ACP5 and chronic apical periodontitis: As shown in Fig. 1, the expression of PI3K (P = 0.009, Fig. 1A), Acp5 (P < 0.001, Fig. 1B) and NFATc1 (P = 0.003, Fig. 1C) genes were all higher in the chronic apical periodontitis samples than in healthy periodontal ligament tissue, and the difference was statistically significant.