Evaluation of apically extruded debris during the removal of canal filling material using three different Ni-Ti systems and hand files in teeth with simulated apical root resorption

Effect of treatment variables on apical extrusion of debris during root canal retreatment: A systematic review and meta-analysis of laboratory studies

Background

This study aimed to systematically and comprehensively review the effect of various treatment variables on apically extruded debris (AED) during non-surgical root canal retreatment (NSRCRT).

Methods

The study protocol is shared in the Open Science Framework database (https://osf.io/kjtdg/?view_only=17060180705745ec9dae9a01614f3880). An electronic search was conducted up to July 2022 to reveal related studies. Two reviewers critically assessed the studies for eligibility against inclusion and exclusion criteria and data extraction. Quantitative data synthesis was performed, and the risk of bias in the studies was also evaluated.

Results

Forty-six studies were included in the systematic review and 14 in the meta-analysis. Conflicting or limited evidence was found for the effect of sealer type, obturation technique, and solvent use. The manual instrumentation increased the amount of AED compared to rotary instrumentation during the removal of filling materials (P<0.001). There was no significant difference in the amount of AED between the use of rotary and reciprocating files during the removal of filling materials (P=0.181).

Conclusion

Rotary instruments can be recommended instead of manual instruments during the removal of filling materials to control the amount of AED. Further studies with a low risk of bias are needed to clarify the effect of other treatment variables on AED during NSRCRT.

ProTaper universal retreatment retreatment potential in oval-shaped canals filled with different obturation techniques-A micro-computed tomography study

Aim

The objective of this in vitro micro-computed tomography investigation is to assess the efficacy of the ProTaper Universal Retreatment System in retreating oval-shaped root canals filled with three obturation procedures.

Materials and Methods

Thirty-six lower incisors with a single oval root canal were prepared using XP-Endo Shaper up to size 30/0.04, and allocated into three equal groups based on the filling technique: Group 1: Warm vertical condensation technique; Group 2: GuttaCore obturators; Group 3: Cold lateral condensation technique. All samples were further retreated using the ProTaper Universal Retreatment system. Micro-CT analysis was performed before and after the retreatment procedure. Statistical analysis was performed with a significance level of 0.05. Data analysis was conducted using the Kolmogorov-Smirnov and Kruskal-Wallis H tests.

Results

The best performance of the files was achieved when the removal of the filling in the entire canal was considered. However, this outcome was not statistically significant when compared with the other observed root canal levels. The retreatment procedure could not ensure thorough cleanliness of the canal walls from filling remnants, regardless of the obturation technique and observational level.

Conclusions

The ProTaper Universal Retreatment system used for the removal of gutta-percha and sealer in oval-shaped root canals demonstrated equal effectiveness, regardless of the obturation technique used.

Intracanal removal and apical extrusion of filling material after retreatment using rotary or reciprocating instruments: A new approach using human cadavers

AIM

This study compared intracanal removal of filling as well as the frequency and volume of extruded material after retreatment with either HyFlex or Reciproc instruments in mandibular teeth from cadavers.

METHODOLOGY

The root canals of 14 pairs of contralateral single-rooted teeth in mandibles of cadavers were instrumented with Reciproc R40 and filled using lateral compaction. The mandibles were scanned in a micro-computed tomographic (micro-CT) device before and after retreatment procedures. The contralateral teeth were assigned to two groups (n = 14) according to the retreatment protocol using either HyFlex or Reciproc instrument systems. In the HyFlex group, the HyFlex Remover instrument was worked 3 mm short of the working length (WL), followed by HyFlex CM 40.04 and 50.04 at the WL. In the Reciproc group, the R50 instrument was worked up at the coronal two thirds, followed by two more cycles until the WL was reached. Pre- and post-operative micro-CT images were analysed for extrusion and intracanal removal of filling material.

RESULTS

After retreatment, extrusion of filling material occurred in 11 (78%) and 14 (100%) teeth from HyFlex and Reciproc groups respectively (p > .05). A similar volume of extruded material was observed after retreatment with both systems (p > .05). A significant decrease in the intracanal filling volume was verified after retreatment with both tested systems (p < .05). However, residual filling material was found in all root canals, regardless of the system. The amount of filling material removed (HyFlex = 80.8%; Reciproc = 65.9%) and the operation time was similar between systems (p > .05).

CONCLUSIONS

A high frequency of filling material extrusion was observed after retreatment with the two systems in a cadaver model, with no significant difference between them. Both protocols obtained similar efficacy in filling material removal procedures, although none completely cleaned the canals.

