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NCA ANZ Pty. Ltd.


When instruments used on a patient are taken to the sterilisation area, they commence the most important process of Infection Control in any surgical facility, this is called the pre-clean and cleaning process. 

Pre-Clean Process 

As per ADA Guidelines and AS4815, dirty instruments are to be hand cleaned and rinsed. It is recommended that a neutral agent is used in this process which contains an enzymatic solution with sufficient concentration to remove residual protein on the instruments. The agent should be end user friendly and not contain high levels of toxic agents such as glutaraldehyde. 

Once the instruments have concluded the pre-clean process they are then placed into the ultrasonic bath for the cleaning process. 

Cleaning Process 

The cleaning process is done after the pre-cleaning of instruments with a detergent holding a pH level of 8+. Most practices have an ultrasonic bath ranging from 4L-20L, depending on the size of the practice and the types on instruments they are cleaning and sterilising. 

On the first daily cycle of the ultrasonic, degassing must be carried out on the machine (check manufacturers instructions). The next step is the al-foil test for validation of the ultrasonic. This should be done with the tank filled standard with water and detergent.. Many practices perform the al-foil test at the end of the day which goes against all logic, because as a technician or dental assistant in charge of this process, one must test the efficacy of the process before any instruments are place in the ultrasonic for validation purposes. 

The AL-FOIL Test

There are many practices within Australia particularly, who do not have a thorough understanding of why they perform the tests within the sterility area. Many practice managers and staff merely "follow suit" on what is verbally instructed, or by word of mouth by other practices, without actually understanding the reasons "why" they are doing it. 

Once the degassing cycle is complete and the water and detergent are ready to be used, the foil sheet is submerged in the bath and held for a period of time (check manufacturers instructions). 

The average time for a 4-6L bath is 45-60 seconds

Many practices tend to run the foil test of the same period of time as the actual cycle. This again comes down to logic and understanding of the process. For monitoring purposes there are many grey areas within standards, and they tend to be guided more by manufacturers rather than science and logic, which is the task at hand by standards.

The monitoring process during any pre-clean, clean or sterilisation process should match "worst case scenario", and should be a challenge to the process at hand leaving no room for greater challenges with instrumentation. In the case of the ultrasonic foil test, this test should be a greater challenge than any instrument that is placed into the bath after this test has been performed. For these reasons, it can be asserted that the foil test is the most difficult challenge, and has hence passed under minimised challenged conditions. Therefore the most complex instruments in the bath have also passed the ultrasonic process. 

It is one thing to explain how a process works or how an instrument performs the task at hand. Standards however have indirectly stated that this is no longer sufficient, because monitoring is still required to give indications and proof that the machines in these processes are performing cycles to efficacy levels that meet with standards. This is why, in this example, the foil test should be performed. 


Ultrasonic baths contain electro-magnetic waves of energy that vibrate, and sometimes dissolve small particles of protein. Because protein is very unstable, it can be removed from surfaces, particularly stainless steel surfaces rather efficiently with the right substances and conditions. There are two main levels of force that remove protein particles (remembering that all of the residual protein and tissue that was visible to the naked eye had been removed in the pre-clean process, now the ultrasonic will remove any remaining micro bacterial protein before the sterilisation stage commences).

1. Ultrasonic magnetic waves

2. Alkaline solution

The foil test can measure only the mechanic force of the waves inside the bath. There is no information the foil test can provide about the condition of the protein remaining inside the ultrasonic. Although the protein has been removed from the instruments through mechanical force, they still remain inside the bath active. This is why detergent is used. 

Most common ultrasonic detergents have two main components: 

1. Alkaline : used to break up water tension and deactivate bacteria

2. Enzymes: use to deactivate bacteria 

Both types of detergents have pros and cons, with the Australian Standards pointing more in the direction of Alkaline to be used in the cleaning process due to the lesser corrosion factor against instruments. 

Although these are not measured by the foil test, most manufacturers provide a Material Safety Data Sheet (MSDS) forms which contain the percentage concentration of these two solutions, in which testing laboratories have certified that the levels provided are efficient enough to deactivate protein. The question still remains on how to monitor the efficacy of these solutions.