Micro–Computed Tomographic Analysis of the Root Canal Morphology of Mandibular Incisors

Introduction

This study aimed to describe the anatomy of mandibular central and lateral incisors using micro–computed tomographic imaging.

Methods

One hundred mandibular incisors were scanned in a micro–computed tomographic device using an isotropic resolution of 22.9 μm. The anatomy of each tooth (length of the roots, presence and location of accessory canals and apical deltas, and number of canals) as well as the 2- and 3-dimensional morphologic aspects of the canal (area, roundness, diameter, volume, surface area, and structure model index) were evaluated. Data were statistically compared using the Student t test (alpha = 0.05).

Results

The mean lengths of the mandibular central and lateral incisors were 20.71 and 21.56 mm, respectively. Most of the central (60%) and lateral (74%) incisors had no accessory canals. An apical delta was observed in only 1 specimen. The cross-section analysis of the apical third showed the presence of 1, 2, or 3 canal orifices. No statistical difference was observed in the comparison of the 2- and 3-dimensional morphologic parameters between central and lateral incisors (P < .05). The qualitative analyses of the 3-dimensional models of the root canal systems of the central and lateral incisor teeth confirm that the most prevalent configurations were Vertucci's types I (50% and 62%, respectively) and III (28%).

Conclusions

Overall, mandibular central and lateral incisors were similar in terms of the 2- and 3-dimensional analyzed parameters. Vertucci's types I and III were the most prevalent canal configurations of the mandibular incisors; however, 8 new types have also been described.     

Morphologic Micro–Computed Tomography Analysis of Mandibular Premolars with Three Root Canals

Introduction

This study aimed to describe the anatomy of mandibular premolars with type IX canal configuration by using micro–computed tomography.

Methods

Mandibular premolars with radicular grooves (n = 105) were scanned, and 16 teeth with type IX configuration were selected. Number and location of canals, distances between anatomic landmarks, occurrence of apical delta, root canal fusion, and furcation canals, as well as 2-dimensional (area, perimeter, roundness, major and minor diameters) and 3-dimensional (volume, surface area, and structure model index) analysis were performed. Data were statistically compared by using analysis of variance and Kruskal-Wallis tests (α = 0.05).

Results

Overall, specimens had 1 root with a main canal that divided into mesiobuccal, distobuccal, and lingual canals at the furcation level. Mean length of the teeth was 22.9 ± 2.06 mm, and the configuration of the pulp chamber was mostly triangle-shaped. Mean distances from the furcation to the apex and cementoenamel junction were 9.14 ± 2.07 and 5.59 ± 2.19 mm, respectively. Apical delta, root canal fusion, and furcation canals were present in 4, 5, and 10 specimens, respectively. No statistical differences were found in the 2-dimensional and 3-dimensional analyses between root canals (P > .05).

Conclusions

Type IX configuration of the root canal system was found in 16 of 105 mandibular premolars with radicular grooves. Most of the specimens had a triangle-shaped pulp chamber. Within this anatomic configuration, complexities of the root canal systems such as the presence of furcation canals, fusion of canals, oval-shaped canals in the apical third, small orifices at the pulp chamber level, and apical delta were also observed.     

3-dimensional Analysis and Literature Review of the Root Canal Morphology and Physiological Foramen Geometry of 125 Mandibular Incisors by Means of Micro–Computed Tomography in a German Population

IntroductionThe aim of this study was to examine the root canal system morphology of mandibular incisors by means of micro–computed tomographic imaging.MethodsThe root canal configuration, physiological foramina, frequency of accessory and connecting canals, and the size and shape of the physiological foramina of 125 mandibular incisors were investigated by means of micro-CT and 3-dimensional imaging software. Root canal configuration of the coronal, middle, and apical thirds and the physiological foramina number are described by a 4-digit system code.ResultsThe most frequent root canal configurations were 1-1-1/1 (56%), 1-2-1/1 (17.6%), and 1-1-1/2 (10.4%); 9 additional different root canal configurations were observed. Single-rooted incisors showed in 80% 1, in 16% 2, and in 4% 3 physiological foramina, respectively. Accessory canals were found in only 13.6% of the investigated teeth. Connecting canals were observed in 36% of the sample, most often in root canal configurations 1-2-1/1 (12.8%) and 2-2-1/1 (7.2%). The morphologic dimensions of a total of 146 physiological foramina were measured. Their mean wide and narrow diameters were 0.24 mm (standard deviation = 0.1 mm) and 0.23 mm (standard deviation = 0.08 mm) when only 1 physiological foramen was present. The physiological foramen shapes observed were oval (56%), round (28.8%), and irregular (15.2%).ConclusionsThe study provides detailed information about the root canal morphology of anterior teeth in a German population. Within the limitations of the study, the authors recommend according to results obtained in this investigation a final physiological foramen preparation size of ISO 30-35; yet, such a decision should be carefully considered on an individual basis.     

