Dental

Class B against Class N dental autoclaves

Chamber loads, cycle types and why the cheaper sterilizer may not sterilise what you put in it.

Departments: Dental · Medical Consumables & Patient Care

Small steam sterilizers are classified by what they can reliably sterilise, using the classification set out in the European small-steriliser standard EN 13060. The classes are not quality grades — they describe cycle capability. Buying the wrong class is the most expensive mistake in a dental practice's decontamination chain, because the equipment works perfectly and still leaves you unable to process your own instruments.

The three classes

Class N — naked solid instruments

N is for "naked". These sterilizers use gravity or simple steam displacement with no fractionated vacuum. They handle unwrapped, solid, non-porous instruments and nothing else. Air trapped in a lumen or in packaging is not removed, and where air remains, steam does not reach the surface. A Class N cycle cannot be validated for pouched instruments or handpieces.

Class B — the full range

B is for "big small steriliser". A fractionated pre-vacuum removes air from the chamber and from within the load before steam is admitted, and a post-cycle vacuum dries the load. Class B handles wrapped and pouched instruments, hollow items including handpieces, and porous loads. For a practice that pouches instruments for storage — which is most practices — this is the class you need.

Class S — manufacturer-defined

S sits between the two, and its capability is defined by the manufacturer for specific load types. It can be entirely appropriate, but you must read the manufacturer's stated load types rather than assuming. If the documentation does not name your load type, it is not covered.

Deciding which one your practice needs

Ask two questions. Do you pouch instruments so they can be stored sterile until use? Do you process hollow items such as handpieces, triple syringes or ultrasonic tips? If either answer is yes, you need Class B, or a Class S explicitly validated for those loads. If instruments go straight from the sterilizer into use, unwrapped, Class N may be sufficient — but very few practices genuinely operate that way.

Sizing the chamber

Chamber volume is not the same as usable load. Trays, cassettes and pouches occupy space inefficiently, and overloading is the most common cause of a failed cycle. Size the chamber against your busiest hour, not your average day, and confirm the number and dimensions of trays supplied as standard.

What has to be bought alongside it

• Water. Most small sterilizers require distilled or demineralised water. Confirm the required quality and whether the unit has an internal reservoir or needs a feed.
• Pouches and a sealer. Self-seal pouches are convenient at low volume; a heat sealer is more reliable and cheaper per pouch at higher volume.
• Cycle monitoring. Chemical indicators inside each pack, process indicators on the outside, and periodic biological indicators. Indicator class matters — confirm which class your protocol requires.
• Record keeping. A printer or data logger for cycle records, and a filing routine that survives staff changes.

Before you sign the order

Ask about installation and commissioning, the validation documentation supplied, the service interval, who performs the service locally, and lead time on spares. A sterilizer out of service closes a surgery.