Whether or not you can simply replace a post and crown after it has come depends on several factors that only seeing a dentist can answer. If there is a cavity or fracture of the remaining tooth may not make it practical or possible to recement it. If it has come out one or more times in the past, it may be time to come up with a better solution. If it can be replaced, ideally it should be placed back with a bonding cement that can help keep it in more securely. Good luck!