Root Canal Morphology Evaluation of Central and Lateral Mandibular Incisors Using Cone-beam Computed Tomography in an Israeli Population

Introduction

Central and lateral mandibular incisors usually have 1 root canal. The purpose of this study was to investigate the prevalence of additional root canals in central and lateral mandibular incisors and to investigate the prevalence of oval and long oval canals in the cervical, middle, and apical thirds of cases with 1 root canal.

Effects of Root Canal Preparation on Apical Geometry Assessed by Micro–Computed Tomography

IntroductionPrevious micro–computed tomography analyses of root canal preparation provided data that were usually averaged over canal length. The aim of this study was to compare preparation effects on apical root canal geometry.MethodsSixty extracted maxillary molars (180 canals) used in prior studies were reevaluated for analyses of the apical 4 mm. Teeth were scanned by using micro–computed tomography before and after canal shaping with FlexMaster, GT-Rotary, Lightspeed, ProFile, ProTaper, instruments or nickel-titanium K-files for hand instrumentation. Apical preparation was to a size #40 in mesiobuccal and distobuccal and #45 in palatal canals except for GT (#20) and ProTaper (#25 in mesiobuccal and distobuccal and #30 in palatal canals, respectively). Data for canal volume changes, the structure model index (quantifying canal cross sections), and untreated surface area were contrasted by using analysis of variance and Scheffé tests.ResultsMean mesiobuccal, distobuccal, and palatal canal volumes increased after preparation (P < .05), but differences were noted for preparation techniques. GT rendered the smallest (0.20 ± 0.14 mm³); K-files and ProFile showed the largest volume increases (0.51 ± 0.20 mm³ and 0.45 ± 021 mm³, P < .05). All canals were slightly rounder in the apical 4 mm after preparation indicated by nonsignificant increases in structure model index. Untreated areas ranged from 4%–100% and were larger in mesiobuccal and palatal canals than in distobuccal ones. Preparation with GT left significantly larger untreated areas in all canal types (P < .05); among root canal types, distobuccal canals had the least amounts of untreated surface areas.ConclusionsApical canal geometry was affected differently by 6 preparation techniques; preparations with GT instruments to an apical size #20 left more canal surface untouched, which might affect the ability to disinfect root canals in maxillary molars.     

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

IntroductionThe purpose of this study was to comprehensively assess by micro–computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.MethodsOne hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.ResultsAll DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.ConclusionsThe novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.     

Detection of Various Anatomic Patterns of Root Canals in Mandibular Incisors Using Digital Periapical Radiography, 3 Cone-beam Computed Tomographic Scanners,and Micro–Computed Tomographic Imaging

Introduction

The purpose of this study was to compare the accuracy of digital periapical (PA) radiography and 3 cone-beam computed tomographic (CBCT) scanners in the identification of various internal anatomic patterns in mandibular incisors.

Methods

Forty mandibular incisors were scanned using micro–computed tomographic imaging as the gold standard to establish the internal anatomic pattern. The number of root canals and internal patterns were classified into type I (single canal, n = 12), type Ia (single oval canal, n = 12), and type III (2 canals, n = 16). The teeth were placed in a human mandible, and digital PA radiography and 3 CBCT scans (Kodak 9000 3D [Carestream Health, Rochester, NY], Veraviewepocs 3De [J Morita MFG Corp, Kyoto, Japan], NewTom 5G [QR Srl, Verona, Italy]) were performed. Two blinded examiners classified each tooth's anatomic pattern, which were then compared with the micro–computed tomographic determinations.

