If you want to make sure they stay dead you need to make sure the area where the base was attached to rock is completely covered in kalk
paste to continue to burn it out. If you don't use enough it won't work. Make sure it is a thick paste. Liquid enough to come out of a syringe but thick enough to stay put where you put it. Also make sure most of your flow is off so it stays in place.
I find lemon juice is best if you can pull the rock out and scrub the area clean with a toothbrush while applying lemon juice.
You just need to make sure all the remaining flesh is dead. Even the tiniest piece.