Authors: Orstavik D, Kerekes K, Eriksen HM.
Title: The periapical index: a scoring system for radiographic assessment of apical periodontitis.
Journal: Endod Dent Traumatol
Date: Feb 1986
Citation: 2(1):20-34
Category: Radiology and Imaging
Evidence-based Ranking: 5
Purpose/Objectives: To present a scoring index for periapical radiographic assessment and test its validity with respect to accuracy, reproducibility, and discrimination.

Materials & Methods: 47 x-rays that had been used in a previous study (in which histological studies verified pathosis) were examined by 11 observers. The radiographs were categorized into subclassifications of 1 – 5 depending upon how they compared to a previously devised system based on standardized radiographs and illustrations.

Results: The periapical index (PAI) is based on comparing radiographs to a set of pre-defined x-rays and illustrations that have been categorized as 1-5. The first results prove that with statistical significance these x-rays can be reproducibly categorized into the PAI. Radiographs that fall into the middle of the system (PAI 3) are difficult to place and the author calculates different results based on filled or unfilled canals, the use of a “cut off” level within the score of 3, and the use of a “true score” that is rounded up into the next higher score.

Author’s Conclusion: The author concludes that the PAI is a valid, reproducible index that can be used for other radiographic and epidemiologic studies.

Validity of Conclusion: The claim that lesions that are radiographically detectable (PAI of 2) is reversible seems difficult to validate. The statistics show that the author’s conclusions are in line with the previous histological diagnosis.

Reviewer’s Comments: The entire study was based on 47 x-rays of max. ant. teeth. The base line results are difficult to ascertain because of being intermixed with the different statistical analysis methods used by the author. With respect to previous endodontic treatment, no timeline is mentioned. The PAI index is still vulnerable to subjective evaluation.