An in vitro assessment of type, position and incidence of isthmus in human permanent molars

Diamond-coated ultrasonic tip decreases debris and uninstrumented surface after preparation of curved canals with isthmus

The aim of this study was to evaluate root canal preparation with nickel titanium rotary instruments and complementary preparation with ultrasonic tip in curved canals of mandibular molars with isthmus. Twenty-eight mesial roots of mandibular molars with curvature between 20° and 40° and presence of isthmus throughout the entire extension of the root canals were prepared using ProDesign Logic CM (PDL) up to size 40.05, or HyFlex EDM (HFEDM) up to size 40.04. Complementary preparation was performed in the isthmus region using the ultrasonic insert E18D (Helse, Istmo Diamantada). The root canals were scanned using micro-CT (SkyScan 1176) at 9 µm voxel size before and after each preparation step. Transportation, percentage of increase in volume, debris and uninstrumented surface (UNS) were evaluated. Mann Whitney, Wilcoxon, paired and non-paired t-tests were used for statistical analysis (α = 0.05). The canals prepared with PDL and HFEDM obtained similar results for all the variables assessed before using E18D (p > 0.05). E18D significantly decreased the percentage of debris and UNS values in both Groups (p < 0.05). The complementary preparations with E18D caused a smaller quantity of debris in the isthmus of the canals previously prepared with PDL in comparison with HFEDM (p < 0.05). PDL and HFEDM provided similar root canal preparation. PDL promoted a smaller quantity of Debris in the isthmus than HFEDM after using E18D. E18D significantly improved cleaning, and reduced Debris and UNS.

Prevalence and morphological analysis of isthmuses in mandibular molars of the Indian population: A micro-computed tomographic study

Objectives

This study evaluated the prevalence, configurations, and correlation of isthmuses at coronal, middle, and apical root 3rd in mandibular molars of the Indian population using micro-computed tomography μCT).

Materials and Methods

One hundred and five permanent mandibular molar teeth were scanned under μCT. The axial sections were analyzed at the coronal, middle, and apical thirds of the root for isthmus types and classified according to Hsu and Kim's classification. Descriptive statistics for each isthmus type were calculated. The correlations between the apical, middle, and coronal thirds of the root were determined using Pearson's correlation coefficient.

Results

Type IV isthmus was the most common in the coronal third of the mesial root of mandibular 1st molar (42.9%), while Type V was prevalent in the coronal third of the mesial root of 2nd molar (42.9%). Type I isthmus was found to be highly prevalent in the middle 3rd (71.4%) and apical 3rd (61.9%) of mesial roots of 1st molars, and in the middle 3rd (71.4%) and apical 3rd (42.9%) of mesial roots of 2nd molars. Type V isthmus was the most prevalent in all the thirds of the distal roots of both 1st and 2nd molars, ranging from 40% to 50%. Furthermore, a strong correlation of 0.965 (P < 0.01) was found between the isthmuses in the apical and middle thirds of roots.

Conclusion

There are variations in the prevalence and type of isthmuses across different sections of the root, including the presence of atypical isthmuses. Micro-CT with high-resolution imaging and three-dimensional reconstruction is crucial for investigating root canal morphology. Clinicians could benefit from considering demographic characteristics to better predict the presence of isthmus variations.

Clinical Relevance

The isthmus configurations and frequency differ at each section of mandibular teeth.

Three-dimensional morphologic classifications and analysis of canal isthmuses in permanent molars

PURPOSE

To investigate the three-dimensional morphology of isthmuses in molars according to their boundary characteristics using micro-computed tomography (micro-CT).

METHODS

Micro-CT reconstructed images of 248 molars were evaluated. Isthmuses were classified into four types based on the boundary characteristics: isthmus with roof, isthmus with floor, band-shaped isthmus, and isthmus without boundary. The tooth and root with isthmuses, the number and location of the isthmuses in the root, and the canal configurations were recorded. The maximum of the major diameter of all canal cross-sections in one isthmus (d_max), the minor diameter of the canal in same cross-section (d_min), the distance between the d_max cross-section and apex (D_m-a), isthmus length (L_i), and distance from the isthmus ending cross-section to apex (D_e-a) were measured and analysed with a significance threshold set to 5%.

RESULTS

Isthmuses were present in 75.4% specimens. The four types of isthmuses were found in various molars and roots. Their distribution in different root locations and canal configurations was significantly different. The d_max, d_min, L_i, and D_e-a were analysed according to different molars and different isthmus types; their respective median values were 2.508 mm, 0.07 mm, 3.09 mm, and 3.96 mm.

CONCLUSION

The three-dimensional classification of isthmuses according to the boundary characteristics provides a comprehensive picture of the isthmus in molars. Their corresponding distributions in different molars, location in roots, and canal configurations will be helpful in predicting the type of isthmus based on the tooth position and canal configurations.

Relationship between canal morphology and isthmus in mesio-buccal roots of maxillary first molars in 9- to 12-year-old children: An in-vivo cone-beam computed tomography analysis

OBJECTIVES

This study aims to analysis the distribution of root canal isthmuses (RCIs), and its relationship with canal morphology in the mesio-buccal roots of maxillary first molars in children aged 9-12 in a Chinese sub-population.

