The link below is to a DrBicuspid article (registration required). Some experts contend we will not be seeing ultrasonic diagnostics in dentistry any time soon because dental anatomy is too complex and ultrasonic diagnostics are too expensive. On the other hand researchers are developing an ultrasonic device to measure perio pockets that they say could be available in about a year.
They are also using ultrasonic technology to detect cracks in teeth similar to how industrial devices detect cracks in airplanes.
“The probe is placed at the gingival margin and pressed against it slightly,” Hinders said. “Only the ultrasound beam goes into the tissues, so it is entirely noninvasive. It is a point-by-point measurement, but since it's painless, there is no reason to not walk the sulcus and take a series of point measurements.”
via DrBicuspid Imaging.