Micro-CT analysis of danger zone thickness in the mesiobuccal roots of maxillary first molars

Micro-Computed Tomographic Analysis of Radicular Dentin Thickness in Mandibular Second Molars Across Diverse Anatomic Root Variations: Identifying Potential Danger Zones

INTRODUCTION

This study aimed to investigate radicular dentin thicknesses in mandibular second molars (MSMs), considering variations in root configuration and the morphology of the pulp chamber floor (PCF). The types of radicular grooves and potential danger zones were also identified.

METHODS

A total of 149 MSMs were scanned with micro-computed tomographic imaging and classified into 4 groups according to root fusion and PCF morphology as follows: (1) 45 with fused roots and C-shaped PCFs, (2) 45 with fused roots and non-C-shaped PCFs, (3) 14 with a single canal, and (4) 45 with separated roots. The first 2 groups were subdivided into Ω-shaped, U-shaped, and V-shaped radicular groove subgroups. Measurements included minimum and mean dentin thickness from the start of the radicular groove or root bifurcation extending 5 mm apically, the ratio of outer to inner dentin thickness, and the distribution of dentin thickness.

RESULTS

Ω-shaped and U-shaped subgroups showed significant thinner minimum inner wall thickness than V-shaped subgroups at 2-5 mm from the starting point of the radicular groove in both C-shaped and non-C-shaped pulp floor categories (P < .05). The mesial roots of separated rooted MSMs showed significant thinner dentin than a non-C-shaped floor regarding minimum and mean inner thickness and mean outer thickness (P < .05). Teeth with a single canal had significantly thicker walls compared with the other 3 groups.

CONCLUSIONS

In MSMs, caution must be exercised, especially in the presence of Ω-shaped and U-shaped grooves in C-shaped roots and around the root furcation of separated roots.

Assessment of Anatomical Dentin Thickness in Mandibular First Molar: An In Vivo Cone-Beam Computed Tomographic Study

Aim

To determine the minimum dentin thickness in the mesial and distal walls of the mesiobuccal (MB) and mesiolingual (ML) canals of the mandibular first molars using cone-beam computed tomography (CBCT).

Materials and Methods

CBCT examinations of 624 mandibular first molars from an Indian subpopulation were analyzed. The mesial and distal minimum dentin thickness was evaluated in 1 mm intervals apical to the furcation area. Independent t-test was used to analyze the data (α = 0.05). Using Cohen's kappa coefficient, the interexaminer and intraexaminer reliability was evaluated.

Results

The mesial dentin thickness was significantly higher than the distal dentin thickness for MB and ML canals (P=0.01). The average dentin thickness in the distal and mesial plane of the MB canal was 1.15 ± 0.15 mm and 1.52 ± 0.19 mm at the 1 mm level and 0.83 ± 0.13 and 1.08 ± 0.18 at the 5 mm level, respectively. For the ML canal, the average dentin thickness in the distal plane and the mesial plane was 1.24 ± 0.18 mm and 1.44 ± 0.21 at the 1 mm level and 0.91 ± 0.16 and 1.01 ± 0.17 at the 5 mm level, respectively. Statistical analysis between the MB and ML canals showed significant differences in the dentin thickness at 4 and 5 mm levels in both the distal and the mesial planes (P=0.01). In more than 85% of the cases, the minimum dentin thickness was seen at the 5 mm level in both the distal and mesial planes in MB and ML canals.

Conclusion

The distal planes of the mesiolingual and mesiobuccal canals were thinner in most cases, making the distal surface more prone to iatrogenic perforations. Considerably, at 4 and 5 mm from the furcation, the distal wall was significantly thinner than the mesial walls. Understanding the anatomy of the danger zone in the mesial roots of the mandibular first molars may serve to minimize the risk of endodontic mishaps such as strip perforations.

Endodontic Treatment of a Maxillary Second Molar With Five Canals: A Case Report and a Literature Review

A thorough understanding of both common and uncommon root canal anatomies is crucial for the success of root canal treatments, as missing a canal can lead to treatment failure. Although the maxillary second molar typically features three canals, the occurrence of five canals, particularly a mesial buccal third canal (MB3) canal in the mesiobuccal root, is extremely rare. This case report documents such a rare occurrence in a maxillary second molar with five canals. With the assistance of a dental operating microscope, all canals were successfully located, and root canal preparation, irrigation, and filling were accomplished. This case report underscores the significance of in-depth knowledge of root canal anatomy and the invaluable aid of a dental operating microscope in achieving successful root canal treatments.