Results

Considering type I and type Ia, which both presented with 1 root canal, there was a high degree of accuracy for all methods used (P > .05). The same result was found for type III. When identifying the shape of single canals (type I), CBCT imaging was more accurate compared with PA radiography. Concerning oval canals (type Ia), there was a significant difference between PA radiography and NewTom CBCT (PA radiography = 44%, NewTom = 88%). However, there were no significant differences between the 3 CBCT units.

Conclusions

Double-exposure digital PA radiography for mandibular incisors is sufficient for the identification of the number of root canals. All CBCT devices showed improved accuracy in the identification of single root canal anatomy when a narrow canal was present. However, the identification of oval canals was improved only with the NewTom CBCT device.     

Anatomic Study of the Buccal Root with Furcation Groove and Associated Root Canal Shape in Maxillary First Premolars by Using Micro–Computed Tomography

IntroductionThe purpose of this study was to investigate the buccal root anatomy of bifurcated maxillary first premolars with furcation grooves and to determine the correlation between the groove depth and the buccal root canal shape by using micro–computed tomography.MethodsThirty-six bifurcated maxillary first premolars with furcation grooves were obtained from native Chinese individuals aged 17–25 years and scanned by micro–computed tomography. Basic parameters including the groove length, depth, and location were recorded. The wall thickness at different portions of the buccal roots was measured by using a customized application framework in MeVisLab software. The root canal shape was quantified by the form factor, and the correlation between the mean form factor and the maximum groove depth was analyzed.ResultsThe minimum wall thickness was less on the palatal aspect (<1 mm) than on the buccal aspect of the coronal two thirds of the buccal roots. The mean form factor value ranged from 0.72–0.91 and correlated negatively with the maximum groove depth (ρ² = ?0.641, P < .001).ConclusionsThe irregular wall thickness of buccal roots of bifurcated maxillary first premolars with furcation grooves and the related changes in the root canal shape should be considered during endodontic and prosthetic treatment.     

Analysis of the Width of Vertical Root Fracture in Endodontically Treated Teeth by 2 Micro–Computed Tomography Systems

Introduction

Early detection of vertical root fracture (VRF) is important for clinical endodontic practice. The purpose of this study was to measure the fracture width (distance between 2 sides of the fracture) of VRF teeth in vitro by using 2 micro–computed tomography (μ-CT) systems with different spatial resolution and voxel size.

Methods

Thirty-seven endodontically treated teeth with VRF were scanned by 80-μm pixel size μ-CT. Fifteen teeth with no obvious fracture line, blurred image, or fracture space less than 100 μm were scanned by 9-μm pixel size μ-CT.

Results

Presence of 2 VRF lines was more common in premolars (82%) than in molars (53%). In 7 premolars (32%) and 9 molars (60%), the VRF lines extended to within the apical 3 mm of the root. All fracture lines were detected by 9-μm pixel size μ-CT, but only 22 of 37 VRF teeth had vertical fracture identified by 80-μm μ-CT. From μ-CT examination, none of the fracture lines showed consistent and uniform fracture space. If 2 fracture lines were present, they were typically in opposite (not linear) directions. There was a significant correlation between 2 fracture lines or fracture lines extending within the 3 mm of the apex and fracture width greater than 100 μm.

Conclusions

Application of 9-μm μ-CT can be accurately used for early detection of VRF. Fracture characteristics (eg, number of fracture lines, extension of fracture line) may affect the fracture width. Appropriate use of μ-CT technology can be helpful for early diagnosis of VRF.     

An Anatomic Investigation of the Mandibular First Molar Using Micro–Computed Tomography

IntroductionThe mandibular first molar is the most frequently endodontically treated tooth and is extremely anatomically challenging. The purpose of this micro–computed tomographic evaluation was to quantitatively investigate the morphology of the mandibular first molar to improve both orthograde and retrograde treatment.MethodsTwenty-two mandibular first molars were scanned, reconstructed, and subjected to various linear measurements. The average, standard deviation, and standard error of the mean of each linear measurement were calculated, and the mode for each nominal data category was determined.Results/ConclusionsThe furcal aspect of the entire mesial root should be considered a “danger zone.” Mesial canals were found to be much more variable than distal canals in morphology, whereas the relative position of the orifices of the mesial canals was relatively consistent at 1.5 mm from the pulpal floor. Root-end resection of 3 mm would remove the majority of lateral canals and apical ramifications.     

