MRI is much lower resolution than X-ray. Dental researchers are speculating about using MRI for some uses, like implant planning, but the laws of physics are not in favor of reducing the voxel size to match the small features identified with X-rays.

My dentist just upgraded their gear, the tech no longer leaves the room when shooting the image, and I didn't get a lead blanket. Presumably that means the technology improved again and the total X-ray energy went down.