Chapter 5

Disinfection

Aim

This chapter explains what disinfection is and its uses in the surgery.

Outcome

After reading this chapter, you should have an understanding of the use of disinfectants on surfaces, drains, appliances and impressions and dental unit water supplies.

Disinfection

Disinfection is the removal or killing of some micro-organisms, but not usually spores. In hospital practice, the type of disinfection used is defined by three levels of risk.

• High risk is where there is a serious risk of transmission of infection. This is usually employed where patients have highly contagious infections, such as viral hæmorrhagic disease.

• Medium risk is where there is a real risk of transmission of infection. The disease is not as infectious but a risk exists.

• Low risk is where there is a risk of transmission of infection, but the chances are only slightly more than in normal life. Social washing, including hand-washing, probably negates this risk.

It is difficult to define the level of risk in dentistry, as there are few well-documented reports of transmissions of infection on which to base a judgement. Most routine dental procedures are thought by microbiologists to justify a medium risk, but this is a cautious approach.

The assessment of risk is important as it dictates what chemical disinfectant procedures are used and when. Chemical disinfectants can be used which, under certain circumstances, kill all cells with which they come into contact, including human cells. In dentistry, chemical disinfectants have to be chosen according to the risks encountered but that will not affect the operators. Disinfectants that can be used on skin or living tissues are called antiseptics.

Cleaning

The removal of dirt and fomites is an essential prerequisite to the process of disinfection. Many disinfectants are inactivated, or their efficacy negated, by the presence of dust or soil. Cleaning can be achieved by washing with a detergent, mopping or simply wiping with a damp cloth. It is important in a dental surgery to decide how areas are to be cleaned and when. Examples include the following.

• Floors are best cleaned with soap and water at the end of each surgery session. Cleaning surgery floors can release micro-organisms into the atmosphere and these need time to dissipate. Surgery floors should never be carpeted as they retain dust and dirt.

• Cabinetry surfaces and handles are best cleaned with soap and water at the end of each session. Working surfaces that will be used during dental procedures are disinfected after cleaning and before operating.

• Lights and dental chairs should be cleaned and disinfected after every patient.

• Sinks and taps should be cleaned with soap and water at the end of each session.

• Polythene covers are used to cover areas such as umbilical hoses for three-in-one syringes. They are effective if discarded after every patient but do not negate the necessity to clean.

Types of disinfectant

Some of the types of disinfectant available for dental purposes are shown in Table 5-1. The type of disinfectant used depends on risk. Most disinfectants have complicated modes of action, but in general have the following properties.

• They are selective in their action. Some, for example, are not good in acting against Gram-positive bacteria and viruses.

• They are inactivated by soil or organic matter.

• They are dependent on the pH of the environment.

• They are only stable for a limited period of time.

• They are time-dependent in their killing action.

• They all can have toxic effects.

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