METHODS

494 healthy, untreated maxillary first molars with fully developed mesio-buccal roots were examined. Cone-beam computed tomography (CBCT) scans were acquired as part of diagnosis and treatment plannings unrelated to the present study. The images were evaluated to identify the canal morphology of mesio-buccal roots according to Vertucci's classification. A map-reading strategy was used to identify RCIs.

RESULTS

In mesio-buccal roots, the most common canal morphology was type Ⅳ (38.5 %). The frequency of type I (1.6 %) was much lower than adults. RCIs were found in 92.5 % mesio-buccal roots. The RCIs which began in the cervical third and ended in the middle third (CT-MT) (31.0 %) had the highest frequency. In type III, the RCIs which began and ended in the middle third (MT-MT) (30.3 %) were most common. For type V, 30.8 % RCIs began in the cervical third and ended in the apical third (CT-AT). No significant differences were found between sexes and sides (P > 0.05).

CONCLUSIONS

For children aged 9-12, the frequency of type I canals was much lower in mesio-buccal roots of maxillary permanent first molars, while the frequency of RCIs was higher than adults, especially in the apical third. The distribution of RCIs had its own characteristics in each canal type, closely related to the structures.

Isthmus Incidence in Human Permanent Mandibular First Molars of a South Indian Population: A Cone-Beam Computerized Tomographic Study

Aim:

This study aimed to analyze incidence of isthmus in human permanent mandibular first molar teeth using cone-beam computed tomographic imaging techniques in a South Indian population.

Materials and Methods:

Three hundred permanent mandibular first molar teeth were collected, cleaned, and stored in normal saline. They were divided into groups (GPs) I and II based on number of roots, and were further subdivided (right and left [RL] subgroups A and B for GP I; and RL subgroups C and D for GP-II). Samples were processed and isthmus incidence was evaluated by cone-beam tomography, compared, and statistically analyzed.

Results:

Overall in mandibular first molars, the isthmus incidence in mesial root was 97.2%, distal root was 39%, and distolingual root was 0%. There was no statistically significant difference between the right and left mandibular first molar teeth with regard to incidence of isthmus (P > 0.05). There was an incidence of type I (38.67%), type II (56.33%), type III (3%), and type IV (2%) isthmuses in mesial root and type I (12.33%), type II (16%), and type III (10.67%) in distal root.

Conclusion:

Incidence of isthmus was very high in the mesial root of the mandibular first molar and should be factored during nonsurgical and surgical endodontic treatment procedures to achieve successful treatment outcomes.

An original micro-CT study and meta-analysis of the internal and external anatomy of maxillary molars-implications for endodontic treatment

The aim of this work was to conduct a radiological micro-CT study and meta-analysis to determine the morphological features of the root canal anatomy of the maxillary molars. The radiological study included micro-CT scans of 110 maxillary first molars and 98 maxillary second molars. To identify articles eligible for inclusion in our meta-analysis, PubMed, Embase, and Web of Science were search comprehensively. The following data were extracted: study type (cadaveric, intraoperative or imaging), Vertucci types of canal configuration, presence/number of canals, roots, apical foramina, apical deltas, and inter-canal communications. The mesiobuccal root was the most variable with respect to canal configuration, type I being the most common configuration followed by type II and type IV. Type I was the most common canal configuration in the distobuccal and palatal root. Regarding the number of canals in the maxillary first and second molars, one canal was most prevalent in all roots of the three molars, except for the mesiobuccal root of maxillary first molar, in which two canals were most prevalent. The most prevalent number of roots in all maxillary molars was three. Knowledge of endodontic anatomy determines the parameters of root canal treatment and significantly affects the probability of success. It is therefore especially important to know the morphology of the root canal system in order to perform endodontic treatment correctly. Clin. Anat. 31:838-853, 2018. © 2018 Wiley Periodicals, Inc.

Frequency of Root Canal Isthmi in Human Permanent Teeth Determined by Cone-beam Computed Tomography

INTRODUCTION

This study evaluated the frequency of root canal isthmi (RCIs) in human permanent teeth by using cone-beam computed tomography.

METHODS

A sample of 1400 teeth of 618 patients (394 women; mean age, 43.4 years) was selected. RCIs were detected longitudinally on 0.1-mm/0.1-mm axial slices of cone-beam computed tomography images of roots scanned from the pulp orifice to the apex, and findings were classified into 7 categories according to RCIs beginning and end: (1) both in the cervical third, (2) begin in the cervical third and end in the middle third, (3) begin in the cervical third and end in the apical third, (4) both in the middle third, (5) begin in the middle third and end in the apical third, (6) both in the apical third, or (7) no isthmus. A χ(2) test with Yates correction or the Fisher exact test was used to analyze categorical variables, described as frequencies (%). The Student t test was used to compare quantitative variables.

RESULTS

RCI is a common anatomic structure in human permanent teeth, except in maxillary anterior teeth.

CONCLUSIONS

The higher frequencies of RCIs (87.9%) were found in mandibular first molars. The frequencies of RCIs according to mean age and tooth group were not significantly different (P > .05), except in mandibular central incisors. RCIs were less frequent among older patients.