This happened to me. When I first moved to Boston I went to a new dentist who kept remarking how great my dental insurance coverage was. It turned out I had a cavity which was fully covered by my insurance so I went to his office, got the novocaine shot and spent an hour with the guy supposedly drilling in my mouth. I saw the dentist for about a year and had three cavities. The only three I'd ever had in my life.

A year or so later I switched to a dentist who was closer to my office. I told him I had had three cavities but they weren't showing up on the x-rays he took. We did two or three sets of x-rays before we figured out they were never going to show up because he had just been billing my great insurance for work he didn't actually do.