How many mm of bottom outer edge of crown can it shave down? mine already have about 6mm round whole for r canal #14. want to shave to maxium limit

Your dentist: Would be best equipped to answer that given I have no benefit if a visual examination. Often root canals are performed through crowns and repaired successfully to last for many years. It all depends on how well the crown was fabricated, the extent of preparation of the underlying tooth, the age of the crown, the materials used to fabricate the crown ... Too many variables. Hope this helps.

RCT through crown: In order to properly gain access to the pulp chamber ; then to the openings into the canals, one must be able to both visualize the area ; then be able to properly instrument the canals. The location of the canals often determines the size of necessary access. Having said that, you always have the option to redo the crown after the rct is completed. What good is crown if poor rct that fails?

Depends: The limits to how much tooth structure can be removed depends on what you are trying to do but is general limited to a certain adequacy of height and width to permit crown retention. You need a minimum of at least 2mm of clearance all the way around but would not want to remove more than 3-4mm all the way around to allow for crown retention. Much more and you risk having the crown come off.

Depends: Different amounts of tooth reduction are needed depending on what type of crown is made. Gold crowns typically need less tooth reduction than porcelain crowns.

Cannot say: Impossible to know without clinical exam , imaging and more info about the crown and the remaining tooth under it. See your Dentist. Worst case, have a new one made with a more streamlined contour. See the specialist in crowns - the Prosthodontist. Good Luck.

Biologic width: The biologic width is essential for preservation of periodontal health and removal of irritation that might damage the periodontium. Therefore your dentist will place all margins according to your individual case. Good luck.