Evaluation of Radicular Dentin Thickness in Maxillary and Mandibular Central Incisor, Canine, and Premolar Teeth

Background This study aimed to compare the radicular dentin thickness in single-rooted maxillary and mandibular anterior and premolar teeth by measuring on four different surfaces (buccal, lingual, mesial, and distal) at three different levels (apical, middle, and coronal). Methods A total of 150 single-rooted human anterior and premolar teeth were included in the present study. The teeth were sectioned at the cemento-enamel junction (CEJ; coronal), 4 mm away from the apex (apical), and the midpoint between these two distances (middle). First, the teeth were divided buccolingually into two parts, and the dentin thickness in the mesial/distal region was measured. Subsequently, both parts were divided again to measure the dentin thickness in the buccal/lingual region. All measurements were recorded, and statistical analysis was performed. Results Apical radicular dentin thickness was significantly less than CEJ (p < 0.001). The maxillary central incisor, maxillary, and mandibular canine exhibited the maximum radicular dentin thickness, whereas the mandibular premolars showed the minimum. Radicular dentin thicknesses on the lingual and buccal surfaces were significantly higher than those on other surfaces (p < 0.001). Conclusion The lowest radicular dentin thickness values were observed in the premolars, especially on mesial and distal surfaces. Considering these areas as danger zones and paying attention during dental procedures are essential to avoid possible complications.

Effect of the progressive taper enlargement of buccal root canals of three-rooted maxillary molars: A stepwise micro-CT study

This study evaluated unprepared canal areas, volume of dentine removal, and dentine thickness after the progressive enlargement of the buccal canals of 22 maxillary molars, with and without the MB2, using instruments with the same tip size (0.25 mm) but 4 different tapers (0.03, 0.05, 0.06 and 0.08 v). Micro-CT scans were performed after each instrument. Data were compared using a general linear mixed model post hoc comparisons with Kenward-Roger for Wald F tests (α = 5%). After each treatment step, it was observed an increase in the percentage volume of removed dentine and a decrease in the unprepared areas and dentine thickness at the pericervical region of all canals (p < 0.05). The percentage reduction of dentine thickness in MB2 canal was higher than in the mesiobuccal and distobuccal canals (p < 0.05). Knowledge of pre-operative dimensions and dentine thickness before enlargement of buccal canals of maxillary molars is an important factor to avoid excessive dentine removal.

Can maxillary molar dimensions predict the presence of the second mesiobuccal canal?

OBJECTIVE

To evaluate the potential of maxillary molar dimensions as predictors of the presence of the second mesiobuccal (MB2) canal.

METHODS

Micro-computed tomography scans were obtained from 47 maxillary molars, out of which 26 had the MB2 canal. The distance between root canals, extension of the canals, and thickness of surrounding dentin were obtained from axial images at the furcation level, 3 mm from the apex, and 5 mm from the apex. The association between the measurements and the presence of the MB2 canal was assessed using multiple logistic regression and odds ratio.

RESULTS

At the furcation level, the bucco-palatal extension of the MB1 canal significantly decreased the chance of the presence of the MB2 canal. Regarding the thickness of surrounding dentin measurements, the mesial and distal aspects of the MB1 canal at 3 mm from the apex were statistically significant to decrease and increase the chance of presence of the MB2 canal, respectively. Regarding the extension of the canals, only buccal-palatal extension seems to decrease the chance of the presence of the MB2 canal.

CONCLUSION

The presence of the MB2 canal in the mesiobuccal root of maxillary molars is associated with the bucco-palatal extension and surrounding dentin thickness of the first mesiobuccal canal, and seems to be unrelated to the dimensions of the distobuccal and palatal roots.

