Evaluation Of Apically Extruded Debris In Retreatment Of Curved Root Canals Using Four Kinds Of Ni-Ti Instruments

Ojective: This study evaluated the amount of apically extruded debris and the working time in the filling removal of curved root canals retreament with four different Ni-Ti instrumentation systems: ProTaper Universal Retreatment,ProTaper Next,Reciproc Blue and Mani GPR.Provide a theoretical guidance for how to choose suitable Ni-Ti instrumentation system in clinical endodontic retreatment.Methods: Forty resin modules with 30°curvature canal were prepared with the M3pro#25.06 Ni-Ti system and filled with gutta-percha.The modules were reserved in the37 ℃ water bath calorstat for 7 days after closure of the crown.The modules were randomly divided into 4 groups(n=10).The canal filling was removed with ProTaper Universal Retreatment,ProTaper Next,Reciproc Blue and Mani GPR.Apically extruded debris and irrigation were collected in a preweighted Eppendorf tubes and reserved in60°drying oven for 7 days.The weight of the debris was assessed by comparing the pre-and post-weight of the tubes using microbalance.The times required for reaching working length(WL)(T1)and complately removing the filling material were also recorded.All the experimental data were statistically analyzed by SPSS 22.0.Results:1.All systems caused apical debris extrusion.The ProTaper Universal Retreatment system(0.00276 ±0.00040g)produced significantly more debris than the other three systems(P<0.05).There was no difference among ProTaper Next system(0.00194 ± 0.00042g),Reciproc Blue system(0.00175 ± 0.00051g)and Mani GPR system(0.00186±0.00028g)(P>0.05).2.The Mani GPR system(71.33±17.89s)required significantly less time of reaching the WL(T1)than the other three systems(P<0.05).There was no significant difference in the time of reaching the WL(T1)among ProTaper Universal Retreatment system(93.77±16.22s),ProTaper Next system(89.09±19.69s)and Reciproc Blue system(99.94 ± 20.11s)(P>0.05).3.The ProTaper Universal Retreatment system(130.35 ± 21.56s)and Reciproc Blue system(139.55 ± 18.09s)required significantly less time to remove the root filling materials(T2)than ProTaper Next group(111.87±21.57s)and Mani GPR group(110.00±14.82s)(P>0.05).Conclusions: 1.In the retreatment of curved root canals,the ProTaper Next,Reciproc Blue and Mani GPR systems extruded significantly less debris than ProTaper Universal Retreatment system,which may beneficial improve the success rate of endodontic retreatment.2.In the retreatment of curved root canals,comparing with ProTaper Universal Retreatment or Reciproc Blue,use ProTaper Next or Mani GPR can remove the filling materials in less time.