This article holds so true to me. My mouth was nothing but over-drilled and filled mercury fillings. Your teeth grow in layers in the shape of an arch. We all know an arch just like used in a bridge or door way is the strongest of building techniques. Drilling into the arch makes little sense to start with much less drilling beyond the cavity is absurd. A cavity can be healed naturally also, look at oil pulling. Below is some very good info for your health.