| Through in vitro research and clinical application of new ni-ti instruments and assisted root canal irrigation technology for removing and retreating dental gum fillings in root canals,this provides experimental reference and clinical basis for root canal retreatment in oral clinical practice.This study is divided into three parts:Experiment one:Comprehensive evaluation of the effects of different ni-ti files on the removal of dental root fillingsObjective Compare the effect,operation time and instrument safety of M3-RT,Pro Taper Next,Reciproc Blue,and Wave One Gold four kinds of Ni-Ti instruments and hand instruments H files to remove the filling materials in the single root canal of permanent premolars in vitro.Meanwhile,detect the amount of apical debris overflow,so as to evaluate its retreatment performance.Methods 100 mandibular permanent premolars were collected.The uniform working length was 16mm,and all were prepared to F2（2508）by the Pro Taper Universal combined with the coronal downward method.The root canals were tightly filled with AH Plus and dental glue using the continuous wave vertical compression method,and temporarily sealed with glass ion cement.After being stored at 37℃and 100%humidity for 4 weeks,they were randomly divided into 5 groups:hand H files（group H）,M3-RT files（group M3-RT）,Pro Taper Next files（group PTN）,Reciproc Blue file（RECB group）,Wave One Gold file（WOD group）to remove root filling.T The amount of debris(10-2g)spilled during retreatment was measured using a modified apical debris collection model.Take the X-ray film after root canal filling and root filling removal,and use Auto CAD2020 image processing software to measure and record the total root canal and the residual area of root filling in each segment of the root canal.At the same time,the total operation time of cleaning and root canal repreparation and the safety of instruments were recorded.Results（1）All test groups produced detritus that could be weighed.Compared with the other four groups,group H had the largest amount of root tip debris overflow（P<0.05）,the amount of debris in RECB group was more than that in M3-RT group,PTN group and WOD group（P<0.05）,the amount of debris in M3-RT group was more than that in PTN and WOD groups（P<0.05）,there was no significant difference between PTN group and WOD group（P>0.05）.（2）All the experimental groups had different degrees of filling residues in the root canal.The total residual rate in group H was significantly higher than that in the other four groups（P<0.05）.Compared with each other,the residual rate of root neck 1/3 and middle 1/3in group H was higher（P<0.05）.There was no significant difference in the residual rates of the five groups at root tip 1/3（P>0.05）.Intragroup comparison,the residual rate of filling material in the root neck 1/3 and the middle 1/3 of the root in the five groups was lower than that in the root tip 1/3（P<0.05）.There was no significant difference in the residual rate of buccal lingual and proximal and distal directions（P>0.05）.（3）The preparation time of group H was the longest（P<0.05）,and the preparation time of M3-RT group and PTN group was longer than that of RECB group and WOD group（P<0.05）.There was no significant difference between M3-RT group and PTN group、RECB group and WOD group（P>0.05）.（4）No lateral root canal perforation or step occurred in all samples.But there are device safety problems.In group H,two 15 H files were broken,two 15 H files are worn,one 20 H file is broken.In M3-RT group,two RT3 is worn.In Pro Taper Next group,two X1 were broken.Experiment two:The effects of New irrigation technology on retreatment with Root canal wallObjective To evaluate the effectiveness of M3 Max1 cleaning file,ultrasound,and PIPS Er:YAG laser swabbing techniques for removing residual root canal filling materials from root canals after standard root canal retreatment surgery using the Wave One Gold reciprocating root canal preparation systemMethods Collect 40 mandibular permanent premolars in vitro.Sample preparation and preservation are the same as in Experiment I.The samples were randomly divided into 4groups（n=10）.The control group:Wave One Gold root canal preparation followed by conventional irrigation with 17%EDTA and 3%Na Cl O solution;M3-Max group:additional M3-Max1 cleaning file,swing washing;PUI group:additional passive ultrasound swing washing;PIPS group:additional PIPS-Er:YAG laser swing cleaning is provided.The cleaned sample was longitudinally cleaved along the buccal and lingual directions,and three segments were