Quantitative radiographic follow-up of apical surgery: a radiometric and histologic correlation

The objective of this study was to establish an objective method for evaluating the treatment outcome of apical periodontitis (AP). AP was induced in the mandibular premolars of beagle dogs and apicoectomies were performed with retrofilling. Standardized periapical radiographs were taken immediately after completion of treatment and at 6 months. Ten pairs of standardized radiographs of 33 treated roots were analyzed. Radiographs were digitized and subtracted after warping and gamma correction. Areas of AP and adjacent normal areas (N) in digitized original and subtraction images were analyzed using eight radiometric computations. These computations were compared with subjective histologic evaluation and objective quantitative histomorphometry of the periapical condition at 6 months. The average gray value for AP on the subtraction images was found to have significant correlation with both objective (multiple regression p < 0.01) and subjective histology (logistic regression p < 0.01). Digital subtraction may be a useful tool in endodontic apical surgery assessment.