A microcomputed tomographic analysis of the morphological variabilities and incidence of extra canals in mandibular first molar teeth in an Egyptian subpopulation

A well-protected microbial habitat may be present in the root and canal morphology, which is varied and complicated. Before initiating effective root canal treatment, a detailed knowledge of the root and canal anatomical variances in each tooth is a must. This study aimed to investigate the root canal configuration, apical constriction anatomy, location of the apical foramen, dentine thickness, and prevalence of accessory canals in mandibular molar teeth in an Egyptian subpopulation using micro-computed tomography (microCT). A total of 96 mandibular first molars were scanned using microCT, and 3D reconstruction was performed using Mimics software. The root canal configurations of each of the mesial and distal root were classified with two different classification systems. The prevalence and dentin thickness around middle mesial and middle distal canals were investigated. The number, location and anatomy of major apical foramina and the apical constriction anatomy analysed. The number and location of accessory canals were identified. Our findings showed that two separate canals (15%) and one single canal (65%) were the most common configuration in the mesial and distal roots, respectively. More than half of the mesial roots had complex canal configurations and 51% had middle mesial canals. The single apical constriction anatomy was the most common for both canals followed by the parallel anatomy. Disto-lingual and distal locations of the apical foramen are the most common location for both roots. Mandibular molars in Egyptians show a wide range of variations in root canal anatomy with high prevalence of middle mesial canals. Clinicians should be aware of such anatomical variations for successful root canal treatment procedures. A specific access refinement protocol and appropriate shaping parameters should be designated for each case to fulfil the mechanical and biological objectives of root canal treatment without compromising the longevity of treated teeth.

Anatomical complexities affecting root canal preparation: a narrative review

A fundamental aspect of the Endodontic field is the knowledge of root canal anatomy. Using a variety of techniques, the internal and external anatomy of teeth have been extensively investigated throughout the past century. Recent improvements in three-dimensional computed tomography have enabled more detailed evaluations of root canal morphology in both clinical and laboratory settings. Essentially, researches have unveiled that the root canal constitutes a complex system, comprising not only the main root canal but also lateral components, including isthmuses, fins, accessory canals and apical ramifications. Undoubtedly, this intricate morphology poses a significant challenge when it comes to the process of shaping, cleaning and disinfecting the root canal system. This article aims to explore the anatomical aspects of the root canal system that impact the chemomechanical procedures.

Anatomic Comparison of Contralateral Maxillary Second Molars Using High-Resolution Micro-CT

The present study aimed to measure and compare anatomic parameters in contralateral maxillary second molars. A total of 18 intact maxillary second molar pairs (n = 36) extracted from 18 patients were scanned with micro-computed tomography (micro-CT) and then reconstructed. Axial, sagittal, and cross-sectional slices were used to analyze the parameters (lengths, widths, and thicknesses) and evaluate the symmetry of the right and left sides. The number of root canals and their internal patterns were classified following Vertucci’s classification. The number of lateral canals and their locations were also noted. Contralateral second molar pairs demonstrated a high degree of similarity in terms of the linear measurements (lengths, widths, and thicknesses). The root canal anatomy configuration symmetry of mesiobuccal, distobuccal, and palatal roots according to Vertucci’s classification were 41.1%, 88.2%, and 94.4%, respectively. In total, 41.6% of mesiobuccal roots, 2.7% of distobuccal roots, and 30.6% of palatal roots had at least one lateral canal. The apical third (38.7%) was the most frequent location of lateral canals, followed by the middle third (32.3%) of the root. This study provides insight into the anatomy of the root canals of contralateral maxillary second molars, which is valuable for both practitioners and researchers.

Can the detection of second mesiobuccal canals be enhanced based on the volume of adjacent canals?

OBJECTIVES

The purpose of this study was to evaluate whether the presence of the second mesiobuccal (MB2) canal is related to volumetric differences on the adjacent canals of maxillary molars.

DESIGN

Forty-seven maxillary first and second molars with and without the MB2 canal were individually scanned using microcomputed tomography (micro-CT). The volume of each canal was measured by an evaluator with experience in micro-CT analysis. The intraclass correlation coefficient (ICC) was obtained. Multiple logistic regression and odds ratio was calculated. To compare the volume of canals in molars with and without MB2, the Mann-Whitney test was applied (α = 0.05).

RESULTS

The intra-examiner reproducibility was almost perfect (ICC=0.97). Multiple logistic regression demonstrated that the volume of the mesiobuccal (MB1) canal can possibly act as a predictor of the presence of the MB2 canal. It was also found that the MB1 canal volume is larger in molars without the MB2 canal (p = 0.01). No statistically significant difference was observed in the adjacent canals (p > 0.05).

CONCLUSIONS

Despite the challenging detection of the presence of MB2 canals, clinicians should be aware that MB1 canals of reduced volume are highly suggestive of their presence.

