THE ENDODONTIC RADIOLUCENCY INDEX: CBCT-ERI

Abstract

Background Objective quantification of periapical disease on radiographs has evolved since the 1980s.1-3 The periapical index (PAI)1 was developed for classifying findings on periapical radiographs to assist in the diagnosis of pulpal disease. The PAI uses subjective, descriptive terminology that is too broad for the degree of detail present with cone beam computed tomography (CBCT) imaging. The CBCT-PAI2 uses measurable objective findings. However, the measurement intervals are large and do not distinguish the fine details of smaller or early-stage lesions seen on CBCT, thus limiting the ability to categorize early periapical disease or healing. The revised CBCT-PAI3 defines in more detail how to position the tooth in 3 fixed and reproducible planes. Tsai4 showed that small-volume, high-resolution CBCT scans could distinguish periapical radiolucencies measuring less than 0.5 mm. Therefore, the CBCT–endodontic radiolucency index (CBCT-ERI) is presented as an objective, repeatable index, with higher sensitivity to documentation of subtle radiographic findings. Objectives The objective was to describe the scoring technique and provide statistical validation of the CBCT-ERI as an objective measurement tool. A second objective was to classify periapical disease early in its progression and to quantify subtle changes in the healing process. Materials and Methods This study was approved by the Loma Linda University institutional review board (#5140049). CBCT data (voxel 0.125 mm3) of 119 endodontically treated roots were classified by using the CBCT-ERI by 2 calibrated radiology faculty. The cases were classified independently and blindly. In the multiplanar reconstructions, the long axis of the selected teeth were uprighted parallel to the sagittal and coronal planes of imaging according to a specific protocol. Roots were evaluated in all planes until the widest area of the periodontal ligament was identified. The linear width of the widest radiolucent area perpendicular to the root surface was measured and assigned a CBCT-ERI numerical score/rank. Results The examiners’ interclass correlation coefficient for the 119 root measurements was 0.96 at a 95% confidence interval. Reliability, using Cronbach's alpha, was 0.981. Conclusions The CBCT-ERI offers a highly sensitive and reproducible tool for evaluating developing or resolving periapical lesions.