Furcation Level Research Articles

Comparison of Micro-CT and Morphometric Outcomes in a Modified Experimental Rat Model of Periodontitis.

To assess the correlation between micro-computed tomography (micro-CT) and linear morphometric measurements in terms of mandibular bone levels in a modified experimental periodontitis model in rodents to study the mechanisms of association between periodontal destruction and neuroinflammation. The proposed invivo experimental periodontitis model involves the administration of oral rinses with Porphyromonas gingivalis and Fusobacterium nucleatum, four times per week during 4, 8 or 12 weeks, in 24 male Wistar Hannover rats (180 g, 5 weeks old). After euthanasia, hemi-mandibles were collected. One hemi-mandible was analysed using morphometry, while the other was assessed with micro-CT. Linear measurements were taken at the buccal aspect and furcation level for both techniques, and volumetric measurements were also obtained with micro-CT. Passing-Bablok regression analysis was used to compare the results of both techniques, with morphometric measurements serving as the reference. Moreover, Lin's Concordance correlation coefficient was calculated to assess the level of agreement. Periodontal clinical variables with neuroinflammatory parameters from the frontal cortex were used to evaluate the association between the resulting condition and neuroinflammation. Twenty-one out of the initial 24 rats were analysed. The micro-CT linear measurements demonstrated high concordance values with the linear morphometric measurements at the buccal surfaces of the roots in molars (r = 0.714) but not at the furcation area (r = 0.052). At 12 weeks, there was a significant impact on neuroinflammation with significant decreases in iNOS levels and p-mTOR levels at 4 and 8 weeks. The proposed invivo experimental periodontitis model demonstrated a high degree of correlation between morphometric and micro-CT measurements in buccal areas but not at the furcation level. Concomitantly, there was a significant temporary modulation of the neuroinflammatory response.

The Impact of Coronal Flaring Files on Pericervical Dentin Thickness in Mandibular Molars

IntroductionThis study aimed to assess the influence of different coronal flaring files on dentin removal in mandibular teeth using cone-beam computed tomographic (CBCT) images. MethodsCBCT images of 48 mandibular molar teeth were acquired and randomly divided into 2 main groups, with each main group further divided into 3 subgroups. In the first main group, root canal preparation was performed using TruNatomy (Dentsply Sirona, Ballaigues, Switzerland), ProTaper Gold (Dentsply Sirona), and One Curve (Micro-Mega, Besancon, France) files without the use of coronal flaring files. In the second main group, root canal preparation was performed using the same files with the use of coronal flaring files. After the completion of root canal preparation, a second set of CBCT images was obtained. Subsequently, the dentin removal and remaining critical dentin were assessed by measuring at 4 distinct points below the furcation level. Data were compared between groups using the Mann-Whitney U and Kruskal-Wallis tests with alpha set at 5%. ResultsThe ProTaper Gold files demonstrated higher dentin removal compared with the TruNatomy files. In the no-flaring groups, the One Curve files exhibited greater dentin removal than the TruNatomy files at specific levels. The use of coronal flaring files generally did not significantly impact dentin removal, except for certain cases in the TruNatomy and ProTaper Gold groups. ConclusionsThe TruNatomy instrument group was more effective in preserving pericervical dentin compared with the other instrument groups. Coronal flaring files can be confidently used to preserve critical dentin during root canal treatment.

Dentinal Microcracks after Root Canal Preparation in Primary Root: An In Vitro Evaluation of ProTaper Gold and Kedo-S Rotary File Systems.

