Effect of powder-to-water ratio on the push-out bond strength of white mineral trioxide aggregate.

AIM: To evaluate the effect of powder-to-water ratio on the retention characteristics of white mineral trioxide aggregate (MTA; Angelus, Londrina, Pr, Brazil) over time. METHODS: One hundred and thirty-five root dentin slices from extracted single-rooted human mandibular premolar teeth were instrumented to achieve a diameter of 1.3 mm. Three MTA groups were prepared using 4:1, 3:1, and 2:1 powder-to-water ratios. The samples were stored for 96 h and 7 and 28 days at 37°C. The push-out bond strengths were measured using an Instron testing machine. Data were analyzed using two-way analysis of variance (anova) with Bonferroni correction. RESULTS: There was a statistically significant difference between the experimental groups at the 96-h and 7-day study periods (P = 0.002). At 96 h, the materials prepared at 2:1 ratio had the lowest bond strength than the samples prepared at the other two ratios (P < 0.001). There was a significant difference between the findings at 96-h and 28-day study periods for 2:1 and 4:1 ratios. The highest bond strength value was found at 28 days of exposure (P < 0.001). CONCLUSION: The powder-to-water ratio significantly interfered with the bond strength properties of white MTA.

Is Pulp Inflammation a Prerequisite for Pulp Healing and Regeneration?

The importance of inflammation has been underestimated in pulpal healing, and in the past, it has been considered only as an undesirable effect. Associated with moderate inflammation, necrosis includes pyroptosis, apoptosis, and nemosis. There are now evidences that inflammation is a prerequisite for pulp healing, with series of events ahead of regeneration. Immunocompetent cells are recruited in the apical part. They slide along the root and migrate toward the crown. Due to the high alkalinity of the capping agent, pulp cells display mild inflammation, proliferate, and increase in number and size and initiate mineralization. Pulp fibroblasts become odontoblast-like cells producing type I collagen, alkaline phosphatase, and SPARC/osteonectin. Molecules of the SIBLING family, matrix metalloproteinases, and vascular and nerve mediators are also implicated in the formation of a reparative dentinal bridge, osteo/orthodentin closing the pulp exposure. Beneath a calciotraumatic line, a thin layer identified as reactionary dentin underlines the periphery of the pulp chamber. Inflammatory and/or noninflammatory processes contribute to produce a reparative dentinal bridge closing the pulp exposure, with minute canaliculi and large tunnel defects. Depending on the form and severity of the inflammatory and noninflammatory processes, and according to the capping agent, pulp reactions are induced specifically.

Detecting Gram-positive anaerobic cocci directly from the clinical samples by multiplex polymerase chain reaction in odontogenic infections.

PURPOSE: Gram-positive anaerobic cocci (GPAC) can be isolated as pathogens from odontogenic infections. Culturing GPAC is time consuming and labor intensive. The objectives of the present study were to examine the utility of polymerase chain reaction (PCR) in directly detecting the presence of GPAC in clinical samples obtained from patients with odontogenic infections and to compare the distribution of GPAC in infected and healthy tissue. MATERIALS AND METHODS: In the present case-control study, the infected tissue from patients and oral mucosal swabs from healthy control subjects were subjected to anaerobic culture and direct PCR analysis for the presence of GPAC. The McNemar, chi-square, and Fisher exact tests and kappa analysis were used for the statistical analyses. P < .05 was regarded as significant. RESULTS: The patient group included 13 men and 14 women, including 9 patients diagnosed with granulation of tooth extraction, 6 with impacted tooth follicles, 4 with peri-implantitis, 3 with abscesses, 2 with epithelial cysts, 2 with infected cysts, and 1 with an oroantral fistula. The control group included 14 men and 12 women. All the patient and control samples contained at least 1 GPAC. The groups did not differ by method of determining GPAC presence, but more microorganisms were detected when clinical samples were directly used for PCR analysis than when cultured bacteria were used (P = .001). CONCLUSIONS: The presence of GPAC in infected tissue cannot be directly related to the development of odontogenic infections. PCR performed directly on clinical material is a sensitive and specific method that can detect GPAC and save time.