Evaluation of the band-shaped isthmuses in the mesiobuccal root canal system using micro-computed tomography

OBJECTIVES

This micro-computed tomography (micro-CT) study analyzed band-shaped isthmuses having their floor at the apical third of the mesiobuccal roots of maxillary molars in terms of 2D and 3D morphological parameters.

MATERIALS AND METHODS

A total of 199 maxillary first molars were scanned with micro-CT. Twenty-seven specimens, confirmed to have a band-shaped isthmus, were further examined in terms of the isthmus length, volume, structure model index (SMI), and surface area. The distance of apical foramina of mesial canals from the isthmus floor and major-minor diameters, roundness, perimeter, and area of the isthmus roof and floor were compared. Statistical analyses were performed with descriptive statistics and t-test with a 5% significance threshold.

RESULTS

The band-shaped isthmus frequency was 13.5% and its length reached up to 5.5 mm. The distances of the apical foramina of mesiobuccal canals (MB1 and MB2) from the isthmus floor were similar (p > .05). Isthmus roof and floor showed significant differences in terms of their major diameter and area (p < .05), whereas their minor diameter, roundness, and perimeter values were similar (p > .05).

CONCLUSION

The band-shaped isthmuses are not rare and can reach through the half of the root length with oval cross-sections in the floor and roof anatomy. The distance between the isthmus floor and apical foramina did not differ between MB1 and MB2.

CLINICAL RELEVANCE

The band-shaped isthmus morphology contributes to the complexity of the apical anatomy of maxillary first molar teeth with various lengths and diameters.

A micro-CT analysis of radicular dentine thickness in mandibular first premolars presenting C-shaped root canals: Identification of potential danger zones

AIM

To describe the radicular dentine thickness in mandibular first premolars presenting C-shaped root canals, in order to identify the canal walls with less thickness as potential danger zones. In addition, to describe the internal and external anatomical characteristics of these teeth and to associate them to the dentine thickness.

METHODOLOGY

A total of 70 mandibular first premolars presenting C-shaped root canals were examined. Their internal morphology was analyzed using Vertucci´s and Fan´s criteria, and their external morphology was analyzed using the ASUDAS score. Besides, the dentine thickness around the root canals was two/three-dimensionally determined at five root planes and quantified in the distal and the mesial aspects.

RESULTS

According to Fan´s, ASUDAS, and Vertucci´s classifications, the most common canal configurations were category C3, grade 3, and type V, respectively. In Vertucci's type III anatomy, the mesial root wall of the lingual canal showed significantly less dentine thickness than the distal wall in the middle plane (p = 0.031). Similarly, in Vertucci's type V anatomy, significantly less dentine thickness was observed in the mesial root wall of the buccal and lingual canals in the middle plane (p < 0.001) and the buccal canal in the middle-apical plane (p = 0.014) than the distal root wall of these canals. In teeth with ASUDAS grade 3 and 4 scores, significantly less dentine thickness was observed in the mesial in comparison with the distal root wall of these canals. These differences were demonstrated in the middle and middle-apical planes (p < 0.001) of grade 3 teeth and the middle-apical plane (p < 0.001) of grade 4 teeth. In these root planes, the Ver1-AS3 and VerV-AS3 combinations presented a 4-times greater risk of presenting walls with a critical dentine thickness of 0.6 mm (OR=4, p = 0.025) than the combinations Ver1-AS2, VerV-AS2, VerV-AS4, and VerIII-AS3.

CONCLUSIONS

The root canal system configuration of mandibular first premolars with C-shaped canals showed a wide range of anatomical variations. The lowest dentine thickness was located in the mesial wall of the canals in the middle and apical root thirds of Vertucci´s type III and V anatomies and in teeth with deep radicular grooves scored as ASUDAS grade 3 and 4. In the middle and middle-apical planes, the presence of the combinations Ver1-AS3 and VerV-AS3 showed a high risk of presenting a critical dentine thickness of 0.6 mm. Therefore, these root canal walls with less dentine thickness represent potential instrumentation danger zones in mandibular first premolars with C-shaped canals.

Impact of several NiTi-thermally treated instrumentation systems on biomechanical preparation of curved root canals in extracted mandibular molars

AIM

To evaluate the shaping ability of several heat-treated nickel-titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro-computed tomography, considering their variation in kinematics and design.