There is a possibility of dentinal crack formation in primary teeth after root canal preparation using rotary files. To evaluate and compare the effect of ProTaper-Gold and Kedo-S rotary files on crack formation after root canal preparation in primary molars. A total of 120 freshly extracted mandibular primary molars (6-9 years) were randomly divided into three groups of 40 each: ProTaper-Gold, Kedo-S, and Hand H-files, respectively. The roots were covered with a snuggly fitting surgical glove and stabilized in the teeth slot of a silicone mold of mandibular mixed dentition. Dental casts were obtained in a mixture of plaster of paris and sawdust. A screw system was incorporated in the cast for stabilization of the cast into the phantom head. All the root canals were instrumented in a standard operating position till 1 mm short of the radiographic apex. All roots were then stained and sectioned perpendicular to the long axis at the furcation level and 2 mm below the furcation to obtain one section per tooth. Sections were examined under a stereomicroscope at 25× magnification for any crack formations and recorded. Data were analyzed using Wilcoxon signed-rank and Kruskal-Wallis tests (p = 0.05). The total number of cracks in terms of percentage following the use of ProTaper Gold, Kedo-S, and H-files were 35, 10, and 0%, respectively, on the upper surface and 15, 5, and 0% on the lower surface. Within the group, there was a statistically significant difference in ProTaper-Gold (p = 0.001). The use of ProTaper-Gold resulted in a greater number of dentinal cracks compared to Kedo-S and H-files. Patil MB, Mandroli PS, Jalannavar P, et al. Dentinal Microcracks after Root Canal Preparation in Primary Root: An In Vitro Evaluation of ProTaper Gold and Kedo-S Rotary File Systems. Int J Clin Pediatr Dent 2023;16(5):692-697.

Farklı tek eğe sistemlerinin alt çene birinci büyük azı dişlerinin tehlike alanındaki dentin kalınlığına etkisi

Background: To compare the dentin thickness in the danger zone of mandibular molars after preparation with one rotating (XP-endo Shaper) and two reciprocating (One Reci and Reciproc Blue) single file systems using a cone beam computed tomography (CBCT).
 Materials and Methods: Thirty-six mesial roots of mandibular first molars having two independent canals were selected. After initial CBCT scans were provided, teeth were assigned into 3 groups related to the single file used: XP-Endo Shaper (XPS), One Reci (OR) and Reciproc Blue (RB). The roots were scanned again after preparation with respective single file systems. The minimum dentine thickness in the danger zone, at 4, 5, 6 and 7 mm below the furcation level, were measured in CBCT scans. Initial and final measurements were used to calculate the removed dentin thickness in the danger zone. Data was analyzed using Repeated-measures ANOVA (p=0.05).
 Results : No significant differences were found related with remaining and removed dentin thickness among single file systems at any level from the furcation (p>0.05). 
 Conclusions: The evaluated single file systems showed similar cutting efficiency in the danger zone of mandibular molars.

Photodynamic therapy as an adjunctive treatment for grade C periodontitis in molar teeth: a preliminary trial.

The present study aimed to evaluate the local effect of antimicrobial photodynamic therapy (aPDT) as adjunctive treatment for grade C periodontitis in molars teeth. Thirty-eight molar teeth from 11 patients were included in this split-mouth randomized clinical trial. The teeth were randomly divided into two groups (n = 19 each) that were submitted to conventional scaling and root planing in addition to aPDT (test group) and to scaling and root planing in addition to aPDT simulation (control group). The following periodontal parameters were obtained prior to treatment (baseline) and at 3 months after the intervention: bleeding on probing, probing depth, gingival recession, clinical attachment level, and furcation level. A 5% significance level was adopted in the statistical analysis. Both groups exhibited improvement in the clinical parameters (p < 0.001). However, the reductions in bleeding on probing and probing depth were greater in the test group (p < 0.001). There were no significant differences in the other clinical parameters between groups (p ≥ 0.13). Molar teeth treated with aPDT and scaling and root planing showed superior clinical improvement compared to those submitted only to scaling and root planning. Antimicrobial PDT may be used as adjunctive treatment for grade C periodontitis affecting molar teeth since it seems to improve the clinical response to conventional debridement.

