Can you have an mri if you have a dental crown?

Simply? Yes. Removable dental work like a brace should be taken out prior to an MRI scan as they might be affected by the magnetic field. Permanent dental work containing metal may affect the image quality around the area where it is situated but it won't cause any problems apart from that.

As always, any questions relating to MRI safety should be checked with the radiographer or technician undertaking the scan prior to entering the MRI room.