Distal Canals In Mandibular Molars Research Articles

Multimethod analysis of three rotary instruments produced by electric discharge machining technology.

This study aimed to compare three rotary instruments produced by the EDM process with the heat-treated ProTaper Gold system regarding design, metallurgy, mechanical properties and shaping ability. HyFlex EDM (25/~), Neoniti (25/.06), EDMax (25/.06) and ProTaper Gold (25/.08v) instruments (n = 58 per group) were compared regarding design, metallurgy and mechanical performance. Unprepared canal areas were calculated for each system after preparation of mesiobuccal, mesiolingual and distal canals of mandibular molars (15 canals per group) using micro-CT technology. Statistical analyses were performed using One-way anova post-hoc Tukey and Kruskal-Wallis post-hoc Dunn's tests (α = 5%). All instruments had asymmetrical blades, no radial lands, no major defects and almost equiatomic nickel/titanium ratios, but different cross-section designs, tip geometries and surface appearances. Although instruments had distinct transformation temperature curves, they showed crystallographic martensitic arrangement at 21°C and mixed austenite plus R-phase at body temperature. Neoniti and HyFlex EDM showed similar results in all mechanical tests (p > .05), while EDMax and ProTaper Gold had similar time to fracture (p = .841), maximum bending load (p = .729), and cutting ability (p = .985). ProTaper Gold showed the highest torque to failure (p < .001) and HyFlex EDM had the lowest buckling resistance (p < .001). Mean percentages of unprepared canal areas ranged from 20.4% to 25.7% in the mesial canals, and from 20.8% to 26.2% in the distal canal, with no statistical differences among systems (p > .05). Instruments' geometry and phase transformation temperatures influenced the results of the mechanical tests, but not their shaping ability.

Shaping ability of non-adaptive and adaptive core nickel-titanium single-file systems with supplementary file in ribbon-shaped canals analysed by micro-computed tomography.

This study compared shaping ability between two single-file systems and before/after using supplementary file in untouched area, volume of removed dentin, maximum cut depth (the highest cut depth by main file) and remaining thinnest dentin (the thinnest root dentin after preparation). Ribbon-shaped distal canals of mandibular molars were prepared with non-adaptive core (WaveOne Gold) or adaptive core (XP-endo Shaper) files (n=15/group) and additionally prepared with a supplementary file (XP-endo Finisher), and the shaping ability was investigated using micro-computed tomography. XP-endo Shaper group demonstrated significantly less overall untouched area than WaveOne Gold group (38.21±6.98% vs. 47.68±9.16%) (p<0.05). No significant difference was detected between XP-endo Shaper and WaveOne Gold groups in volume of removed dentin (1.85±0.53 vs. 1.66±0.33mm3 ), maximum cut depth (0.10-0.28 vs. 0.10-0.29mm) and remaining thinnest dentin (0.66-0.80 vs. 0.78-0.88mm). Supplementary XP-endo Finisher treatment significantly decreased untouched area (11%-23% reduction) (p<0.05) with minimally cut root dentin (0.01-0.02mm).

The shaping ability of WaveOne Gold, TRUShape and XP-endo Shaper systems in oval-shaped distal canals of mandibular molars: A microcomputed tomographic analysis.