Is “danger zone” really dangerous? - An endodontic perspective

Aim: To evaluate the accuracy of panoramic radiography in determining dentin thickness of danger zone (DZ) using cone-beam computed tomography (CBCT) imaging to examine the dentin thicknesses of the mandibular molars at different levels. Materials and Methods: For the study, 250 mandibular molars were selected. Dentine thicknesses were measured on panoramic radiography. On the CBCT view, dentine thicknesses of mesiobuccal (MB), mesiolingual (ML), and distal roots were measured. The reference point was determined as 3 mm, 4 mm, and 5 mm below the furcation of mandibular molars. Statistical analysis was performed. Results: The discrepancy between CBCT and panoramic was 0.5 mm for MB, 0.48 mm for ML, and 0.43 mm for distal. The difference in the dentin thickness between 3 mm and 5 mm is not statistically significant(P&gt;.05), whereas the 4 mm furcation level was significantly lower in either 3 mm and 5 mm for each root canal. This study showed that 0.5 mm distortion occurred in the danger zone on panoramic radiography. Conclusion: Our study showed that the dentin thickness of less than 1 mm in panoramic radiography is more prone to perforation because of distortion. The dentin thickness was lowest at 4 mm below the furcation. Our results can be a guide the clinicians in clinics or institutions where periapical radiography is not available.

Impact of Minimally Invasive Endodontic Procedures on the Development of Dentinal Microcracks

IntroductionTo evaluate the impact of root canal preparation in teeth with ultraconservative access cavities (UltraAC) on the development of dentinal microcracks using a nondestructive longitudinal micro–computed tomography (micro-CT) imaging experimental model. Root canal preparation in teeth with traditional access cavities (TradAC) was used as control. MethodsForty mandibular molars were scanned in a micro-CT device, anatomically matched, and distributed into 4 groups according to the type of access cavity and instrumentation system: traditional/Reciproc (TradAC/RC), traditional/XP-endo Shaper (TradAC/XP), ultraconservative/Reciproc (UltraAC/RC), and ultraconservative/XP-endo Shaper (UltraAC/XP). After root canal preparation, the teeth were rescanned. After reconstruction and co-registration procedures, the images were screened from the furcation level to the apex to identify the presence of dentinal microcracks. ResultsFrom a total of 15,340 cross-section images, 19.65% (3014 slices) had some dentinal microcracks. The qualitative analysis demonstrated the presence of some dentinal microcracks in 11%, 33%, 19%, and 15% of the images of cross-sections in TradAC/RC, TradAC/XP, UltraAC/RC, and UltraAC/XP groups, respectively. All dentinal microcracks observed after root canal preparation were already present in the corresponding images before canal instrumentation. Therefore, no new microcracks were detected, regardless of the access cavity and root canal instrumentation system. ConclusionsRoot canal preparation with Reciproc or XP-endo Shaper under traditional or ultraconservative access cavities did not create dentinal microcracks in extracted mandibular molars.

Transverse Analysis of Maxilla and Mandible in Adults with Normal Occlusion: A Cone Beam Computed Tomography Study.

Objectives: To study the transverse widths of maxilla and mandible and their relationship with the inclination of first molars. Materials and Methods: Fifty-six untreated adults (12 males, 44 females) with normal occlusion were included. On each Cone Beam Computed Tomography (CBCT) image of the subject, inter-buccal and inter-lingual bone widths were measured at the levels of hard palate, alveolar crest and furcation of the first molars, and maxillomandibular width differentials were calculated. In addition, the buccolingual inclination of each first molar was measured and its correlation with the maxillomandibular width differential was tested. Results: At the furcation level of the first molar, the maxillary inter-buccal bone width was more than the mandibular inter-buccal bone width by 1.1 ± 4.5 mm for males and 1.6 ± 2.9 mm for females; the mandibular inter-lingual bone width was more than the maxillary inter-lingual bone width by 1.3 ± 3.6 mm for males and 0.3 ± 3.2 mm for females. For females, there was a negative correlation between the maxillomandibular inter-lingual bone differential and maxillary first molar buccal inclination (p < 0.05), and a positive correlation between the maxillomandibular inter-lingual bone differential and mandibular first molar lingual inclination (p < 0.05). Conclusions: This is a randomized clinical study on transverse analysis of maxilla and mandible in adults with normal occlusion using CBCTs. On average: (1) At the furcation level of the first molars, the maxillary inter-buccal bone width was slightly wider than mandibular inter-buccal bone width; whereas the mandibular inter-lingual bone width was slightly wider than maxillary inter-lingual bone width; (2) A statistically significant correlation existed between the maxillomandibular transverse skeletal differentials and molar inclinations.