Comparison of Canal Transportation, Centering Ratio by Cone-beam Computed Tomography after Preparation with Different File Systems.

AIM: One Shape Apical 1 (OSA 1) is a new file for preparing the apical aspect of the root canal after One Shape (OS, Micro Mega, Besançon, France). This study compared apical transportation and centering ratios in curved root canals, which were instrumented with ProTaper Next (PTN, Dentsply Tulsa Dental Specialties, Tulsa, OK) up to size X3 and with OS up to OSA 1. MATERIALS AND METHODS: Forty-eight mesial canals of mandibular molars were assigned into two groups (n = 24) with respect to canal length and curvature. Root canals were accessed conventionally and preperation was completed with PTN files up to X3 or with OS up to OSA 1 according to the manufacturer's protocols. Apical transportation was assessed pre- and postinstrumentation using cone-beam computed tomographic (CBCT) scans of 1, 2, 3, 4, and 5 mm sections. A Friedman test was performed to assess the significance between file systems. RESULTS: No significant difference was found between the file systems regarding apical transportation and centering ratio values (p > 0.05). Transportation in the mesial direction was greater than the distal transportation for both file systems. CONCLUSION: Considering apical transportation and centering ratio in curved canals, two systems provided similar results. CLINICAL SIGNIFICANCE: Preparation up to One Shape Apical 1 or ProTaper Next X3 was shown similar results regarding apical transportation and centering ratio. Both systems were safe to use in curved molar root canals.

Apical extrusion of debris and irrigant using novel preparation systems.

AIM: The aim of this in vitro study was to assess the amount of apically extruded debris and irrigant using Reciproc vs self-adjusting fle (SAF) and to investigate the effect, if any, of gravitational force via mandibular and maxillary positioning of the teeth. MATERIALS AND METHODS: Forty human mandibular premolars were randomly assigned to four groups of 10 teeth each. The root canals were instrumented according to the manufacturers' instructions using the Reciproc and SAF. Sodium hypochlorite was used as the irrigant. The apically extruded debris was collected in pre-weighted glass vials using the Myers and Montgomery method, and teeth were placed in vials both in downward and upward positions. After drying, the mean weight of debris was assessed with a microbalance and statistically analyzed using two-way ANOVA with Bonferroni correction. RESULTS: All instrumentation techniques and positions caused measurable apical extrusion of debris. A significant difference was observed according to position and instrument used (p < 0.05). The Reciproc extruded significantly more debris than SAF and vial downward position extruded significantly more debris than upward position (p < 0.05). CONCLUSION: Under the conditions of this study, all systems caused apical debris extrusion, especially in the downward position. CLINICAL SIGNIFICANCE: According to results of this study, the SAF was associated with less debris extrusion compared to the Reciproc in both mandibular and maxillary positions.

Antimicrobial efficacy of octenidine hydrochloride, MTAD and chlorhexidine gluconate mixed with calcium hydroxide.

OBJECTIVE: The aim of this in vitro study was to investigate whether mixing with calcium hydroxide [Ca(OH)2] affects the antimicrobial action of Octenidine hydrochloride (Octenisept), MTAD and chlorhexidine against Enterococcus faecalis and Candida albicans. MATERIALS AND METHODS: Freshly grown cultures of Enterococcus faecalis, Candida albicans and a mixture of both strains were incubated in agar plates containing brain-heart infusion broth (BHIB). Zones of inhibition were measured at 24 and 48 hours. Statistical analysis was performed using Mann-Whitney U test and Kruskal-Wallis one-way analysis of variance (ANOVA, both p=0.05). RESULTS: Mixing with Ca(OH)2 significantly increased the antibacterial effect of Octenisept (p<0.05), but did not alter its antifungal activity. Only chlorhexidine showed more antibacterial and antifungal efficiency compared to its Ca(OH)2-mixed version (both p<0.05). Mixing with Ca(OH)2 decreased the antibacterial efficacy of MTAD, but increased its antifungal effect (both p<0.05). CONCLUSION: These results demonstrate the differential effects of Ca(OH)2 addition on the antimicrobial action of the tested endodontic medicaments in vitro. Ca(OH)2 was as effective as its combination with all of the tested medicaments.