Matching the Dimensions of Currently Available Instruments with the Apical Diameters of Mandibular Molar Mesial Root Canals Obtained by Micro–computed Tomography

IntroductionThis micro–computed tomographic study investigated the original anatomic diameters of the apical portion of mandibular molar mesial canals and matched them to the dimensions of instruments that are currently available and commonly used for apical preparation.MethodsOne hundred eight mandibular molar mesial roots with Vertucci type IV configuration were scanned by micro–computed tomographic imaging, and the largest anatomic diameter of both mesial canals at 1, 2, 3, and 4 mm short of the apical foramen was measured. Canal diameters were compared with the dimensions of 10 endodontic instruments for simulation of preparation 1 mm short of the apical foramen. Accordingly, the instruments with a diameter larger than the largest canal diameter were regarded as having the potential to prepare 100% of the canal walls at each specific point or over the 4-mm apical segment.ResultsAt 1 and 2 mm short of the apical foramen, a 45/.02 instrument had a larger diameter than the mesiobuccal canal diameter in 73% and 55% of the teeth, respectively. Corresponding figures for the mesiolingual canal were 65% and 55%. When the entire 4-mm apical segment was considered, a 40/.06 instrument had better results, being larger than the apical canal in about 20% of the specimens. Overall, 78% of the apical canals would not be completely prepared by any instrument. Based on the mean (median) anatomic diameters, the adequate instrument dimensions would be 40/.10 (40/.08) for mesiobuccal canals and 45/.08 (40/.09) for mesiolingual canals.ConclusionsThe dimensions of the available instruments are not compatible with complete apical preparation in the majority of cases. The ideal instrument size/taper to include all the canal walls in apical preparation is too large and may not be safe for clinical use.     

3-Dimensional Analysis and Systematic Review of Root Canal Morphology and Physiological Foramen Geometry of 109 Mandibular First Premolars by Micro–computed Tomography in a Mixed Swiss-German Population

IntroductionThe aim of this study was to systematically revise the root canal configuration (RCC) literature and to investigate the root canal morphology of mandibular first premolars (Ma1Ps) of 2 populations by means of micro–computed tomographic imaging.MethodsThis systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines including RCC randomized controlled trials and cross-sectional, cohort, comparative, validation, and evaluation studies. Furthermore, the RCC, physiological foramina, the frequency of accessory and connecting canals, and the physiological foramina morphology of 109 Ma1Ps were investigated by means of micro–computed tomographic imaging. The RCC results are described using a 4-digit system code.ResultsThe most frequent RCCs observed were 1-1-1/1 (70.6%), 1-1-2/2 (7.3%), 1-2-2/2 (7.3%), and 1-2-1/1 (5.5%). Accessory canals were observed in 31.2%. Connecting canals were observed in 1-1-2/2 (4.6%), 1-2-2/2 (4.6%), 1-1-2/1 (1.8%), and 1-2-1/1 (1.8%) RCCs. Accessory foramina were observed in 52.3%; 30.3% of the Ma1Ps had 1 accessory foramen, 12.8% had 2, 2.8% had 3, 2.8% had 4, 2.8% had 5, and 0.92% had 6. The narrow and wide diameter mean of 136 physiological foramina was 0.28 mm (±0.9) and 0.37 mm (±0.11) when only 1 physiological foramen was present.ConclusionsThis study provides detailed root canal morphology of Ma1Ps in a Swiss-German population. Within the limitations of the study, the authors recommend a final physiological foramen preparation size of instrument tip sizes 30–40; yet, such a decision should be carefully considered on an individual basis.     