Dentin Thickness at Danger Zone and Canal Morphology of Maxillary Molars.

ObjectivesDentin thickness in concave areas of the root creates risk for complications such as strip perforation during endodontic treatment. The study aims to examine dentin thickness of the danger (DZ) and safety zone (SZ), canal configuration, and the presence of isthmus in the mesiobuccal root of maxillary molars.Material and MethodsCone-beam Computed Tomography (CBCT) images of 1251 teeth belonging to 642 patients were retrospectively reviewed. The dentin thicknesses at DZ and SZ in maxillary molars with one (MB) or two mesiobuccal canals (MB1, MB2) were measured at the 3 mm apical to the furcation level. Vertucci's canal configurations and the isthmus rate were recorded. The Chi-square test andThe Student’s t-test were performed.ResultsMB2 rate was higher in maxillary first molars (61.68%) than second molars (39.36%). Isthmus rates were 27.3% and 44.11% in first and second molars. DZ thickness was thinner than the dentin thickness in the SZ in both first and second molars with one or two mesial canals (p< 0.05). In teeth with single canal, the mean DZ thickness was 0.88mm. In teeth with two canals, the mean DZ thicknesses were 0.83mm and 0.80mm for MB1 and MB2 canals, respectively.ConclusionMB2 rate was higher in the first molar (61.68%), and the isthmus rate was higher in the second molar (44.11%). DZ and SZ were thinner in MB2 than in MB1 at the maxillary molars with two mesial canals. The results indicated that more conservative preparation must be applied to the MB2 canal in the maxillary molars.

Influence of access cavity preparation on the dentine thickness of mesial canals of mandibular molars prepared with reciprocating instruments

To evaluate the influence of traditional and conservative access cavity preparations on the remaining dentine thickness in the coronal third of mesial canals of extracted mandibular molars prepared with reciprocating instruments using micro-computed tomography as the analytical tool. Seventy extracted mandibular molars were scanned at a pixel size of 19μm. From this initial sample, 20 teeth were selected, pair-matched and distributed into two groups (n=10) according to the access cavity preparation: traditional (TradAC) or conservative (ConsAC). The root canals were sequentially enlarged with Reciproc Blue R25 (size 25, 0.08v taper) and R40 (size 40, 0.06v taper) instruments. A new scan was performed and the postoperative stacks were coregistered with their respective preoperative datasets. A colour-coded cross sections of the roots were created and used to identify and measure the smallest dentine thickness related to both MB and ML canals at 1.0-mm intervals from the furcation level of up to 5mm in the apical direction, in both mesial and distal aspects of the roots, before and after preparation. The statistical analyses were performed with paired-samples t-test, independent-samples Student T-test and Chi-Square test with a significance level of 5%. At all levels of both groups, dentine thickness before preparation was greater than after preparation (p<.05). No difference in the percentage of dentine reduction was observed between TradAC and ConsAC groups (p>.05), but a significantly greater reduction was observed to the distal aspect of the roots (p<.05). After root canal preparation, dentine thinner than 0.5mm was observed mostly along the distal aspect of the root (10% to 15%) of the MB and ML canals, with no influence of the access cavity type on its incidence to either mesial (X2 =1.66; p=.2) or distal (X2 =0.40; p=.5) directions. In the TradAC group, dentine thickness in most slices was greater than 1.0mm after preparation (n=124) whilst, in the ConsAC, it ranged from 0.5 to 1.0mm (n=136). Traditional or conservative access cavity preparation in extracted mandibular molars did not influence the remaining dentine thickness in the coronal third of mesial canals enlarged with thermomechanically treated nickel-titanium reciprocating instruments.

