| Objective:To compare the changes in dentin collagen fiber morphology in the root canal wall after different final irrigation solutions(2.5% Na Cl O,5.25% Na Cl O,2% CHX,OCT,NS)and to compare the effects of different root canal sealers(AH Plus,Vitapex,i Root SP,Guttaflow bioseal)on the bonding strength of the root canal wall after different final irrigation solutions.To investigate the relationship between the structural changes of dentin collagen fibers and the bonding strength of the sealants,and to investigate the optimal combination of the final irrigation protocol and the root canal sealants in order to achieve good bonding between the sealants and dentin.Methods:Collect A total of 148 freshly extracted live pulp teeth for orthodontic reasons were collected.The root lengths were standardized to 13±0.5 mm by crown truncation and randomly grouped(2.5% Na Cl O in group A,5.25% Na Cl O in group B,2% CHX in group C,OCT in group D and saline in group E,and no preparation in group F),and all samples from groups A to E were prepared to ML3 by the TF-A machine with a nickel-titanium system and treated with the corresponding final irrigation protocols,respectively.(1)Scanning electron microscopy experiment: 5samples were randomly selected from groups A～E,respectively,and 3 samples from group F: 2.5% Na Cl O in group Aa,5.25% Na Cl O in group Ba,2% CHX in group Ca,OCT in group Da,saline in group Ea(positive control group),and no preparation in group Fa(negative control group).All samples were split into two halves along the long axis of the tooth and examined by scanning electron microscopy(SEM)to observe the morphology of the dentin tubule lumen and collagen fiber network in the crown 1/3,middle 1/3 and apical 1/3 of the root,respectively.(2)Push-out bond strength experiment: The remaining samples from each group A～E were then randomly divided into 4 subgroups(n=6)according to different sealants: Group I AH Plus,Group II Vitapex,Group III i Root SP,Group IV Guttaflow bioseal.all samples were root canal filled by single tip method.Hard tissue sections of the crown 1/3,middle 1/3 and apical1/3 of the root canal were prepared after one month of root canal storage with a thickness of 1 mm±0.1 mm.each section was pushed out experimentally using a universal testing machine with a loading force at a speed of 0.5 mm/min until separation of the filling material from the root canal wall occurred,the maximum load(N)at this time was recorded,and the adhesive strength(Mpa)was calculated.The mode of adhesive failure of the sealant was also observed under a stereomicroscope.KruskalWallis and Bonferroni correction tests and Chi square test were used for statistical analysis.Results:(1)Scanning electron microscope experiment:Group Aa:The canal lumen of dentin tubules in the crown 1/3 of the root is irregular,and the peri-canal dentin collagen fiber network is fractured and collapsed;The lumen of dentin tubules in the middle 1/3 of the root is regular,and the dentin collagen fiber network is collapsed;the lumen of dentin tubules in the apical 1/3 of the root is regular,and the dentin collagen fibers are interwoven into a network.Group Ba: Erosion of peri-canal dentin in the crown 1/3 and mid-root 1/3 of the dentin tubules,collapse of the pericanal and intra-canal collagen fiber mesh;regular lumen of the apical 1/3 of the dentin tubules,collapse of the peri-canal and intra-canal collagen fiber mesh.Group Ca: The canal lumen of dentin tubules in the crown 1/3,middle 1/3 and apical 1/3 of the root is regular,and collagen fibers are interwoven into a network within the canal wall.Group Da: The lumen of 1/3 root crown,1/3middle root and 1/3apical dentin tubules was regular,and collagen fiber network structure was found in the lumen without obvious collapse.Group Ea: The canal lumen of the crown 1/3 dentin tubules was regular,and collagen fibers were interwoven into a network within the canal wall;The canal lumen of dentin tubules in the middle 1/3 of the root is regular and the collapsed collagen fiber network in the canal lumen;the canal lumen of dentin tubules in the apical 1/3 of the root is regular and the collagen fiber network in the canal lumen is not completely exposed.Group Fa: The canal lumen of dentin tubules in the crown 1/3,middle 1/3 and apical 1/3 of the root was regular,with dense and interwoven collagen fiber bundles in the peri-canal,inter-canal and lumen.(2)Push out the bonding strength test:1)The effect of filling with the same root canal sealer after the action of different final rinsing solutions on the adhesive strength of the inner wall of the root canal was analyzed with the following results:When the root canal sealer was AH Plus,the bond strength values at the crownside 1/3 and the mid-root 1/3 were similar in the 2% CHX and OCT groups(P>0.05),but greater than those in the NS,2.5% Na Cl O,and 5.25% Na Cl O groups(P<0.05).Among them,the bond strength values were significantly lower in the 5.25% Na Cl O group at the crown side than in the NS group(P<0.01).At the apical 1/3 of the root,the bond strengths of the 2.5% Na Cl O,2% CHX,and OCT groups were similar and not statistically significant(P>0.05);however,they were all statistically greater than those of the 5.25% Na Cl O and NS groups(P<0.05).When the root canal sealer was Vitapex,the bond strength values at the crown 1/3were similar in the 2.5% Na Cl O,OCT,and 2% CHX groups(P>0.05),but were significantly greater than those in the NS group as well as the 5.25% Na Cl O group(P<0.05).The greatest adhesive strength was observed in the middle 1/3 of the root in the 2.5% Na Cl O group,followed by the 2% CHX group,both of which were not statistically significant(P>0.05).there was a statistical difference