Assessing the impact of obturation techniques, kinematics and irrigation protocols on apical debris extrusion and time required in endodontic retreatment

The aim of the study was to evaluate the impact of kinematics and irrigation protocols on the extrusion of apical debris during removal of different obturation techniques. A total of 144 single-rooted teeth were instrumented and obturated with Thermafil+AH Plus, Thermafil+AH Plus Bioceramic and single gutta-percha cone+AH Plus Bioceramic. Samples were divided according to the retreatment kinematics: continuous rotation or Jeni motion. Each sub-group was subjected to conventional irrigation or irrigation activated by EDDY. Extruded debris was collected in Eppendorf tubes, weighted and retreatment time was digitally recorded. Data were analysed with two-way ANOVA (p < 0.05). Debris extrusion was not significantly different between all groups. EDDY activation system and CanalPro Jeni required significantly longer time compared with other groups to remove Thermafil+AH Plus and single cone+AH Plus Bioceramic. Within current limitations, obturation technique, irrigation protocol and kinematics tested had no influence on apical extrusion debris, while they significantly impacted the retreatment time.

In vitro apical extrusion of debris and instrumentation time following root canal instrumentation with Reciproc and Reciproc Blue instruments and a novel stainless steel rotary system (Gentlefile) versus manual instrumentation

Background

This study compared apical extrusion of debris and instrumentation time following root canal instrumentation with Reciproc, Reciproc Blue, and Gentlefile (GF) rotary instruments versus the manual step-back technique.

Methods

This in vitro study was conducted on 80 extracted mandibular premolars with mature apices and a root curvature of<10°. The teeth were randomly assigned to 4 groups (n=20), standardized regarding working length, and placed in pre-weighed vials. The root canals were instrumented with Reciproc, Reciproc Blue, and GF systems and the manual step-back technique in the four groups. The vials containing the collected debris were then dried and weighed. The instrumentation time was also recorded for each group. Data were analyzed with one-way ANOVA and post hoc Games-Howell test (α=0.05).

Results

Minimum apical debris extrusion was noted in Reciproc, followed by Reciproc Blue, GF, and manual technique (P<0.05). Pairwise comparisons showed significantly lower apical extrusion of debris in the Reciproc compared with GF (P=0.015) and manual instrumentation (P=0.011) groups. The Reciproc system also had the shortest instrumentation time, followed by Reciproc Blue, GF, and manual instrumentation (P<0.05). Pairwise comparisons showed significant differences between all the systems (P<0.05) except between Reciproc and Reciproc Blue (P>0.05) in this respect.

Conclusion

Although all systems caused apical extrusion of debris, manual instrumentation caused maximum extrusion of debris. In contrast, the Reciproc system was superior to others regarding minimal apical extrusion of debris and the shortest instrumentation time.

Evaluation of Apically Extruded Debris During Retreatment Procedures Using Various File Systems in Teeth With Simulated Apical Root Resorption: An In Vitro Study

Aim The aim of this study was to compare the amount of debris produced apically during the removal of root canal obturating material by using various files in extracted teeth with simulated apical root resorption. Materials and methods An in vitro study was conducted in the root canals of 90 extracted mandibular premolar teeth that were prepared with a ProTaper Gold rotary file (Dentsply Maillefer, Ballaigues, Switzerland) and filled with gutta-percha and an AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland) using a cold lateral compaction technique. A total of 45 mandibular premolar teeth were randomly assigned to three control groups (i.e., the ProTaper Universal retreatment file (Dentsply Maillefer), the Reciproc Blue file (VDW, Munich, Germany), and the HyFlex Remover file (Coltene/Whaledent, Altstatten, Switzerland) for the removal of root canal filling material, whereas the remaining 45 teeth were treated as the experimental group and their apical portion was modified to simulate apical root resorption. The teeth of this experimental group were randomly divided into three subgroups according to the same three techniques used with the control groups for the removal of root canal filling materials. The apically extruded debris was collected into pre-weighed borosilicate glass tubes and then dried. The mean weight of the apically extruded debris was assessed using an analytical balance to an accuracy of 10^-4 g. Further, the data were analyzed using the Kruskal-Wallis test and Tukey's post hoc test. Results In the simulated apical root resorption groups, all file systems were associated with significantly more debris extrusion than the groups without simulated root resorption (a < 0.05). In both the control groups and experimental groups, the ProTaper Universal retreatment file was associated with the least weight of the apically extruded debris (a < 0.05), followed by the Reciproc Blue file and the HyFlex Remover file. Conclusion The amount of debris extruded apically was significantly greater in the teeth with simulated apical root resorption than in those without it. Further, during the removal of the root canal filling materials, HyFlex Remover was associated with significantly more apically extruded debris in all groups.