Analysis of stress in periodontium associated with orthodontic tooth movement: a three dimensional finite element analysis

It is well known that the initiating factor for the biologic changes is the stress induced in the periodontal tissue; but as of now there is no gauge to measure the stress in the PDL directly. Therefore finite element model can be used to study the stress-strain relation through simulation of the PDL. The aim of the study was to simulate the stress response in the periodontium for different moment to farce ratios induced by tipping, translation, rotation, intrusion, extrusion and root torque by means of finite element method. The three-dimensional finite element model of the mandibular first molar was constructed. The pattern of Von misses stress and the maximum displacement of the mandibular molar was recorded on application of different combination of moment to force ratio. The periodontium was sensitive to changes in the load values. The stress pattern in the periodontal ligament for a lingually directed force without counterbalancing moments showed high concentration at the cervical level of the root. With addition of counter-tipping and counter-rotation moments, a relatively even distribution of stress throughout PDL was obtained. Additionally, high stress concentration was observed on the root surface at the furcation level for forces applied parallel to the long axis. Translation type of tooth movement showed relatively even distribution of the stress in the PDL and makes the tooth less susceptible to root resorption.

Middle Mesial Canal Preparation Enhances the Risk of Fracture in Mesial Root of Mandibular Molars

IntroductionThe aim of this investigation was to evaluate the effect of the presence and preparation of middle mesial (MM) canals on the fracture resistance of the mesial root of mandibular molars. MethodsForty intact mesial roots of mandibular first molars having 2 (n = 20) or 3 (n = 20) independent canals from the furcation level for up to at least 5 mm apically were selected based on preoperative micro–computed tomographic scanning. The selected roots were then distributed into 2 experimental (n = 10) and 2 control groups (n = 10) according to the root length, canal configuration (2 or 3 independent canals), and root thickness at the furcation level. In the experimental groups 1 (2 independent canals) and 3 (3 independent canals), root canals were enlarged up to the ProTaper Next X3 rotary instrument (Dentsply Sirona, Ballaigues, Switzerland), whereas in groups 2 (2 independent canals) and 4 (3 independent canals) root canals were not prepared. The specimens were embedded in acrylic resin after their surfaces were coated with a thin layer of silicone and subjected to a fracture strength using a universal testing machine. The types of fracture extension and course were recorded and statistically compared with the chi-square test, whereas fracture strength was analyzed using 1-way analysis of variance and post hoc Tukey tests (α = 5%). ResultsNo statistical difference in fracture strength was observed between nonprepared roots with 2 (group 2, 696.1 ± 186.3 N) or 3 (group 4, 558.4 ± 154.6 N) independent canals (P > .05), whereas the lowest values were obtained in the prepared roots with an MM canal (groups 3, 377.1 ± 77.2 N) (P < .05). The mean fracture strength observed in the prepared roots with 2 canals (group 1, 528.4 ± 134.3 N) showed no statistically significant difference compared with nonprepared roots with 3 canals (group 4, 558.4 ± 154.6 N) (P > .05). The chi-square test revealed no significant differences in fracture extent, types, and courses among groups (P > .05). Fracture extensions in all groups were mostly central and buccal-central types, whereas the highest frequency of fracture course was the curved and zigzag types. ConclusionsThe fracture resistance of the mesial roots of the mandibular molars decreased after the preparation of mesial canals with large-tapered instruments. Preparation of the MM canal further diminished the fracture resistance of the mesial roots. The resultant fracture displayed a distinct pattern in the buccolingual plane.

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

ObjectivesThe aim of the present study was to evaluate the influence of bifid and non-bifid configurations of the mesial root of mandibular first molars in the canal anatomy using micro-computed tomography (micro-CT). DesignThirty mesial roots with bifid apex were pair-matched with 30 non-bifid roots by means of micro-CT. Bifid and non-bifid mesial roots were compared regarding morphological aspects at the apical third, dentin thickness, and the presence of isthmus and middle mesial canal (MMC). Data were analyzed using Chi-square test and Student’s t-test with a significant level of 5 %. ResultsMain foramen of mesiobuccal (MB) and mesiolingual (ML) canals were positioned within 2.5 mm from the anatomic apex, and origin and exit of accessory canals were observed mostly between 1.0 and 2.0 mm from the apex in the groups. Despite no statistical difference was observed between bifid and non-bifid roots regarding the number of canal orifices (p > 0.05), the frequency of accessory canals was significantly higher in bifid roots (p < 0.05). Regarding the dentin thickness, a statistically significant difference was observed between bifid and non-bifid roots at the furcation level (p < 0.05). Only 3 mesial roots with bifid apex (10 %) had isthmuses, mostly at the coronal third, while a high incidence of MMC was observed in this group (n = 10, 33.3 %). ConclusionsPresence of bifid apex in the mesial root of mandibular first molars might be a predictive factor for a complex canal anatomy at the apical third with an increasing number of accessory canals.

