By evaluating anti-PD-1 antibody the action of the solution in the different thirds, no significant difference was observed when EDTA, citric acid, and phosphoric acid gel were used. The use of phosphoric acid was more effective in the cervical and middle thirds than in the apical third. At 1 minute, the control group showed the worst results compared with

the experimental ones. The phosphoric acid solution was more effective than EDTA, citric acid, and phosphoric acid gel in the apical and middle thirds. In the cervical third, the phosphoric acid solution was significantly better than citric acid and EDTA, and no statistical difference was observed between phosphoric acid solution and gel. With regard to the action of the same solution in different thirds, EDTA showed better activity in cervical third than in middle and apical thirds. The citric acid was shown to be more effective in the cervical and middle thirds than in the apical third. The use of phosphoric acid solution and gel did not show difference between the thirds. At 3 minutes, phosphoric acid solution was the most effective chemical agent used in the apical third, followed by citric acid, EDTA, and phosphoric acid gel. In the middle and cervical thirds, no significant differences were observed. Again, the control group showed

the worst results. By comparing the same solutions in different thirds, EDTA and citric acid were more effective see more in the cervical third than in the middle

and apical thirds. The phosphoric acid gel was more efficient in the cervical (-)-p-Bromotetramisole Oxalate and middle thirds than in the apical third. Phosphoric acid solution did not show significant difference between the thirds. When the phosphoric acid gel was used in all periods of time, it was possible to verify in some samples the persistence of a residual layer of this substance. Regarding the dentinal integrity, all substances generated some degree of erosion in the cervical and middle thirds for irrigation at 1 minute or longer. It is noteworthy that the literature describes a variety of chemicals with a broad range of concentrations and different irrigation regimens to remove the smear layer. This study used EDTA, a well-known chelating agent widely used to remove inorganic components of the smear layer 18 and 19, citric acid, a weak organic acid with relatively low cytotoxicity used as an aqueous acidic solution 20 and 21; and finally, phosphoric acid, a strong acid routinely used in dentistry to remove the smear layer and smear plugs formed during coronal cavity preparations (22). Although some studies on the ability of phosphoric acid in removing smear layer from root canals are available in the literature, the concentrations used are rather low (below 5% and 24%) compared with the ones used to remove the smear layer from coronal dentin. In addition, there is no consensus on the ideal time of irrigation 7, 16 and 17.