What is the ideal amount of time that instruments should shake in an ultrasonic unit with settings of 6, 12, 20, 30 and 60 minute?

Since ultrasonically cleaning instruments does not sterilize them, there is not a mandatory time limit for the cleaning process. The purpose of ultrasonic cleaners is primarily to debride the instrument surfaces before sterilization. Therefore, the ultrasonic process is directly related to the amount of debris left on instruments. If you are finding that the setting you are using does not completely debride your instruments, you can either increase the time, or you can ask the assistants to brush the instruments before placing in the ultrasonic to remove most of the large debris first, so the cycle can be kept to a minimum. Ultrasonic presoaking solutions (see Product Comparison Table – Instrument Cleaning at THE DENTAL ADVISOR Online) are also available.