METHODOLOGY

Curved-mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n = 10), established by determining homogeneous 3D parameters of volume and surface area: R-Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP-endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10 ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross-sectional measures of area, perimeter, roundness, major/minor diameters and 3-dimensional (volume, surface area, structure model index - SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro-CT. Data were analysed using analysis of variance and post hoc Tukey tests (α = 5%).

RESULTS

Reciproc Blue and XPS had significantly greater mean increases in cross-sectional area measurements, only in the middle third, when compared with RM and HFX (p < .05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p > .05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p < .05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p < .05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p < .05). The smallest dentine thickness was observed after the use of RCB (p < .05), in the danger and safety zones.

CONCLUSIONS

XP-endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved-mesial canals of extracted molar teeth treated on a laboratory benchtop.

Morphological characteristics of the mesiobuccal root in the presence of a second mesiobuccal canal: a micro-CT study

Objectives

This study investigated the internal morphology of mesiobuccal (MB) roots of maxillary molars with a second mesiobuccal (MB2) canal.

Materials and Methods

Forty-seven maxillary first or second molars from Brazilians were scanned using micro-computed tomography. The following measurements were obtained from the MB roots: root thickness, root width, and dentin thickness of the buccal aspect of the first mesiobuccal (MB1) canal, between the MB1 and MB2 canals, and the palatal aspect of the MB2 and MB1 canals at 3 mm from the root apex and in the furcation region. For statistical analysis, the Student’s t-test and analysis of variance with the post-hoc Tukey test were used (α = 0.05).

Results

In maxillary molars with an MB2 canal, MB roots were significantly thicker (p = 0.0014) and narrower (p = 0.0016) than in maxillary molars without an MB2 canal. The dentin thickness of the palatal aspect of the MB1 canal was also significantly greater than that of MB roots without an MB2 canal at 3 mm from the root apex (p = 0.0007) and in the furcation region (p < 0.0001). In the furcation region of maxillary molars with an MB2 canal, the dentin thickness between the MB1 and MB2 canals was significantly smaller than that in the buccal and palatal aspects (p < 0.0001).

Conclusions

The internal morphology of MB roots of maxillary molars with an MB2 canal revealed differences in dentin thickness, root diameter, and distance between the canals when compared with maxillary molars without an MB2 canal.

The effect of rotary instrumentation on dentin thickness in the danger zone of the MB2 canal of maxillary first molars

The aim of this study was to measure the initial and remaining dentin thickness in the danger zone of the second mesiobuccal (MB2) canal of maxillary first molars after rotary instrumentation using cone beam computed tomography (CBCT) imaging. After determining initial dentin thickness, each sample was subjected to a standardized protocol of rotary instrumentation files: ProTaper Gold Sx Orifice Opener (maximum depth of 7 mm); Vortex Blue 15.04, 20.04, 25.04, ProTaper Gold S1, S2, F1, F2, and finally Vortex Blue 30.06. Subsequent CBCT measurements were made to compare changes in remaining dentin thickness in comparison to initial presentation. Preoperative dentin thickness in the danger zone had a mean of 0.82 ± 0.17mm. Significant levels of dentin removal in the danger zone were noted after all instrumentation groups when compared to the pre-instrumentation mean (Sx P < 0.001, 25.04 P < 0.0006, F2 P < 0.0001, 30.06 P < 0.0001). It was concluded that a thin area of dentin exists along the distal wall of the MB2 (danger zone) from the furcation to 4 mm apically.

Micro-CT evaluation of maxillary first molars: interorifice distances and internal anatomy of the mesiobuccal root

This study aimed to describe the morphometric relationship of root canal orifices on the pulp floor in the presence/absence of mesiobuccal second canal (MB2) in the maxillary first molars and other aspects of its internal anatomy. Sixty-two maxillary first molars were scanned by micro-CT. The presence of the MB2 canal was verified. The distance between the center points of the MB1, MB2, distobuccal (DB), and palatal (P) canal orifices on the pulp floor were measured (MB1-MB2, MB1-DB, MB2-DB, MB1-P, and DB-P). The MB1-P to DB-P ratio was calculated. The distances between the anatomic apex and the MB1 and MB2 apical foramina were measured. The length of the band-shaped isthmus was also measured. Student's t-test was applied to verify the association between the presence of an MB2 canal, the interorifice distances, and the ratio of the MB1-P to DB-P distance (α = 5%). The MB2 canal was present in 43 roots (69.35%). Statistics showed significant differences when MB2 was present for the largest MB1-P distance (p < 0.05) and higher values for the MB1-P to DB-P ratio (p < 0.05). A band-shaped isthmus was detected in 25.8% of MB roots. The mean distance from the apical foramen to the isthmus floor ranged from 1.74 for MB1 canals to 1.42 for MB2 canals. Canal orifice distances on the pulp floor may predict the presence of MB2 canals. There was a high incidence of isthmus, accessory canals, and apical delta in the critical apical zone in MB roots of maxillary first molars.

