Bowie & Dick test
What is it and why is it important?
In dental practises, sterilization is very important, both for the protection of patients and operators, as these are areas where contact is frequently made with potentially infected mucous membranes and blood.
For all types of loads and cycles, the EN 13060 standard requires
users to verify that their autoclave is functioning properly by carrying out tests:
- To check that the autoclave is functioning properly, the Vacuum Test, Bowie & Dick Test and Helix Test are carried out before the autoclave is used;
- Biological and chemical checks (sterilisation indicators) are performed during the sterilization cycle to ascertain whether or not sterilisation parameters are met.
The Bowie & Dick test enables you to ensure that air is properly removed from the sterilisation chamber and, as a result, that porous loads are fully penetrated with steam (e.g. surgical bandanas or gowns).
With the Bowie & Dick test, the device is run and sterilisation of porous loads is evaluated, particularly:
- the effectiveness of the initial vacuum phase and, therefore, how well steam penetrates cavities;
- the temperature and pressure of saturated steam during the sterilisation phase.
Procedure and operation
The indicator is a heat-sensitive sheet placed in the middle of a pack consisting of several layers of paper and foam. This sheet changes colour when exposed to a certain level of pressure from the saturated steam. For the autoclave to be working efficiently, it must be able to evenly sterilise the porous pack. When this is the case, the pack will be evenly penetrated and the Bowie-Dick test sheet will be uniform in colour, without different-colour stains. The required resulting colour depends on the manufacturer and will be detailed in the manufacturer’s instructions.
The test must be carried out in the following way:
- The vacuum test is performed
- We take the Bowie & Dick test pack, which must be the only thing in the autoclave (no other instruments), and place it in the middle of the lower shelf in the sterilization chamber (if these conditions are applied, the amount of air to be removed is greater and the test is more discerning). The test pack has a sheet of paper inside with special ink (chemical indicator) applied to it, which will change colour evenly from the outer edges to the middle.
- The appropriate programme to carry out the Bowie & Dick Test is then selected and started on the autoclave (the program will perform a complete sterilisation cycle at 134 °C and 2.1 atm. for 3 minutes and 30 seconds).
- We then examine the sheet to see whether or not the colour has changed evenly, and with the same intensity, from the middle to the outer edges. We then compare the result obtained with the supporting examples.
Test not passed
If the test fails, it means that the sterilisation system is inefficient due to a number of possible reasons:
- Poor-quality steam emitted by the sterilisation machine;
- Failure to create a vacuum with air being present;
- A leak during air removal (initial vacuum phase).
If the result is a failure, the Bowie & Dick test is repeated: if this test is successful, a third confirmatory test is carried out, which, if successful, means you can proceed with sterilisation. If the second test was a failure, the autoclave must be taken out of service immediately.
The Bowie & Dick test does not provide information regarding causes of failures, so further investigation will be required to identify and remedy the cause should your sterilisation system be inefficient.
When to perform the Bowie & Dick test?
The Bowie & Dick test must be performed:
- After repairs or maintenance of sterilisation devices;
- After long periods of autoclave inactivity;
In addition to the two previous examples, periodic tests must be carried out, the frequency of which depends on how the autoclave is used. In any case, it is recommended that the test is performed before sterilising porous loads.
The Bowie & Dick test is a cost-effective test that not only enables you to safeguard the health and well-being of doctors, assistants and patients, but also allows the dental practise to demonstrate that it complies with all sterilisation procedures in a timely manner.
The results of each Bowie & Dick test can be archived in consecutive order with the date of the test in your sterilisation-cycle records. In the event of litigation, these constitute evidence.