The 411 on magneto and piezo ultrasonics

When it comes to ultrasonic scaling, the terms magneto, piezo, and ultrasonic are often used interchangeably. While both magnetostrictive (magneto) and piezoelectric (piezo) systems are ultrasonic scalers, they function differently and require different clinical techniques.

Understanding how magneto and piezo differ allows clinicians to use each technology safely, effectively, and with greater confidence. This article provides the "411" on magneto vs. piezo ultrasonics and why those differences matter.

Magneto and piezo are both ultrasonic scalers

Clinicians often say they use "ultrasonics" or "piezo." The correct way to express the technology is magneto or piezo, since both are ultrasonic.

Frequency multiplied by amplitude affects tip speed

Ultrasonic frequency ranges between 18,000 cycles per second (cps) and 42,000 cps. The number of cycles per second is the frequency. For example, magneto 30K means a frequency of 30,000 cps.

Frequency alone does not determine speed. The formula for speed requires the number of cycles per second multiplied by amplitude, which is the distance the tip moves.

Auto-tuned vs. manually tuned

Tuning refers to the ability to change the frequency. All piezo units are auto-tuned, meaning the frequency cannot be changed by the clinician. When the power setting is adjusted, only the amplitude changes, not the frequency.

Early magneto units allowed the frequency to be tuned with one knob and the amplitude with a second knob. Most magneto units today are auto-tuned rather than manually tuned.

History of magnetostrictive ultrasonic technology

Magnetostrictive ultrasonics were developed in the mid-1950s by Cavitron Corporation for cavity preparation. These early magneto inserts could not create the undercuts required for amalgams. In the early 1960s, Borden high-speed air motors were introduced for cavity preparation.

Cavitron initially cut off tips from hand instruments and brazed them onto magneto stacks in an effort to clean teeth. The result was dental inserts with elliptical motion that fractured calculus (figure 1).

History of piezoelectric ultrasonic scalers

Piezoelectric ultrasonics have been used in Europe since the early 1970s, when French engineers at Satelec, now Acteon, applied a voltage to piezo crystals. This produced a tip with linear motion (figure 2). Acteon is known for its color-coded tips that correspond to designated power settings.

Several years later, EMS introduced a piezo scaler differentiated primarily by the threads on the tips that screw into the handpiece. EMS and its Guided Biofilm Therapy (GBT) protocol have brought increased attention to piezo technology in the North American market. Companies such as HuFriedyGroup, Woodpecker, and others also market piezo units.

Why clinical application differs

Many faculty members and clinicians first learned ultrasonic scaling using Cavitron magneto systems. Clinical application of magneto and piezo technologies is not totally interchangeable.

Two major differences are tip angulation, or tilt, against the tooth and root surfaces, and required fluid flow. With piezoelectric ultrasonic scalers, only the lateral sides of the tip should be adapted to the tooth surface.

For piezo scaling, the tilt of the tip should not exceed 5 degrees. A tilt greater than 5 degrees will cause the tip to roll toward the back surface producing a screeching noise.

Magnetostrictive technology is more forgiving because the tilt can be more open, and the back of the tip can be used. One similarity between the two technologies is the highest concentration of energy is at the point. Never direct the point to the tooth, which can create gouging (figure 3).

Adequate water flow is always required to cool the tip-to-tooth interface during ultrasonic scaling. Piezo scalers can operate with lower flow levels because they do not need to cool crystals in the handpiece, whereas magneto stacks require higher flow rates for cooling.

Clinical confidence counts

Understanding the differences between magnetostrictive and piezoelectric ultrasonic scalers helps clinicians adapt their technique regardless of the equipment available. When clinicians know how each technology works and how it should be applied, clinical confidence and patient outcomes improve. 

Financial Disclosure: Ultrasonics Plus receives consulting fees and sponsorship from Acteon and other corporate sponsors.

Editor's note: This article appeared in the January/February 2026 print edition of RDH magazine. Dental hygienists in North America are eligible for a complimentary print subscription. Sign up here.