Observer variation in the assessment of root canal curvature

Comparison of Curvature Severity Between Sagittal and Coronal Planes of Mesiobuccal Canals in Permanent Maxillary First Molars Using Multiple Complexity-risk Criteria: A CBCT Cross-sectional Study of a Brazilian Subpopulation

INTRODUCTION

This study aimed to compare the curvature severity of mesio-buccal (MB) canals between sagittal and coronal planes using cone-beam computed tomography.

METHODS

In a Brazilian subpopulation, untreated MB1 (n = 141) and MB2 (n = 72) with single curvatures in sagittal and coronal planes were measured to determine their angle and radius (r), plus the prevalence of S-shaped canals was recorded. Curvature severity was defined according to the American Association of Endodontists Case Difficulty Assessment form (AAE) and EndoApp (EA), as well as their modified versions that consider angle and radii (AAE-r, EA-r). Data were converted into mean angle and r, percentage of canals >30°, AAE, EA, AAE-r and EA-r categories. The influence of r on case severity was assessed. Statistical analysis was performed using t-tests and chi-squared tests. The level of significance was set as P ≤ .05.

RESULTS

For single curvatures, significantly higher mean degrees (SD) angles were found in the sagittal views in both canals (MB1 sagittal: 35 [11]; MB1 coronal: 13 [13]; MB2 sagittal: 29 [14]; MB2 coronal: 22 [15] [P < .05]). A greater percentage of angles >30° (MB1: 56.7% vs 6.4%; MB2: 44.4% vs 22.2%) in sagittal planes compared to coronal planes was also found. Conversely, a higher prevalence of S-shaped canals (MB1: 33.3% vs 7.1% MB2: 31.9% vs 15.3%) was observed in coronal planes. Significant differences between AAE and AAE-r were present with greater case severity when radii were considered (P < .05).

CONCLUSIONS

Sagittal planes were associated with more severe single curvatures, while coronal planes had a greater prevalence of S-shaped canals.

Present status and future directions -Management of curved and calcified root canals

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field.

Usefulness of an Endodontic Case Difficulty Assessment Form of Root Canal Treatments in Dental Education in Finland

According to current care guidelines, it would be beneficial to evaluate the difficulty of a root canal treatment (RCT) after the decision of an indicated RCT. For this matter, several difficulty assessment forms have been developed. In this pilot study, fifth-year dental students evaluated the usefulness of the Endodontic Case Difficulty Assessment Form (ECAF) presented in the Finnish Current Care Guidelines for Endodontic Treatment (2014). Another aim was to postoperatively investigate how well the evaluation by dental students using the ECAF associated with the outcome of RCT evaluated by a specialist in endodontics. The dental students’ (n = 33) and the supervisor’s assessments of the RCTs were compared postoperatively at the Dental Educational Unit, Oulu, Finland. After completing the ECAF, the students’ experiences of its use were explored with a structured form. In ECAF, patient-derived factors, such as gagging, deviant crown morphology, and complications in previous endodontic treatment, were all significantly associated with complications in RCTs by the dental students (p < 0.05). The assessments by students and the supervisor differed in 55% of cases, especially in moderately difficult cases. In the majority of these cases (71%), the students evaluated the case to be easier than the teacher. Students found the ECAF user-friendly, even if it did not demonstrate their competence in accomplishing RCTs. The ECAF appears useful for junior dentists, specifically in terms of distinguishing the least and most difficult cases. A simpler form could be useful for students and clinicians.

Intra- and Interobserver Agreement during the Assessment of the Different Stages of Root Development Using 4 Radiographic Classifications

INTRODUCTION

This study analyzed intra- and interobserver agreements during radiographic assessment of the different stages of root development using the dichotomous, Moorrees, Demirjian, and Cvek classifications, as well as the effect of the observer's level of experience on the result.

METHODS

Two hundred eighty-five digital periapical radiographs were examined via visual inspection by 3 experienced and 3 nonexperienced observers (n = 6) under strict technological and viewing conditions. After observer calibration, determination of the presence or absence of an open apex and the assignment of a root development stage according to the different subdivisions of the 4 indexes were performed. This evaluation was carried out by each observer in duplicate in the first round (n = 8) and repeated in the second round (n = 8). The 16 examinations performed by each observer (N = 96) were analyzed to determine the percentage of concordance followed by intraobserver, interobserver, and global observer agreement using the kappa coefficient and a weighted kappa. Additionally, to determine the level of concordance between the visual determination of an open or closed apex and the apical foramen width measured in millimeters, a dichotomized kappa coefficient was applied.

RESULTS

A good level of global observer agreement was found for the dichotomous, Demirjian, and Cvek classifications. However, a significantly low percentage of total concordance and global observer agreement (6.66% and 0.498, respectively) was obtained using the Moorrees classification, which was more pronounced among nonexperienced observers (0.247). Apical foramen width measurements indicated the presence of 143 roots with an open apex (50.2%) and 142 with a closed apex (49.8%), and the dichotomized kappa coefficient test revealed a good level of agreement during the visual determination of an open or closed apex (range, 0.611-0.636).

