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Disease Transmission

Aims & Objectives

  • To teach readers about the existence and dangers of pathogens in the dental environment.
  • To communicate how the route of infection comes into being.
  • To teach readers about how to break the routes of infections and prevent their spread.

Learning Outcomes

  • Readers will be aware of the existence and dangers of pathogens in the dental environment.
  • Readers will understand how infections are spread.
  • Readers will learn effective hygiene methods to break the routes of infections and prevent them spreading.

Stopping pathogens in their tracks

Preventing the spread of infection is a number one priority for dental practices, not only to be compliant with HTM 01-05, but also importantly to protect both patients and staff from the dangers of exposure to harmful pathogens. Without proper infection control procedures everything from a dental chair to a light switch can become a source of infection, so we should not just be aiming to control infectious diseases in a practice, we should be aiming to prevent them in the first place.

In the simplest terms the route of infection within a practice is akin to lighting a fire. A fire needs three things in order to burn: oxygen, fuel and a source of ignition, and without any one of these the fire will go out. In the same way the spread of infection begins with an infective agent that alone is not a risk unless it is able to infect a susceptible host, making the final key component the actual route of infection.

Infection control is about breaking one or more links in the route of infection by removing the infectious agent, known as a pathogen, which causes disease or illness. Breaking any of the links in the chain through rigorous infection control procedures and the use of correct cleaning agents, makes infectious disease less likely to spread.

Dangers of pathogens

Pathogens are the first link in the chain of infection and the main pathogens of concern within the dental surgery are bacteria, viruses and prions. Bacteria are found in every environment and are all around us, but in general most do not cause disease. However, in ideal conditions some harmful bacteria can multiply rapidly and with a route of infection can result in serious bacterial infections such as MRSA, Salmonella, Clostridium difficile and E coli. A bacterial disease that is of concern, once thought to be in decline, is tuberculosis (TB), which in the UK is once again being reported widely.

The very nature of dental procedures means members of the dental team can come into direct contact with pathogens, especially those found in blood and saliva. Amongst the most serious of these are blood-borne viruses that cause hepatitis B and C, which can be readily transmitted from an infected patient to the dental worker especially via accidental punctures to the skin from blood-contaminated needles, scalpels or other sharps.

Prions are the least understood pathogen type. Prions are proteinaceous infectious particles, responsible for transmissible spongiform encephalopathies (TSEs), rare but fatal neurodegenerative diseases affecting humans and animals. Although to date there have been no confirmed cases linking TSEs to dentistry, there is a theoretical, but real risk of prion disease being transmitted from contaminated dental instruments.

Routes of infection

The biggest potential infection route within a practice is hand to surface/hand to patient contact. Patients attending with a cold, for example, can easily spread that virus by hand contact with surfaces such as the reception desk or doorknobs, posing a possible infection risk to the next person who touches them. In the same way, it is possible that any patient visiting a dental surgery could potentially be carrying an undiagnosed infection or be at risk of acquiring an infection if hygiene standards are not maintained.

Aside from direct contact, transmission of infections can also arise from sharps injuries, especially when team members are handling contaminated instruments in preparation for cleaning and sterilisation and every care should be taken in disposing of sharps in a safe and secure manner.

Airborne transmission can occur when tiny droplets containing infectious agents are generated when an infected person coughs, sneezes or is having certain dental procedures. The splatter of oral fluids from conventional high speed handpieces or rotary instruments is a real and common threat and necessitates regular and rigorous cleaning of the surgery environment between every patient.

Another potential infection route, where pathogens can reside and multiply, is within dental unit waterlines. The quality of DUWL output water entering a patient’s mouth can be limited by the quality of the input water, and both supplies should be regularly tested and results logged to ensure compliance. Bacteria detected in the output water would indicate the presence of biofilm that readily builds up in the narrow tubing of the treatment centre’s waterline.

Biofilms are almost impossible to remove with conventional cleaners or by simply flushing the unit through with water. To maintain output water quality at a level below 200cfu/ml as required by HTM 01-05, it is important to treat DUWLs regularly with a CE marked, commercially available waterline treatment system. If left untreated the resultant biofilm contamination can become a risk to human health and can potentially block the waterline tubing, leading to downtime and costly repairs.

Break the chain

The simplest way to break the routes of infection is with frequent, thorough cleaning and disinfection of practice surfaces, instruments and equipment with proven and effective cleaning and disinfection products. It is recommended that work surfaces should be cleaned with a wide spectrum, microbiocidal wipe or spray which should have proven efficacy against mycobacteria, fungi, yeast and enveloped viruses such as HIV, HBV, and HCV. When used on medical device surfaces, these cleaning and disinfection products must conform to the requirements of the Medical Device Directive 93/42/EEC.

Understanding the chain of infection and how pathogens are transmitted makes it far easier to take action against them. Eliminating just one of the steps in transmission can stop infections in their tracks, making it far less likely that infections will spread.