TLR4 and alkaline phosphatase measurement: To explore the role of TLR4 in pulp pain of AP, the AP-1 rats received eritoran (selective TLR4 inhibitor, E), ibuprofen (analgesic, I) and vehicle (0.9% NaCl solution, V); and were categorized as AP-1 + E group, AP-1 + I group and AP-1 + V group, respectively.