Hi! I Have Been Eating Slate Pencil Since The Age

Hi! I have been eating slate pencil since the age of 10 and now I'm 36. I had stopped eating slate pencil in beetween from 2011 to 2015 but now I have started eating again. I think because of this habbit my teeth have badly erroded and pain. They are in very bad condition and dentists tell me I need extensive denture recreation. Also I suffer from acute pimple and acne problem. My face is always covered with pimples and marks since the age of 16. Please tell is it because of slate pencil? Also does eating slate pencil causes kidney stone or other serious problem?