Problem in premolar due to habbit of penetrating sharp things like compass in gum during study.now it is going black.is 3m lava crown is right choice?

Many issues: You have many issues here. Obviously one is to stop such dangerous habits. The type of crown that you mentioned is merely a name brand of one of many different types of tooth colored ceramic crown. You need to be in the hands of a dentist that you trust, and then follow his\her recommendations regarding treatment options. Ask questions so you understand what is best for you.

See your dentist.: You need to see your dentist and have him treat the problem. You also need to grow up and stop destroying your gums like a little kid. If its turning black its trying to tell you to get it treated. Do you even have a dentist? Go see him asap.