Comparison of cleaning effectiveness of three nickel titanium rotary instruments in root canal preparation of premolars with two root canals

WANG Xinyuan; YANG Zongqiang; GUO Zeyu; GU Yuanping; ZHANG Guoyu

doi:10.3969/j.issn.1002-266X.2025.12.025

Abstract：Objective To observe and compare the cleaning effectiveness of three nickel titanium(NiTi)rotary instruments,PLEX-2.0,M3Pro,and EZ-PASS,in the root canal preparation of premolars with two root canals.Methods Thirty extracted human premolars with two root canals,which were indicated for extraction because of peri-odontal disease or orthodontic treatment and met the inclusion criteria,were randomly assigned into groups A,B and C(n=10 per group).Root canals in groups A,B and C were prepared mechanically using the PLEX-2.0,M3Pro and EZ-PASS NiTi rotary instruments,respectively,followed by chemical preparation with 3%sodium hypochlorite(NaOCl)and 17%ethylenediaminetetraacetic acid(EDTA).After preparation,the teeth were split longitudinally.The coronal third,middle third,apical third and root canal isthmus of each specimen were examined under a scanning electron microscope(SEM)to evaluate debris remaining on the canal walls and removal of the smear layer.Results In all three groups,dentinal tu-bules in the coronal third were clearly visible and regularly arranged,with almost no smear layer.In the middle third,part of the canal wall showed clearly visible and relatively well aligned dentinal tubules,whereas other areas were partly cov-ered by smear layer.In the apical third,the orifices of the dentinal tubules were clearly obstructed,with large clumps of debris on the canal walls and relatively poor cleanliness.In the root canal isthmus,almost no mechanical cutting marks were observed on the canal walls,and abundant debris occluded the surface with a widely scattered smear layer,indicating poor cleaning in this region.In all three groups,smear layer scores of the canal walls showed a gradual decrease from the apical third towards the coronal third.In the coronal third,smear layer scores decreased in the order of groups B,A and C.In the middle third,scores in the groups A and C were lower than those in the group B,and in the apical third,scores in the group C were lower than those in the groups A and B(all P<0.05).Smear layer scores in the root canal isthmus were high in all three groups,with no statistically significant differences among them.Conclusions When combined with chemical irrigation,the NiTi rotary instruments PLEX-2.0,M3Pro and EZ-PASS provide good cleaning in the coro-nal,middle and apical thirds of premolars with two root canals,whereas their cleaning effectiveness in the root canal isth-mus is relatively poor.For the coronal and apical thirds,EZ-PASS shows better cleaning ability than the other two instru-ments,while in the middle third M3Pro performs better.