Micro-computed tomographic analysis of the mesial root of mandibular first molars with bifid apex

Root and canal anatomy of mandibular first molars using micro-computed tomography: a systematic review

BACKGROUND

A thorough understanding of root and canal anatomy is crucial for successful root canal treatment outcomes. This systematic review aims to explore the published micro-CT studies investigated the anatomy of root and canal system in permanent mandibular first molars.

METHOD

An electronic search was performed on Web of science, PubMed, and Scopus. Micro-CT journal studies investigated the root and canal anatomy of permanent double-rooted mandibular first molars were included. Data on study characteristics, objectives of interest, specifications of the studies, and micro-CT specifications were extracted. Risk of bias assessment (ROB) of the included studies was performed using Anatomical Quality Assessment (AQUA) tool. The extracted data were presented in tables and figures to present and synthesise the results. A meta-analysis was performed for the studies related to the prevalence of Vertucci's canal configurations, middle mesial canal (MMC) configurations, and Fan's isthmus types.

RESULTS

Amongst 1358 identified studies, thirty met the inclusion criteria. In terms of the objectives, the selected studies showed high anatomical variability in mandibular first molars. Twenty-two (73%), 25 (83%), and 12 (40%) of the studies reported the population/ethnicity, micro-CT specifications, and ethical approval, respectively. 28 (93%) studies did not disclose the method of sample size estimation. In only 6 (20%) of the studies, the authors had calibrated the assessment approaches. Mostly, a potential ROB was reported in domain 1 (objective(s) and subject characteristics) and domain 3 (methodology characterization). Whilst, low risk was reported in domains 2 (study design), 4 (descriptive anatomy), and 5 (reporting of results). The overall ROB was reported to be ''moderate'' in the vast majority of the studies (27/30). Meta-analysis results showed high levels of heterogeneity among the studies related to MMCs (I² = 86%) and Fan's isthmus (I² = 87%). As for the root canal configuration, pooled prevalence showed that Vertucci type IV and type I were the most prevalent in mesial and distal root canals, respectively.

CONCLUSION

Based on moderate risk of bias level of evidence, micro-CT studies have shown wide range of qualitative and quantitative data presentations of the roots and canals in mandibular first molars. Protocol and registration. The protocol of this systematic review was prospectively registered in the Open Science Framework database ( https://osf.io ) on 2022-06-20 with the registration number 10.17605/OSF.IO/EZP7K.

Shaping outcome of ProTaper NEXT for root canal preparation in mandibular incisors: a micro-CT study

Background

Relatively high incidence of single canals with oval or round shape were observed in human mandibular incisors. In order to investigate the influence of the root canal morphology on root canal preparation, the shaping outcome of ProTaper NEXT in oval and round canals of mandibular incisors were evaluated by using micro-computed tomography (micro-CT) analysis.

Methods

This experiment was approved by the School Medical Ethics Committee. The sample size calculation was conducted using G*Power software. Intact mandibular incisors with a single canal were selected. Oval canals (2 < aspect ratio (AR) ≤ 4) and round canals (AR ≤ 2) were pair-matched according to canal length, and assigned to two experimental groups (13 per group). ProTaper NEXT was used for root canal preparation for both groups. Untouched canal wall (UCW), root canal morphological parameters and three-dimensional (3D) dentin thickness were evaluated in the entire root canal and each canal third after micro-CT scanning. Statistical analysis: Data were collected and analyzed with Mann–Whitney test and Friedman test using SPSS statistics software 25 (P < 0.05). Additionally, correlations of UCW area with canal morphological parameters were also investigated.

Results

After root canal preparation, no significant difference was observed in all analyzed parameters in the apical third between oval and round canal groups (P > 0.05). In the coronal two thirds of the canal, the post-operative structure model index (SMI), form factor and roundness were significantly increased, while the AR was significantly decreased in both groups (P < 0.05). In addition, in the coronal two thirds, significantly more UCW and higher UCWΔ% was observed in oval canal group (P < 0.05). Furthermore, UCW correlated very strongly to canal major diameter (0.924) and initial volume (0.938), and strongly to canal form factor (− 0.724), minor diameter (0.799) and canal area (0.882). Proximal dentin wall was associated with significantly thinner pre-operative dentin thickness and higher amount of dentin removal after root canal preparation in both oval and round canal groups.