Effect of Low-surface Tension EDTA Solutions on the Bond Strength of Resin-based Sealer to Young and Old Root Canal Dentin.

INTRODUCTION: The purpose of this study was to evaluate the effect of low-surface tension EDTA solutions on the push-out bond strength of resin-based sealer to young and old root canal dentin. METHODS: Root canals from 64 (n = 32 age <30 years old and n = 32 >60 years old) extracted, decoronized, single-rooted human teeth were prepared with ProTaper rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to size F4 using 3 mL 2.5% sodium hypochlorite (NaOCl) between each file. Each group was divided into 4 subgroups as follows: 3 mL EDTA, REDTA (17% EDTA + 0.84 g cetyltrimethylammonium bromide; Sigma-Aldrich, St Louis, MO), EDTA-T (17% EDTA + 1.25% sodium lauryl ether sulfate, Sigma-Aldrich), and saline as the control (n = 8). The final irrigation was completed with 3 mL saline after 3 mL NaOCl in the experimental groups and 3 mL saline in the control group. After root canal filling with gutta-percha (GP) cones/AH Plus sealer (Dentsply, Petropolis, RJ, Brazil), samples were stored at 37°C and 100% humidity for 2 weeks. One-millimeter-thick horizontal sections from the coronal and midthirds of each root were sliced, and push-out bond strength values were measured using a universal testing machine. Data were analyzed using 2-way analysis of variance followed by the Bonferroni test (P < .05). RESULTS: EDTA-T, REDTA, and EDTA significantly increased the bond strength values of GP/AH Plus to the root canal dentin compared with saline in both young and old groups (P < .05). EDTA-T treatment provided higher bond strength values in young dentin compared with EDTA and EDTA-T-treated old dentin (P < .05). CONCLUSIONS: The bond strength values of GP/AH Plus could be altered depending on age and the type of EDTA compounds.

Evaluation of dentinal tubule penetration depth and push-out bond strength of AH 26, BioRoot RCS, and MTA Plus root canal sealers in presence or absence of smear layer.

Background. This study compared the effect of smear layer on the penetration depth and push-out bond strength of various root canal sealers. Methods. A total of 90 extracted human mandibular premolars were assigned into 2 groups: smear layer preserved and smear layer removed. Then the roots were further divided into 3 subgroups according to the sealer tested: AH 26, BioRoot RCS and MTA Plus. Obturation was performed with gutta-percha and the relevant sealer was mixed with 0.1% rhodamine B. Three 1-mm-thick slices were obtained from the mid-third area of each root. Two slices were selected for the push-out test and the remaining slice was used to calculate the dentinal tubule penetration depth and percentage. Results. The retention of MTA Plus and BioRoot RCS was higher than that of AH 26 when the smear layer was preserved (P<0.05). BioRoot RCS showed the lowest penetration depth when the smear layer was removed (P<0.05). Conclusion. Dentinal tubule penetration of root canal sealers had a limited effect on their adhesion to root canal wall.

Fracture resistance of simulated immature teeth after internal bleaching procedures.

The aim of this study was to evaluate the fracture resistance of simulated immature teeth after internal bleaching. The teeth were assigned as follows (n = 12/group); Group-1: The pulp chamber was filled with ProRootMTA and bleached intracoronally with sodium perborate mixed with 37% carbamide peroxide gel; Group-2: The pulp chamber was filled with ProRootMTA without bleaching; Group-3: The pulp chamber was filled with Biodentine and bleached intracoronally as Group-1; Group-4: The pulp chamber was filled with Biodentine without bleaching; and Group-5: Teeth received no intervention (control). The specimens were loaded vertically until root fracture occurred. The data were analysed with Kruskal-Wallis and Dunn tests. There was no significant difference between the fracture resistances of the experimental groups (P > 0.05). However, all experimental groups had significantly lower fracture resistance than the control group (P < 0.05). Neither the tested calcium silicate cements nor the bleaching procedures had a significant impact on fracture resistance values.

Fracture Resistance of Teeth with Simulated Perforating Internal Resorption Cavities Repaired with Different Calcium Silicate-based Cements and Backfilling Materials.

