Every instrument that touches a patient comes back through the sterilizer, which makes the autoclave the one piece of equipment a dental office cannot work without. Undersize it and the schedule stalls. Pick the wrong type and some instruments get processed in cycles their manufacturers never approved. Neglect it and you find out through wet packs, error codes, or a failed spore test.
This is the flagship guide in our sterilization section: how tabletop steam sterilizers remove air, what the European Class N, S, and B labels mean for a US buyer, how to size a chamber to your instrument flow, and how to load, dry, maintain, and buy one. For a shorter comparison, see tabletop sterilizers compared; for a quick used-buyer screen, see five signs a used autoclave is a bad buy.
Key takeaways
- Autoclave types differ mainly in how they remove air: gravity displacement, pre-vacuum (dynamic air removal), or steam-flush pressure-pulse. Hollow and porous loads need the more aggressive methods.
- Class B is a European (EN 13060) cycle term. In the US, what matters is FDA 510(k) clearance and the cycles listed in the sterilizer's instructions for use (IFU), matched against your instruments' reprocessing instructions.
- Size sterilization by instrument turnaround in your busiest block, not by operatory count. Door-to-door cycle time, including drying, is the number that counts.
- Loading and drying cause more daily failures than the machine: overloading, pouches laid flat, and opening the door early all produce wet or unsterile packs.
- Use the water your manufacturer specifies. Tap water shortens sterilizer life.
- A used autoclave is a reasonable buy if the model is supported, a technician verifies it, and it passes spore testing before patient use.
How a dental autoclave works
A steam sterilizer kills microorganisms by holding saturated steam at a set temperature for a set exposure time. The steam must contact every surface. Air is the problem: a pocket trapped inside a handpiece, a folded pouch, or a packed cassette stays cooler than the steam around it. Every autoclave design is about three phases: remove air, hold sterilizing conditions, and dry the load so it stays sterile after the door opens.
For reference, the CDC's general sterilization guideline lists minimum exposure times for wrapped items of 30 minutes at 121°C (250°F) in a gravity displacement sterilizer and 4 minutes at 132°C (270°F) in a prevacuum sterilizer, with steam-flush pressure-pulse cycles typically 3 to 4 minutes at 132°C to 135°C. Your sterilizer's cleared cycles are what you actually follow, and total cycle times run much longer because of heat-up and drying.
Parts you should know
- Chamber or cassette: the pressure vessel that holds the load.
- Door gasket: holds pressure; the most common source of leaks and failed cycles.
- Reservoir: holds the distilled or purified water used to make steam. Some units use fresh water each cycle and send used water to a waste tank.
- Heating element or steam generator: makes the steam.
- Vacuum pump: on pre-vacuum and many cassette units, removes air before exposure and moisture after.
- Filters: chamber drain, dust, and on some units bacteriological air filters.
- Safety valve and door interlock: prevent overpressure and stop the door opening under pressure. Technician territory.
- Controller, printer, or data port: records time, temperature, and pressure for each cycle.
Gravity displacement
Steam enters the chamber and, being lighter than air, pushes air down and out a drain. It is simple, durable, and effective for solid instruments and many wrapped loads, but slower and less reliable at clearing narrow lumens and porous materials. That is why gravity cycles are long and why some instrument makers do not accept them. Many older automatic units and manual units are gravity designs.
Pre-vacuum (dynamic air removal)
A vacuum pump pulls air out before steam enters, usually in several pulses (fractionated vacuum), and most units pull a vacuum afterward to speed drying. Steam penetrates lumens and porous items almost immediately. SciCan's BRAVO G4, for example, uses a fractionated pre-vacuum and post-vacuum drying. The trade-offs are more parts (pump, valves, sensors) and daily air-removal testing: the BRAVO G4 manual calls for a daily Bowie-Dick and vacuum test.
Steam-flush pressure-pulse (SFPP)
Instead of a vacuum pump, the sterilizer alternates steam flushes with pressure pulses above atmospheric pressure to drive air out. It improves on simple gravity without vacuum hardware. Midmark's current M9 and M11 use SFPP. Whether an SFPP cycle suits a given hollow instrument is answered by two IFUs: the sterilizer's and the instrument's.
Chamber vs. cassette, and what Class N, S, and B mean in the US
Chamber sterilizers
A chamber unit has a cylindrical chamber, a door, and removable trays. It processes large mixed loads: wrapped cassettes, pouches, handpieces, and on some models textiles and plastics. Sizes are given by diameter and depth (Midmark lists the M9 at 9 by 15 inches and the M11 at 11 by 18 inches) or by volume (SciCan offers the BRAVO G4 in 17 and 22 liters).
