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Ultrasonic Cleaning blog

How to Sonic Clean Dental Instruments

Ultrasonic Cleaners and Infection Control in Dental Clinics

Ultrasonic cleaners are important contributors to achieving strict infection control procedures in dental clinics. Reusable dental instruments (as with surgical and medical instruments) in contact with patients' blood and tissue must undergo a rigid three-part procedure that first removes gross contaminants, then thorough scrubbing/washing and finally either sterilizing or disinfecting. The role of an ultrasonic cleaner in cleaning dental instruments comes into play in the middle of this cycle.

The Role of Ultrasonic Cleaners in Dental Clinics

The American Dental Association calls attention to ultrasonic cleaning in their publication Sterilizing and Disinfection of Dental Instruments by noting that "(ultrasonic cleaners) may be used to reduce direct handling of dental instruments." The publication points out that a major hazard of manually handling sharp or pointed dental tools is risking inadvertent punctures or cuts that could lead to an infection.

The Centers for Disease Control's Guidelines for Infection Control in Dental Health Care Settings states that "removal of debris and contamination is achieve either by scrubbing…or by an automated process (e.g. ultrasonic cleaner or washer-disinfector) using chemical agents. " The CDC further notes that if visible debris is not removed it will compromise the sterilizing or disinfecting steps.

The Association of Surgical Technologies goes into more detail in their Standards of Practice for the Decontamination of Surgical Instruments. Section V of the AST publication places on the healthcare facility the decision on whether to use an ultrasonic cleaner. Here we summarize some of the points they relate to using the technology:

  1. Cleaning instruments and devices not considered safe for handling by healthcare workers
  2. Pre-rinsing instruments to remove gross contaminants before the ultrasonic cleaning process
  3. Changing the cleaning solution every 8 hours or when visibly "dirty"
  4. Using a low-foaming cleaning solution formula
  5. Following the operating instructions provided by the ultrasonic cleaner manufacturer

We'll go into more detail on operating recommendations later in this post but first let's take a look at

How Ultrasonic Cleaners Work in Dental Clinics

The hazards of manually scrubbing sharp or pointed dental instruments has been presented. Mechanical washers, also cited, are effective but not able to provide the thorough cleaning action delivered by ultrasonic energy - called ultrasonic cavitation - in the cleaning bath. But as effective as the technology is, it's important to keep in mind that ultrasonic cleaning dental instruments is a pre-step to either disinfecting or sterilizing, whichever process is employed by the clinic.

Dental instrument ultrasonic cleaners consist of a tank to hold the cleaning solution (more on this later). To the tank are bonded ultrasonic transducers powered by a generator and excited to ultrasonic frequencies such as 37,000 cycles per second (37 kHz).

These frequencies cause the tank bottom to vibrate as a membrane, thus creating millions of microscopic vacuum bubbles that implode on contact with items being cleaned. The implosions blast loose and carry away contaminants. Because the bubbles are so small they reach into cracks, crevices and other areas difficult or impossible to clean using manual cleaning or mechanical washers. And despite the violence of implosion, the action is so fast that it does not damage parts being cleaned.

Ultrasonic dental instrument cleaners are also equipped with control panels providing an on-off switch, thermostats and timers that allow technicians to program cleaning cycles. Other useful features include a "Sweep" mode that slightly and automatically varies the ultrasonic frequency to avoid what are called "hot spots" of intense cavitation, "dead zones" of little or no cavitation and harmonic distortion. The Sweep mode assures an overall uniform cleaning action.

And to review an important point one more time: any contaminants remaining on dental instruments before they are disinfected or sterilized will remain a source of contamination.

With this, let's take a look at

A Typical Ultrasonic Cleaning Cycle for Dental Instruments

We say "typical" because procedures may vary from practice to practice, and in any case should be spelled out in the dental clinic's standard operating procedure manual.

At the very beginning it is important that dental instruments be flushed and rinsed immediately after use to remove any gross contaminants. If allowed to remain dry and harden on surfaces they become much more difficult to remove. This step also helps prolong the life of the ultrasonic bath because fewer or no loose particles are introduced during the cleaning cycle. Dental clinics that hold instruments for batch sonic cleaning at the end of the day should immerse these tools in a germicidal presoak after rinsing.

