Effectiveness Of Er:YAG Laser-activated Irrigation On Removal Of Smear Layers In Root Canals:an In Vitro Study

Objective:To evaluate the effectiveness of Er:YAG laser activated irrigation in the removal of root canal smear layers compared to ultrasonic activated irrigation,and conventional syringe irrigation in assistance to chemical preparation,as well as to provide the theoretical evidence for Er:YAG laser assisted irrigation in clinical application.Methods:?48 single-rooted anterior teeth longer than 20mm with mature apices were selected and resected to 20 mm in working length.The teeth were prepared with ProTaper rotary instrumentations up to F5(50/0.05)taper,and 17%EDTA was used for the finishing chemical preparation for 30s.Samples were divided into four experimental groups(n=12)based on techniques in assistance to chemical preparation:(A)Conventional syringe irrigation;(B)Ultrasonic assisted irrigation;(C)PIPS laser assisted irrigation technique;(D)SWEEPS laser assisted irrigation technique.? 108 molar teeth longer than 18mm with mature apices were resected to 18mm in working length.The selected teeth were placed into 3 groups according to mechanical preparation tapers(n=36):A:Preparation with Pathfile to P3(19/0.02);B:Preparation with ProTaperNext to X1(20/0.04);C:Preparation with ProTaperNext to X2(25/0.06).Group samples were then divided into 3 subgroups(n=12)according to the technique used in assistance to chemical preparation:Conventional syringe irrigation,Ultrasonic assisted irrigation and SWEEPS assisted irrigation.17%EDTA was used with 5.25%sodium hypochlorite for 60s as the finishing chemical preparation respectively.The specimens were prepared in longitudinal resections for examination,and markings were made at 1 mm,4 mm and 8 mm away from the apex.The status of root canal smear layer density was evaluated under scanning electron microscopy(SEM)and investigated scores were analyzed statistically.Results:? In anterior teeth mechanical preparation to F5(50/05)taper,examined at the 8mm line to the apex,ultrasonic assisted irrigation(group B),PIPS assisted irrigation(group C),and SWEEPS assisted irrigation(group D)have all shown superior results in the elimination of smear layers than conventional irrigation(group A)(P<0.001).From 4mm to the apex,SWEEPS assisted irrigation(group D)had presented better results over conventional(group A)(P<0.001)and ultrasonic techniques(group B)(P<0.05),PIPS technique(group C)however,had only displayed a more prominent result over ultrasonic technique(group B)(P<0.05).Conventional irrigation(group A)and ultrasonic assisted irrigation(group B)revealed no statistical difference(P>0.05).From 1mm to the apex,SWEEP assisted irrigation(group D)results persisted to be greater than convention irrigation(group A)(P<0.001/P<0.05)and ultrasonic assisted irrigation(group B)(P<0.001/P<0.05).SWEEPS(group D)technique had shown slightly better result than PIPs(group C)technique,but statistical difference was not present(P>0.05).(2)In posterior teeth mechanical preparation to P3(19/0.02)taper,SWEEPS assisted irrigation only exceeds ultrasonic assisted irrigation in the apical 1mm(P<0.05);in similar result of preparation to X1(20/0.04)taper,SWEEPS assisted irrigation only showed superior result over conventional irrigation(P<0.05)and ultrasonic assisted irrigation(P<0.01)in the apical 1mm as well;however,in mechanical preparation to X2(25/0.06)taper,SWEEPS assisted irrigation exhibited an overall advantage in the full length of the root canal over ultrasonic assisted irrigation and conventional syringe irrigation,which prevailed substantial statistical significance(P<0.01).Conclusion:?In anterior teeth mechanical preparation of F5(50/05)taper,both ER:YAG laser assisted irrigation techniques(PIPS and SWEEPS)have shown superior results in removal of smear layers in the apical 1/3 of the root canals over ultrasonic assisted irrigation and conventional syringe irrigation,however,statistical significance between the two was not shown?In posterior teeth mechanical preparations to X1(20/0.04)taper,SWEEPS assisted irrigation showed superior result in removal of smear layers in the apical 1mm over conventional irrigation and ultrasonic assisted irrigation;in mechanical preparation to X2(25/0.06)taper,SWEEPS assisted irrigation demonstrated better effectiveness in smear layers removal in the full length of the root canal than ultrasonic assisted irrigation and conventional syringe irrigation.