Some drs/dentists don't believe that cavitations are a problem. But cavitations are caused by improper tooth removal. They may not want to be indicted by showing up a cavitation which they, or a fellow disbelieving dentist has caused. Also, is the equipment suitable to show if there is a cavitation. I don't know what a voll machine is, but I was tested by an EAV machine. No one even looked in my mouth, but they tested areas on my hand and foot. That's because they are using energy fields. An area of low energy indicates a problem, and because they know what they are doing, they are able to pinpoint the problem. I thought it was silly, and probably a scam, but then they found no cavitations. I didn't have a CLUE, so they could have told me that they found plenty of cavitations! I was also told that there was a definite mercury problem and the most problematic area was my liver. I had not told them that I have had pain in my liver for over 20 years.