Vertucci’s Root Canal Configuration of 14,413 Mandibular Anterior Teeth in a Brazilian Population: A Prevalence Study Using Cone-beam Computed Tomography

IntroductionThis cone-beam computed tomographic (CBCT)-based study evaluated the root canal configurations of mandibular anterior teeth in a large Brazilian population, along with the influence of sex and the frequency of symmetry between the contralateral teeth.MethodsOverall, 2543 CBCT scans, including those of 4773 lower central incisors (LCIs), 4835 lower lateral incisors (LLIs), and 4805 lower canines (LCs), were analyzed. The scans were obtained from a private radiologic clinic using the PreXion 3D device (Yoshida Dental Mfg Co, Ltd, Tokyo, Japan) with a 0.14-mm voxel size; exposure parameters of 90 kV, 4 mA, and 19 seconds; and a field of view of 80 × 80 mm. Root canal anatomy was analyzed according to the Vertucci classification. Sex influence on the canal distribution and symmetry between the contralateral teeth were analyzed. The data were analyzed statistically and were considered significant when P < .05.ResultsAll LCIs and LLIs had 1 root, whereas 2.4% of LCs had 2 roots. Two root canals were observed in approximately 20% of LCIs and LLIs and in approximately 11% of LCs. The most common configuration was type I followed by type III. Bilateral symmetry occurred in a majority of the individuals (ie, 91% in LCIs, 87% in LLIs, and 87% in LCs). No sex influence was noted with LLIs and LCs (P > .05). However, LCIs showed a higher prevalence of 2 canals in men (P < .05).ConclusionsThe prevalence of 2 root canals in the mandibular anterior teeth in Brazilians was approximately 20% for central and lateral incisors and 10% for canines.     

Root Canal Preparation of Mandibular Molars with 3 Nickel-Titanium Rotary Instruments: A Micro–Computed Tomographic Study

Introduction

The aim of this study was to describe the canal shaping properties of ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Universal (PTU; Dentsply Tulsa Dental Specialties, Johnson City, TN), and WaveOne (Dentsply Maillefer) nickel-titanium instruments in mandibular first molars by using micro–computed tomographic (micro-CT) scanning.

Methods

A total of 36 maxillary first molars with 2 separate mesial canals and 1 distal canal were selected and scanned preoperatively and postoperatively by using micro-CT scanning with a voxel size of 30 μm. Canals were prepared with PTU, PTN, and WaveOne systems under hypochlorite irrigation. The volume of the untreated canal; the volume of dentin removed after preparation; the amount of the uninstrumented area; and the transportation to the coronal, middle, and apical thirds of canals were measured. The preparation time and instrument failure were also recorded.

Results

Instrumentation of canals increased their volume and surface area. The distal canals had a significantly higher proportion of unprepared surfaces than mesial canals (P < .05). The PTN system produced less transportation than the WaveOne and PTU systems in the apical third of the mesial canals (P < .05). There was no significant difference on apical transportation in distal canals among the 3 instrument systems. Instrumentation with WaveOne was significantly faster than with the other 2 instruments (P < .05).

Conclusions

The PTN, PTU, and WaveOne instruments shaped root canals in mandibular first molars in vitro without significant shaping errors. The curved canals prepared using PTN had less apical transportation than the canals prepared using WaveOne and PTU.     

Cone-beam Computed Tomographic–based Assessment of Filled C-shaped Canals: Artifact Expression of Cone-beam Computed Tomography as Opposed to Micro–computed Tomography and Nano–computed Tomography

IntroductionThe present study investigated the assessment of root canal fillings in a series of cone-beam computed tomographic (CBCT) images obtained from endodontically treated mandibular molars with C-shaped canals.MethodsClinically comparable high (HR) and normal (NR) resolution protocols were selected in 3D Accuitomo 170 (J Morita Corporation, Kyoto, Japan), NewTom VGi evo (Cefla QR Verona, Verona, Italy), ProMax 3D Max (Pro; Planmeca, Helsinki, Finland), and Pax-i3D Green Premium (Pax; Vatech, Gyeonggi, South Korea). Micro–computed tomographic and nano–computed tomographic images were considered as the reference standard. The set of images was evaluated according to beam hardening artifact patterns (dark streaks, hypodense areas, and volume distortion).ResultsRegarding dark streaks, the Fleiss kappa test showed that Pax HR and NR and Pro HR images showed the highest artifact expression. Hypodense areas were detected in 100% and 99.1% of the images obtained using Pax HR and NR, respectively. Kappa tests showed highest distortion for images derived from the Pax and Pro CBCT devices. Root canal filling assessment was considered appropriate in 100% of the 3D Accuitomo 170 HR, NewTom VGi evo NR, micro–computed tomographic, and nano–computed tomographic images.ConclusionsThe present study confirms the large variability in CBCT-derived artifact expression. Highlighting the increased artifact expression for particular CBCT systems, it may be concluded that for diagnosis of endodontically filled molars with C-shaped canals, the choice of CBCT unit and protocol is essential.     

