Careful with the dental schools. I had a dead tooth from a football tackle I made way back and it finally cracked in a basketball game knocking heads again. The replacement itself broke very quickly. So, I got a crown at NYU School of Dentistry. It was inexpensive but it took a lot of visits and they cut away at my gum (this was a front tooth), so that it doesn't look quite right and the crown itself is off color from my other teeth. It has lasted now about fifteen to seventeen years but it does not look good.
As for the cavity diagnoses, studies have shown that different dentists almost always diagnose cavities but not in the same teeth! There is something like a 50% margin of error. At the same time, if you go many years without going to the dentist, as I have, and you're a runner who drank a lot of Gatorade and the like for dehydration headaches, who knows what's going to happen? I lost a tooth after eating some bbq and picking at my tooth--it started breaking right off and over the past few years basically all of it has come out. The one thing you can do without going to the dentist is to rinse with some warm salt water before bed if you have some pain. In addition, recent studies have said that untreated oral infections lead often to heart and other ailments.