Are some dental crowns, fillings, or braces a problem with MRI machines?

Not a problem. Hi, dental fillings or braces can induce artifacts that may spoil the image quality in structures just close to them. It is very local so if the reason of doing mr is not related to structures within a quarter of an inch, that is not a problem.
Nope. "dental crowns, fillings, or braces" are non-magnetic metals, not affected by mri. Radiologists trained to interpret appearance of dental appliances on mri's. If you need an mri, don't hesitate.
No. Dental crowns or fillings do not interfere with MRI machines.
Depends.. We have been asked to remove orthodontic braces for mri's of the head. Depending upon the structures to be imaged, the metal may interfere with the procedure. Any other structures, no problem.