in the adhesive strength values between the 2% CHX group and the remaining three groups(P<0.05).The bond strength values at the apical 1/3 of the root were not significantly different from each other,although they were not identical(P>0.05).When the root canal sealer was i Root SP,the bond strength values in the crown1/3 were slightly higher in the OCT group than in the 2% CHX group,with no statistically significant difference(P>0.05);the bond strength values in the 2% CHX group were higher than those in the 2.5% Na Cl O,5.25% Na Cl O,and NS groups,with significant differences(P<0.05).The bond strength values at the middle 1/3 of the root were in descending order for the 2.5% Na Cl O group,NS group,5.25% Na Cl O group,OCT group,and 2% CHX group;the 2.5% Na Cl O group was significantly different from the OCT group(P<0.05)and 2% CHX group(P<0.01).In the apical 1/3 of the root,the 2.5% Na Cl O group had the highest bond strength value,followed by the OCT group,with significant differences between them(P<0.05);followed by the 5.25%Na Cl O and NS groups,which had the weakest and similar bond strength values,with no statistical significance between them(P>0.05),but lower than the OCT group,with significant differences(P<0.05).When the root canal sealer was Guttaflow bioseal,the bond strength values at the coronal 1/3 were slightly higher in the 2.5% Na Cl O group than in the 2% CHX group,and the difference was not statistically significant(P>0.05);secondly,the bond strength values in the 5.25% Na Cl O,OCT,and NS groups were similar to each other and not statistically different(P>0.05),but they were all lower than the 2.5% Na Cl O group’s(P<0.05).The greatest bond strength values were observed in the middle 1/3 and apical1/3 of the root in the 2% CHX group,which did not differ significantly and were not statistically significant after treatment with different final rinsing solutions.2)Analysis of the effect of the same final rinse solution action on the adhesive strength of the inner wall of the root canal under different sealer fillings,with the following results:When the final rinse solution was 2.5% Na Cl O,the bond strength values at the coronal 1/3,mid-root 1/3 and apical 1/3 showed no significant difference between the AH Plus and i Root SP groups(P>0.05),but both were significantly higher than the Guttaflow bioseal group as well as the Vitapex group(P<0.001).When the final rinse solution was 5.25% Na Cl O,the bond strength values at the coronal 1/3 and mid-root 1/3 showed no significant difference between the AH Plus group and the i Root SP group(P>0.05),but both were significantly higher than the Guttaflow bioseal group as well as the Vitapex group(P<0.05).However,at the apical1/3,the AH Plus group showed the highest bond strength values and was significantly different from the remaining three groups(P<0.05).When the final irrigation solution was 2% CHX or OCT,the bond strength values at the coronal 1/3,mid-root 1/3 and apical 1/3 showed no significant difference between the AH Plus group and the i Root SP group(P>0.05),but both were significantly higher than the Guttaflow bioseal group as well as the Vitapex group(P<0.01).When the final irrigation solution was NS,the bond strength values at the crown1/3 were higher in the AH Plus group than in the i Root SP group,with a statistically significant difference(P<0.05);secondly the i Root SP group was much greater than the Guttaflow bioseal group as well as the Vitapex group,with a significant difference(P<0.001).In the middle 1/3 of the root,no significant difference was observed between the AH Plus group and the i Root SP group(P>0.05);secondly,the bond strength values of the i Root SP group were greater than those of the Guttaflow bioseal group as well as the Vitapex group,with a significant difference(P<0.05).In the apical1/3 of the root,although there were differences in bond strength with different sealer fillings,there were no significant differences between them(P>0.05).3)Analyze the relationship between the fracture form of the sample and the final flushing solution,root canal sealer and root canal lysis site.The results are as follows:There were significant differences in the composition of fracture forms between different root canal sealers(P<0.001).The fracture forms of AH Plus Group and iroot SP group are mainly mixed,reaching 70.0% and 66.7% respectively,and the composition ratio of adhesive fracture is less than 10%,8.9% and 7.8% respectively.In the sealant Vitapex group,76.7% showed adhesive fracture;The Guttaflow bioseal group was mainly adhesive fracture(45.6%)and cohesive fracture(47.8%).There was significant difference in the composition ratio of fracture forms in different anatomical parts(P<0.001).Most of the failure modes in the crown are mixed fracture(64.2%);In the middle of the root,adhesive fracture(42.5%)was the most common;In the apical part,adhesive fracture was the main type(49.2%).Conclusion: 1.The use of high concentration Na Cl O(5.25%)in final flushing will cause significant erosion and damage to the dentin of the inner wall of the root canal,while CHX and OCT do not cause significant damage to the dentin collagen fibers.2.Iroot SP and ah plus have similar bonding strength to dentin on the inner wall of root canal,which is recommended.Vitapex is not suitable for permanent root canal filling.Guttaflow bioseal dentin bonding strength is significantly lower than ah plus.Its properties need to be further studied.3.The collapse of dentin collagen fiber mesh is not conducive to its bonding with dentin.Therefore,the combination of CHX/OCT +iroot SP/AH Plus is recommended for the combined use of terminal flushing solution and root canal sealer. |
PDF Full Text Request