CONCLUSIONS

The classifications of Cvek and Demirjian provided reliable results when determining the different stages of root development. In contrast, the Moorrees classification provided the lowest agreement values, with a significant negative effect among nonexperienced observers. Finally, the visual estimation of the presence (or absence) of an open apex provided a good level of concordance with the radiographic apical foramen width.

Effect of a Modified Irrigation Protocol on the Cleanliness of Moderately Curved Canals

Objectives  This study tested the hypothesis that modifying the sequence of sodium hypochlorite (NaOCl)/ethylene diamine tetra-acetic acid (EDTA) irrigation during root canal shaping would improve apical cleanliness in moderately curved canals.

Materials and Methods  Forty-five root canals were prepared using Protaper Gold with three irrigation protocols. Standard irrigation (SI) used 0.5 mL 3% NaOCl between each instrument, followed by 5 mL 17% EDTA manually agitated for 30 seconds. Reverse irrigation (RI) used 0.5 mL of 17% EDTA between each instrument, then 5 mL of 3% NaOCl, manually agitated for 30 seconds. Reverse irrigation plus (RI+) was similar to RI, except NaOCl (5 mL), used as a final rinse, was allowed to interact for 3 minutes with dentin before manual agitation (30 seconds).

Root canal cleanliness was evaluated under the scanning electron microscope (SEM) (Hulsmann score); the chemical composition of dentin after irrigation was analyzed by energy dispersive X-ray (EDX).

Statistical Analysis  Results were compared using Kruskal–Wallis ANOVA by ranks and Wilcoxon matched paired posthoc tests. A Chi-square test assessed whether the best cleanliness would demonstrate a significant association with one irrigation protocol; odds ratio calculation was performed using score “1” versus score “2 or more” (2+) ( p < 0.05).

Results  In the apical region, cleanliness was better in RI+ than SI and both significantly better than RI. Odd ratios indicate that the cleanliness in RI+ was significantly better than RI and SI groups ( p < 0.000 and 0.003, respectively). Independently of the irrigation protocol, EDX analyses showed no chemical alteration of root dentin.

Conclusions  Using 17% EDTA during shaping, followed by 3% NaOCl rinse for 3 minutes, improved apical cleanliness without inducing erosion of dentin.

Methods for measurement of root canal curvature: a systematic and critical review

The assessment of root canal curvature is essential for clinical and research purposes. This systematic review presents an overview of the published techniques for the measurement of root canal curvature features using imaging and to provide a critique of their clinical application. A database search in PubMed, PubMed Central, Embase, Scopus, EBSCO Dentistry & Oral Sciences Source and Virtual Health Library was conducted, using appropriate key words to identify measurement methods for root canal curvatures. The search strategy retrieved 10594 records in total, and 31 records fulfilled the inclusion criteria. From 2D image acquisitions, eleven studies measured exclusively the angle of curvature, an additional thirteen measured other curvature features (level, height, radius, length and shape). Seven reports described methods from 3D imaging (CBCT, μCT). Root canal curvatures should be measured, for clinical proposes, to facilitate endodontic treatment planning, and in research, to reduce the risk of selection bias. This review has revealed that there are many methods described in the literature; however, no consensus exists on which method should be used. Some of the methodologies have potential clinical translation, whereas others are suitable for research purpose only, as they require a specific software or radiographic exposure in the mesiodistal direction.

Shaping ability of four root canal instrumentation systems in simulated 3D-printed root canal models

Introduction

The aim of this study was to compare the shaping ability of four root canal preparation systems in newly developed 3D-printed root canal models.

Materials and methods

For this study, 1080 3D-printed acrylic resin blocks with nine different root canal configurations were produced. They were prepared with Reciproc R25 (#25), F6 SkyTaper (#25 and #30) F360 (#25 and #35) and One Shape (#25) (N = 30 per system). Pre- and post-instrumentation images were superimposed for evaluation of the centering ratio of the different systems. Ledges, instrument fractures and preparation times were also recorded. Analysis of variance (ANOVA) and post-hoc Tukey tests were conducted, comparing the mean canal centering ratios and the mean preparation times.

Results

There were significant differences between all systems regarding the centering ratios in the different root canal configurations (ANOVA p < 0.001). The root canal configuration had considerable effect on the centering ratio of the instruments. The best overall mean centering ratios were achieved with F6 SkyTaper #25 instruments especially in canal configurations with big curvature angles and radii, while F360 #35 was least centered especially in canals with small curvature angles and radii. Most ledges occurred with OneShape, while it was the significantly (p < 0.001) fastest preparation system (86.7 s (SD 13.53)) and Reciproc the significantly (p < 0.001) slowest (103.0 s (SD 20.67)).

Conclusion

3D-printed root canals are suitable to produce challenging canal configurations and to investigate the limitations of root canal instruments. We found that all instruments caused canal transportations. However, F6 SkyTaper #25 files had better overall centering ratios than the other instruments. In canal configurations with small curvature radii, the centering ratio of some instruments is low and the probability for ledges is increased.