Cassette sterilizers
A cassette sterilizer uses a small, flat, removable cassette that heats and purges fast, so cycles are short. SciCan's STATIM line is the best-known example; our tabletop comparison lists its published cycle times. The trade-off is capacity: a few handpieces or a small set per cycle. Cassette units shine for handpiece turnover and urgent instruments, not as the only sterilizer in a busy office.
EN 13060 classes: the European vocabulary
"Class B autoclave" appears in listings, brochures, and instrument IFUs. It comes from EN 13060, the European small steam sterilizer standard, which defines cycle types:
- Type N: unwrapped solid instruments only.
- Type S: the specific load types the manufacturer states, and nothing more.
- Type B: all load types, including wrapped, porous, and narrow-lumen hollow items. In practice this means fractionated vacuum.
Two points trip up buyers. The classes describe cycles, not whole machines: SciCan's US manual for the BRAVO G4 labels some cycles S and others B. And the 2018 amendment to EN 13060 renamed "hollow load A" and "hollow load B" as "narrow lumen" and "simple hollow items," so older and newer documents use different words for the same thing.
What US buyers should check instead
In the US, steam sterilizers are Class II medical devices under 21 CFR 880.6880 and reach the market through FDA 510(k) clearance. The North American tabletop standard, ANSI/AAMI ST55, groups cycles by air removal method (gravity or dynamic air removal) rather than N, S, and B. The CDC's dental guidance calls for FDA-cleared sterilizers used according to the manufacturer's instructions. So "Is it Class B?" becomes three questions:
- Does this model have FDA 510(k) clearance? Search the FDA 510(k) database by manufacturer or model. Units built for other markets may not be cleared for US use.
- Which cycles and load types does the US operator manual list, and at what maximum load?
- What do your instrument manufacturers require? Handpieces, scanner tips, and implant kits each have reprocessing instructions that may specify a pre-vacuum cycle, temperature, exposure, or drying time. Some scanner tips specify a Class B or pre-vacuum cycle outright.
Which type does your practice need?
| Type | Best for | Limitations | Typical role |
|---|---|---|---|
| Manual gravity chamber | Solid instruments, pouches, simple wrapped loads | Operator sets the cycle; long cycles; manual records | Backup unit, low-volume offices |
| Automatic gravity chamber | Mixed solid and wrapped loads with preset cycles | Longer cycles and drying; hollow claims vary by model | Main unit in many established offices |
| SFPP chamber | Mixed loads including handpieces, per IFU | Check specialty instruments against their IFUs | Main unit; common in current US installs |
| Pre-vacuum chamber (Class B style) | Wrapped cassettes, hollow and porous loads, instruments that require vacuum | Higher price; vacuum pump; daily air-removal test | Main unit for high-volume, surgical, and implant practices |
| Cassette | Handpieces, small urgent loads | Small capacity; cassette and seal wear | Handpiece and overflow unit beside a chamber unit |
Decision guide: who should buy what
- Startup, one to three operatories: one automatic chamber unit sized for your projected schedule, plus a backup plan (a used second unit or a loaner agreement). Add a cassette unit when handpieces become the bottleneck.
- Four to eight operatories: usually two chamber units, or one large chamber unit plus a cassette unit. Two units also means one failure does not cancel the day.
- Surgical, implant, or periodontal emphasis: a pre-vacuum unit. Wrapped surgical kits, hollow instruments, and porous items are where vacuum air removal matters, and many surgical instrument IFUs specify it.
- Handpiece-heavy restorative schedules: a cassette sterilizer often costs less than more handpieces or a second large chamber.
- Tight space or utilities: check counter depth, door swing, heat and steam ventilation, and the circuit. Midmark lists the M9 and M11 at 115 VAC and 12 amps; some manufacturers require a dedicated circuit.
Check your instrument IFUs before you shop. If your handpieces, scanner tips, or implant kits require a dynamic air removal cycle, that settles part of the decision before price enters the conversation.
Sizing: matching chamber size to instrument throughput
What you are sizing is how many sets and handpieces must come back sterile, dry, and cool during your busiest stretch, given how many you own. Work through the worksheet with your own numbers.
