Reliability of the periapical index scoring system.

Data accumulated in one methodological and two longitudinal clinical studies employing the periapical index (PAI) scoring system were analyzed to assess the usefulness and reliability of the PAI system. More than 93% of pairs of PAI scores were either identical or deviated from each other with one step only for intra- and interexaminer agreement in scoring the same radiograph as well as for intraexaminer agreement in scoring two radiographs of the same root. Untreated roots which on completion of the longitudinal studies were judged to have healthy periapices, were scored as diseased less than 3% of the time during the study. Diseased teeth were scored as healthy less than 7% of the time. The results suggest that the PAI scoring system may be used with a high degree of reliability.