Lifting the Lid to Optimize Ultrasonic Cleaner Performance in Dentistry
Have you ever been curious about what is actually going on underneath the lid of your practice’s ultrasonic cleaner?
In this short guide I will start by figuratively removing the ultrasonic lid (don’t try this at your practice) and reveal just what is happening to your instruments when you turn on the ultrasonic. Once that topic is covered, the remainder of this blog post will look at the factors which affect the ultrasonics’ performance.
Here we go.
When you turn that ultrasonic dial to ON or for more fancy machines, hit GO on the touchscreen, what is actually happening?
The all too familiar high-pitched whine of the ultrasonic is probably ringing in your ears right now.
What is happening just underneath the lid is a phenomenon known as cavitation.
To be clear, this phenomenon of cavitation differs significantly from dental cavitations which dentists’ may see present in patients who have a hole or holes in their jaw. A clinical phenomenon known as neuralgia-induced cavitational osteonecrosis. Very different!
Ultrasonic cavitation refers to the formation and implosion of tiny bubbles in the cleaning solution due to ultrasonic sound waves. The implosion of these bubbles generates tremendous energy, creating shockwaves which dislodge contaminants from dental instruments. This microscopic scrubbing action reaches even the most difficult to reach surfaces, effectively removing debris, bacteria, and other organic contaminants on the dental instruments.
A recent study by Vyas, Wang, and Walmsley (2021), found that since cavitation bubbles can effectively penetrate small crevices, this process can remove bacterial biofilm very efficiently even on roughened surfaces like dental implants (Vyas, Wang and Walmsley, 2021).
So, ultrasonic cleaning (cavitation) is both highly effective and highly important!
There are several factors that can affect the ultrasonics’ cavitational performance which will be discussed, beginning with degassing.
Degassing
What exactly is degassing? Degassing is the removal of air or gas bubbles from the ultrasonic cleaning solution before the first load of the day is added. Without degassing, these air or gas bubbles would absorb some of that scrubbing bubble energy (cavitation) otherwise used for cleaning and reduce the overall performance and effectiveness of this ultrasonic cleaning step.
After reading this you may be asking yourself, how should I degass the ultrasonic unit in my practice?
Here’s a quick guide:
(Please note that this is a generic guide. You should always check your manufacturer instructions for use before degassing your practice’s ultrasonic).
To best optimize your time, degassing should be done at the beginning of each day, while waiting for your biological indicator (BI) to cook.
- To degas the cleaner, begin by filing the tank with distilled water, avoiding overfilling.
- Switch on the unit and allow it to run for a specific period, generally around 10-15 minutes, to expel any air bubbles.
- Once the degassing process is complete, drain the water and refill the tank with the appropriate cleaning solution and you are good to go for the day!
Selecting an Appropriate Cleaning Solution:
Choosing the right cleaning solution another important factor for optimizing the ultrasonic cleaning process.
When deciding on which ultrasonic cleaner to purchase, dental professionals should consider:
- The type of instruments being cleaned
- The instruments manufacturer instructions for use
- The type of soil being cleaned (i.e., blood, saliva, amalgam, polish etc.)
There are various specialized ultrasonic cleaning solutions available for dental use. No matter which cleaner you select, it is vital that all manufacturer’s recommendations and guidelines are followed for the preparation. This may include ensuring the appropriate temperature (hot water vs warm vs cold), dilution ratio for concentrated solutions, and the right amount for your size of ultrasonic (usually expressed in gallons), whether that is tablets or a liquid.
Water Quality
Two factors can influence the performance of your ultrasonic cleaner: pH and hardness. The pH level of the water you use can affect the detergent and enzymatic action of the ultrasonic solution. Since water hardness pertains to the concentration of calcium and magnesium ions, the harder the water the more likely these ions will bind to the ultrasonic cleaner and reduce or prevent their action on the dental instruments. Hard water can also cause premature wear on the ultrasonic unit. Water should ideally have a hardness of less than 200 ppm. Since these parameters fluctuate, testing the pH and water hardness levels regularly using a recognized testing method is recommended.
Water Temperature
I can recall a conversation about the temperature of the ultrasonic solution with a dental hygienist who asked me, isn’t hotter always better?
In truth, hotter is not always better.
Each ultrasonic solution has a water temperature at which it dissolves and functions most optimally. It is important to know what this magic temperature level (found in the MIFUs) is and to monitor any large changes in solution temperature throughout the day. Why would monitoring be important? Cavitation works through the popping of these tiny bubbles, and that popping creates tremendous energy. Some of this energy kinetic and some it is thermal. Especially on busier days where the ultrasonic is working overtime, these small releases of thermal energy can heat up the solution and impair the quality and performance of the ultrasonic cleaning.
