Radiographic methods in the evaluation of periodontal therapy.

Radiographic methods are commonly utilized to assess periodontal bone changes in clinical trials. Radiographs are unique as a data source in that they provide a permanent visual record of the bone support and allow for linear, area, and volume measurements of periodontal lesions. The major limiting factors in the use of radiographic outcomes measures are geometric distortion and radiographic processing errors. The use of standardized methods and computer algorithms has reduced the effect of these errors on data from radiographs. Radiographic analysis in clinical trials is largely done in digital format by indirect digitizing film with a video camera. Direct digital detectors are now available for intra-oral use. The use of a direct detector eliminates the need for film processing and allows for dose reduction. The detectors currently available are limited in size and resolution. Subtraction radiography allows for area and volume estimates of bone gain or loss. The subtraction methods are highly precise, but are also technically exacting and labor intensive. The clinical trial hypothesis, size, length, and accuracy required should be the final consideration in choosing a radiographic method.