INTRODUCTION: This study assessed the fracture resistance (FR) of teeth with simulated perforating internal resorption cavities repaired with different calcium silicate-based cements (CSCs) and backfilling materials. METHODS: Ninety-six mandibular premolar teeth were used. Twelve of the teeth were assigned as negative control group. Remaining roots were instrumented with rotary files, and standardized internal resorption cavities were prepared on the middle half of roots with burs. Twelve of the samples were not further interfered and were assigned as a positive control group. The apical 4 mm of the remaining 72 root canals was obturated with single-cone technique and divided into 6 groups according to CSCs used for repairing of cavities and backfilling materials as follows: MTA + MTA, MTA + gutta-percha/sealer, Biodentine + Biodentine, Biodentine + gutta-percha/sealer, MTA Plus + MTA Plus, and MTA Plus + gutta-percha/sealer. Specimens were embedded in acrylic resin and then subjected to fracture testing. The forces when the fracture occurred were analyzed with analysis of variance and Bonferroni tests at P = .05. RESULTS: No significant difference was found among CSCs irrespective of backfilling materials (P > .05). Groups MTA + gutta-percha/sealer, Biodentine + gutta-percha/sealer, and MTA Plus + gutta-percha/sealer showed significantly lower FR compared with groups MTA + MTA, Biodentine + Biodentine, and MTA Plus + MTA Plus, respectively (P < .05). The highest FR was observed in group Biodentine + Biodentine, and the lowest was in group MTA Plus + gutta-percha/sealer. FR of positive control group was statistically lower than groups completely filled with CSCs (P < .05), whereas FR of negative control group was statistically higher than the groups combined with gutta-percha and sealer (P < .05). CONCLUSIONS: The backfilling with CSCs may be a preferable material rather than gutta-percha/sealer combination for the roots with perforated internal resorptions.

Mineral content analysis of root canal dentin using laser-induced breakdown spectroscopy.

OBJECTIVES: This study aimed to introduce the use of laser-induced breakdown spectroscopy (LIBS) for evaluation of the mineral content of root canal dentin, and to assess whether a correlation exists between LIBS and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) methods by comparing the effects of irrigation solutions on the mineral content change of root canal dentin. MATERIALS AND METHODS: Forty teeth with a single root canal were decoronated and longitudinally sectioned to expose the canals. The root halves were divided into 4 groups (n = 10) according to the solution applied: group NaOCl, 5.25% sodium hypochlorite (NaOCl) for 1 hour; group EDTA, 17% ethylenediaminetetraacetic acid (EDTA) for 2 minutes; group NaOCl+EDTA, 5.25% NaOCl for 1 hour and 17% EDTA for 2 minutes; a control group. Each root half belonging to the same root was evaluated for mineral content with either LIBS or SEM/EDS methods. The data were analyzed statistically. RESULTS: In groups NaOCl and NaOCl+EDTA, the calcium (Ca)/phosphorus (P) ratio decreased while the sodium (Na) level increased compared with the other groups (p < 0.05). The magnesium (Mg) level changes were not significant among the groups. A significant positive correlation was found between the results of LIBS and SEM/EDS analyses (r = 0.84, p < 0.001). CONCLUSIONS: Treatment with NaOCl for 1 hour altered the mineral content of dentin, while EDTA application for 2 minutes had no effect on the elemental composition. The LIBS method proved to be reliable while providing data for the elemental composition of root canal dentin.

Interaction of backfilling techniques and MTA plugs with additives: Fracture strength and adaptation analyses.

The aims were to evaluate the effects of different additives on the adaptation of mineral trioxide aggregate (MTA) plugs before and after different backfilling techniques and analyze the interference of filling procedures on the fracture resistance of simulated immature teeth. The apical parts of 60 teeth were filled with MTA mixed with distilled water (DW), propylene glycol (PG) or calcium chloride (CaCl2) and backfilled with cold lateral condensation (CLC) or warm vertical compaction (WVC). The specimens were subjected to adaptation analysis and fracture testing. CaCl2 addition resulted in poor marginal adaptation, while PG addition significantly decreased the fracture values (p<0.05). WVC technique negatively affected the marginal adaptation of MTA-CaCl2 plugs and decreased the fracture values of teeth with MTA-PG plugs (p<0.05). Mixing MTA with DW can be recommended as apical plug when the remaining root canal space is going to be filled with either CLC or WVC techniques.

