Inside Dentistry
April 2007
Volume 3, Issue 4

Comparison of Ultrasonic Cleaning Schemes: A Pilot Study

Howard E. Strassler, DMD

Walker N, Burke FJ, Palenik CJ. Prim Dent Care. 2006;13(2):51-56.


OBJECTIVE: Ultrasonic cleaning is an effective method for cleaning dental instruments prior to sterilisation. However, there are few studies that directly compare precleaning and ultrasonic cleaning solutions. This study evaluated the efficacy of different ultrasonic cleaning schemes. METHOD AND MATERIALS: Twenty representative dental instruments, five of which were soiled with a mixture of blood and hydroxyapatite, were used in a series of cleaning runs. Cleaning employed a presoaking agent, ultrasonic cleaning, or a combination of both. Two presoaking agents (Non-ionic Ultrasonic Cleaning Solution and ProEZ Foaming Enzymatic Spray) plus five ultrasonic cleaning cleaners (UltraDose, General Purpose Cleaner, Coenzyme Concentrate, Enzol Enzymatic Detergent, and Non-ionic Ultrasonic Cleaning Solution) were compared, with tap water serving as the control. There were two cleaning times: seven and 15 minutes. After rinsing, the working ends of the instruments underwent scrubbing for 20 seconds using a dental polishing brush held in a haemostat. After scrubbing, the brush and instrument were placed in a tube containing sterile saline. Vortexing of the tube lasted 30 seconds. Testing for the post-cleaning presence of blood involved Hemastix dipsticks. These sticks measure minute amounts of blood in urine and can detect as few as 35 red blood cells per ml. Comparisons of colour change were made to a standard scale followed by assignment of numeric values. RESULTS: Tap water was the poorest cleaning solution, while UltraDose was the most effective. Blood removal improved when cleaning time was increased from seven to 15 minutes. The combined effect of a presoak immersion followed by ultrasonic cleaning was the most effective cleaning scheme overall. Cleaning by either ultrasonic or presoaking only was less effective. Some instruments were more difficult to clean than others. CONCLUSION: Within the constraints of the small number of test runs preformed, it was concluded that application of a presoak agent before ultrasonic cleaning produced the most effective instrument-cleaning regime.


Before presoaking agents and ultrasonic cleaners were used for precleaning before sterilization, instruments were generally scrubbed with a brush using soap and water. One risk of cleaning instruments using this method was the potential to sustain a sharp injury of the fingers or hands. Ultra-sonic cleaning has been shown to be more effective at removing dried blood, soft tissue, plaque, dental cements, and other debris than manual scrubbing. Using precleaning solutions before sterilization minimizes this risk. Also, it has been shown that all debris must be removed from instruments so that disinfection and sterilization is not compromised. If blood and saliva are allowed to dry on instruments, they are more difficult to clean; in fact, when instruments have dried blood after sterilization, they need to be recleaned and sterilized.

The authors of this study provide the clinician with sound guidance by offering a superior protocol for cleaning instruments before sterilization. In other studies there have been recommendations that difficult-to-clean instruments (eg, endodontic files and burs) should be designated for single use only. Based on this study, dentists should be presoaking instruments before using an ultrasonic cleaning solution, and should bear in mind that not all ultrasonic cleaning solutions are alike.

Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School, Baltimore, Maryland

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