Radiographs

• Radiographs taken at one examination provide useful estimates of past damage to periodontal structures but they cannot identify sties with ongoing periodontal destruction. Longitudinal radiographic observations from at least 2 examinations are needed to determine if there has been a change in the level of supporting bone.

• Unaided eye can only detect radiographic changes when approximately 50% of the bone material has been lost. Radiographs underestimate the true amount of bone loss.

• What is the threshold distance? At what distance between the CEJ and alveolar crest, is it considered bone loss? Histologic observation demonstrated in normal sties, the CEJ to alveolar crest ranged from 0.04 to 3.36 mm. Hausmann 1991 and Kallestal 1989 indicated that >2 mm CEJ to alveolar crest distance is an appropriate threshold for radiographic bone loss on bite-wing radiographs.

• Fuzziness and a break in the crestal lamina dura is NOT one of the earliest radiographic signs of periodontitis. Rams 1994 demonstrated that the vast majority of sites (96.8%) that did not break down, also lacked an intact lamina dura. ie. absence of lamina dura does NOT indicate increased risk of breaking down, but the presence of a lamina dura means there is a high probability the sites is stable.