Ultrasonic baths

July 10, 2013
Sometimes I don't pay attention. But everywhere I go this month I keep seeing miracles! The roses in my front yard wave their heads with the rising of the sun ...

Consider reading these columns by Kelsch


by Noel Brandon Kelsch, RDHAP

Sometimes I don't pay attention. But everywhere I go this month I keep seeing miracles! The roses in my front yard wave their heads with the rising of the sun and spread their fire and ice petals to greet me with a glorious aroma as I walk out the door each morning.

As I walk into dental offices, there is a machine I have been paying special attention to this month. This mighty little tank not only makes our lives easier but if used properly it can help reduce the need for scrubbing, prevent cross contamination, and keep staff safe and free of sharps injuries.

What is an Ultrasonic bath?

Mounted deep inside your ultrasonic tank are ultrasonic transducers. These are placed according to size and shape of the unit. These transducers create microscopic bubbles in the ultrasonic solution that is placed in the unit. The act of cavitation is the rapid formation and collapse of millions of tiny bubbles in a liquid.

Alternating high and low pressure waves generated by the high frequency sound called ultrasonic produces the bubbles. During the low-pressure phase, they grow from microscopic size until during the high-pressure phase they are compressed and implode.

One sound I love is the hissing sound of the bubbles literally imploding on dental instruments (cleaning them, as a result). If you peek in, you will see moving waves as a result of these bubbles imploding. These actions allow us to follow the directions from the CDC and OSHA to limit hand scrubbing.

  • Liquid: Liquid is a vital part of this process. It is important to keep the level of the fluid at the level the manufacturer recommends. Low fluid level can decrease the effectiveness, change the frequency, and even damage the unit. When the proper solution level is in place, it protects the unit and transducers from overheating and allows the solution to flow around the parts, maximizing contact with cavitation and the fluid. Monitoring the fluid level throughout the day is a must. As you take instruments out, you are removing solution. The unit's function will give off heat, which causes evaporation that lowers the fluid level.
  • Length of time: See the manufacturer's directions for the time needed, but be aware that this may change due to the variables. Variables can include type of solution, temperatures, length of time that allows drying of soil and debris, amount of soil, etc. Very dirty instruments that have sat out for a long period of time can increase the time needed. Most units will remove debris on the average item within three to five minutes.
  • Monitoring: With each load, you should be monitoring to see if the instruments are debris free. If they are not, you should first check the liquid level, the clearness of the fluid, and the amount of instruments in the load. If those are normal, then there are tests that you can run.

Monthly, we should all be checking our units to see if they are working. Two tests allow you to see if your unit is working properly and creating cavitation. With proper personal protective equipment on (utility gloves, eye protection, mask and gown) perform one of the following tests:

  • Foil test: With the basket out of the ultrasonic unit, fill your unit to the recommended level of water. Fold a piece of aluminum foil in half the width of the unit. Do not touch the bottom of the unit with foil. Run the unit for one minute. You should see pin holes and pock marks. Never put your hands inside the unit when it is running.
  • Glass slide test: Take a glass slide and wet the frosted part. Mark with a number 2 pencil with an X from one corner to the other. Put the slide vertically into the solution and turn the unit on. Hold in place not touching the bottom of the unit. The X should disappear in about 10 seconds.

Commercially available soil, protein, and aluminum foils tests are available. RDH

NOEL BRANDON KELSCH, RDHAP, is a syndicated columnist, writer, speaker, and cartoonist. She serves on the editorial review committee for the Organization for Safety, Asepsis and Prevention newsletter and has received many national awards. Kelsch owns her dental hygiene practice that focuses on access to care for all and helps facilitate the Simi Valley Free Dental Clinic. She has devoted much of her 35 years in dentistry to educating people about the devastating effects of methamphetamines and drug use. She is a past president of the California Dental Hygienists' Association.

Some tips for ultrasonic baths
  1. The unit should have the lid on the entire time it is running to limit aerosols and lower the noise level.
  2. Do not overfill the load with instruments as this will limit the cavitation process and make the unit less effective.
  3. A fresh solution should be used when the fluid becomes visibly cloudy, filled with debris, visibly dirty, or you are doing large amounts of instruments. The minimum is once a day. In busy practices, you may be changing the fluid multiple times a day.
  4. The type of fluid is as important as the amount of fluid. Do not use chlorides or corrosives. Stay with no-foam chemicals, or you will have a big mess! Do not use items that the manufacturer does not recommend. They may interfere with cavitation. Never run without fluid.
  5. Follow recommendations by instrument manufacturers as well as the recommendations for the ultrasonic unit when choosing the additive for the unit. Follow manufacturer's directions for use of both the fluid and the unit.
  6. Most manufacturers will tell you to degas the unit before adding instruments. This is the act of adding the solutions/water/tablet without the basket and allowing it to mix and "degas," or run the unit for five minutes and remove any other gasses before using.
  7. After the instruments have been through the ultrasonic bath, rinsing is recommended to remove any chemicals and residual debris.
  8. At the end of the day, empty all fluid from the unit and flush your entire unit with clear water. Allow to dry with the lid off over night.
  9. Do not set the unit in the sink to fill. This is an electrical item and should not be wet. Bring the water to the unit. Do cover vents or set on wet towel.
  10. Do not place items directly on the bottom of the unit with no basket. This can impact the transducers and limit the cavitation.
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