Crowns are recommended when too much tooth structure has been lost to decay or a tooth has fractured due to trauma, such as motor vehicle accidents or physical abuse. The dentist will determine whether the tooth needs to be root treated before the crown can be placed. If the fracture is so severe that the nerves are exposed, the tooth can only be saved by root canal treatment prior to crowning work. Crowning involves partial filling and then shaving or trimming the filled tooth so that it can be capped or crowned.