My dental hygienist seemed to be spending more time spraying my teeth than scraping them, so I decided to check up on this. Turned out she was using an ultrasonic tooth scaler. I decided to poke around a bit to find out more.
Ultrasound is sound above the limit of human hearing, around 15,000 Hertz (Hz, vibrations per second). Supposedly, the Beatles included some ultrasound on their Sgt. Pepper's Album to drive dogs crazy.
On a more practical level, difference frequencies of ultrasound can be used in all kinds of applications, from scanning a developing baby, to controlling pets, to cleaning teeth.
Ultrasonic tooth scalers use transducers that convert electricity into mechanical energy using materials like quartz crystals or specialized ceramics that change shape with electricity (piezoelectric) which generate up to 50,000 vibrations per second or by changing magnetic fields (magnetostrictive) which go up to 25,000 vibrations per second.
These vibrations produce microscopic high and low pressure areas. This results in cavitation, which might sound bad for cavity prone teeth, but it means the formation of bubbles filled with water vapour rather than air. The vibration stretches and compresses these tiny bubbles until they implode and release a burst of heat and pressure. This energy loosens stuck particles, but it happens on a tiny scale with enough water as coolant so I don't notice this tempest in my tooth spot.
I find it more pleasant to have my teeth cleaned this way and less with the scraping, but ultrasound may add extra wear on metal implants, so it might be worth discussing the pros and cons of this technology with your dentist or hygienist.