
| Failures and corrective action | What happened, retest results, repairs, recalls, dates |
| Maintenance and service | Service reports, calibration checks, parts replaced |
Digital logs from connected sterilizers and auto-readers make this easier, but make sure the data is backed up and exportable. Our compliance chapter covers how sterilization records fit with the rest of your program.
Maintenance schedule
| Task | Frequency | Who | Notes |
|---|---|---|---|
| Mechanical record review and filing | Every load, reviewed daily | Sterilization staff | Flag any out-of-range cycle |
| Air removal test (pre-vacuum units) | Daily | Sterilization staff | Per sterilizer IFU |
| Spore test each sterilizer | At least weekly; every implant load | Designated staff member | Matching control from same lot |
| Check incubator or auto-reader temperature and function | Each use or per IFU | Designated staff | Wrong temperature invalidates results |
| Rotate indicator stock; check expiration dates and storage conditions | Monthly | Office manager | Store per the indicator label |
| Audit records for gaps | Monthly or quarterly | Infection control coordinator | Missing weeks are the most common finding |
| Staff training and protocol review | Annually and at hire | Office manager | Include the failed spore test protocol |
| Incubator or reader service | Per manufacturer | Manufacturer or technician | Keep the service record |
Troubleshooting
| Symptom | Likely causes | What to try | When to call a technician |
|---|---|---|---|
| Control BI shows no growth | Expired or mishandled BIs, incubator not at temperature, control not activated | Test is invalid; check incubator and lot; repeat with a new pair | Incubator temperature is off |
| Positive spore test | Loading, packaging, wrong cycle, handling contamination, sterilizer malfunction | Follow the failed spore test protocol above | Repeat positive |
| Internal chemical indicator not fully changed | Overloading, air entrapment, wrong indicator type, cycle problem | Do not use package; check indicator label and loading; reprocess | Repeated failures with correct loading |
| External indicator changed, internal did not | Steam not penetrating package; dense or overwrapped packs | Reduce pack density; check wrapping and orientation | Persists with correct packaging |
| Bowie-Dick or air removal test fails | Air leak, gasket, vacuum pump problem, test run incorrectly | Repeat per instructions with empty chamber | Second failure |
| Mechanical readout out of range | Aborted cycle, sensor or heating problem | Treat load as not sterile; rerun | Recurring |
| Mail-in results late or missing | Shipping delays, lost envelope | Contact service; retest | Not applicable |
| BI used does not match method | Steam BI used in dry heat or chemical vapor | Repeat with the correct method-specific BI | Not applicable |
Safety and compliance
- CDC: mechanical, chemical, and biological monitoring; weekly spore tests; every implant load; matching controls; records. See the CDC's sterilization and disinfection summary and monitoring FAQ.
- FDA: biological and chemical sterilization process indicators are Class II devices under 21 CFR 880.2800. Use cleared indicators labeled for your method and cycle.
- Method-specific BIs: Geobacillus stearothermophilus spores are used for steam, and CDC's general guideline notes Bacillus atrophaeus spores for dry heat. Buy BIs made for your exact method.
- OSHA: handling indicators is part of instrument reprocessing under the bloodborne pathogens standard. Self-contained BIs are activated by crushing an inner ampule; follow the maker's instructions and wear eye protection.
- State rules vary: spore test frequency, use of outside services, and record retention periods are not uniform across states. Confirm your own board's rule rather than assuming the CDC's weekly minimum is the whole requirement.
Buying new vs. used
Monitoring is mostly consumables, but incubators and auto-readers do change hands, especially when practices close. A used reader is only useful if it works with indicators you can buy and holds its temperature.
Monitoring equipment checklist
- Incubator or reader model identified; compatible BIs still sold
- Incubation temperature verified with the manufacturer's method
- All wells or slots working; display and alarms functional
- Manual available
- Internal chemical indicators of the correct type for each of your sterilizers and cycles
- BIs for each method you use, in date, stored per label
- A written failed spore test protocol and a log format ready before first use
- For a used sterilizer: a passing spore test before patient use
Red flags: surplus indicators with no lot documentation or past expiration; a reader that only accepts a discontinued BI; indicators labeled for a different method or cycle; a practice acquisition with gaps of months in the spore test log (see buying a practice for due diligence).
Cost
Monitoring costs are ongoing: internal indicators for every package, a weekly BI per sterilizer, plus either a mail-in subscription or an incubator and its indicators. Prices vary by brand, volume, and service level, so compare the annual cost per sterilizer, including the price of the extra tests you will run after any failure or repair.
Brands and products you will see
Examples include:
- Attest biological indicators and auto-readers: a long-running line of rapid-readout BIs, steam test packs, chemical integrators, and auto-readers originally developed by 3M, whose health care business became Solventum in 2024.
- Sterilizer makers' indicators: many sterilizer manufacturers and dental suppliers sell chemical indicators and BIs labeled for their cycles.
- Mail-in monitoring services: offered by several monitoring companies; compare turnaround time, how failures are reported (phone, email, portal), and the format of their reports.
Related guides
Put a correct indicator in every package, label every package with its load, test every sterilizer weekly, and keep the failed test protocol posted by the sterilizer. That routine turns a positive spore test from a crisis into a checklist.
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- Chemical vapor and dry heat sterilizers
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- Compliance: OSHA, HIPAA, infection control, and more
- Browse sterilizers on the marketplace
Always follow the manufacturer's instructions for use (IFU) for your specific model. Repairs involving electrical, pressure vessel, radiation, or gas line work belong with a qualified technician. Infection control and radiation rules vary by state. Prices are rough ranges that vary by model, condition, region, and year. ChairsideSource is not affiliated with any manufacturer named here.