Periapical radiolucencies as evaluated by bisecting-angle and paralleling radiographic techniques

Two groups of patients were included in the study. The first group consisted of patients who received root canal treatment of single-rooted teeth (n = 63). The completed roof fillings were exposed to two different radiographic techniques, the paralleling and the bisecting-angle technique. The second group consisted of 1-year review radiographs of patients who had received apicectomies of single-rooted teeth (n = 105). Three observers examined the radiographic images. First, they were asked to identify teeth with a normal apical condition and those with an apical radiolucency. Thereafter pairs of radiographs were compared; cases judged as normal by all observers were excluded. The observers were now asked to ascertain whether the apical radiolucency was largest in the first image, the apical radiolucency was largest in the second picture or both radiolucencies were the same size. Both intraobserver and interobserver agreement, calculated as Cohen's kappa, was high with respect to the presence of lesions within both samples and it was at the same level for both radiographic techniques. The evaluation of the size of the lesions proved to be more inconsistent. Kappa values were in the range 0.38-0.71 for intraobserver comparisons and in the range 0.25-0.48 for interobserver comparisons. No significant difference was found between the size of lesions as recorded by the two techniques (P > 0.05). It is concluded that, when correctly adjusted the bisecting-angle technique and the paralleling technique provide similar diagnostic results.