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Because active bacteria present a higher abundance of ribosomal RNA (rRNA) than DNA (rRNA gene), the rRNA/DNA ratio of next-generation sequencing (NGS) data was measured to search for active bacteria in endodontic infections.Paired complementary DNA and DNA samples from 5 root canals of teeth with apical periodontitis were subjected to polymerase chain reaction with bar-coded primers amplifying the 16S rRNA gene hypervariable regions V4-V5. High-throughput sequencing was performed using MiSeq (Illumina, San Deigo, CA), and data were analyzed using Quantitative Insights Into Microbial Ecology and Human Oral Microbiome Database. Statistical analysis was performed for relative abundance of bacteria in the DNA- and rRNA-based NGS data using the Mann-Whitney test, whereas differences in the diversity and richness indexes were assessed using a nonparametric 2-sample t test (P.05). For bacterial taxa detected in both approaches, the rRNA/DNA ratios were calculated by dividing the average abundance of individual species in the respective analysis.Although no significant difference was found in the indexes of bacterial richness and diversity, the relative abundance of bacterial members varied in both analyses. Comparing rRNA with DNA data, there was a significant decrease in the relative abundance of Firmicutes (P.05). The bacterial taxa Bacteroidales [G-2] bacterium HMT 274, Porphyromonas endodontalis, Tannerella forsythia, Alloprevotella tannerae, Prevotella intermedia, Pseudoramibacter alactolyticus, Olsenella sp. HMT 809, Olsenella sp. HMT 939, Olsenella uli, and Fusobacterium nucleatum subsp. animalis were both dominant (DNA ≥ 1%) and active (rRNA/DNA ≥ 1).The integrated DNA- and rRNA-based NGS strategy was particularly important to disclose the activity of as-yet-uncultivated or difficult-to-culture bacteria in endodontic infections.

Transforming growth factor beta 1 (TGF-β1) is a key morphogen in regenerative endodontics; yet, its location within the hard tissue phase of dentin and its availability in mature roots have not been fully elucidated.Young mature (n = 8) and immature (n = 11) roots from sound premolars were obtained from 13 orthodontic patients aged 17 ± 1 and 12 ± 1 years, respectively. Roots were cleaned of organic remnants in 5% sodium hypochlorite. The width of the minor foramen was measured using a digital microscope. TGF-β1 distribution was assessed in 3 roots per group by immunostaining combined with confocal laser scanning microscopy. The root dentin of the remaining 13 roots was powdered and decalcified in 17% EDTA to determine the overall levels of hard tissue-embedded TGF-β1 by enzyme-linked immunosorbent assay. Data were compared between groups using the Student t test (α = .05).The minor foramen was 168 ± 49 μm versus 557 ± 295 μm in mature compared with immature roots (P.05). TGF-β1 was highly stainable toward the pulp space in both groups. It was clearly associated with peritubular dentin and apparently absent in nontubular outer dentin. TGF-β1 content was 115 ± 31 pg and 74 ± 35 pg/100 mg mature versus immature root dentin, respectively (P.05).TGF-β1 is deposited into the peritubular dentin. It should be possible to release this molecule in regenerative endodontic procedures from young mature roots as well as immature roots.

Introduction A clinically useful all-in-one endodontic irrigant with combined proteolytic and decalcifying properties is still elusive. In this study, the chemical effects of dissolving the tetrasodium salts of 1-hydroxyethane 1,1-diphosphonic acid (Na 4 HEDP) or Na 4 EDTA directly in sodium hypochlorite (NaOCl) irrigants in polypropylene syringes were assessed during the course of 1 hour. Methods The solubility of the salts in water was determined. Their compatibility with 1% and 5% NaOCl was measured by iodometric titration and in a calcium complexation experiment by using a Ca 2+ -selective electrode. Results The salts dissolved within 1 minute. The dissolution maximum of Na 4 HEDP in water (wt/total wt) was 44.6% ± 1.6%. The corresponding dissolution maximum of Na 4 EDTA was 38.2% ± 0.8%. Na 4 HEDP at 18% in 5% NaOCl caused a mere loss of 16% of the initially available chlorine during 1 hour. In contrast, a corresponding mixture between NaOCl and the Na 4 EDTA salt caused 95% reduction in available chlorine after 1 minute. Mixtures of 3% Na 4 EDTA with 1% NaOCl were more stable, but only for 30 minutes. Na 4 HEDP lost 24% of its calcium complexation capacity after 60 minutes. The corresponding loss for Na 4 EDTA was 34%. Conclusions The compatibility and solubility of particulate Na 4 HEDP with/in NaOCl solutions are such that these components can be mixed and used for up to 1 hour. In contrast, short-term compatibility of the Na 4 EDTA salt with NaOCl solutions was considerably lower, decreasing at higher concentrations of either compound. Especially for Na 4 HEDP but also for Na 4 EDTA, the NaOCl had little effect on calcium complexation.