Root Canal Morphology of 116 Maxillary Second Premolars by Micro–Computed Tomography in a Mixed Swiss-German Population with Systematic Review

IntroductionThe aim of this investigation was to examine the root canal system morphology of maxillary second premolars (Mx2Ps) of a Swiss-German population by means of micro–computed tomography and provide systematic review of the root canal configuration (RCC) literature of Mx2Ps.MethodsThe RCC, main foramina as well as accessory canals and foramina frequency of 116 Mx2Ps, were investigated by means of micro–computed tomography and 3-dimensional software imaging. The RCC from the coronal to apical thirds of the root as well as the main foramina number were described by using a four-digit system code. The literature review follows the PRISMA guideline analyzing randomized controlled trials and cross-sectional, cohort, comparative, validation, and evaluation studies on RCC in Embase, grey literature, PubMed, and Scopus.ResultsMost frequently observed RCCs of Mx2Ps were 1-1-1/1 (35.3%), 1-1-1/2 (21.6%), and 2-1-1/1 (14.7%). Another 11 less frequent RCCs were observed. All Mx2Ps had 1 root. One main foramen was observed in 59.5% and two in 37.9%. Accessory foramina were observed in 46.6%. Thirty-one percent of the Mx2Ps showed accessory canals. One connecting canal between the buccal and palatal was observed in 12.1%.ConclusionsDetailed RCC information of Mx2Ps in a Swiss-German population and the results of a systematic literature review of different populations and research methods used to investigate root canal morphology and configuration of Mx2Ps are given. Within the limitations of the study, a high RCC, connecting and accessory canals variability occur in maxillary second premolars.     

Comparison of Alternative Image Reformatting Techniques in Micro–Computed Tomography and Tooth Clearing for Detailed Canal Morphology

Introduction

Micro–computed tomography (MCT) shows detailed root canal morphology that is not seen with traditional tooth clearing. However, alternative image reformatting techniques in MCT involving 2-dimensional (2D) minimum intensity projection (MinIP) and 3-dimensional (3D) volume-rendering reconstruction have not been directly compared with clearing. The aim was to compare alternative image reformatting techniques in MCT with tooth clearing on the mesiobuccal (MB) root of maxillary first molars.

Methods

Eighteen maxillary first molar MB roots were scanned, and 2D MinIP and 3D volume-rendered images were reconstructed. Subsequently, the same MB roots were processed by traditional tooth clearing. Images from 2D, 3D, 2D + 3D, and clearing techniques were assessed by 4 endodontists to classify canal configuration and to identify fine anatomic structures such as accessory canals, intercanal communications, and loops.

Results

All image reformatting techniques in MCT showed detailed configurations and numerous fine structures, such that none were classified as simple type I or II canals; several were classified as types III and IV according to Weine classification or types IV, V, and VI according to Vertucci; and most were nonclassifiable because of their complexity. The clearing images showed less detail, few fine structures, and numerous type I canals. Classification of canal configuration was in 100% intraobserver agreement for all 18 roots visualized by any of the image reformatting techniques in MCT but for only 4 roots (22.2%) classified according to Weine and 6 (33.3%) classified according to Vertucci, when using the clearing technique.

Conclusions

The combination of 2D MinIP and 3D volume-rendered images showed the most detailed canal morphology and fine anatomic structures.     

Rotary Nickel-Titanium GT and ProTaper Files for Root Canal Shaping by Novice Operators: A Radiographic and Micro–Computed Tomography Evaluation

