Answers to FAQs on instrument decontamination

What is the purpose of pre-soaking instruments prior to reprocessing?

Effective cleaning is fundamental within the decontamination process and is essential to enable the subsequent disinfection and sterilisation of instruments to be carried out reliably[i]. If biological matter is not removed prior to sterilisation it will become ‘baked on’ to the instrument during autoclaving, rendering it non-sterile and unable to be used.

HTM 01-05 section 3.5 states that instruments cleaned as soon as possible after use may be more easily cleaned than those left for a number of hours before reprocessing. Where this is not possible, immersing instruments in water, or the use of a foam spray intended to maintain a moist environment, is considered useful in aiding subsequent decontamination and removal of protein and debris[ii].

However, using water as a holding solution is not recommended as it promotes spotting, staining and corrosion of stainless steel, which can impair instrument function. For example, forceps may not open because of corrosion in the box area, scissors and scalpels can become dull, and instruments could break during surgery as a result of corrosion. Spotting, staining and corrosion can also interfere with sterilisation[iii].

A ready-to-use, pH-neutral foam spray applied directly onto soiled instruments after use immediately starts the decontamination process, helping to loosen debris and protein. Products containing an integral non-drying component and rust-inhibitor prevents biological matter from becoming dried onto the instruments’ surface and prolongs instrument life. Once instruments are ready to be cleaned, the holding solution is simply rinsed away with water and reprocessing takes place in the usual way.

Many practices use alcohol wipes. Why are alcohol-free alternatives preferable?

While alcohol-based wipes are commonly used within dental settings to reduce bacterial contamination, they have several drawbacks. 

Research has shown that alcohol can bind blood and protein to stainless steel. If proteins are present and an alcohol solution is used as a disinfectant, proteinaceous material can be fixed to the surface, potentially trapping microorganisms and providing additional surface roughness to aid adhesion of further soiling[iv]. Alcohol also evaporates rapidly in use, reducing the effective contact time.

This issue is highlighted in HTM 01-05 Section 6.57: “If there is obvious blood contamination [on surfaces] the presence of protein will compromise the efficacy of alcohol-based wipes. Note: Alcohol has been shown to bind blood and protein to stainless steel. The use of alcohol with dental instruments should therefore be avoided.[v]”

This means that the use of alcohol-based wipes to clean the outside of dental handpieces is not recommended because alcohol fixes proteins found in blood, saliva and tissues onto the stainless steel surface. This fixed, dried protein becomes difficult to remove and acts as a barrier to sterilisation.

Alcohol is not compatible with many common surgery surfaces such as PMMA and synthetic upholstery, and can cause discolouration, swelling, hardening and cracking of rubber and certain plastics[vi]. In contrast, alcohol-free wipes are less likely to cause damage, but care must be taken when selecting a wipe to ensure the formulation provides the best material compatibility.

Why is it recommended to use a vacuum autoclave?

After cleaning and disinfection, handpieces and instruments must be sterilised in an autoclave. There are three types of sterilisation cycles: Type N, Type B and Type S. These cycles differ in the way air is removed, the types of loads they can sterilise, and whether or not items can be wrapped during sterilisation[vii].

Type N non-vacuum autoclaves are only suitable for unwrapped, non-hollow and non-air retentive instruments[viii]. Type S autoclaves are designed to reprocess specific load types, which may include handpieces, according to manufacturers’ instructions.

Type B vacuum autoclaves are used to process hollow, air-retentive and packaged loads, including handpieces. They incorporate a vacuum pump to remove air from the chamber before steam is introduced, ensuring the steam can penetrate all parts of the load, including the complex internal components (lumens) of handpieces. Type B autoclaves meet a defined standard i.e. EN13060 that specifies the performance requirements and test methods for small steam sterilisers and sterilisation cycles.

Are vacuum autoclaves mandatory in the UK?

Type B vacuum autoclaves are not mandatory anywhere in the UK but are considered ‘best practice’. Many handpiece manufacturers state that their instruments must be processed in a Type B autoclave or the warranty may be invalidated.

Is sterilisation a validated process?

It is important that the manufacturer’s instructions are followed for the use and servicing of an autoclave to ensure it performs to the correct standard. The process should be validated, and records kept for not less than two years. If automatic records are not produced, then manual record keeping is required[ix].

All vacuum autoclaves (Type B and Type S) and non-vacuum (Type N) require routine testing and maintenance on a daily and weekly basis by practice teams with annual testing (servicing) and validation carried out by a qualified engineer.

What is the difference between testing and validation?

Testing refers to routine, periodic tests that must be carried out on a daily, weekly, quarterly and annual basis. This provides ongoing assurance that equipment meets validated parameters and is performing consistently to the same standards of the original validation as specified by the manufacturer during installation. Each test system used should always follow manufacturer’s instructions. 

Validation is the means by which the cleaning or sterilisation processes of decontamination equipment are documented, tested, and shown to be repeatable. This ensures equipment is performing as expected, meets specified criteria in accordance with manufacturers’ instructions, and provides evidence that equipment is safe to use. Validation is required for all new equipment at installation by an accredited engineer and annually thereafter.

Do practices need to keep records of testing and validation of decontamination equipment?

Testing schedules for washer disinfectors, ultrasonic cleaners and autoclaves should always follow manufacturers’ guidance. In the absence of manufacturers’ guidelines national guidance (i.e. HTM 01-05, WHTM 01-05, SHTM 01-05) should be followed. The results of periodic tests should be recorded, documented and filed securely in electronic or paper format to provide evidence of completed testing schedules and maintenance and service work undertaken and retained locally for audit and inspection purposes.

Universal log books are one of the most convenient methods of keeping records of compliance with regulatory requirements and to provide evidence of a full audit trail of completed and successful decontamination protocols in one place.

How long can instruments be stored?

• Wrapped instruments can be stored for a maximum of 1 year. They should be date stamped. The type of autoclave used determines when the instruments should be wrapped i.e. pre-sterilisation if Type B or S, post sterilisation if Type N.
• Unwrapped instruments in the clinical area: maximum storage 1 day.
• Unwrapped instruments in a non-clinical area (e.g. the clean area of a separate decontamination room): maximum storage 1 week[x].

The self-seal, flexible pouches suitable for use in vacuum autoclaves and for packing instruments after sterilisation in non-vacuum autoclaves must conform to BS EN 11607-1 as specified in HTM 01-05.

Are there regional variations in regulations and types of cleaning processes for practices operating in England, Scotland, Northern Ireland and Wales?

There are some significant regional differences. In Scotland and Northern Ireland, having a separate decontamination room and a washer disinfector are mandatory requirements, while in England and Wales having these means practices can reach ‘best practice’ status, but they are not mandatory. In Scotland it is mandatory to have a process in place if a washer disinfector fails. A type N autoclave is mandatory in all four nations, while a type B autoclave is considered ‘best practice’[xi].