Does a tool even need to touch the patient during scaling and root planing? A new study suggests maybe not. The ultrasonic scaler is one of the primary tools for intervention when a patient presents with calculus buildup, but patients often dislike the noise and sensation of the vibrating tool despite its effectiveness at removing the stubborn buildups. Good news may be on the horizon for these patients, as new, high-speed imagery reveals the source of the ultrasonic's efficacy and suggests new designs which may never need to physically touch the tooth.
Researchers at the University of Birmingham used microscopy and ultra-high-speed photography to investigate what's actually happening at the tip of an ultrasonic scaler during use. Conventional thought holds that the physical vibration of ultrasonics is more effective in knocking calculus off the tooth surface than manual scraping alone, but the researchers discovered another mechanism at play with the ultrasonics: cavitation, occurring as a zone of tiny bubbles around the tip of the instrument.
This phenomenon occurs in systems like propellers and fluid pumps. At its most basic, cavitation is a bubble of vapor precipitated out of a fluid under conditions of extremely low pressure. For example, as a propeller forces water in one direction to move a boat, the blades of the propeller create low-pressure regions on the outer regions of the blades. Just as water boils at lower temperatures at higher altitudes, when the pressure of the surrounding fluid drops due to the motion of the propeller, bubbles of vapor precipitate out, essentially boiling for a moment before collapsing on themselves with immense energy. The energy of cavitation bubbles can be beneficial or harmful. Turbines and fluid pumps like those in hydroelectric dams often require repairs due to cavitation damage, where the metal has been eaten away by the collapsing bubbles. Some animals are even able to harness the power of cavitation. The pistol shrimp for example, can snap its claw shut so fast that it creates a cavitation bubble, the implosion of which can stun fish and injure predators.
However, this same destructive power is also immensely useful for cleaning many surfaces. The microchip industry uses cavitation to clean silicon wafers, and some electric toothbrushes derive their cleaning action from weak zones of cavitation at the tips of the bristles. Ultrasonic scalers create much more powerful zones of cavitation that can both break up biofilms and lyse bacterial cells, which cleans the teeth and reduces inflammation without antibiotics.
The next step the researchers will undertake is designing new shapes for the ultrasonic tips that will enlarge and extend the zone of cavitation so that periodontal scaling can be completed with as minimal contact with the instrument on the tooth as possible. Through the power of cavitation, patients can be more comfortable and practitioners able to perform treatment more efficiently. Best of all, the overall impact on the teeth is gentler and may be more effective at cleaning hard-to-reach spots than traditional scaling.