Recently, my last back molar cracked after eating some popcorn. The tooth had a root canal about 8-months ago. The dentist recommends an extraction, rather than a crown, because of the way the crack occurred.My teeth have always been crowded and I was wondering whether I need to replace the tooth after the extraction? If nothing is done after the extraction will the bottom teeth shift now that there will be some room? Is an implant the better way to go?Also, I keep hearing that there is no way to tell how deep the crack is and yet the x-ray looks like the root is intact. Why would crowning the molar be a problem if the root is intact?