Impact of different file systems on the amount of apically extruded debris during endodontic retreatment.

OBJECTIVE: The goal of present study was to determine the effect of different nickel-titanium file systems on the amount of apically extruded debris during endodontic retreatment: D-RaCe retreatment systems, EdgeFile XR retreatment rotary files, and Reciproc R40. MATERIALS AND METHODS: Thirty-six single-rooted prepared mandibular premolar teeth were filled with Gutta-percha and AH Plus sealer. The teeth were then randomly assigned into three groups (n = 12) for retreatment. The endodontic retreatment was performed as follows: D-RaCe, EdgeFile XR, Reciproc 40. Debris extruded apically during the retreatment was collected into preweighed Eppendorf tubes. An incubator was used to store tubes at 70(°) C for 5 days. The initial weight was subtracted from final weight of the Eppendorf tubes to calculate the weight of the dry extruded debris for each group. The data obtained were evaluated using Welch analysis of variance and Games-Howell post-hoc tests (P < 0.05). RESULTS: All files resulted in apical extrusion of debris. Reciproc caused significantly less debris extrusion compared to D-RaCe and EdgeFile XR (P < 0.05). CONCLUSIONS: The findings revealed that during endodontic retreatment, number, and taper of files might have an influence on the amount of apically extruded debris during endodontic retreatment.

Final Irrigation Regimens Affect Fracture Resistance Values of Root-filled Teeth.

INTRODUCTION: The purpose of this study was to compare the effect of different final irrigation solutions on fracture resistance values (FRVs) of endodontically treated teeth. METHODS: Eighty extracted decoronated human incisors were used. Ten randomly selected roots were used as the negative control group. The remaining roots were prepared by the ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland) up to F2. Ten prepared roots were selected as the positive control. The other prepared roots were divided into 6 (n = 10) groups according to the final irrigation solution used: 5 mL saline, 17% EDTA, EDTA with a surfactant (REDTA), chlorhexidine, QMix (Dentsply Tulsa Dental Specialties, Tulsa, OK), and BioPure MTAD (Dentsply Tulsa Dental Specialties). In all groups, the final irrigation was performed for 1 minute except for the BioPure MTAD group; in this group, it was applied for 5 minutes according to the manufacturer's instructions. The specimens were filled with a single gutta-percha cone and AH 26 sealer (Dentsply, De Trey, Konstanz, Germany). After being stored under 37 °C and 100% humidity for a week, the specimens were loaded in a vertical direction at 1 mm/min speed until they were vertically fractured. The results were analyzed by the Kruskal-Wallis and Siegel Castellan tests. RESULTS: The negative control group showed the highest FRV. There were statistically significant differences between the negative and positive control groups (P < .05). Specimens irrigated with REDTA and QMix showed a higher FRV compared with the positive control group (P < .05). Specimens exposed to chlorhexidine and BioPure MTAD showed a lower FRV compared with the negative control group (P < .05). CONCLUSIONS: Root canal preparation weakens the tooth. The final irrigation regimen has an impact on the FRV. A short time exposure to irrigation solutions (REDTA and QMix) that include surfactants probably contributed to the higher FRV, instead of a long time exposure as done with BioPure MTAD.

Efficacy of Combined Use of Different Nickel-Titanium Files on Removing Root Canal Filling Materials.

