I came across an interesting claim that ultrasonic power scalers, besides for removing and crushing existing hard plaque on the teeth, create shockwaves that disrupt harmful bacterial cells that cause tooth decay:
How they work: These instruments use the energy of ultrasonic vibration to crush and remove hard, calcified deposits of calculus. They also create shockwaves that disrupt bacterial cells. Use of these tools includes washing and flushing the pockets and any exposed root surfaces with water.
I found one report that showed conflicting results when testing low and high frequency ultrasound on certain types of bacteria (not including streptococcus mutans - which have been implicated in causing tooth decay). Low frequency ultrasound seem to promote bacterial growth while higher frequencies stunt it.
Ultrasound was employed to increase the growth rate of bacterial cells attached to surfaces. Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli cells adhered to and grew on a polyethylene surface in the presence of ultrasound. It was found that low frequency ultrasound (70 kHz) of low acoustic intensity (<2 W/cm2) increased the growth rate of the cells compared to growth without ultrasound. However, at high intensity levels, cells were partially removed from the surface.
Do ultrasonic scalers disrupt and damage bacterial cells that cause tooth decay? (And by extension do they prevent tooth decay?)