Conclusions

(1) Both types of canals were more conical after root canal preparation, but oval root canals tend to leave more UCW area than round canals in the coronal two thirds of mandibular incisors, which contributes to the challenge for endodontic infection control. (2) Root canal preparation usually results in excessive dentin removal in the proximal dentin wall comparing with buccal and lingual walls in both types of canals of mandibular incisors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02335-7.

Root and Root Canal Configuration Characterization Using Microcomputed Tomography: A Systematic Review

This systematic review’s objective was to conduct a complete analysis of the literature on the root canal morphology using advanced micro-computed tomography. The electronic web databases PubMed, Scopus, and Cochrane were examined for research papers concerning the chosen keywords, evaluating the root canal morphology using Micro-CT, published up to 2021. The articles were searched using MeSH keywords and searched digitally on four specialty journal websites. DARE2 extended (Database of Attributes of Reviews of Effects) was used to assess bias risk. The information was gathered from 18 published studies that strictly met the criteria for inclusion. In the included studies, a total of 6696 samples were studied. The studies were conducted on either maxillary (n-2222) or mandibular teeth (n-3760), permanent anteriors (n-625), and Third molars (n-89). To scan samples, a Scanco Medical machine in was used in 10 studies, Bruker Micro-CT in 34, and seven other machines were utilized in the rest. Bruker Micro-CT software from Kontich, Belgium, VG-Studio Max 2.2 software from Volume Graphics, Heidelberg, Germany, was the most commonly used software. The minimum Voxel size (resolution) adopted in the included studies was 11.6 µm. However, 60 µm was the maximum. Most studies classified the root canal morphology using Vertucci’s classification system (n-16) and the four-digit system (n-6).

Micro-tomographic analysis of the root trunk and pre-furcation area of the first mandibular molars

This study analyzed the root trunk (RT) and the pre-furcation area (PFA) of mandibular first molars. Thirty lower first mandibular molars extracted due to advanced periodontal disease were evaluated in a high-energy spiral computerized micro-tomography. Two gutta-percha markings on the cementoenamel junction (CEJ) and at the furcation entrance (FE) at buccal and lingual surfaces served as reference points for measurements of RT length, and PFA width and depth, at the levels of CEJ, 1 mm apical to CEJ, 2 mm apical to CEJ, and at the FE. The mean RT length was 2.49 mm at buccal and 3.18 mm at lingual sides. The mean widths of the PFA at CEJ, at 1 and 2 mm apical to CEJ, and at FE were 2.9, 3.4, 3.9 and 4.3 mm, respectively, while the mean depths were 0.19, 0.32, 0.57 and 1.1 mm, respectively. The PFA coincided with CEJ in 10 buccal and 10 lingual surfaces, representing 33.33% of the sample. There was a negative correlation between RT length and PFA dimensions. This study concludes that the RT length was smaller than previous studies. From the CEJ up to the furcation entrance, the PFA showed a progressive increase in width and depth. The coincidence of the PFA area beginning at the CEJ in 1/3, and the negative correlation between RT length and PFA dimensions may represent greater risk factor for the early development of furcation lesions.

Application of a new system for classifying root and canal anatomy in studies involving micro-computed tomography and cone beam computed tomography: Explanation and elaboration

Adequate knowledge and accurate characterization of root and canal anatomy is an essential prerequisite for successful root canal treatment and endodontic surgery. Over the years, an ever-increasing body of knowledge related to root and canal anatomy of the human dentition has accumulated. To correct deficiencies in existing systems, a new coding system for classifying root and canal morphology, accessory canals and anomalies has been introduced. In recent years, micro-computed tomography (micro-CT) and cone beam computed tomography (CBCT) have been used extensively to study the details of root and canal anatomy in extracted teeth and within clinical settings. This review aims to discuss the application of the new coding system in studies using micro-CT and CBCT, provide a detailed guide for appropriate characterization of root and canal anatomy and to discuss several controversial issues that may appear as potential limitations for proper characterization of roots and canals.

Geometric Analysis of the Distolingual Root and Canal in Mandibular First Molars: A Micro-computed Tomographic Study

INTRODUCTION

The purpose of this study was to comprehensively assess by micro-computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.

METHODS

One hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.

RESULTS

All DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.

CONCLUSIONS

The novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.