Periodontal diseases are diagnosed on the basis of clinical signs, with radiographs assisting in treatment planning decisions and in the delivery of periodontal care. In the first instance, use of a screening system, to screen out patients with minimal or no disease, and to screen in those with disease requiring full diagnosis and treatment planning for periodontitis, is a very helpful approach. The full diagnostic approach relies on periodontal probing and the response to probing. Periodontal probing depth measurements and periodontal attachment level registrations are recordings of clinical findings, which depend upon the state of health of the periodontal tissues to a large extent.