Sodium hypochlorite (NaOCl) solutions with added wetting agents are advertised to dissolve necrotic tissue in root canals faster than their counterparts without a lowered surface tension. This was tested in the current study, and the null hypothesis formulated was that there was no difference between a commercially available NaOCl solution with a lowered surface tension (Chlor-XTRA; Vista Dental Products, Racine, WI) and a counterpart containing the same amount of available chlorine without added wetting agents regarding the soft tissue that remains in oval-shaped canals after mechanical preparation and irrigation.Formerly vital extracted teeth (N = 44, 22 pairs) with similar anatomy were radiographically paired and chemomechanically prepared. In 1 tooth from each pair, a 5.25% NaOCl solution with reduced surface tension was used; in the other, a pure, technical-grade NaOCl solution of 5.25% was used. The percentage of remaining pulp tissue (PRPT) was histologically assessed in root cross-sections. The non-Gaussian raw data were subjected to Kruskal-Wallis and Mann-Whitney U tests to verify the respective effect of the cross-section level and solution on the PRPT. The relationship between the cross-section level and the PRPT was estimated by the Spearman correlation test. The alpha-type error was set at 5%.The cross-section level significantly influenced the PRPT (P.05), whereas the PRPT was not influenced by the solution used (P.05). A significant inverse correlation was found between the cross-section level and the PRPT (P.05, r = -0.330). The lower the distance to the apex, the higher the PRPT regardless of the solution used.Contrary to the advertised statement, the dental solution with a reduced surface tension did not dissolve vital pulp tissue in oval root canals any better than a conventional NaOCl solution of similar strength. Closer to the apex, pulp tissue dissolution is less efficient irrespective of the solution.

Many clinicians use household bleach to irrigate root canals. Sodium hypochlorite solutions are also available from dental suppliers. We compared physicochemical features of these products and investigated their impact on pulp tissue dissolution.Six different brands of household bleach were bought from drugstores. These were compared with Chlor-XTRA and technical NaOCl solutions of controlled concentration and alkalinity regarding their chlorine content (wt% NaOCl), pH, alkaline capacity, osmolarity, surface tension (Wilhelmy plate method), and price. Bovine pulp tissue (n = 10 specimens per group) dissolution at 37°C by test and control solutions adjusted to 1.0% NaOCl was assessed. Reduction in tissue weight was compared between groups by one-way analysis of variance, followed by Bonferroni correction (P.05).The pH of undiluted solutions ranged between 11.1 and 12.7. Batches of the same product differed in NaOCl content. No product contained more than an equivalent of 0.1 mol/L NaOH. One household bleach brand (Safeway Bleach Summit Fresh) was slightly alkalized; the other solutions under investigation were not. Osmolarity was similar between products. The surface tension of Chlor-XTRA and Safeway Bleach Summit Fresh was about half that of the other solutions. Tissue dissolution was statistically similar (P.05) among all solutions. Price was about 100-fold higher per liter of Chlor-XTRA compared with household bleach.Other than its price, the Chlor-XTRA solution had no unique features. In contrast to an earlier report, reduced surface tension did not result in greater soft tissue dissolution by NaOCl.

