Ultrasonic scalers: magnetostrictive and piezoelectric move the tip differently

The ultrasonic scaler has largely replaced manual instrumentation in calculus removal, and the differences between the two available systems bear on how the tip is used.

The magnetostrictive unit generates an elliptical motion: the whole tip surface is active, including the lateral faces. That makes it tolerant of angulation but demands care not to touch with the point.

The piezoelectric unit produces a linear motion, mainly back and forth. The lateral surfaces are chiefly active, and the tip must be held parallel to the tooth surface.

The practical consequence is that angulation matters more with piezoelectric units. A tip used perpendicular works with its point, which is the part that damages the root surface.

Correct inclination is a few degrees to the surface, with a continuous sweeping motion. A hand curette is placed and pulled; an ultrasonic tip moves without dwelling.

Dwelling on one spot is the error that produces grooves in the root surface, and these are permanent injuries the patient experiences as sensitivity in the months that follow.

Power should be set to the deposit rather than left at maximum out of habit. Heavy supragingival deposits call for medium power; subgingival debridement is performed at low power.

Irrigation serves two purposes. It cools the tip, which would otherwise generate enough heat to damage the pulp, and produces cavitation, the phenomenon that helps disrupt biofilm.

A partly blocked nozzle reduces flow without stopping it, and the drop goes unnoticed until the patient reports pain. The spray should be checked at the start of the appointment.

Absolute contraindications are few but should be known. Patients with implanted cardiac devices require assessment, particularly with magnetostrictive units, because of electromagnetic interference.

On implants and restorations standard metal tips are contraindicated. Plastic or coated tips are required, because metal scratches titanium and chips ceramic margins.

Tips wear and lose efficiency silently. A shortening of one millimetre reduces efficiency substantially, and manufacturers supply check cards that almost nobody uses.

In summary: piezoelectric units need the tip parallel to the surface, one never dwells on a spot, power follows the deposit, irrigation must be verified, and implants and ceramics require dedicated tips.