To compare the shaping ability of a heat-treated centric reciprocating file system (WaveOne Gold), a heat-treated eccentric rotary multifile system (TRUShape 3D Conforming Files), and a heat-treated expandable one-file rotary system (XP-endo Shaper) extending its activation time, in preparing oval-shaped root canals in extracted mandibular molars by means of microcomputed tomography (micro-CT) analysis. Thirty moderately curved oval-shaped distal roots of mandibular molars were selected. The normality of canal length, curvature angle, volume, surface area, structure model index, and aspect ratio were confirmed. The samples were randomly divided into three groups (n=10). Micro-CT scans were taken before and after canals were instrumented using WaveOne Gold (size 35, .06 taper), or TRUShape (size 30, .06v taper), both following the manufacturer's instructions, or XP-endo Shaper following a new protocol with extended activation time. The mechanical preparation time for each sample was recorded. Pre- and postoperative images were analysed for the percentage of unprepared canal areas and the percentage of removed dentine. Data were compared between groups using the statistical analyses one-way ANOVA and Tukey tests (p<.05). The percentage of unprepared canal areas was significantly higher with WaveOne Gold (% 11.5±4.0) and TRUShape (% 12.4±5.8) compared with XP-endo Shaper (% 5.2±2.6) (p<.05). XP-endo Shaper removed significantly more dentine (3.3±1.5mm3 ) than WaveOne Gold (1.8±0.8mm3 ) and TRUShape (1.9±0.8mm3 ) (p<.05). No significant differences were seen for mechanical preparation time between WaveOne Gold (79±31s), TRUShape (104±41s) and XP-endo Shaper (71±23s) (p>.05). The comparison of three recognized root canal filing systems has shown that with similar preparation times, the XP-endo Shaper removed more dentine (mm3 ) leaving less unprepared canal wall area (%) than WaveOne Gold and TRUShape when preparing oval-shaped root canals of extracted mandibular molars.

Effect of obturation technique using a new bioceramic sealer on the presence of voids in flattened root canals.

The aim of this study was to evaluate the filling ability of a new ready-to-use calcium silicate-based sealer using thermoplastic or single-cone technique in flattened root canals. Twenty-four flattened distal canals of mandibular molars with a buccolingual diameter 4 or more times larger than the mesiodistal diameter were selected. The root canals were prepared and filled (n = 12), according to the following techniques: thermoplastic or single-cone technique using Bio-C Sealer. The teeth were scanned using Skycan 1176 micro-computed tomography (micro-CT) - voxel size 8.74 µm, before and after filling the root canal. The percentage of voids in the filled root canals was evaluated, and the data were statistically analyzed using the unpaired t-test (α = 0.05). The root canals filled using the thermoplastic technique created a smaller percentage of voids in the cervical/middle thirds than those filled using the single-cone technique (p < 0.05). There was no difference in the percentage of voids using either technique in the apical third (p > 0.05). The flattened root canals in the cervical/middle thirds were better filled using the ready-to-use calcium silicate-based sealer associated to the thermoplastic technique, compared with the single-cone technique. In the apical third, the techniques showed similar filling ability.

Glide Path with Reciprocating Driven Pathfinding Instrument: Performance and Fracture Rate

IntroductionThis study assessed the number of mesial and distal canals of mandibular molars in which the R-Pilot pathfinding reciprocating instrument reached the working length (WL) during macro glide path procedure. Fracture and deformation rates were also evaluated. MethodsOne hundred fifty-six root canals of 52 teeth were scouted to the length of the apical foramen. Then the R-Pilot instrument was positioned at the canal orifice and activated. The instrument was moved by using a pecking motion and light apical pressure. This procedure was repeated in an attempt to reach the WL. The type of fracture and/or instrument deformation was assessed by scanning electron microscopy, whereas the roots with fractured instruments were scanned through micro-computed tomography. The percentage frequency distribution of fractures, deformations, and root canals in which the R-Pilot reached the WL were recorded and statistically compared by using the Pearson’s χ2 test with α = 5%. ResultsR-Pilot instruments reached the WL in 139 root canals (89.10%), and χ2 test showed a significant difference between the observed frequencies and the expected frequencies (χ2 = 95.41, P = .000). The observed frequencies of fractures (2.56%) and deformations (1.92%) were also significantly lower than the expected (fracture: χ2 = 140.41, P = .000; deformation: χ2 = 144.23, P = .000). Fractures occurred mostly at the apical and curved parts of the root canals. ConclusionsR-Pilot reached the WL in 89.10% of the root canals of mandibular molars with fracture and deformation rates of 2.56% and 1.92%, respectively.