Introduction C-shaped canals are anatomic features that present the clinician with both diagnostic and operational challenges. The aim of this study was to compare the efficacy of the Self-Adjusting File (SAF; ReDent, Ra’anana, Israel) in shaping C-shaped canals with that of the rotary ProTaper file system (Dentsply-Maillefer, Ballaigues, Switzerland). Methods Sixteen mandibular second molars and 4 maxillary second molars with C-shaped canals were obtained, originating from native Chinese population. They were divided into 2 equal groups of 10 teeth each, based on similar canal morphology as presented in preliminary micro–computed tomography–derived images. One group was shaped using the SAF, whereas the other was shaped using the ProTaper file system. Reconstructed micro–computed tomographic images before and after treatment were superimposed over each other, and the percentage of the canal wall unaffected by the procedure was calculated. Comparison of the 2 groups for this parameter was performed using the Student t test. Results When treated with the SAF, 41% ± 14% of the canal walls remained unaffected by the procedure, whereas 66% ± 6% of the wall area was unaffected when using ProTaper, which was significantly higher than that of the SAF-treated group ( P Conclusions The SAF was more effective than the ProTaper file system in shaping the walls of C-shaped root canals.

Introduction A preparation technique with only 1 single instrument was proposed on the basis of the reciprocating movement of the F2 ProTaper instrument. The present study was designed to quantitatively assess canal preparation outcomes achieved by this technique. Methods Twenty-five extracted human mandibular first molars with 2 separate mesial root canals were selected. Canals were randomly assigned to 1 of the 2 experimental groups: group 1, rotary conventional preparation by using ProTaper, and group 2, reciprocate instrumentation with 1 single ProTaper F2 instrument. Specimens were scanned initially and after root canal preparation with an isotropic resolution of 20 μm by using a micro–computed tomography system. The following parameters were assessed: changes in dentin volume, percentage of shaped canal walls, and degree of canal transportation. In addition, the time required to reach working length with the F2 instrument was recorded. Results Preoperatively, there were no differences regarding root canal curvature and volume between experimental groups. Overall, instrumentation led to enlarged canal shapes with no evidence of preparation errors. There were no statistical differences between the 2 preparation techniques in the anatomical parameters assessed (P > .01), except for a significantly higher canal transportation caused by the reciprocating file in the coronal canal third. On the other hand, preparation was faster by using the single-file technique (P < .01). Conclusions Shaping outcomes with the single-file F2 ProTaper technique and conventional ProTaper full-sequence rotary approach were similar. However, the single-file F2 ProTaper technique was markedly faster in reaching working length.

When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH.NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α.05).Both solutions contained 5% NaOCl. One milliliter of the standard and the stabilized solution consumed 4.0 mL and 13.7 mL of a 0.1-mol/L HCl solution before they reached a pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P.05) than the control solutions, whereas the standard solution did not.NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts.

Pulpal diagnostics might be improved by using molecular markers found in dentinal fluid. In the current pilot study, we tested whether matrix metallopeptidase 9 (MMP-9) levels in dentinal fluid were detectable and differed between pulps from symptomatic teeth diagnosed with irreversible pulpitis and healthy counterparts.Thirty-one patients participated; 19 were diagnosed with irreversible pulpitis, and 12 were in need of replacement of a filling close to the pulp space in a clinically healthy tooth. Dentinal fluid was collected during a period of 2 minutes from dentin cavities by using folded polyvinylidene difluoride (PVDF) membranes, which were then transferred to microcentrifugation tubes containing physiologic saline solution. Total MMP-9 levels in these solutions were assessed by using a human MMP-9 fluorescent assay, detection limit 0.25 ng/mL. MMP-9 levels between groups were compared by using Mann-Whitney U test (alpha0.05).Three specimens from the symptomatic teeth were not included because coronal pulps proved to be necrotic on access. Dentinal fluid samples from symptomatic teeth had significantly higher MMP-9 levels than those from clinically healthy counterparts (P.05). However, merely 7 of the 16 pulpitis samples contained detectable levels of MMP-9. None of the clinically healthy control specimens contained any detectable amounts of MMP-9.With a sensitive assay, it was possible to detect an enzyme linked with pulp tissue destruction (MMP-9) in dentinal fluid. However, the collection method needs to be improved to provide predictable fluid yields. Longitudinal studies should be performed to assess the predictive value of molecular markers in dentinal fluid on pulpal pathosis.