INTRODUCTION: The aim of this study was to estimate the remaining amount of residual filling materials in root canals after retreatment using ProTaper Universal Retreatment (PTUR) files (Dentsply Maillefer, Ballaigues, Switzerland) alone or with the additional use of the Self-Adjusting File (SAF; ReDent-Nova, Ra'anana, Israel), Reciproc (VDW, Munich, Germany), or Hedström-files (H-file; VDW, Antaeos, Munich, Germany) with volumetric estimation using the stereologic method via cone-beam computed tomographic images. METHODS: Forty-eight mandibular premolars with single canals were used. The canals were instrumented with ProTaper rotary instruments up to F4 and filled with gutta-percha and AH26 sealer (Dentsply De Trey, Johnson City, TN). All the samples were placed into the silicone models. Samples were scanned with cone-beam computed tomographic imaging and assigned into 4 groups (n = 12) according to retreatment files: the PTUR system group, the PTUR system plus SAF group, the PTUR system plus Reciproc group, and the PTUR system plus H-file group. The specimens were rescanned after retreatment procedures, and the volume estimations of the remaining filling materials were performed using the stereologic method. Data were analyzed using Kruskal-Wallis and Dunn tests. RESULTS: There was no significant difference among the groups regarding mean percentage volumes of the filling materials before retreatment procedures (P > .05). None of the retreatment procedures provided complete removal of the filling materials. The additional use of the SAF did not significantly improve the removal of filling materials when compared with the PTUR system alone (P > .05). However, the additional use of Reciproc or hand H-files significantly improved the removal of filling materials when compared with the PTUR system alone (P < .05). CONCLUSIONS: The additional use of files with different motion kinetics improved the removal of root canal fillings; however, none of the systems completely removed the root canal filling material from the root canals.

A comparison of different irrigation systems and gravitational effect on final extrusion of the irrigant.

BACKGROUND: The aim of this study was to compare manual needle irrigation (MNI), RinsEndo (RE), and passive ultrasonic irrigation (PUI), and assess the effect of gravity on extrusion from the apex in vitro. MATERIAL AND METHODS: The distobuccal roots of molars were used and the canals were instrumented up to F2. Teeth were mounted on models, which permitted visualization and manipulation of the apices for necessary procedures. The models were placed in articulator to simulate the jaw. Six groups (G) were formed as: G1, G2 and G3 represented mandibular positioning of teeth and were irrigated with MNI, RE, and PUI, respectively, while G4, G5, and G6 represented maxillary positioning of teeth and were also irrigated in same sequence. Prior to the final irrigation, 72 cube-shaped foam pieces covered with aluminum foil were weighed and the values were recorded as the initial weights. The cubes were then placed on the apical part of each sample. Final irrigation was performed with distilled water and the cubes were weighed again to determine their final weight. Data were analyzed using Kruskal-Wallis and Mann-Whitney U post-hoc test (p<0.05). RESULTS: Irrespective of the irrigation technique used, the amount of irrigant extruded from the apex showed a statistically significant difference related to the effect of gravity (p<0.05). There was no statistically significant difference between irrigation methods (p>0.05). When the irrigation systems were compared to examine the effect of gravity, the significant difference was found between G2 and G5 (p<0.05). CONCLUSIONS: Within the limitations of this study, MNI and PUI were found to be reliable irrigation systems. Caution should be exercised when using RinsEndo. Key words:Final irrigation, manual needle irrigation, passive ultrasonic irrigation, RinsEndo.

Influence of a glide path on the dentinal crack formation of ProTaper Next system.

OBJECTIVES: The aim was to evaluate dentinal crack formation after root canal preparation with ProTaper Next system (PTN) with and without a glide path. MATERIALS AND METHODS: Forty-five mesial roots of mandibular first molars were selected. Fifteen teeth were left unprepared and served as controls. The experimental groups consist of mesiobuccal and mesiolingual root canals of remaining 30 teeth, which were divided into 2 groups (n = 15): Group PG/PTN, glide path was created with ProGlider (PG) and then canals were shaped with PTN system; Group PTN, glide path was not prepared and canals were shaped with PTN system only. All roots were sectioned perpendicular to the long axis at 1, 2, 3, 4, 6, and 8 mm from the apex, and the sections were observed under a stereomicroscope. The presence/absence of cracks was recorded. Data were analyzed with chi-square tests with Yates correction. RESULTS: There were no significant differences in crack formation between the PTN with and without glide path preparation. The incidence of cracks observed in PG/PTN and PTN groups was 17.8% and 28.9%, respectively. CONCLUSIONS: The creation of a glide path with ProGlider before ProTaper Next rotary system did not influence dentinal crack formation in root canals.

Apical root canal transportation of different pathfinding systems and their effects on shaping ability of ProTaper Next.