Multislice computed tomography evaluation of the expansion achieved by the nonextraction treatment of orthodontic cases using Damon system

Objectives The purpose of this study is to evaluate the dental, alveolar changes and behavior of teeth movement during expansion achieved by the nonextraction treatment approach of crowding cases using the Damon system. Materials and methods High-resolution multislice computed tomography (MSCT) imaging was performed pretreatment (T1) and posttreatment (T2) on a sample composed of twenty patients aged 17.8 ± 3.7 years in average selected based on a pretreatment class I skeletal and molar relationships, and moderate crowding range between 4.0 and 9.0 mm for the maxilla and 2.0 and 6.0 mm for the mandible. On the Digital Imaging and Communications (files obtained from MSCT scans, dental and alveolar measurements were recorded including interocclusal, interapical widths, angulations of the maxillary and mandibular teeth and four bilateral bone thickness distances at the furcation level. Results The evaluation of the study was performed by detecting the dental and alveolar changes between pretreatment and posttreatment MSCT scans. Paired t test was used for statistical analysis. The interocclusal to interapical ratio indicated that, the roots moved by the same distance as the crowns except the canines roots moved 15 times as the crowns. While in the mandible, the roots of the premolars and molars moved less than the crowns but in the canines the opposite was happened. There was a significant increase of the axis angles of the maxillary canines and a significant decrease of the axis angles of the mandibular second premolars and first molars. This expansion resulted in a significant decrease of the buccal bone thickness and alveolar width and a significant increase of the palatal and lingual bone thickness. Conclusion The results of this study revealed that the expansion produced a small amount of uprighting in the maxillary teeth and a more significant degree in the mandibular teeth except the mandibular first premolars, were tipped buccally.

Incidence of Middle Mesial Canals Based on Distance between Mesial Canal Orifices in Mandibular Molars: A Clinical and Cone-beam Computed Tomographic Analysis

IntroductionThis study evaluated the presence of midmesial canals (MMCs) in a random sample of mandibular molars and the relationship of the intracanal distance between mesiobuccal (MB) and mesiolingual (ML) canal orifices. MethodsFifty-one extracted mandibular molars were divided into samples of 3 to 4 teeth, mounted in plaster and boxing wax, and immersed in water before cone-beam computed tomographic (CBCT) imaging. Two endodontic residents completed the access openings. The teeth and the CBCT images were interpreted for the presence of MMCs and the mesial intracanal distance. CBCT software measured the distance between the buccal of the MB canal to the lingual of the ML canal at the pulpal floor to determine the average length between the canals. ResultsSeven distinct MMCs were seen both clinically (incidence of 13.725%) and on the CBCT images. Twenty-seven teeth (52.94%) had ambiguous broad isthmi between the MB and the ML orifices. MMCs were present at the furcation level but merged with the MB or ML canal toward the apex in 6 of 7 teeth (85.71%). The mean distance between the mesial canals in teeth with MMCs was 3.643 mm, and it was 3.818 mm for teeth without MMCs. According to independent sample t testing, the P value was >.05. ConclusionsThe incidence of MMCs in mandibular molars appears consistent with the literature. However, there does not appear to be a statistically significant difference in the mesial intracanal distance in teeth with and without MMCs. Visualization of MMCs on CBCTs may be subjective. There does not appear to be a correlation between the presence of MMCs and an increased or decreased mesial intracanal distance.

Evaluation of dentine thickness of middle mesial canals of mandibular molars prepared with rotary instruments: a micro-CT study.