New Ultrasonic Tip Decreases Uninstrumented Surface and Debris in Flattened Canals: A Micro–computed Tomographic Study

IntroductionThe preparation of flattened root canals using reciprocating or rotary nickel-titanium instruments associated with the Flatsonic ultrasonic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was evaluated by micro–computed tomographic imaging. MethodsTwenty-four flattened distal canals of mandibular molars with a buccolingual diameter 4 or more times larger than the mesiodistal diameter were selected. The root canals were randomly divided into 2 experimental groups for preparation: a Reciproc Blue (RB; VDW GmbH, Munich, Germany) 40/.06 file in reciprocating motion or ProDesign Logic (PDL; Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) 40/.01 and 40/.05 files in rotary motion (n = 12). A complementary preparation was performed with the Flatsonic ultrasonic tip for both preparations. Micro–computed tomographic scanning at a resolution of 8.74 μm was performed before and after preparation with the nickel-titanium instruments and after the use of the Flatsonic tip. The percentages of increase in volume, debris, and uninstrumented surface were analyzed. The data obtained were submitted to the paired and unpaired t test, analysis of variance, and the Tukey test (α = 5%). ResultsThe percentage increase in volume, debris, and uninstrumented surface was similar between RB and PDL in the entire root canal (P > .05). The PDL promoted a lower percentage of debris in the cervical third and a lower percentage of increase in volume in the apical third in comparison with RB (P < .05). The Flatsonic decreased debris and uninstrumented surface after PDL preparation in all thirds (P < .05). After preparation with RB, the Flatsonic decreases the debris in the cervical third and the uninstrumented surface in the cervical and middle thirds (P < .05). ConclusionsThe preparation of flattened root canals using RB or PDL produced a high percentage of debris and uninstrumented surface. The Flatsonic ultrasonic tip significantly improved the cleaning of flattened root canals.

Impacts of 3 Different Endodontic Access Cavity Designs on Dentin Removal and Point of Entry in 3-dimensional Digital Models

IntroductionThe purpose of this study was to evaluate the tooth structure theoretically required to be removed in the coronal and cervical regions to accomplish 3 different endodontic access preparations in a novel digital model. The deviation of the center of access cavity from the central fossa will also be measured and compared among the 3 endodontic cavity designs, which in turn may serve as suggested points of entry for different access openings. MethodsTwenty-one maxillary molars and 15 mandibular molars were selected and 3-dimensionally imaged with cone-beam computed tomographic imaging. Three-dimensional (3D) volume reconstructions were made and converted into stereolithography files. Digital access cavity preparation was performed on each 3D reconstruction model with the 3 most commonly used endodontic access preparations: minimally invasive (MI), modified straight-line (MS), and traditional straight-line (TS) techniques. After the access cavity outlines were determined, digital sectioning of each reconstructed 3D tooth model was performed orthogonal to the long axis of the tooth at 3 levels: (1) passing through the central fossa, (2) 1.5 mm apical to the central fossa, and (3) 2 mm apical to the cementoenamel junction. The linear distance from the centroid of the access opening to the central fossa was measured to calculate the point of entry, and the amount of tooth structure removal at the pericervical area was measured to calculate the theoretically minimum amount of linear dentin removal required. Two-way repeated measures analysis of variance was performed for the interactions between different access designs and the amount of cervical dentin removal. Other data were statistically analyzed with 1-way repeated measures analysis of variance. The Tukey post hoc test was used for multiple comparisons. Significance was set at .05. ResultsThe amount of deviation of the center of the access cavity from the central fossa in all test groups was less than 1 mm. The dimensions of access openings differed significantly among the 3 access forms (TS > MS > MI, P < .0001). The amount of required cervical dentin removal was the greatest in the TS method followed by the MS and MI methods (P < .0001). ConclusionsThe central fossa could serve as good starting points in all access preparations in both maxillary and mandibular molars. Dentin removal in the coronal and cervical regions was the greatest in the TS design followed by the MS and MI designs. When comparing different canals in the same access form, less cervical dentin was sacrificed in the palatal canals of maxillary molars and the distal canals of mandibular molars.

