Infection Control and Decontamination

Introduction to Infection Control

Infection control is paramount in the dental environment to prevent the transmission of infectious agents between patients, and between patients and dental staff. This involves standard precautions, often referred to as universal precautions, which treat all patients as potential carriers of infectious diseases. The primary guidance for decontamination in primary care dental practices in the United Kingdom is the Health Technical Memorandum 01-05 (HTM 01-05). It defines two standards: Essential Quality Requirements, which all practices must meet as a minimum, and Best Practice, which is the gold standard all practices should strive to achieve.

The Decontamination Cycle

The decontamination cycle is a continuous process designed to render reusable dental instruments safe for use. A breach at any stage of the cycle compromises the sterility of the instruments. The cycle consists of several distinct stages:

1. Acquisition: Selecting instruments that are suitable for effective decontamination.
2. Cleaning: The removal of visible debris and organic matter.
3. Disinfection: Reducing the number of viable microorganisms to a safe level.
4. Inspection: Visually checking instruments for cleanliness and structural integrity, often using a magnifying lamp.
5. Sterilization: The complete destruction of all living microorganisms, including bacterial spores.
6. Storage: Storing instruments in a way that maintains their sterile state until use.
7. Use: Utilizing the instruments during a clinical procedure.

Transport and Pre-cleaning

Used instruments should be transported safely from the clinical area to the decontamination room in a rigid, leak-proof, and easily cleanable container, which must be clearly labeled. Instruments should be kept moist until cleaning begins to prevent organic matter (such as blood or saliva) from drying, which makes it significantly harder to remove.

Cleaning Methods

Cleaning is the critical first step before sterilization. If an instrument is not clean, it cannot be sterilized, as organic matter can shield microorganisms from the sterilization process. There are three primary methods of cleaning:

Washer-Disinfectors

According to HTM 01-05, the use of a washer-disinfector (WD) is the preferred method for cleaning dental instruments. A washer-disinfector automates the cleaning and thermal disinfection processes, providing a highly reproducible and validated cycle. A typical cycle includes a flush (below 45°C to prevent protein coagulation), a wash (using appropriate detergents), a rinse, thermal disinfection (typically maintaining 90°C for 1 minute or 80°C for 10 minutes), and finally, drying.

Ultrasonic Cleaning

Ultrasonic baths utilize high-frequency sound waves to create microscopic bubbles in the cleaning solution. When these bubbles implode (a process known as cavitation), they dislodge debris from the instruments. While effective, especially for complex instruments like burs and endodontic files, ultrasonic cleaning requires manual intervention to load and unload, and does not include a disinfection phase. Instruments must be thoroughly rinsed after ultrasonic cleaning. Regular performance testing, such as the foil test, is required to ensure the ultrasonic bath is functioning correctly.

Manual Cleaning

Manual cleaning is the least preferred method due to its variability, the difficulty in standardizing the process, and the increased risk of sharps injuries to staff. It should primarily be used as a backup when automated methods are unavailable, or for instruments incompatible with automated cleaning. If performed, it must follow a strict protocol: using a dedicated sink, long-handled brushes, appropriate detergent (not household washing-up liquid), and keeping instruments submerged during scrubbing to prevent the creation of aerosols.

Sterilization and Autoclaves

Sterilization is achieved using autoclaves, which utilize saturated steam under pressure to destroy microorganisms. Autoclaves operate at specific temperature and pressure parameters, typically 134°C to 137°C at a pressure of 2.1 to 2.25 bar, with a holding time of at least 3 minutes. There are three main types of autoclaves used in dentistry:

Type N Autoclaves

Type N (Non-vacuum) autoclaves rely on passive air displacement. Steam enters the chamber and physically pushes the air out. They are only suitable for sterilizing solid, unwrapped instruments. They must not be used for hollow items (like handpieces) or wrapped instruments, as air pockets can remain, preventing the steam from reaching all surfaces.

Type B Autoclaves

Type B (Vacuum) autoclaves use a vacuum pump to actively remove air from the chamber before steam is introduced. This ensures steam penetration into every part of the load. They are suitable for sterilizing all types of loads, including solid instruments, hollow A and hollow B items (such as narrow-lumened handpieces), porous loads, and wrapped instruments. Instruments sterilized in a Type B autoclave can be pouched and stored for up to one year.

Type S Autoclaves

Type S autoclaves are specialized sterilizers designed by the manufacturer for specific loads. Their capabilities fall between Type N and Type B. They may use single or multi-stage vacuums but are only validated for the specific types of instruments and packaging specified by the manufacturer.

Hand Hygiene

Effective hand hygiene is the cornerstone of infection prevention. It is the most effective action to reduce the spread of pathogens. Hand hygiene must be performed:

• Before and after every patient contact.
• Before putting on and after removing Personal Protective Equipment (PPE).
• After exposure to blood or bodily fluids.
• When hands are visibly soiled.

The World Health Organization (WHO) handwashing technique should be followed. This involves a systematic process of rubbing all parts of the hands, including the palms, backs of hands, fingers, interlocked fingers, thumbs, and wrists. When hands are visibly clean, an alcohol-based hand rub can be used. However, if hands are visibly soiled, they must be washed with liquid soap and water. Proper drying with disposable paper towels is crucial, as damp hands can harbor and transfer bacteria more readily than dry hands. Furthermore, maintaining short, clean nails (without polish or extensions) and removing all hand and wrist jewelry (except for a plain wedding band) is essential for effective hand hygiene.