Hypothetical example (illustrative numbers only): a six-operatory general practice sees 40 patients on a full day, 24 in hygiene and 16 in restorative. Each patient uses one instrument cassette; restorative patients also use two handpieces each. Its chamber sterilizer holds four cassettes per load with a 60-minute door-to-door time for a wrapped cycle with drying and reload. Its cassette sterilizer holds six handpieces on a 15-minute door-to-door cycle.
| Worksheet line | Example | Yours |
|---|---|---|
| A. Cassettes (or set equivalents) used per day | 40 | |
| B. Handpieces used per day | 32 | |
| C. Cassettes per chamber load (from the IFU) | 4 | |
| D. Door-to-door chamber cycle in minutes (heat-up, exposure, drying, cooling, reload) | 60 | |
| E. Realistic sterilizer hours per day (minus warm-up, tests, gaps) | 7 | |
| F. Chamber loads per day = E x 60 / D | 7 | |
| G. Cassette capacity per day = C x F | 28 | |
| H. Shortfall = A minus G | 12 cassettes | |
| I. Handpiece capacity per day = 6 x (E x 60 / 15) | 168 |
Here the chamber unit runs out by mid-afternoon while handpieces are easily covered. The options: add a second chamber unit, move to a larger chamber or shorter cycle, or buy enough extra cassettes that morning sets can wait for end-of-day loads. A second chamber unit also provides the backup the office needs anyway.
Check peak demand too. If 14 of those 40 patients fall in a two-hour morning block and the office owns 20 cassettes, the question is whether sets come back fast enough within that block. Published cycle times often exclude heat-up, cool-down, and reload. Many offices plan to use no more than about three-quarters of theoretical capacity so a late start or a reprocessed wet pack does not break the day; treat that as a planning margin, not a rule. For a new office, fold this into equipment planning and the sterilization area layout in operatory buildout.
Cycle types, loading, and drying
Cycle types
Most automatic sterilizers offer preset cycles named for the load. Two real examples show how much they vary:
| Load type | Midmark M9/M11 (SFPP), operator manual | SciCan BRAVO G4 (pre-vacuum), US manual |
|---|---|---|
| Unwrapped solid instruments | Unwrapped: 132°C, 3 min, 30 min dry | S Solid Unwrapped: 132°C, 4 min |
| Pouched or wrapped instruments | Pouches: 132°C, 4 min, 30 min dry | S Solid Wrapped: 132°C, 4 min |
| Hollow items | Per IFU | S Hollow Unwrapped or B Hollow Wrapped: 132°C, 4 min |
| Handpieces | Handpieces: 132°C, 4 min, 30 min dry | Hollow cycles per IFU |
| Textiles, packs | Packs: 121°C, 30 min, 30 min dry | Per IFU |
| Rubber and plastics | Per IFU | B Rubber and Plastic: 121°C, 20 min |
Exposure is a small slice of the cycle. SciCan lists about 27 minutes total for its fastest solid unwrapped cycle on the 17 liter BRAVO G4 and about 47 minutes for hollow wrapped, including drying. Plan around the total.
The CDC's dental guidance treats unwrapped processing as limited use: instruments must be cleaned and dried first, the cycle is still monitored, and unwrapped critical instruments should be used right away rather than stored.
Loading technique
- Load clean, dry instruments. Sterilization does not remove debris. See ultrasonic cleaners and instrument washers.
- Open hinged instruments and disassemble multipart items as their IFUs direct.
- Stand pouches on edge in a rack. Midmark directs users to rest pouches on edge, plastic side of one facing the paper side of the next, with at least 1/4 inch (6.4 mm) between packs. Flat, stacked pouches trap air and water.
- Place cassettes as the sterilizer IFU shows, not touching chamber walls.
- Do not overload. Midmark lists maximum loads of 8 pounds (M9) and 9 pounds (M11).
- Put an internal chemical indicator in every package and label with sterilizer, load number, and date.
- Run the cycle the most demanding item needs. One hollow wrapped item means the whole load runs that cycle.
Drying and handling
A wet package can wick microorganisms through the paper, which is why the CDC recommends letting packages dry in the sterilizer before handling. Let the full dry phase finish (opening early is the top cause of wet packs), let loads cool on the rack before stacking, and check every package: indicator changed correctly, wrap dry and intact. Wet, torn, or questionable packs get reprocessed. Store sterile packages in covered or closed cabinets.
