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
RadiologyInfo.org: 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