Prevalence of middle mesial and middle distal canals in mandibular molars in an Egyptian subpopulation using micro-computed tomography.

To study the prevalence of middle mesial and middle distal canals in permanent mandibular molars in Egyptian subpopulation using micro-computed tomography. Two hundred and forty extracted mandibular permanent molars of Egyptian patients were scanned using micro-computed tomography, then the images were reconstructed to allow for the detection of the middle mesial (MM) and middle distal (MD) canals of the molars examined. The path of each extra canal was studied to determine the configuration of each canal. Data were analyzed statistically using the Chi-square test with a level of significance set at P< 0.05. The evaluation of three-dimensional (3D) images of this study showed that no significant difference was found between the percentage of MM (27.5%) and MD canals (22.5%) (P = 0.2064); however, there was a significant difference between the percentage of teeth having both extra canals (10%) and teeth having only one of these canals (P < 0.05). The confluent configuration (71%) was significantly higher than the other configurations (P < 0.05). A higher percentage of MM canal was detected followed by the MD canal. The least significant was both canals occurring within the same molar. The percentage of the confluent configuration was the highest. The apt knowledge of the variations of the root canal system anatomy and the respect of the discrepancies associated with diverse demographic areas will ensure the proper management of each tooth with endodontic involvement and its long-term success.

Removal of calcifications from distal canals of mandibular molars by a non-instrumentational cleaning system: A micro-CT study.

Pulpal calcifications can present problems in endodontic treatment. This micro-CT study examined the removal of calcifications by a multisonic cleaning system in uninstrumented mandibular molar distal canals. The teeth were accessed and distal canals located and their patency ensured. Micro-CT images were obtained, and 15 teeth with distal canal calcifications were selected. The volume of distal canals and calcifications were calculated from the micro-CT images before and after cleaning with the GentleWave system. Calcifications were observed in all thirds of the canals. Attached and free calcification were detected. Root canal volumes were slightly increased after GentleWave treatment, whereas the calcifications were completely or partially removed in all canals. Mean reduction percentage of calcification was 86.4±3.9%, in individual canals from 60% to 100%. Calcifications in the distal canals of mandibular molars could be partially or completely removed by the multisonic cleaning system without instrumentation.

Evaluation of Root Canal Filling with a Bioceramic Sealer Using Micro-Computed Tomography: A Pilot Study

This pilot study aims to define a protocol for optimizing the micro-computed tomography (micro-CT) settings to evaluate in the future research the root canal filling in oval shaped canals. Thirty distal canals of mandibular molars were used. After preparation of the canals, the roots were randomly divided into five groups. The canals were filled with two types of sealers (Endosequence BC Sealer or AH Plus) and two types of gutta percha (Protaper Next cones and Endosequence BC cones), using thermal obturation in comparison with a single cone obturation technique. Each specimen was scanned three times using a micro-CT device at a resolution of 30,1 μm. The first scan was done for selecting the specimen according the inclusion criteria, the second one post-instrumentation and the last micro-CT scan after obturation the specimens. For the present study, the images were only evaluated with qualitative criteria and the settings for acquisition, reconstruction and analysis of micro-CT images were tested.

Comparative evaluation of instrumentation timing and cleaning efficacy in extracted primary molars using manual and NiTi rotary technique – Invitro study

