Experimental Study And Clinical Application Of Nickel-titanium Instruments For Root Canal Retreatment

Objective:1.Compare the central location ability of ProTaper Retreatment、Fengdu O-file and M3-RT three kinds of nickel-titanium root canal retreatment instruments and hand stainless instruments K-file、H-file in single-bend resin simulated root canals.2.Compare the clearance rate,preparation time ofProTaper Retreatment,Fengdu O-file,M3-RT three kinds of nickel-titanium root canal retreatment instruments and hand stainless instruments K-file,H-file,and observe the form of the root canal wall under the Scanning Electron Microscope(SEM).3.Choosing the appropriate retreatment clinical case,compare the preparation time of single canal and inter-diagnosis pain after using the hand instruments、ProTaper Retreatment、Fengdu O-file and M3-RT nickel-titanium root canal retreatment instruments for root canal preparation.Methods:1.To randomly divide 40 simulated resin blocks with the same specification into four groups(n=10).Each group was separately prepared with hand stainless instruments K-file and H-file(Group A),ProTaper retreatment(Group B),Fengdu O-file(Group C),and M3-RT(GroupD).Using EPSON V700 scanner to obtain the pre-and post-operative images and overlapping the images through Photoshop CS6.Take the root tip hole as the center of the circle,and make a concentric circle every 1 mm as an observation point,taking a total of 10 observation points.Measuring the root canal inner and outer wall resin removal with Image J,compared the central location ability of the four group.2.Collect 60 mandibular single root premolars for orthodontic need of Department of Maxillofacial Surgery,Stomatological Hospital of Hebei.Open dental pulp with high speed carborundum needle,extirpation the pulp,cutting the crown with carborundum piece at the enamel bone boundary.Preparethe root canal using standardized technique,then using the lateral condensation technique fill root canal.Temporary seal the root canal with glass ionomer and take X-ray film.All the teeth were stored at 37℃ in 100% humidity environment for 4 weeks to allow complete setting of the sealer.Then the teeth were randomly divided into 4 groups of 15 each.Usehand stainless instruments K-file,H-file(groupⅠ),ProTaper Retreatment(groupⅡ),Fengdu O-file(groupⅢ),M3-RT(groupⅣ)to remove the filling materials.The roots were longitudinally sectioned,and the image of the root surface was photographed under the 10 x magnification microscope.The Auto CAD software was used to trace the area of the root canal wall and residual root filling,and the root filling clearance rate of each group was calculated.Two teeth were randomly selected and observed under SEM.Simultaneously record the preparation time of each group in the preparation process.3.Collection of 40 patients who underwent root canal retreatment in the Department of Endodontics,Stomatological Hospital of Hebei Medical University from April 2018 to December 2018.Randomly divided into 4 groups of 10 each according to the order of treatment,separately use hand stainless instruments(group S),ProTaper Retreatment(group P),Fengdu O-file(group O),M3-RT(group M3)to prepare.Record and calculate the average time required to remove each root canal fill during the preparation process.At 24 hours and 7 days after surgery,pain assessment was performed by telephone follow-up.4.Each group of data was statistically analyzed by SPSS21.0 software.Results:1.The results of the central location ability test:within 9 mm from the root tip hole,the central location ability of three nickel-titanium instruments was better than that of the hand instruments(P<0.05).At 4mm from the root tip hole,M3-RT has the best central location ability(P<0.05),the hand stainless instruments K-file、H-file had the largest offset.There was no difference of the four instruments at a distance of 10 mm from the root tip hole(P>0.05).2.After thefour groups of instruments for retreatment canal preparation,there are various degree of filling material remained in the root canal.The clearance rate of group Ⅰ was(82.14±5.16)%,group Ⅱ was(91.88±1.30)%,group Ⅲ was(91.58±1.10)%,Group Ⅳ was(92.40±0.76)%.There was no significant difference between three kinds of nickel-titanium instruments(P>0.05),and both were higher than the hand instrument group(P<0.05).3.Scanning electron microscope observation results shown,the root canal wall prepared by the nickel-titanium instruments was more smooth and continuous than the hand instruments,and the residual filling material was less.4.The preparation time for the three kinds of nickel-titanium instruments is:group Ⅱ(328.80±13.48)s,group Ⅲ(320.60±10.80)s,Group Ⅳ(318.20±9.81)s,there was no significant difference between the three groups(P>0.05),and both were significantly shorter than the preparation time of the hand instruments(610.60±12.42)s(P<0.05).5.The preparation time of single canal was : Group S(567.60±14.94)s,Group P(266.60±5.94)s,Group O(268.00±11.51)s,Group M3(267.20±10.66)s,the three kinds of nickel-titanium instruments were shorter than the hand instrument group(P<0.05),and there was no significant difference between the them(P>0.05).6.Post-preparation pain rate:at 24 hours after root canal preparation,the post-operative pain of the patients after preparation with the nickel-titanium instruments was less than that of the hand instruments(P<0.05).The pain rate of the M3-RT group was lower than that of the other two nickel-titanium instruments,which was statistically significant(P<0.05).There was no significant difference in pain rate between the four kinds of instruments at 7 days after preparation(P>0.05).Conclusion:1.The the central location ability of three kinds of nickel-titanium root canal retreatment instruments is significantly better than that of hand stainless instruments.ProTaper Retreatment、Fengdu O-file and M3-RT three kinds of nickel-titanium root canal retreatment instruments showed good performance in the study,the central location ability of M3-RT is slightly better.2.Nickel-titanium root canal retreatment instruments are more efficient than traditional hand stainless instruments in removing root fillings,less root canal preparation time,and the root canal wall after preparation is smoother and has good continuity.3.Clinical application of root canal retreatment of nickel-titanium root canal retreatment instruments,the post-preparation pain for patients is less than that use of hand instruments.