The effect of alignment errors on bitewing-based bone loss measurements.

Alveolar bone loss measurements made using digitized dental radiographs have been shown to be precise and accurate. We determined the influence of alignment errors introduced when exposing the radiographs on the precision and accuracy of bone loss measurements. Bitewing radiographs of 15 day skulls were obtained using a positioning device (modified after the methods of Duckworth and associates). The sequence of radiographs was taken while the alignment of the main Roentgen beam was systematically varied within a 10 degree cone. Angular displacements were calculated from the digitized radiographs. Space variant digital image enhancement was performed to improve visualization of the cementoenamel junctions and alveolar crests. Corresponding bone loss measurements were made on dry skulls and radiographs. The criterion for truth in these measurements was established by 2 expert observers who measured the skulls with periodontal probes. Radiographic measurements were statistically compared with the criterion using validity coefficients. We found beam positioning errors of up to 10 degrees do not substantively affect alveolar bone loss measurements of mandibular molars taken from enhanced digital images of bitewing radiographs.