INTRODUCTION: The purpose of this study was to assess canal preparation outcomes in vitro by novice clinicians after standardized teaching sessions. METHODS: All 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. RESULTS: In experiment 1, canal curvature decreased by 7.6 degrees and 7.8 degrees 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

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files. The specimens were divided into two groups (n = 11), after radiographing the roots from the buccolingual and mesiodistal planes with pathfinding files in situ. More strongly and less strongly curved canals were, respectively, assigned to the Lightspeed and nickel-titanium K-file groups. Using a reassembly technique, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were made of the experimental roots embedded in clear plastic. Stereomicroscopic 35-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and size 40 Master Apical Files, for the Lightspeed and K-file groups, respectively. Similar 35-mm slides of the instrumented canals were taken and electronically superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional areas of the prepared root canals were evaluated at specific levels. No significant differences in displacement of canal centers or between the mean cross-sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar displacement of canal centers after preparation.

Root canal morphology changes during canal preparation, and these changes may vary depending on the technique used. Such changes have been studied in vitro by measuring cross-sections of canals before and after preparation. This current study used nondestructive high-resolution scanning tomography to assess changes in the canals' paths after preparation. A microcomputed tomography scanner (cubic resolution 34 microm) was used to analyze 18 canals in 6 extracted maxillary molars. Canals were scanned before and after preparation using either K-Files, Lightspeed, or ProFile .04 rotary instruments. A special mounting device enabled precise repositioning and scanning of the specimens after preparation. Differences in surface area (deltaA in mm2) and volume (deltaV in mm3) of each canal before and after preparation were calculated using custom-made software. deltaV ranged from 0.64 to 2.86, with a mean of 1.61 +/- 0.7, whereas deltaA varied from 0.72 to 9.66, with a mean of 4.16 +/- 2.63. Mean deltaV and deltaA for the K-File, ProFile, and Lightspeed groups were 1.28 +/- 0.57 and 2.58 +/- 1.83; 1.79 +/- 0.66 and 4.86 +/- 2.53; and 1.81 +/- 0.57 and 5.31 +/- 2.98, respectively. Canal anatomy and the effects of preparation were further analyzed using the Structure Model Index and the Transportation of Centers of Mass. Under the conditions of this study variations in canal geometry before preparation had more influence on the changes during preparation than the techniques themselves. Consequently studies comparing the effects of root canal instruments on canal anatomy should also consider details of the preoperative canal geometry.

The purpose of this study was to test some effects of preheating NaOCl solutions using a commercially available syringe heating device. Irrigating solution temperatures in 10-ml syringes were measured. Stability of 5.25, 2.62, and 1% NaOCl solutions for 60 min at 20, 45, and 60 degrees C was assessed using iodine/thiosulfate titration. Human pulp tissue dissolution capacity of a 1% NaOCl solution was gauged at the latter temperatures, and compared to corresponding values with a 5.25% solution at 20 degrees C. Killing efficacy of diluted NaOCl solutions against 48-h incubations of Enterococcus feacalis ATCC 29212 was compared at 45 degrees C and 20 degrees C. Using the heating device, a 20 degrees C solution reached 45 degrees C and 60 degrees C in 7 and 20 min, respectively. Solutions remained stable during the observation period. The 1% NaOCl solution at 45 degrees C dissolved pulp tissues as effectively as the 5.25% solution at 20 degrees C, while the 60 degrees C/1% solution was significantly more effective (p < 0.05). A 100-fold increase in killing efficacy was observed between corresponding NaOCl solutions at 20 degrees C and 45 degrees C.