labeled:apical（11mm from the apical foramen）,medial（7mm from the apical foramen）,and cervical（3mm from the apical foramen）.Under scanning electron microscopy,the debris and smear layer residues in each segment were observed.Quantitative scoring was performed using Hussmann’s scoring criteria.Results In comparison between groups,there was a significant difference in the scores of residual debris and smear layer in the root cap and middle segment between PIPS<PUI<M3Max<Control group（P<0.05）.At 1/3 of the root tip,there was no significant difference between the PUI group and the PIPS group（P>0.05）,while the differences between the other two groups were statistically significant（P<0.05）.Intragroup comparison,the scores of each group in the root crown and middle segment were lower than those in the apical segment（P<0.05）,and there was no significant difference between the root crown and middle segment（P>0.05）.Experiment three:Comparative observation of pain intensity after root canal retreatment using different nickel titanium files combined with PIPS Er:YAG laser swing washing techniqueObjective Select clinical cases suitable for root canal retreatment,and compare the degree of postoperative pain and duration of root canal retreatment with hand and machine Ni Ti instruments M3-RT,Pro Taper Next,Reciproc Blue,Wave One Gold after root canal filling removal combined with PIPS-Er:YAG laser ablation.Methods 135 patients aged 20-65 who were diagnosed as chronic periapical periodontitis at our hospital were included in the study.A total of 135 teeth with single root canal disease（including 88 anterior teeth and 47 premolars）were randomly divided into 5groups（n=27）.The root canal was prepared with manual file（group K）,M3-RT（group M）,Pro Taper Next（group P）,Reciproc Blue（group R）,and Wave One Gold（group W）.PIPS-Er:YAG laser activated 3%Na Cl O and 17%EDTA solution for disinfection,dry root canal,AH Plus and hot gutta-percha continuous wave vertical compression method tightly filled root canal,finally 3M composite resin repair crown.The effect of root canal filling after retreatment was compared among the five groups.Pain intensity and duration were analyzed at 24h,48h,72h,and 7d after the root canal retreatment,and analgesic medication was recorded.Results（1）There was no significant difference in gender,age,dental position and preoperative pain and other general information among the five groups（P>0.05）.（2）There was no significant difference in root canal filling after retreatment among the five groups（P>0.05）,and there was no root canal underfilling or overfilling.（3）The pain intensity of the five groups was the highest 24 hours after retreatment,and the pain intensity decreased with time.At 24,48 and 72 hours after operation,the pain intensity in group K was higher than that in other group（P<0.05）.After 7 days,there was no significant difference in pain intensity among all groups（P=0.466）.（4）Regarding the intake of painkillers,patients in each group took ibuprofen capsules within 24 hours after surgery,with no significant difference between the groups（P>0.05）.Patients in the five groups did not take painkillers during the other time.Conclusion1、During root canal retreatment,the new Ni-Ti system Pro Taper Next and Wave One Gold produced less apical overflow debris,which had little stimulation effect on periapical tissue.However,the study in vitro lacked periapical barrier,and the experimental results could not be directly applied to clinical practice,and further clinical trials were still needed to verify.2、After root canal removal with all instruments,a certain amount of filling material remains in the root canal.The removal effect of mechanical nickel titanium instruments is superior to that of hand instruments,and the reciprocating preparation systems Wave One Gold and Reciproc Blue have fast root canal removal speed and excellent safety performance.3、After the removal of root canal filling by the Wave One Gold preparation system,assisted with PIPS-Er:YAG activated Na Cl O and EDTA irrigations can significantly reduce residual filling debris and smear layers in the root canal,and improve the cleanliness of the root canal wall.4、The clinical application of Ni-Ti instruments to complete root canal retreatment at one time can significantly reduce the postoperative pain of patients compared with manual instruments,which can meet the requirements of patients with high postoperative requirements and bring them a comfortable treatment experience. |
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