TGFB1 and chronic apical periodontitis: Our result is also consistent with the tendency for the case number of root-end surgery to be decreased due to better clinical application of the shaping and cleaning of root canals in time.35 Mechanically, bone remodelling activity is a complicated event for maintaining bone volume, during which TGF-β plays a key role in orchestrating this event.45 By analysing the expression of pSmad2/3 in the apical area, TGF-β signalling was found to be aberrantly activated in chronic apical periodontitis from patients, which suggests that TGF-β signalling is involved (Supplementary Fig. 1a).