INTRODUCTION The temperature and related shrinking kinetics of gutta-percha injected from heat guns are not known; therefore, we investigated them in this study. METHODS The temperatures of 3 different backfill gutta-percha brands extruded from 3 commercially available heat guns set to 200°C were studied. To validate the results, temperature development of 1 gutta-percha brand injected from a heat gun during a simulated backfilling procedure was assessed in single-rooted human teeth containing thermocouples in a water bath of 37°C. These values were compared with the counterparts obtained in a tabletop testing device for shrinkage at an ambient temperature of 37°C. Using this device, linear shrinkage upon cooling was assessed for all 3 gutta-percha brands under investigation. Results were compared by parametric statistics (alpha = .05). RESULTS The temperatures of extruded gutta-percha differed significantly (P < .05) between heat guns and gutta-percha brands. Mean temperatures ranging between 57.6° ± 4.5°C and 103.9° ± 7.8°C could be observed with different combinations. The temperature of extruded gutta-percha in tabletop experiments equaled that observed in the root canals. However, the cooling of gutta-percha was (P < .05) faster in the tabletop measuring device compared with the root canal environment. Within the controlled temperature drop from 75°C to 37°C, the total shrinkage differed significantly (P < .05) between the 3 gutta-percha brands under investigation and ranged between 0.96% ± 0.20% and 2.31% ± 0.26% after 10 minutes (P < .05). Shrinking kinetics showed different patterns between the gutta-percha brands. CONCLUSIONS Gutta-percha designed for thermoplastic application shrinks quickly and extensively upon cooling.

INTRODUCTION In pulpless immature human premolars implanted in rodents, this study investigated whether fibrin gel offered advantages over leaving the root canal empty regarding soft tissue ingrowth and cell differentiation. METHODS Root canals of extracted human immature premolars (n = 12) were accessed and then irrigated with 5% sodium hypochlorite followed by 17% ethylenediaminetetraacetic acid. Root canals were then either left empty or filled with a fibrin gel (n = 6 each) before being placed subcutaneously on top of the calvarial bone of rats (1 tooth per rat) for 12 weeks. After sacrifice, teeth were histologically assessed. Tissue ingrowth was quantified and compared between groups using the Mann-Whitney U test (P < .05). Cells adhering to the pulp canal wall were immunohistochemically screened for the presence of bone sialoprotein (BSP) and dentin sialoprotein (DSP). RESULTS More tissue grew into the pulp space when teeth were filled with fibrin gel (P < .05). The presence of fibrin gel affected not only the extent of tissue ingrowth but also tissue morphology and differentiation of cells contacting the dentinal wall. In the fibrin gel group, newly formed tissue was similar to normal pulp, constituted of inner pulp, cell-rich zone, cell-free zone, and an apparent odontoblast layer, which stained positive for BSP and DSP. Newly formed blood vessels were also more abundant compared with the initially empty root canals. CONCLUSIONS Under the conditions of this study, fibrin gel improved cell infiltration and cell-dentin interaction. Both are necessary for pulp tissue regeneration.

This study evaluated temperature changes during passive ultrasonic irrigation. Root canals of three extracted maxillary canines were enlarged to size #45. Thermocouples were mounted 3, 6, and 9 mm from the apical foramen. Teeth were placed in a water bath at 37 degrees C. Distilled water (20 degrees C) was continuously delivered through an ultrasonic unit (group 1) or deposited into the root canal before ultrasonic activation (group 2); for activation, noncutting nickel-titanium (NiTi) inserts or stainless steel K-files #15, #25, and #35 were used. Before and during ultrasonic activation, temperatures were continuously measured for 210 seconds. Statistical analysis was performed using analysis of variance and Scheffe post hoc tests. Temperatures initially decreased by up to 7.4 degrees C; these drops were significantly smaller in group 1 than in group 2 (p < 0.001) in the middle and apical root canal third. The decreases were followed by temperature rises for all inserts in group 2. However, in group 1, temperatures just reached baseline values in middle and apical thirds; in the coronal root canal third, lower temperatures were measured. In group 2, mean temperature rises were 7.7 degrees , 7.5 degrees , and 4.2 degrees C in coronal, middle, and apical root canal thirds. Here, K-file type inserts size #35 generated highest and inserts size #15 the lowest temperatures rises; NiTi inserts were more effective than size #15 K-files and less effective than #35 K-files. Continuous flow negated the potential of ultrasonic activation to heat irrigation solutions. Noncutting NiTi instruments and large K-files were more effective than small K-files in warming deposited irrigants.