Apical transportation using Mtwo or Reciproc retreatment systems in severely curved canals: a micro-computed tomographic study

OBJECTIVE

To assess apical root canal transportation using Mtwo or Reciproc during retreatment of severely curved canals, using a multi-analytical approach.

METHODS

Forty mesial canals from mandibular molars (Vertucci type IV) were evaluated before and after endodontic retreatment to compare apical transportation with Mtwo retreatment or Reciproc. The systems were used on the same root but alternating the mesial canals. The analyses were performed by micro-computed tomography. Four evaluations were performed: (a) longitudinal transportation, (b) horizontal transportation, (c) variation in the angle of curvature of the canal, and (d) canal-root width ratio. Horizontal transportation and canal-root width ratio were evaluated in 1-, 3-, and 5-mm levels.

RESULTS

Longitudinal transportation occurred in all samples, with a mean of 0.13 mm for Mtwo and 0.17 mm for Reciproc. Horizontal transportation increased as distant from the apex was the evaluated level, in mean. However, the transport was not observed in all samples. The mean angle of curvature was 4.16 for Mtwo and 3.03 for Reciproc. Canal-root width decreased as distant from the apex was the evaluated level. No significant differences were observed considering all tested variables, independently of the retreatment system or evaluated level (p > 0.05).

CONCLUSION

Mtwo retreatment and Reciproc presented similar apical transportation (horizontal or vertical).

CLINICAL RELEVANCE

Both Mtwo retreatment and Reciproc systems could be considered safe regarding apical transportation.

Effect of different retreatment files using different kinematics on the release of inflammatory mediators in root canal retreatment of single-rooted teeth: a randomized clinical trial

OBJECTIVES

This randomized clinical trial aimed to evaluate the effect of two rotaries (ProTaper Universal Retreatment (PTUR)), D-Race (DR) + XP-Endo Finisher R (XPFR) and one reciprocating (Reciproc Blue (RB) retreatment techniques on the release of neuropeptides (Substance P, calcitonin gene-related peptide (CGRP)), and cytokines (IL-6 and IL-10) in periapical fluid in root canal retreatment of single-rooted teeth.

MATERIALS AND METHODS

In this randomized clinical trial (ClinicalTrials.gov ID: NCT05039502), seventy-five patients scheduled for retreatment were randomly divided into 3 groups according to the file system used to remove root canal filling materials (n = 25): PTUR, RB, and DR + XPFR. After reshaping and disinfection of the root canals, periapical fluid samples were taken, and the levels of Substance P, CGRP, IL-6, and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA) test. Data were analyzed using the Kruskal-Wallis and chi-square tests. The level of significance was set as p = 0. 05.

RESULTS

All the allocated participants received the intervention and were analyzed. There was no statistically significant difference among groups in terms of gender, age, tooth localization, and the distribution of analgesic use after treatment (p values 0.799, 0.095, 0.637, 1.000, respectively). No statistically significant difference was found in terms of the levels of Substance P, CGRP, and IL-10 among groups (p > .05), except IL-6.

CONCLUSIONS

PTUR, RB, and DR + XPFR files have comparable results in the expression of inflammatory mediators.

CLINICAL RELEVANCE

Retreatment files powered with rotary or reciprocating motion produced similar neuropeptide and cytokine levels in patients.

Quantitative evaluation of apically extruded debris using TRUShape, TruNatomy, and WaveOne Gold in curved canals

Objective

This study compared the quantity of extruded debris after instrumentation with TRUShape 3D Conforming files, TruNatomy files, and the WaveOne Gold reciprocating system.

Materials and methods

Fifty-one mesiobuccal canals with severe curvatures (25–40°) were assigned to three equal groups according to the rotary system used for preparation, either TRUShape, TruNatomy, or WaveOne Gold files. The extruded debris was collected in pre-weighed glass vials. The data were statistically analyzed using a one-way ANOVA test and Tukey’s post hoc test.

Results

The least extruded debris was obtained with the WaveOne Gold instruments compared to the TRUShape and TruNatomy files (p < 0.001).

Conclusions

Debris extrusion occurs independently of the motion or design of the instrument. The WaveOne Gold system outperformed TRUShape and TruNatomy files in this study.

Influence of pecking frequency at working length on the volume of apically extruded debris: A micro-computed tomography analysis

Background/purpose

There is no consensus to date on how many repetitive pecking motions at working length (WL) should be regarded as optimal during instrumentation. Therefore, this study aimed to evaluate the effect of pecking frequency at WL on the volume of apically extruded debris using three single-file systems in curved, oval-shaped canals.

