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Revisiting Orstavik's PAI score to produce a reliable and reproducible assessment of the outcomes of endodontic treatments in routine practice.

INTRODUCTION
Orstavik's periapical index is widely used for radiographic assessment of periapical status. This study analyzes the reliability and reproducibility of a modified guide for the interpretation of the Periapical index (PAI) scores recorded by undergraduate students.


MATERIALS AND METHOD
Two groups of 4th year students were asked to assess the PAI scores of 100 X-rays two or three times depending on the group. The reliability of their judgment was evaluated by comparing the students' assessments to those of a standard, based on the evaluations made by three teachers. Short-term stability was evaluated for two lengths of interval separating the Test and Retest phases, respectively one week for Group 1 and two weeks for Group 2. Long-term stability was evaluated by having Group 1 repeat the Retest phase after fifteen months.


RESULTS
Overall mean success rates ranged from 61% to 65% according to the student group and the study phase. Intergroup comparisons showed no statistical difference. The reliability of the PAI score evaluation by students was excellent in both groups. Short and long-term stability were also excellent regardless of the duration of the interval between the study's phases.


DISCUSSION
The image misinterpretations are discussed according to the study phases and the PAI score values.


CONCLUSION
Undergraduate students can be trained to use the modified guide for scoring PAI for self-evaluation of the outcomes of the root canal treatments and retreatments they are asked to perform during their clinical sessions.