Ultrasonic Instrumentation

As our knowledge continues to increase, technology has evolved to keep up with research findings, resulting in a multitude of ultrasonic units and insert tips. With so much choice available, dental hygiene practitioners should become informed about operation and clinical protocols recommended for certain ultrasonic devices. The efficacy of instrumentation is dependent on the technique and experience of the operator.¹ For example, an overview of terminology and clinical concerns is helpful in understanding and optimizing the capabilities of currently available ultrasonic units.

Acoustic streaming or turbulence refers to the swirling phenomenon created by the continuous vibration of an ultrasonic tip in a liquid environment.^2,3 The pressure produced by the continuous stream of fluid flowing into the confined space of the sulcus or periodontal pocket creates turbulence, producing high shear forces.³ Research has shown that acoustic streaming is likely effective at disrupting bacterial biofilm and is especially effective against Gram negative motile rods.⁴ Because of the favorable effects of acoustic turbulence generated by ultrasonic instrumentation, practitioners rely on powered scaling when delivering periodontal therapy to achieve desired clinical outcomes in oral biofilm disruption.

Amplitude (or “displacement amplitude”) is the distance the tip moves during one cycle. Amplitude can be regulated by the operator—the higher the electromagnetic power setting, the greater the amplitude.^2,5 Tip displacement has a role in both acoustic microstreaming and cavitational forces. The extent of displacement is influenced by the tip design.⁶

Cavitation is the atomization action producing the “halo effect” as the irrigant flows along the ultrasonic tip and exits the instrument in multiple directions.⁵ Defined as the “rapid formation and collapse of local bubbles or ‘cavities’ within a liquid environment,” cavitational forces release energy against the tooth as a result of the implosion of the bubbles, resulting in bacterial cell wall lysis and disruption of the microbial environment.^2,5,7 Image analysis used to measure cavitation activity with high speed images indicates that cavitation could disrupt biofilm without contact.⁸ As deposit disruption can occur beyond the ultrasonic tip, the power scaler is an ideal option to employ when debriding difficult-to-access areas, as it increases the likelihood of achieving adequate biofilm interruption for all surfaces. In addition, research suggests that future ultrasonic inserts may be designed such that contact between the insert tip and root surfaces is not necessary to achieve adequate debridement.

The frequency of an ultrasonic unit is the number of times an instrument tip vibrates per second, measured in kilohertz units (KHz). Most magnetostrictive scalers perform at 25KHz or 30KHz, and studies have proven that there is no significant difference in efficacy between them. The higher frequency may seem more comfortable to operator and patients as it is somewhat quieter.⁹ The frequency is hard-wired into the scaler: This is important because the insert tip must be designed to operate at the unit’s frequency.⁹

Ultrasonic tips require a continuous irrigant or coolant to minimize temperature increases that might cause injury to tissues.10 While some ultrasonic units employ water irrigation through the dental operatory line, more recent units have self-contained irrigation devices that enable the addition of therapeutic agents.¹¹ In addition to the cooling effect, the flow of an irrigant through the insert results in a lavage effect, constantly flushing bacterial by-products and blood from the treatment site.^2,7 Another important function of the ultrasonic irrigant is its role in cavitational activity. When the ultrasound wave passes through the irrigant at high frequency, multitudes of bubbles expand and collapse, releasing a shock wave of energy.¹²

While the benefits of ultrasonic use in periodontics are many, there are a few concerns associated with their use in the clinical setting. Aerosol production, patient sensitivity, and unit decontamination are some issues that warrant discussion.

Aerosol production during the use of ultrasonics raises the risk of generating blood borne aerosols. Operators should consult the ultrasonic unit manufacturer recommendations for the necessary level of irrigant. As recommended by the American Dental Association and the Centers for Disease Control and Prevention, the use of high volume evacuation has been shown to best way reduce aerosols.¹¹ Use of a pre-procedural antimicrobial rinse by the patient has been shown to decrease aerosol bacterial counts by more than 90%.² While the presence of aerosol is undeniable, control with adequate suction or pre-rinsing eliminates most clinical concerns.

Decontamination of ultrasonic equipment can also be challenging. The tips can be sterilized, however other components of the instrument may not be accessible for decontamination. Operators can select ultrasonic devices that have handpieces that can be sterilized and irrigant reservoir bottles to improve infection control.²

Maximizing patient comfort while delivering periodontal debridement is essential to the patient experience. Proper use of the ultrasonic instrument, including tip adaptation and selection, power setting, and irrigant flow, will lessen discomfort. In addition, areas of hypersensitivity and demineralization should be avoided to avert damage to tooth structures and patient discomfort.²

As an essential component, ultrasonic instrumentation presents treatment options that can be individualized to meet the periodontal needs of the patient. Understanding how these instruments can be used to maximize clinical outcomes provides the opportunity to deliver comprehensive periodontal care in a safe, comfortable manner.

Betsy Reynolds, RDH, MS
Consultant
Boise, Idaho