Yet perhaps the most common place for cavities is in the grooves on the tops of our back teeth. My own tooth, no cavity in those grooves on the biting surface:
The grooves are blocked out, sealed, and it makes it very difficult to get a cavity in the top surface of the teeth. Not impossible, any system can be overloaded, in this case with too much constant sugar use. But it's nearly impossible to get a cavity in the grooves of a tooth with a sealant in place.