Effect of canal preparation with XP-endo Shaper and ProTaper Next on root canal geometry and dentin thickness of mandibular premolars with radicular grooves and two canals: a micro-CT study

OBJECTIVES

This study aimed to evaluate the effects of different shaping protocols on the root canal geometry and remaining dentin thickness of mandibular premolars with radicular grooves (RG) and two canals by means of micro-CT.

MATERIALS AND METHODS

Mandibular premolars with RG and two canals were matched based on their similar morphological dimensions and assigned to 2 experimental groups according to the canal preparation (n=8): XP-endo Shaper (XPS) and ProTaper Next (PTN) systems. Before and after preparation, morphometric measurements of the volume, surface area, structure model index, area, perimeter, roundness, major and minor diameters, as well as untouched canal walls, canal transportation, and dentin wall thickness were evaluated. Data were statistically compared within and between groups using the independent sample t test (α=5%).

RESULTS

XPS revealed less changes in volume, surface area, area, perimeter, and major and minor diameters (P<0.05). There was no significant difference in structure model index (SMI), roundness, and percentage of untouched canal walls between groups (P>0.05). XPS resulted in less apical canal transportation and a higher remaining dentin thickness toward the RG compared to PTN in lingual canals (P<0.05).

CONCLUSIONS

XPS revealed fewer changes in root canal geometry as well as lower transportation and a greater remaining dentin thickness in the lingual canals toward the RG compared to PTN.

CLINICAL RELEVANCE

Internal and external anatomical characteristics of mandibular premolars might have an influence on biomechanical preparation. Considering the risk of perforation, the canal preparation using XPS appears to be more conservative compared to PTN.

Temperature and time variations during apical resection

OBJECTIVE

The aim of this study was to investigate temperature and time variations during root-end resection.

MATERIAL AND METHODS

Sixty human premolars were selected. The root canals were enlarged up to ProTaper X3 rotary instrument. A thermocouple was placed into the root canal 1 mm behind the resection line. The teeth were randomly divided into six groups according to the apical resection method: steel bur, tungsten carbide bur, Lindeman bur, diamond bur, laser and ultrasonic surgical piezo with a diamond tip. The root ends were resected 3 mm away from the root apex. The temperature of the root dentine during resection was recorded as maximum temperature, mean temperature and temperature change. The time required for apicectomy was recorded for each group. The Kruskal-Wallis method was used to analyse the differences between temperature changes during apical resections. The significance level was set at 5%.

RESULTS

There was no significant difference between bur groups in terms of temperature increase. The maximum temperature in piezo surgery was significantly higher than the Lindeman, tungsten and steel burs (p < .001). In addition, the maximum temperature in laser surgery was higher than the Lindeman bur (p < .05). An increase in the temperature was mostly seen in piezo surgery and the least temperature change occurred in the Lindeman bur. Mean time stayed under 1 min in each group.

CONCLUSIONS

Although piezo caused the highest temperature increase, the measured temperature increase was within physiological limits in all tested techniques.

Comparison of Dentinal Wall Thickness in the Furcation Area (Danger Zone) in the First and Second Mesiobuccal Canals in the Maxillary First and Second Molars Using Cone-Beam Computed Tomography

Objective:

Differences in the morphology of the root canal system might result in favorable or adverse treatment outcomes. The present study compared the thickness of the dentinal wall in the danger zone (furcation area) of the first and second mesiobuccal canals in the maxillary first and second molars using cone beam computed tomography.