Time
Time may seem like an odd topic to include in this discussion. Most ultrasonic cleaners have built in timers, so I don’t need to worry about time. Cleaning times vary based on the amount and type of soil, the solution used, and the temperature. The type of ultrasonic basket used, and the number of instruments placed in the basket have a direct effect on the amount of time needed to adequately clean the instruments. If your machine has a variable time setting, be sure to adjust accordingly to the factors that were discussed to optimize the ultrasonic cleaning performance.
Loading of Instruments
Before loading instruments into the ultrasonic, remember to pre-clean and rinse. Pre-cleaning and rinsing should be done for instruments with visible gross soil, and for instruments that have been sprayed with an enzymatic. Failing to pre-clean and rinse gross soil from instruments before loading them into the ultrasonic, reduces the cleaning power and effectiveness of the solution. These organic materials reduce the overall concentration of the cleaning solution by tying up the active cleaning ingredients.
Recently, I’ve seen an increase in the number of practices using elastic ties to bind instruments together before they are loaded into the ultrasonic. This is not advised, as binding these instruments together can create an electrolytic reaction between instruments of different metals (i.e., stainless steel instruments interacting with aluminum, brass, or copper).
Careful placement of instruments within the ultrasonic cleaner’s basket or tray is another essential element. Instruments must be arranged in a manner that allows for maximum exposure to the cleaning solution and the ultrasonic waves. Overcrowding the basket can hinder cavitation and diminish the cleaner’s effectiveness. On the other hand, underloading the cleaner is also suboptimal, as it wastes energy and resources.
The final factor to discuss are human factors.
Human Factors
To minimize any human factors become an impediment to performance of the ultrasonic cleaner, it is vital that staff are appropriately trained on using reprocessing equipment.
This should include:
- E-learning modules (i.e., Public Health Ontario or IPAC Consulting)
- On-site hand-on training facilitated by an expert from IPAC Consulting
- Mandatory attendance by all staff involved in reprocessing
- Documentation of this training
- Annual review of IPAC best practices, protocols, and policies
- Annual refresher training
- Bi-yearly staff competency assessments
After following these guidelines, and putting the time in, you are going to want to make sure that your ultrasonic cleaner is always performing at its best.
The gold standard for assessing ultrasonic cleaning performance is the foil test. You may also use commercially prepared cleaner efficacy tests, basically fancy foil.
Performance Monitoring Using the Foil Test
The foil test involves placing a small, folded piece of aluminum foil vertically in the tank. Next, turn on the machine and let it run for about 60 seconds (Strange, 2021). Lift the lid and remove and inspect the foil for uniform surface pitting. If the pitting is absent or uneven, it may indicate suboptimal cavitation which may require you to do some investigation and make some adjustments using the guide provided.
Source: www.dentsplysirona.com
A failed foil test means that your equipment may need some extra TLC (a.k.a. maintenance).
Proper maintenance of ultrasonic cleaners prolongs their lifespan and ensures consistent performance. Regularly inspecting the unit for any damage, such as cracks in the tank or loose transducers, is essential. Cleaning the tank after each use, including removal of debris and cleaning solution residues, is crucial. Always following the manufacturer’s guidelines for descaling, changing water, and replacing worn-out parts are necessary steps to maintain optimal cleaning efficiency.
This guide is intended to be used to increase the cleaning performance of the ultrasonic cleaner at your practice. There are topics such as rinsing and drying that were not discussed. Remember to follow whatever the best practices are for your area and any manufacturer instructions for use.
Through using this guide dental professionals can maximize the cleaning efficiency and longevity of their ultrasonic cleaning equipment, ultimately benefiting patient care, safety, and your bottom line.
References
Kovach, S. M. (2011). Improving the quality of the sonic cleaning process. Improving the Sonic Cleaning Process. https://multimedia.3m.com/mws/media/479020O/improving-the-quality-of-the-sonic-cleaning-process.pdf
Powell, E. (2021). National Infection Control Week: Utilizing Effective Sterilization Processes for Optimal Practice Safety [web log]. Retrieved July 21, 2023, from https://www.dentalcorp.ca/site/blog/2021/10/18/national-infection-control-week-utilizing-effective-sterilization-processes-for-optimal-practice-safety.
Strange, M. (2021). The 5 most overlooked cleaning guidelines for your ultrasonic bath. RDH Magazine. Retrieved July 21, 2023, from https://www.rdhmag.com/infection-control/article/14187982/the-5-most-overlooked-cleaning-guidelines-for-your-ultrasonic-bath.
Vyas, N., Wang, Q. X., & Walmsley, A. D. (2021). Improved biofilm removal using cavitation from a dental ultrasonic scaler vibrating in carbonated water. Ultrasonics Sonochemistry, 70, 105338. https://doi.org/10.1016/j.ultsonch.2020.105338