As another point, instruments with hinges such as extraction tools should be disassembled if feasible to allow better access for the cleaning solution and cavitation.

Additionally,

  • for best results instruments of like composition should be cleaned together. Avoid mixing stainless steel, aluminum, copper and brass in the same cycle.
  • chromium-plated dental tools should not be cleaned ultrasonically
  • do not "stack" instruments in the basket. This not only lowers cleaning efficiency but can also result in them vibrating against each other.
  • If hinged instruments cannot be disassembled, clean them in the open position.

Selecting an Ultrasonic Cleaner for Dental Practices

Start out with cleaning tank size in terms of solution capacity and internal tank dimensions. You'll want a tank that holds without crowding the number of instruments cleaned in a single cycle (without crowding, as indicated above). Cleaning is accomplished in mesh baskets that have dimensions slightly less than internal tank dimensions.

Dental tools must be completely immersed in the solution. This relates to what is called the working depth of the tank, or the distance between the bottom of the basket (not the tank) and the surface of the cleaning solution.

Should you select a heated dental instrument ultrasonic cleaner?

A good question. An example of where heat is not desirable is in cleaning medical, surgical and dental instruments unless they are contaminated with dried blood or other difficult-to-remove substances. (Refer to the importance of pre-rinsing and soaking.)

To cite an example blood and tissue should be removed from instruments at a temperature below 40⁰C (104⁰F). Elevating the temperature can cause protein in blood to harden and become more difficult to clean. If this happens, higher temperatures i.e. 60⁰C (140⁰F) are required to remove dried blood.

Note that heat is a natural byproduct of cavitation action, so simply operating your unit will, over time, cause solution temperature to increase. We recommend not engaging the heater in an ultrasonic dental instrument cleaner unless you are faced with removing dried blood and tissue.

Put your Ultrasonic Dental Equipment Cleaner to Work

A candidate ultrasonic cleaner is the 37 kHz 0.75-gallon capacity Elmasonic EP 30H. Its optional stainless steel mesh-bottom basket dimensions are 7.8 x 4.2 x 2 in. deep. A larger model with 1.5 gallon capacity is the Elmasonic EP60H with an optional basket 10 x 4.5 x 3 in deep. These and other units in the Elma E+ series are equipped with a heater, timer, and permanent sweep for uniform cleaning.

They also have a power tracking feature that adjusts the cleaning power to the load in the basket and a dental technician-controlled pulse function that serves to degas fresh solutions and send bursts of increased power into the bath to attack tenacious contaminants.

For a cleaning solution we suggest biodegradable enzymatic alkaline liquid detergent concentrate MedClean C7. This is formulated to remove all contaminants common to dental instruments.

A Representative Dental Instrument Cleaning Procedure

Dental professional associations may have recommendations for ultrasonic cleaning. Here’s a way it can be done using MedClean C7:

  • To begin, fill the tank half way with water. Although tap water can be used deionized or distilled water is a better choice to avoid minerals dissolved in tap water.
  • Add 1-3 ounces MedClean C7 per gallon of water and continue adding water to the fill line. Tip: take into account displacement and do not overfill or under-fill the tank.
  • Turn on the ultrasonic cleaner and allow it to operate for 10 minutes or activate the pulse mode to mix the solution and remove trapped air.
  • Now you are ready. Position instruments in the basket taking care that they do not come in contact with each other. It is preferable to do more than one cleaning cycle than to overfill the basket. An option is placing the instruments in a cassette.
  • Lower the basket into the solution and set the timer for 10 minutes. If you use a cassette cleaning will take longer. At the end of the cycle remove the basket or cassette and examine the instruments. If satisfied, rinse them in running water and allow them to dry. To avoid spotting, you can rinse in distilled or DI water. They are now ready for sterilizing or disinfecting.

If not satisfied, repeat the cycle. As you build experience you’ll establish a routine.

Dental associations may have recommendations on when to replace ultrasonic cleaning solutions. Otherwise we suggest daily. Drain the tank and dispose of the spent solution following local regulations. Clean the tank according to instructions in the user manual. Then replace the solution and you’re ready to continue.

Questions? Call the iUltrasonic professionals for recommendations on equipment and procedures regarding ultrasonic cleaning equipment and cleaning solution options.

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