Methods:

In this cross-sectional study, 50 CBCT images of maxillary first and second molars were evaluated from one of the specialized radiology centers in Kerman, Iran. The images were prepared by a Planmeca Promax 3D Max machine (Planmeca, Helsinki, Finland), with a field of view (FOV) of 8×8 cm and a resolution of 0.1 mm and analyzed with Romexis Viewer software version 3.1.1 (Planmeca, Helsinki, Finland). In the 0.1-mm-thick axial cross-sections with a distance of 1 mm, the distances from the center of the MB1 and MB2 root canals to the furcation area were measured in three areas: A) furcation area, B) 2 mm below the furcation area, and C) 4 mm below the furcation area (at a magnification of ×10). The data were then analyzed with paired t-test.

Results:

The thickness of the dentinal wall in the MB2 root canal was significantly less than that in the MB1 root canal in all the specimens (P<0.05). In both maxillary first and second molars, the thicknesses of the MB1 and MB2 root canals were significantly different in the furcation area and 4 mm below the furcation area (P=0.001). There was no significant difference between the maxillary first and second molars 2 mm below the furcation area; however, the difference was marginal (P=0.07).

Conclusion:

Considering the low thickness of the dentinal wall in the MB2 root canal compared with the MB1 root canal in the maxillary first and second molars, the anti-curvature techniques away from the furcation should be used to prepare this root canal to reduce the risk of strip perforation. On the other hand, it might indicate that highly tapered instruments and other aggressive instruments, such as Gates-Glidden drills, should be used with caution in these root canals.

Accuracy of an endoscope to detect root canal anastomoses in mandibular molar teeth: a comparative study with micro-computed tomography

Objective: The aim of this study was to investigate the accuracy of endoscopic visualization to detect root canal anastomoses at the coronal half of the mesial root canals of mandibular molars using micro-computed tomographic (micro-CT) images as reference.Material and methods: Seventy-four mesial roots of mandibular first molars with (n = 47) or without (n = 27) intercanal anastomosis were selected based on the micro-CT scans of 269 mandibular first molars at a pixel size of 10 µm. The specimens were mounted on the mannequins and their root canals were evaluated using dental operating microscope (DOM) and endoscope. The endoscopic probe was inserted into the main mesial root canals and 2 blinded observers evaluated the presence of a divergence point of anastomosis (where the branching occurs) as 'present' or 'absent'. The scorings were compared with the three-dimensional reconstructed images of the specimens and recorded as 'correct' or 'incorrect' evaluation. Degree of agreement between evaluators was assessed with Kappa test and the accuracy of endoscopic visualization according to the presence and location of anastomosis was compared using Fisher exact tests with a significance threshold at 5%.Results: High inter-examiner reliability was reported (0.91). None of the divergence points were identified using DOM whereas 11 divergence points were detected using endoscope, corresponding the 23.4% of the intercanal anastomoses. The endoscope also showed the absence of an intercanal anastomosis correctly in all of the specimens without an anastomosis. Detectability of a divergence point using endoscope was not affected by its location within the coronal half of root canal (p > .05).Conclusions: The endoscopes were able to visualize the divergence points of 23.4% of the intercanal anastomoses located at the coronal halves of root canals.

Perforation of the maxillary sinus floor during apical surgery of maxillary molars: A retrospective analysis using cone beam computed tomography

This retrospective analysis assessed a possible correlation of perforation of the maxillary sinus floor during apical surgery of maxillary molars and the distances from the treated apices/periapical radiolucencies to the sinus floor. The material included 168 apical surgeries of maxillary first or second molars performed from 1999 to 2016. In 22 (out of 33) perforation cases, a preoperative cone beam computed tomography (CBCT) was available. These cases were defined as the test group. From the pool of operated cases without sinus floor perforation, matching cases - that is, same treated tooth, similar age and same gender - were selected as a control group (N = 26). Mean linear distances from root apices or radiolucencies to sinus floor were significantly shorter in the test group compared to the control group. In conclusion, perforation cases were significantly closer to the sinus floor than cases without perforation.

Radicular Grooves and Complex Root Morphologies of Mandibular Premolars Among Israeli Population

INTRODUCTION

Mandibular premolars usually have one root and one root canal. Different studies found that up to 30% of mandibular premolars have more than one root canal, and up to 24% of mandibular premolars have C-shape canals. The purpose of this study was to investigate the root anatomy and the prevalence of complex root canal morphology in mandibular premolars in Israeli population.

