Cavities along the gum line are a common thing. A lot of these types of cavities happen along the base of bottom teeth. Reason for this is simply gravity. When you are done eating, or drinking, something the remnants of what didn't get swallowed settle to the floor of the mouth and end up eroding the bottom teeth along the gum line.
But, these cavities can be fixed. And with proper oral hygiene, and an understanding of what causes them in the first place, they can be prevented in the future.
Dr. Jim Ellis, DDS
1220 33rd Street Suite C
Ogden, UT 84403