IntroductionThe purpose of this study was to assess canal preparation outcomes in vitro by novice clinicians after standardized teaching sessions.MethodsAll students received a training session. In experiment 1, twenty canals of mandibular molars were prepared with GT and ProTaper rotaries by 10 students. Standardized radiographs were exposed before and after canal preparation, and canal curvature was measured; canals were assessed for patency and preparation time. In experiment 2, mandibular molars (20 canals) were submitted to microcomputed tomography before and after canal preparation with ProTaper and GT rotaries by 2 dental students. Canals were metrically assessed for changes (volume, surface, cross-sectional shape, transportation) during canal preparation by using software.ResultsIn experiment 1, canal curvature decreased by 7.6° and 7.8° for GT and ProTaper preparations; there were no broken instruments, and 2 canals lost patency. The time for GT preparation was longer than for ProTaper (29.7 ± 6.8 vs 19.4 ± 8.1 minutes, P <.05). In experiment 2, canal volumes and surface areas increased (P < .001), and prepared canals were rounder in cross-section and more tapered. Mean canal transportation ranged between 0.14 ± 0.05 mm and 0.23 ± 0.09 mm for apical and coronal canal thirds. There were no significant differences between the instruments or the operators regarding center of mass shifts; qualitative and quantitative data for canal transportation were similar to earlier studies with experienced operators.ConclusionsBoth rotary instruments performed adequately with inexperienced operators who received a brief structured training session.     

Comparison of the Accuracy of 3-dimensional Cone-beam Computed Tomography and Micro–Computed Tomography Reconstructions by Using Different Voxel Sizes

Introduction

Cone-beam computed tomography (CBCT) data are, in principle, metrically exact. However, clinicians need to consider the precision of measurements of dental morphology as well as other hard tissue structures. CBCT spatial resolution, and thus image reconstruction quality, is restricted by the acquisition voxel size. The aim of this study was to assess geometric discrepancies among 3-dimensional CBCT reconstructions relative to the micro-CT reference.

Methods

A total of 37 permanent teeth from 9 mandibles were scanned with CBCT 9500 and 9000 3D and micro-CT. After semiautomatic segmentation, reconstructions were obtained from CBCT acquisitions (voxel sizes 76, 200, and 300 μm) and from micro-CT (voxel size 41 μm). All reconstructions were positioned in the same plane by image registration. The topography of the geometric discrepancies was displayed by using a color map allowing the maximum differences to be located.

Results

The maximum differences were mainly found at the cervical margins and on the cusp tips or incisal edges. Geometric reconstruction discrepancies were significant at 300-μm resolution (P = .01, Wilcoxon test).

Conclusions

To study hard tissue morphology, CBCT acquisitions require voxel sizes smaller than 300 μm. This experimental study will have to be complemented by studies in vivo that consider the conditions of clinical practice.     

Adjunctive Steps for the Removal of Hard Tissue Debris from the Anatomic Complexities of the Mesial Root Canal System of Mandibular Molars: A Micro–Computed Tomographic Study

IntroductionThis in vitro study sought to compare the efficacy of a sonic irrigant activation device with ultrasonic activation and needle irrigation in removing hard tissue debris (HTD) from anatomic complexities of the root canal system.MethodsTwenty-seven mesial roots of extracted human mandibular molars with 2 canals connected by an isthmus were selected based on micro–computed tomography scans (12-μm voxel size). The mesial canals were mechanically prepared to ProTaper Next X3 (Dentsply Maillefer, Ballaigues, Switzerland) and anatomically distributed into 3 groups (n = 9) according to the final irrigation protocol: sonically activated irrigation (SAI) using the EDDY system (VDW GbmH, Munich, Germany) for 3 × 20 seconds, ultrasonically activated irrigation (UAI) using a size 20 Irrisafe tip (Satelec Acteon, Mérignac, France) for 3 × 20 seconds, and conventional irrigation using a 30-G needle adapted to a syringe. Micro–computed tomographic scans were taken after instrumentation and after supplementary activation of the irrigant. After reconstruction and coregistration, the volume filled with HTD before and after irrigant activation was calculated, and the mean percentage of HTD reduction after final irrigation was compared within and among groups using the paired sample t test and 1-way analysis of variance post hoc Tukey test, respectively (α = 5%).ResultsA significant reduction in the volume filled with HTD after irrigant activation was observed in all groups (P < .05). The percentage reduction of HTD in the UAI group (66.8%) was significantly higher than that in the SAI group (36.4%) (P < .05), whereas the conventional irrigation group result (43.7%) did not differ statistically from the UAI or SAI groups (P > .05).ConclusionsAll tested supplementary irrigation steps significantly reduced the amount of debris created during root canal preparation. Ultrasonic activation resulted in the highest mean debris reduction.