Materials and methods

Forty-five single-rooted mandibular premolars with curved, oval-shaped canals were prescanned by micro-computed tomography, anatomically paired-matched, and randomly divided among three groups (n = 15 each): Reciproc Blue (RB), WaveOne Gold (WOG) and XP-endo Shaper (XPS). Samples were embedded in agarose gel to collect extruded debris. After preparation to the WL, each sample was rescanned after one, two, four, 10, and 20 pecking motions at WL, respectively. The debris volume was innovatively calculated by a modification of an existing method using micro-computed tomography. The apical preparation size was also measured. Data were compared using a two-way repeated-measures analysis of variance.

Results

All single-file systems extruded debris apically, irrespective of the pecking frequency at WL. The extruded debris volume correlated positively with the minor foramen size (P < 0.05); both increased with pecking frequency for each single-file system (P < 0.05). The minor foramen size corresponded to the instrument tip size when reaching the WL once.

Conclusion

To produce less debris extrusion and obtain a predictable foramen size corresponding to the instrument tip size, a single pecking motion may be preferred when using single-file systems. Caution should be exercised when applying the current results to clinical situations.

Retreatment of Experimental Carrier-Based Obturators with the Remover NiTi Instrument: Evaluation of Apical Extrusion and Effects of New Kinematics

The objective of this study is to evaluate the retreatment time and weight of apically extruded debris yielded by two different kinematics during the removal of different root canal filling materials. Forty straight single-rooted extracted teeth were instrumented with HyFlex CM files and obturated with two different techniques: 25.04 HyFlex experimental carrier-based obturators (Coltène/Whaledent, Altstätten, Switzerland) (group 1) or 25.04 single gutta-percha cones (Roeko Coltène/Whaledent, Altstätten, Switzerland) (group 2) and Guttaflow Bioseal as the sealer. Samples were divided into four subgroups (n = 10) according to the used kinematics for the removal of root canal filling materials: continuous rotation (A) or retreatment motion (B) with a Remover and HyFlex EDM Nickel-Titanium instruments activated with a CanalPro Jeni micromotor (Coltène/Whaledent, Altstätten, Switzerland). Time for retreatment was digitally recorded, and debris extruded from the apex was collected in Eppendorf tubes and weighted with an analytical balance. Data on retreatment time and apical extrusion were statistically analyzed with the Kruskal–Wallis test (p < 0.05). Working length was achieved in all the retreated samples. The removal of root filling material resulted significantly faster with the Jeni mode (p < 0.001), and the difference was significant for the removal of both filling materials (p < 0.05). No significant differences on debris extrusion between single cone and experimental obturators groups were noted (p > 0.05), and no significant differences between kinematics (continuous rotation vs. Jeni motion) were observed (p > 0.05). All the tested retreatment strategies lead to an extrusion of material from the apex, and the weight of apically extruded debris was similar. The use of the innovative CanalPro Jeni kinematics accelerates the time for the removal of root filling materials.

Critical analysis of research methods and experimental models to study removal of root filling materials

Despite enjoying high favourable outcome rates, root canal treatment is not always successful. Root canal retreatment is a widely practised option for managing a non-healing root treated tooth. A basic distinction between retreatment and initial treatment is the requirement to remove the existing root filling material occupying the root canal space. Only then, can the technical deficiencies and possible causes of failure be addressed. Hence, the successful removal of the root filling material is critical to achieving the objectives of retreatment. Many different materials and techniques have been used for root canal filling, which have been documented in a plethora of studies; these are mainly laboratory studies investigating the removal of root filling materials. To help guide future research, which may then better inform clinical practice in relation to retreatment procedures, the focus of this narrative review is on the research methods and experimental models employed to study the removal of root filling materials. The current available literature demonstrates great variation in the research methodologies used to study the removal of root filling material, including direct visualization by splitting tooth samples or clearing, three-dimensional radiographic imaging including using microcomputed tomography or cone-beam computed tomography, and a combination of these techniques. Depending on the research method employed, variation also exists in quantification of root filling material removal; these include measurements of surface area, volume or weight, and criteria-based (semi-quantitative) assessment. Experimental models, using human teeth or resin models, differ with respect to standardization techniques and replication of the clinical scenario including initial sample preparation, canal filling, allocation and technical aspects of retreatment procedures. Future models should replicate, as closely as possible, the clinical scenario. Currently, microcomputed tomography provides a highly detailed, non-invasive and non-destructive method of objectively assessing and quantifying root filling removal.