A significant number of dental practices use an ultrasonic bath to clean instruments prior to or after manual scrubbing and then on to the autoclave. HTM 01-05 suggests that ultrasonic baths are optional, they are not required to meet either essential quality requirement or best practice. Ultrasonic cleaners can be more effective than manual cleaning, especially with complex and hinged instruments. They also reduce the incidence of splashes and sharps injuries that can occur with manual cleaning. Compliant ultrasonic cleaners with lockable lids are also easier to validate as they are automatic and the process is repeatable.
Ultrasonic baths require solution changing as a minimum every session and more often if soiled. They also require an ultrasonic activity test every 3 months and the processed instruments require a protein residue test every week. At the start of the day add the correct volume of water to the clean ultrasonic cleaner. Then add the correct quantity of detergent as specified by the manufacturer. Detergents are often supplied in pre-measured dose sachets for ease of use. Then check the temperature of the water if there is no built-in temperature sensor, ensuring that the temperature does not exceed 45°C. Temperatures above this encourage proteins to denature and adhere more to instrument surfaces. Blood residues also tend to coagulate and make cleaning more challenging. The lid should be fitted as specified by the manufacturer and the bath should be run in order to degas the solution. Dissolved gasses in the water will absorb the ultrasonic energy and reduce the cleaning effect on the instruments.
Protein residue testing
A protein residue test is a chemical test used to detect levels of protein on processed instruments that cannot be seen by visual inspection. The test is looking for a certain type of protein which is found in blood. At the end of the cleaning cycle, a random instrument should be taken from the bath, rinsed ideally with RO or distilled water, then swabbed for protein residue. If the instrument passes this test, all instruments may be moved to the next stage of reprocessing.
Ultrasonic activity test
This test determines that every possible area of the ultrasonic bath has cavitation happening within it and is carried out quarterly. Strips of foil are suspended in the solution. Once the foil is in place, the bath should be run on a standard cycle, or a time determined by the manufacturer. Once completed, the foil is removed and blotted dry, and then inspected for cavitation. This will appear as little perforations in the foil. The foil should be cross-referenced with that of the previous quarter to make sure that the perforations are in the same place, or as close as they were previously. If they are not, or there are no perforations, this is an indication that cavitation is not taking place in that part of the bath. These foil pieces should then be stored in a logbook, for reference in the following quarter.
All maintenance records must be kept for 2 years.