AimTo compare the timing of instrumentation and cleaning efficacy between manual K files and NiTi rotary files in extracted primary molars. Study designin-vitro study was conducted in 90 root canals of extracted primary molars which were subdivided in three groups viz. Control (No instrumentation), Manual (K files), Rotary (ProFiles) with 30 canals in each group. Mesiobuccal (MB) and Mesiolingual (ML) canals of mandibular molars, and MB and Distobuccal (DB) canals of maxillary molars were included in the test group whereas Distal canals in mandibular molars and Palatal canals in maxillary molars were included in the control group. MethodTeeth were mounted and canals were injected with India ink to stain the canal walls. Canal preparation was done as per the group. After instrumentation, teeth were demounted, decalcified and cleared to make them transparent for scoring according to the extent of removal of India ink. Timing of instrumentation and cleaning efficacy of canals in coronal, middle and apical thirds were assessed in each sample. ResultsMean timing of instrumentation in rotary group was 3.54 ± 1.14 min and 4.32 ± 1.04 min in manual group. Mean cleaning efficacy scores in manual and rotary groups were 2.03 and 1.66 in coronal third, 1.08 and 1.18 in middle third and 0.67 and 1.08 in apical third respectively. Inter-group comparisons showed no statistically significant difference in cleaning efficacy among test groups in all thirds of root canals. ConclusionNiTi rotary technique has comparable cleaning efficacy, with significantly less timing of instrumentation compared to manual K-files.

Evaluation of various filling techniques in distal canals of mandibular molars instrumented with different single-file nickel-titanium systems.

The aim of this study was to evaluate the quality of various filling techniques in distal canals of mandibular molars instrumented with different single-file nickel-titanium (NiTi) systems. A total of 150 distal roots of mandibular molar teeth were randomly assigned into three main groups and instrumented by using Reciproc (VDW, Munich, Germany), WaveOne (Dentsply Tulsa, Tulsa, OK, USA), or One Shape (MicroMega, Besancon, France) NiTi file systems. The roots were then treated using one of five filling techniques: (1) Matched-single-cone, (2) cold lateral compaction with matched gutta-percha (GP) cone, (3) Thermafil filling, (4) System B/Obtura II, and (5) lateral compaction with standardized GP cones. The roots were then sectioned at three levels (coronal, middle, and apical). Photographs were acquired under a stereomicroscope, and the percentage of GP-filled areas (PGFAs), percentage of sealer-filled areas (PSFAs), and voids were measured using the ImageJ software. Comparisons between groups were applied using Student's t-test or one-way ANOVA for normally distributed data. The Mann-Whitney U-test or Kruskal-Wallis test was used when variables were not normally distributed. Canals filled with the System B/Obtura showed the highest PGFA and lowest PSFA, whereas those filled with matched-single-cone showed the highest PSFA and lowest PGFA (P < 0.05). The cold lateral compaction with matched GP cone group, lateral compaction group, and Thermafil filling group showed no statistically significant differences in PSFA and PGFA (P > 0.05). System B/Obtura technique appears to be the best technique to properly fill root canals, whereas the matched-single-cone technique in oval-shaped distal canals of mandibular molars was inadequate.

Radiographic Study of the Problems and Failures of Endodontic Treatment

The aim of the present study was to determine radiographically the different reasons and problems of endodontic treatment failure. The periapical radiographs of 100 patients with one hundred teeth (130 root canals) were examined to identify the problems and failures of endodontic treatment. The various reasons of failure that is under filling, poor filling, over filling and presence of procedural errors were recorded for each root filled canal. Chi square test was used to determine statistical significance between different parameters. Under fillings were found in 46.9% of the root canals. The percentage of poor fillings and over fillings were 28.5% and 13% respectively. Separated instruments and strip perforations were present in 4% and 3% of the teeth, while the presence of furcal perforation and coronal leakage was observed in one case each (1%).Endodontic problems and failures were most commonly observed in molars compare to anterior and premolar teeth. Mesiobuccal, mesiolingual and distobuccal root canals were the most frequently canals with endodontic problems and failures. The relationship between mesiobuccal, mesiolingual and distal canals in mandibular molars and mesiobuccal, distobuccal and palatal canals in maxillary molars in terms of endodontic failures were statistically significant by chi square analysis (P≤0.05). The most common cause of endodontic treatment failure was under filling followed by poor filling and over filling and first molar was the most frequently involved tooth with endodontic problems and failures.