Water quality
Manufacturers publish water specifications. Midmark's M9/M11 manual cites AAMI ST46 values: conductivity of 50 microsiemens per centimeter or less and total dissolved solids of 25 ppm or less. SciCan's BRAVO G4 manual calls for conductivity under 15 microsiemens per centimeter. Tap water scales valves, filters, and heating elements, stains instruments, and pits chambers; bottled drinking water is not a substitute. A distiller or RO system that meets the spec can replace jug purchases; see water distillers and RO systems.
How to use it: daily operation
These steps are generic. Your model's IFU controls warm-up, test cycles, and cycle selection.
Start of day
- Check the reservoir and top up with the specified water only.
- Inspect the door gasket and chamber for debris or damage.
- Run any required warm-up or daily test (pre-vacuum units often need a Bowie-Dick or vacuum test in an empty chamber). Record the result.
- On spore test day, run the biological indicator in a representative load per the indicator instructions.
- Confirm the printer or data log is recording.
Every load
- Load per the technique above and choose the right cycle.
- Afterward, confirm time, temperature, and pressure met the cycle parameters and save or initial the record.
- Let the load dry and cool, then check indicators and package integrity.
- If a cycle aborts or errors, treat the load as not sterile, reprocess after the problem is fixed, and log it.
End of day
- Remove all loads; do not leave packs in a closed chamber overnight.
- Wipe the exterior and gasket per the IFU.
- Drain the reservoir or waste tank if the IFU calls for daily draining.
- Leave the door ajar if the manufacturer recommends it.
- File the day's cycle records.
Maintenance schedule
Typical intervals drawn from current manuals (Midmark M9/M11 and SciCan BRAVO G4). Intervals vary by model and are often stated in both time and cycle counts; your IFU wins.
| Task | Frequency | Who | Notes |
|---|---|---|---|
| Wipe exterior; clean and inspect door gasket | Daily | Sterilization staff | Use only IFU-approved cleaners |
| Daily air-removal or vacuum test, if required | Daily | Sterilization staff | Common on pre-vacuum units; record results |
| Spore test | At least weekly; every load with an implantable device | Designated staff | Per CDC; see sterilization monitoring |
| Drain and refill reservoir; clean chamber and trays | Weekly (Midmark schedule) | Sterilization staff | No abrasive pads in the chamber |
| Clean chamber and dust filters | Weekly to quarterly by model | Staff per IFU | BRAVO G4: chamber filter every 250 cycles or 3 months |
| Deep clean with manufacturer cleaner | Monthly | Staff per IFU | Midmark specifies Speed-Clean for M9/M11 |
| Pressure relief valve check | Per IFU (Midmark lists monthly) | Only as the IFU describes | A leaking or sticking valve is a service call |
| Replace gasket and filters | By cycle count or annually | Staff if IFU allows; otherwise technician | BRAVO G4: gasket every 1,000 cycles or one year |
| Preventive maintenance and calibration check | Annually or per manufacturer | Factory-trained technician | Keep the service report |
| Major service or performance verification | Per manufacturer | Factory-trained technician | BRAVO G4: every 3,000 cycles or 3 years; Midmark M9/M11: every 10 years or 10,000 cycles |
Troubleshooting
Staff can check loading, water, filters, and settings. The pressure vessel, safety valves, heating elements, wiring, and internal plumbing belong to a qualified technician.
| Symptom | Likely causes | What to try | When to call a technician |
|---|---|---|---|
| Wet packs | Overloading, flat pouches, door opened early, clogged filter | Reload per IFU, stand pouches on edge, let drying finish, clean filters | Continues with correct loading |
| Cycle aborts or will not reach temperature | Low water, dirty filters, poor door seal, overload | Check reservoir, gasket, and load | Repeated aborts or heating and sensor error codes |
| Steam leaking at door | Worn or dirty gasket, debris on sealing surface | Clean gasket and surface; inspect for cracks | Leak persists with a clean or new gasket |
| Door will not open | Residual pressure or heat, interlock fault | Wait the cooling time in the IFU; never force it | Still locked after that time |
| Failed Bowie-Dick or vacuum test | Air leak, gasket, pump wear, test error | Repeat per instructions, empty chamber | Second failure; stop hollow and porous loads |
| Chemical indicator incomplete | Wrong cycle, overload, air entrapment, wrong indicator | Do not use the package; reprocess | Repeats with correct loading |
| Positive spore test | Loading or operator error, cycle problem, malfunction | Follow your written protocol; retest immediately | Repeat positive; unit stays out of service |
| Stained instruments or spotting | Water quality, detergent residue, poor rinsing | Verify water spec; rinse and dry instruments well | Chamber pitting or rust appears |
| Cycles getting longer | Scale, clogged filters, low line voltage | Clean filters and chamber; confirm water | Heating or electrical fault suspected |
Safety and compliance
- CDC: the dental sterilization and disinfection summary calls for cleaning first, internal chemical indicators in every package, heat sterilization of critical and most semicritical items including handpieces, mechanical, chemical, and biological monitoring, and records. It remains the national reference even though CDC's Division of Oral Health was eliminated in the 2025 federal restructuring.