METHODS

A total of 1020 Israeli patients' cone-beam computed tomography scans were screened and evaluated. A total of 1835 mandibular first premolars and 1678 mandibular second premolars were examined. Irregular root anatomy and different root canal morphologies were recorded and analyzed.

RESULTS

The overall prevalence of complex root morphology (types II-VIII) in mandibular first and second premolars was 21% and 2.8%, respectively. The bilateral prevalence of complex root morphology in mandibular first and second premolars was 46% and 29%, respectively. The prevalence of radicular grooves in mandibular first and second premolars with complex root morphology was 48% and 36%, respectively. No significant difference was found according to gender or the side of occurrence. However, complex root canal morphology was significantly found in mandibular premolars with radicular grooves.

CONCLUSIONS

Complex root canal morphology frequently occurs in mandibular first premolars in the population of Israel. Radicular groove existence in mandibular first and second premolars is significantly related to complex root canal morphology.

The MB3 canal in maxillary molars: a micro-CT study

OBJECTIVES

To assess the internal and external morphologies of the mesiobuccal (MB) root of maxillary molars presenting a third root canal (MB3), using micro-computed tomography (micro-CT).

MATERIAL AND METHODS

Two-hundred and sixty-five extracted maxillary first and second molars with different root configurations were imaged in a micro-CT scanner at 19.6-μm pixel size. Sixteen teeth presenting MB3 canal were selected and evaluated regarding root configuration, minimal dentine thickness 2 mm under the furcation area, canal configuration of the MB root, MB3 canal morphology (location, independent or confluent orifice, and anatomy types), and the apical anatomy (aspect ratio, number of accessory canals and foramina, presence of isthmus, and independent MB3 foramen).

RESULTS

Overall, a high variability in canal configuration was detected in the MB root. MB3 canal was observed in 10 maxillary first molars and 6 maxillary second molars (n = 16). Minimal dentine thickness related to the MB3 canal at the coronal third was smaller than that of the MB1 canal. A complex internal anatomy comprising 13 different root canal configurations was observed. A high number of independent MB3 orifices at the pulp chamber floor was observed in the first molars (7 out of 10 teeth), while most of the specimens (n = 14) showed a confluent anatomy of the MB3 canal. A varied number of accessory canals and foramina were observed. At the apical third, isthmus could be observed in 6 specimens, while an independent MB3 foramen was present in 37.5% of the MB roots.

CONCLUSIONS

MB3 canal is a rare anatomical variation present in maxillary first and second molars. Its presence can be associated to a complex internal anatomy of the MB root which includes the presence of isthmuses and multiple accessory canals and foramina at the apical third, but also a thin dentine thickness at the coronal third and a confluent anatomy of the MB3 with the other main canals.

Morphological measurements of two separate mesiobuccal canals in maxillary first molars using micro-computed tomography

OBJECTIVES

To obtain radicular measurements of two separate mesiobuccal (MB) root canals in maxillary first molars using micro-computed tomography (μCT) with customized software.

MATERIALS AND METHODS

Human maxillary first molar MB roots (N = 36) with two separate canals (MB1, MB2) and apical foramina were scanned by μCT and analyzed with Kappa2 software to reconstruct three-dimensional (3D) surface models of roots and canals. These models were sectioned at 0.1 mm intervals perpendicular to the central axis of each canal. Canal widths, 3D curvatures, and surrounding dentine thicknesses were measured concurrently on each section. Dentine thicknesses were analyzed statistically for differences between each direction and the different levels of both canals.

RESULTS

Dentine walls around MB1 were thicker than MB2 (p < 0.05). Thinnest dentine was most often located at disto-inside direction in both canals. Canal widths were significantly smaller in MB2 than MB1 (p < 0.01). Apical constrictions were smaller (p < 0.05) and further (p < 0.05) from the apex in MB2 than MB1. Canal curvatures were greatest in the apical third of both canals (p < 0.001), and they were greater in MB2 than MB1 (p < 0.05).

CONCLUSIONS

MB2 canals had shorter lengths, smaller widths, and more severe curvatures and were surrounded by thinner dentine walls. In MB2, apical constrictions were between 1 and 2 mm from the apex, compared to about 1 mm for MB1.

CLINICAL RELEVANCE

These detailed measurements and in-depth 3D analyses of maxillary first molar MB roots with two separate canals and apical foramina provide morphologic references for root canal therapy.