To evaluate, using micro-CT, the remaining dentine thickness after preparation of the mesiobuccal (MB), mesiolingual (ML) and middle mesial (MM) canals of mandibular first molars with the ProTaper Next rotary system. Eleven mesial roots of mandibular first molars having three independent canals from the furcation level up to at least 5mm towards the apical direction were selected. Preparation of MM canals was performed in two steps using ProTaper Next X2 (step 1) and X3 (step 2) instruments, whilst MB and ML canals were prepared in a single step up to X3 instruments. The roots were scanned (pixel size of 10µm) before and after each step, and the dentine volume was calculated. Postoperative models of the roots were coregistered with their preoperative dataset and colour-coded cross-sections of the roots were used to measure the smallest dentine thickness surrounding each canal at 1.0-mm intervals from the furcation level up to 5mm in the apical direction, in both mesial and distal aspects of the roots. Changes in the remaining wall thickness between mesial canals were analysed with repeated-measures anova and post hoc Tukey test. Significance level was set at 5%. Mean percentage reduction of dentine volume after steps 1 and 2 was 4.66% and 5.16%, respectively. Overall, pre- and postoperative dentine thickness of the MM canal walls, in both mesial and distal aspects of the root, were significantly thinner than those of MB and ML canals (P<0.05). No significant difference was observed when comparing dentine thickness in the mesial and distal directions of MM canal after preparation step 1 (0.88±0.18mm and 0.73±0.26mm, respectively) or 2 (0.83±0.17mm and 0.67±0.26mm, respectively) (P >0.05). Dentine thickness values less than 0.5mm were observed mostly towards the distal aspect of the MM canal. Mesial roots were not associated with strip perforations after canal preparation procedures. A significant decrease in the thickness of canal walls at all levels evaluated in the mesial roots of mandibular molars suggests that files with small tapers should be used in preference to instruments with large tapers to prepare mesial canals in mandibular molars.

Adaptation of Single-Cone Gutta-Percha in Curved Canals Prepared and Obturated with Protaper and Heroshaper Systems by Using Cone Beam Computed Tomography.

Objective:The aim of this study is to prepare and obturate the curved canals of the mesiobuccal root of maxillary first molar with four different file systems that is protaper hand files, rotary pro taper (RP) files, heroshaper hand files, and rotary hero shapers files and to evaluate the adaptation of their single-cone Gutta-percha by cone beam computed tomography (CBCT).Materials and Methods:Eighty teeth were selected and were divided into two groups (G1A1, G1A2 and G2A1, G2A2 as hand and RP file system, G1A3, G1A4 and G2A3, G2A4 as hand and rotary hero shaper files system) of fourth teeth each. After access opening working length of the mesiobuccal canal was established. The distobuccal and palatal roots of the samples were removed using the diamond disc at the furcation level. “Endoanalyser” software was used to measure Schneider's angle on the preoperative radiograph. This angle was measured by drawing two lines-one parallel to the long axis of the canal, in the coronal third, and the second line from the apical foramen to intersect the point where the first line left the long axis of the canal. The canals of each group were then prepared according to the manufacturer's instructions for protaper hand files, RP files, heroshaper hand files, and rotary hero shapers files systems. Direct digital radiography image of all the samples was obtained. And then, the samples were exposed to CBCT to evaluate their single-cone adaptations. The data were analyzed using SPSS 20, IBM, Armonk, NY, United States of America.Results:The null hypothesis that there will not be any gap area in the adaptation of their single-cone of different file system was rejected. Minimal gap area was seen in rotary hero shapers file system (0.001 mm2) and was maximum in hand protaper (HP) file system (0.015 mm2).Conclusion:CBCT is a useful tool in detecting the gap area after obturation in curved canals. The HP single-cone adaptation showed the maximum gap area and rotary heroshaper single-cone adaptation showed the minimum gap area.