- FDA: use a cleared sterilizer, only the cycles its US IFU lists, and indicators labeled for those cycle parameters.
- OSHA: handling contaminated instruments falls under the bloodborne pathogens standard. Burns from hot trays and steam are the main physical hazard.
- Pressure and electrical: never defeat an interlock, force a door, or have staff work on valves, heating elements, or wiring.
- State rules vary: many boards adopt CDC guidance by reference, and some set their own spore test frequency or record retention. Confirm with your state dental board; see our compliance chapter.
Buying new vs. used
Condition varies widely on the used market because sterilizers wear with cycles, water quality, and maintenance. Used makes sense for a backup, a second unit, or a cash-constrained startup, if the model is supported and verified. New makes sense for your primary unit when you want warranty, current cycle claims, data logging, and full cycle life. Midmark says its current M9 and M11 are designed for a 25,000 cycle life: design life is counted in cycles, not years.
Used autoclave inspection checklist
- Exact model and generation identified; manufacturer still supplies parts
- US operator manual with cleared cycles and load types
- Model found in the FDA 510(k) database
- Cycle counter reading compared with design life, where tracked
- Recent service report verifying temperature and pressure
- Seller's recent spore test log
- Chamber or cassette free of pitting, rust, and scale
- Gasket intact; latch and interlock work smoothly
- Reservoir clean; seller confirms specified water was used
- Vacuum pump (if equipped) reaches vacuum quietly and passes a test
- Trays, racks, cassette, hoses, and printer or data module included
- Electrical requirements match your circuit
- Any app or cloud logging account can be transferred or reset
Red flags: no manual and no way to confirm cleared cycles; error codes "cleared" without a repair record; chamber rust or a warped cassette; white scale that signals tap water; a slow or noisy vacuum pump; a seller who refuses a technician inspection; a discontinued model with no service kits.
Rough price ranges
Rough ranges that vary by model, condition, region, and year: new tabletop units run from the mid four figures for basic automatic chamber and cassette units to about $10,000 or more for large pre-vacuum units (a national medical supplier listed a new Tuttnauer T-Edge 11 at about $9,800 in 2026). Refurbished units commonly list in the low to mid thousands; the same supplier listed refurbished Midmark M11 units at roughly $3,400 to $4,200 depending on generation and a refurbished SciCan BRAVO 17V at about $4,300, before shipping. Private-party units can be cheaper, with more risk. Budget for a service visit, gasket, filters, and a spore test before first use.
Expect roughly 7 to 12 years from a well-maintained tabletop sterilizer, with water quality the biggest variable (see our equipment lifespan guide). For the broader decision, read new vs. used equipment and refurbished vs. used vs. new.
Brands and models you will see
Examples include the following. Confirm the specific model, generation, and US clearance.
- Midmark: M9 and M11 chamber sterilizers (current units use SFPP), the newer Smart M9 and Smart M11, and older M9, M11, and M3 units on the used market. Ritter-branded M9 and M11 units are Midmark designs.
- SciCan: STATIM 2000 and 5000 G4 cassette sterilizers, the STATIM 6000B vacuum unit, STATCLAVE G4 and BRAVO G4 chamber units, and older BRAVO 17, 17V, and 21V models.
- Tuttnauer: manual and automatic units such as the 2340 and 2540 families and EZ Plus series, the Elara 11 pre-vacuum unit, and the newer T-Edge 10 and 11 and T-Top 10 and 11.
- W&H: Lexa Plus and Lexa Mini, which have US 510(k) clearances; W&H's Lisa and Lina models are common in other markets.
Related guides
Pick the type your instruments require, size it to your busiest block, give it the water, loading, and maintenance it was designed for, and build the records around it.
- Sterilization monitoring: spore tests, indicators, and record keeping
- Ultrasonic cleaners and instrument washers for the cleaning step
- Automated handpiece maintenance systems
- Chemical vapor and dry heat sterilizers
- Tabletop sterilizers compared and five signs a used autoclave is a bad buy
- Browse sterilizers on the ChairsideSource 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.