The significance of locating and filling the canal isthmus in multiple root canal systems. A scanning electron microscopy study of the mesiobuccal root of maxillary first permanent molars

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.

Comparison of microstructural imaging of the root canal isthmus using propagation-based X-ray phase-contrast and absorption micro-computed tomography

Clear and complete microstructural imaging of the root canal isthmus is an important part of pathological investigations in research and clinical practice. X-ray micro-computed tomography (μCT) is a widely used non-destructive imaging technique, which allows for distortion-free three-dimensional (3D) visualisation. While absorption μCT typically has poor contrast resolution for observing the root canal isthmus, especially for weak-absorbing tissues, propagation-based X-ray phase-contrast imaging (PBI) is a powerful imaging method, which in its combination with μCT (PB-PCμCT) enables high-resolution and high-contrast microstructural imaging of the weak-absorbing tissues in samples. To investigate the feasibility and ability of PB-PCμCT in microstructural imaging of the root canal isthmus, conventional absorption μCT and PB-PCμCT experiments were performed. The two-dimensional (2D) and 3D comparison results demonstrated that, compared to absorption μCT, PB-PCμCT has the ability to image the root canal isthmus more clearly and completely, and thus, it has great potential to serve as a valuable tool for biomedical and preclinical studies on the root canal isthmus.

Selective Retreatment and Sinus Lift: An Alternative Approach to Surgically Manage the Palatal Roots of Maxillary Molars

Endodontic microsurgery on the palatal root of maxillary molars presents a clinical challenge because of the root position and approximation from the maxillary sinus floor. Attempting a buccal or a palatal approach to address the root is associated with limited accessibility and visibility as well as the risk of injury to the maxillary sinus membrane and/or the greater palatine nerves and vessels. If all the maxillary molar roots require surgical intervention, two flaps may even be needed, which can make the procedure technically more difficult and lengthier. This case report presents 2 clinical cases in which apicoectomy was needed on the palatal roots of maxillary molars. The treatment includes selective nonsurgical retreatment of the palatal root and obturation using a root repair material followed by a surgical intervention from a buccal approach to treat the buccal roots, sinus lift using piezosurgery, and root resection of the palatal root. The approach was successful in both cases without any untoward events. We monitored the radiographic changes using cone-beam computed tomographic imaging immediately after the surgery and at multiple follow-up appointments. The cone-beam computed tomographic images revealed healing of the periapical disease around all the roots up to 14 and 24 months and apical repositioning of the maxillary sinus floor.

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.

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

Root canal anatomical complexities, such as isthmus, may limit the action of the endodontic instruments, irrigant solutions and intracanal medications, leading to endodontic treatment failure.

[Localisation of main and ancillary foramina within the mesial and distal roots of the first lower molars]

INTRODUCTION

Understanding the morphology of the root canal system, and especially its apical third, represents the basic precondition for the successful treatment of diseased pulp and the apical endodontium.

AIM

The aim of this study was to precisely locate the main and ancillary foramina in the mesial and distal first lower molars.

METHOD

One hundred extracted first lower molars, originating from persons of both sexes and three different age groups, were used in the study.

RESULTS

The analysis of the sampled molars' apical third was carried out using a binocular magnifier and a digital X-ray scanner (Trophy). The results showed that the main mesial and distal root foramina were located mostly on the distal surface. The ancillary mesial and distal root foramina were located at the lingual end, in most cases. Statistical analysis demonstrated the congruence of results achieved using the binocular magnifier and digital x-ray in 100% of cases if the main foramen is located on the very top of the mesial root (chi2 = 17.23; p < 0.001), and in 92.9% of cases if the main foramen is localised on the very top of the distal root of the first lower molar (chi2 = 12.07; p < 0.001).

CONCLUSION

The most common localisation of the main foramina for all age categories and in both mesial and distal roots is on the distal surface of the root. The greatest number of ancillary foramina was observed in the youngest age category, while they were localised most often on the lingual side of the mesial and distal root.

Apical Anatomy in Mesial and Mesiobuccal Roots of Permanent First Molars

The purpose of this in vitro study was to investigate the canal configuration types, and the prevalence and location of anatomical variations in the mesiobuccal (MB) and mesial roots of permanent maxillary and mandibular first molars after instrumentation. The number and the type of canals were determined before instrumentation using conventional methods. All root canals from the 47 MB roots and 42 mesial roots were then instrumented to size #30 with ProFile .04 taper rotary instruments in a crown-down method and then filled with a single gutta-percha cone and sealer. Transverse 1 mm-thick cross-sections at 2, 3, 4, and 5 mm from the apex were obtained, stained and examined using a stereomicroscope. The canal configuration types and the prevalence and location of isthmi and accessory canals in roots with two canals were evaluated. The prevalence of two canals was 80.8% in the maxillary MB roots and 95.2% in the mandibular mesial roots. There were six types of canal configurations in the instrumented root apices. The prevalence of anatomical variations was highest at the apical 4 mm level, and was more frequent in mandibular first molars, and in roots with Weine type III canal. chi test showed that the prevalence of the anatomical variations was statistically higher in the maxillary MB roots with Weine type III canals than in those with Weine type II canals (p < 0.05). Different canal configurations were often found at different levels in the same root. The results indicate that anatomical variations persist following instrumentation of roots with two canals in first molars. These anatomical variations should be considered during surgical or nonsurgical endodontic procedures of the permanent first molars.

A 5 Yr Clinical Investigation of Second Mesiobuccal Canals in Endodontically Treated and Retreated Maxillary Molars

An examination of 5616 endodontically treated and retreated maxillary first and second molars was made in an attempt to determine the percentage of MB2 canals that could be located routinely, and evaluate if there were any significant differences between initial treatments and retreatments. The teeth examined were 3578 first molars and 2038 second molars treated consecutively over a 5-yr period by six endodontists. Overall the MB2 canal was found in 2133 (60%) first molars, and 712 (35%) second molars. The incidence of a MB2 canal in first molar retreatments was 66% compared to a 58% incidence in initial treatments. Whereas in second molars the retreatment incidence was 40% compared to 34% in initial treatments. The significant difference in the incidence of a MB2 canal between initial treatments and retreatments suggests that failure to find and treat existing MB2 canals will decrease the long-term prognosis.

Clinical investigation of second mesiobuccal canals in endodontically treated and retreated maxillary molars

An examination of 1873 conventionally treated and retreated maxillary first and second molars was made in an attempt to determine the percentage of second mesiobuccal (MB2) canals that could be located routinely and evaluate if there were any significant differences between initial treatments and retreatments. The teeth examined were 1193 first molars and 680 second molars treated consecutively over a 2-yr period by five endodontists. Overall the MB2 canal was found in 724 (61%) first molars and 245 (36%) second molars. The incidence of a MB2 canal in first molar retreatments was 67% compared to a 59% incidence in initial treatments. Whereas in second molars, the retreatment incidence was 44% compared with 35% in initial treatments. The significant difference in the incidence of a MB2 canal between initial treatments and retreatments suggests that failure to find and treat existing MB2 canals will decrease the long-term prognosis.