BACKGROUND: This study aimed to compare glide path preparation of different pathfinding systems and their effects on the apical transportation of ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) in mesial root canals of extracted human mandibular molars, using digital subtraction radiography. MATERIAL AND METHODS: The mesial canals of 40 mandibular first molars (with curvature angles between 25° and 35°) were selected for this study. The specimens were divided randomly into 4 groups with 10 canals each. Glide paths were created in group 1 with #10, #15 and #20 K-type (Dentsply Maillefer, Ballaigues, Switzerland) stainless steel manual files; in group 2 with Path-File (Dentsply Maillefer) #1, #2, and #3 and in group 3 with #16 ProGlider (Dentsply Maillefer) rotary instruments; in group 4 no glide paths were created. All canals were instrumented up to ProTaper Next X2 to the working length. A double digital radiograph technique was used, pre and post-instrumentation, to assess whether apical transportation and/or aberration in root canal morphology occurred. Instrument failures were also recorded. The data were analyzed statistically using ANOVA and Tukey tests (p<0.05). RESULTS: No significant differences were found among groups regarding apical transportation (p>0.05). Two ProTaper Next instruments failed in-group 4. CONCLUSIONS: Within the parameters of this study, there was no difference between the performance of path-finding files and ProTaper Next system maintained root canal curvature well and was safe to use either with path-finding files or alone. Key words:Glide path, PathFile, ProGlider, ProTaper Next, transportation.

The Effect of Increased Temperatures of QMix and EDTA on the Push-out Bond Strength of an Epoxy-resin Based Sealer.

BACKGROUND: Bond strength of root canal sealers is mainly influenced by the surface tension of the root canal wall. Heat, or the use of a surfactant might reduce surface tension and it is known that surface tension of an EDTA solution significantly affected from temperature rise. QMix is a novel endodontic irrigant for smear layer removal containing EDTA, chlorhexidine and a detergent. There is no data regarding the influence of the temperature of the EDTA and QMix on the push-out bond strength of root canal sealers. AIM: To evaluate effect of temperatures of QMix and EDTA on the bond-strength of AH Plus. MATERIALS AND METHODS: Sixty premolars were prepared with ProTaper F4. During preparation 3% NaOCl was performed. Specimens were divided into 4 groups as follows: 5-mL 17% EDTA at 22°C and 37°C; 5-mL QMix at 22°C and 37°C. Three specimens from each group were prepared for observation using SEM. Remaining roots were obturated and prepared for a push-out test. Data was analysed using Anova and Bonferroni tests (p<0.05). RESULTS: Samples irrigated with QMix had higher push-out bond strength values than those irrigated with EDTA (p=0.01), regardless of temperature. Samples irrigated with 37°C EDTA resulted in higher bond-strength values than those irrigated with 22°C EDTA (p<0.001). CONCLUSION: Temperature of the final irrigant does affect the bond strength values of AH plus to root dentin irrigated with EDTA. Bond strength of AH Plus sealer to root canal dentin may improve with QMix.

Evaluation of apically extruded bacteria associated with different nickel-titanium systems.

INTRODUCTION: The aim of this in vitro study was to evaluate the amount of apically extruded bacteria associated with several root canal preparation systems. METHODS: Forty-four extracted human mandibular premolar root canals were contaminated with an Enterococcus faecalis suspension. After incubation at 37°C for 24 hours, the root canals were instrumented using the Twisted File (SybronEndo, Orange, CA), OneShape (Micro Mega, Besançon, France), and ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland). During instrumentation, apically extruded bacteria were collected into vials containing 0.9% NaCl. The microbiological samples were taken from the vials and incubated in brain-heart agar medium for 24 hours. The numbers of colony-forming units were determined. The data obtained were analyzed using Welch analysis of variance followed by post hoc Games-Howell tests. RESULTS: ProTaper Next extruded the highest amount of bacteria, whereas OneShape extruded the least compared with all the other instruments (P = .004). There was a significant difference between OneShape and ProTaper Next in the number of colony-forming units (P = .007) but not between OneShape and Twisted File (P > .05). CONCLUSIONS: All instrumentation systems extruded bacteria beyond the foramen. The OneShape system extruded less bacteria compared with the Twisted File and ProTaper Next systems.