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

To evaluate dentine thickness from both distal ('danger zone') and mesial ('safety zone') aspects of the MB1 and MB2 canals of maxillary first molars at the furcation level using micro-CT imaging. One hundred maxillary first molars with two canals in the MB root were selected from a Brazilian subpopulation and scanned at a resolution of 19.6μm in a micro-CT device. From each specimen, two axial cross-sectioned images were selected at 2 and 3mm apical to the furcation level of the MB root and evaluated for the smallest dentinal thickness. Measurements were made from the outer perimeter of the MB1 and MB2 canals towards the external root surface from both distal (danger zone) and mesial (safety zone) aspects of the root. The influence of an isthmus was also considered in the analysis, and samples were classified according to the presence or absence of an isthmus in the axial sections. Non-parametric Wilcoxon signed-rank tests were used to compare dentinal thickness between MB1 and MB2 canals with a significant level set at 5%. Colour-coded 3D models of dentine thickness throughout the MB root were created and evaluated qualitatively. At both levels, median dentine thickness of the MB2 canal was significantly lower in both distal and mesial aspects of the root in comparison with the MB1 canal (P<0.01). The presence of an isthmus was not a variable that influenced dentinal thickness. Colour-coded models indicated that dentine thickness was dependent on the cross-sectional shape of the MB root. At least 50% of the sample had <1mm of dentine thickness at the danger zone of the MB2 canal. Danger zones in the MB roots of maxillary first molars were not symmetrical. MB2 canals had less dentine thickness on both aspects of the root compared to the MB1 canal.

Preliminary investigation of the variations in root canal morphology of hypomineralised second primary molars.

To investigate the root canal morphology of hypomineralised second primary molars(HSPM) using micro-CT(μCT) compared with non-hypomineralised second primary molars (non-HSPM). Ten HSPM and 10 non-HSPM were divided into Group 1(maxillary HSPM), Group 2 (mandibular HSPM), Group 3(maxillary non-HSPM), and Group 4 (mandibular non-HSPM). All teeth were scanned using μCT to assess the following parameters: (i) root canal configuration, (ii) pulp volumes, and (iii) the influence of the root canal system landmarks on access cavity outline forms and canal curvature. Two-way ANOVA was employed for descriptive analysis (P<0.05). At the furcation level, there was minimal variation in the number of canals. In the mesiobuccal root, Group 1 showed higher frequency of multiple canals in the middle (85.7%) and apical (85.7%) thirds compared with Group 3. In the mesial root, Group 4 demonstrated multiple canals at the furcation (60%) compared with Group 2(33.3%). In the distal root, Group 2 demonstrated a higher percentage of multiple canals at the apical level (100%) compared with Group 4. The mean pulp volumes of Group 2 and Group 4 were 54.1mm3 (16.7) and 30mm3 (5.12), respectively, which was statistically significant (P<0.05). The canal curvature values did not differ significantly between HSPM and non-HSPM groups. HSPM exhibited greater variations in their root canal configuration when compared to non-HSPM.

Root Dentine Thickness and Concavity Depth in Mandibular Molars: A Cone Beam Computed Tomography Population Study.

Objective:The purposes of the present study were to evaluate dentine thickness and concavity depth below the furcation level of the mesial canals of the mandibular first and second molars, to examine differences between gender, age, and quadrant, and to prove if there is a relationship between root length and dentine thickness.Methods:Two hundred eleven mandibular first and second molars were included in this study. Samples were divided according to age, gender, quadrant, and root length. Measurements of dentine thickness from the external border of the root canal to the external root surface and concavity depth were recorded 1, 2, and 4 mm below the furcation level. Kruskal–Wallis and Wilcoxon rank sum tests were performed to estimate the influence of different variables, and a multiple regression analysis was performed to evaluate the influence of dentine thickness below the furcation level.Results:First molars had a deeper concavity depth with significant differences in both 1 mm and 2 mm levels than second molars (P<0.05). According to concavity depth, there was no relationship with teeth length (P>0.05). The distal concavity was significantly deeper in the 1 and 2 mm levels (P<0.05). According to gender, the female group had a reduced dentine thickness in both mesiolingual and mesiobuccal canals in both 1 mm and 2 mm levels (P<0.05).Conclusion:Female patients have a reduced dentine thickness below the furcation level. In order to select the most appropriate instrumentation procedure in every specific case, clinicians must be aware of the dentine reduced thickness measurements to avoid procedural iatrogenic damage.