Just a while ago I cracked a tooth that had a root canal a year ago. The tooth also had a cavity. I never got it crowned. Now if I go to a dentist. What are some things they can do to fix my tooth with out pulling it? My Dad told me with his cracked tooth they just fill it with this white substance making it look like a tooth again. Is this possible?

It depends if the crack runs down the root of the tooth. Often with root canalled teeth they become brittle since there is no longer a nerve in the roots and do break. If the break is horizontal above the gum a filling can be placed but should have a crown put on it after to prevent breaking beyond repair. If the root is cracked you are looking at having the tooth pulled and ideally an implant placed to replace it.