There are many on-line resources which discuss the considerations for oral & maxillofacial CBCT scanning in great detail.

Dental Tribune: Facing the Facts – dental CBCT and medical CT scans Dental Cone Beam CT

Dear Doctor Dentistry & Oral Health: CAT Scans In Dentistry

Implant Practice US: Reconstruction of resected jaw assisted by 3D technologies

RSNA Radiology: Dental CT Imaging: A Look At The Jaw