Fig. 3: Periapical index (PAI) median scores for retreated maxillary central incisors after retreatment with BC formation (BC) and platelet-rich fibrin (PRF) at different follow-up intervals.

The difference between the BC and PRF groups was tested using Mann–Whitney U test, which was statistically significant after 3 and 6 months. While the PAI medians were similar in both groups after 12 and 24 months. *P ≤ 0.05, ** P ≤ 0.01, ***P ≤ 0.001, **** P ≤ 0.0001.