Nickel-titanium Rotary Instruments Research Articles

Light-emitting Diode Assessment of Dentinal Defects after Root Canal Preparation with Profile, TRUShape, and WaveOne Gold Systems

IntroductionThe objective of this study was to use light-emitting diode (LED) transillumination to assess the presence of dentinal defects in roots instrumented with 3 different root canal preparation systems: ProFile (Dentsply Tulsa Dental Specialties, Tulsa, OK), TRUShape (Dentsply Tulsa Dental Specialties), and WaveOne Gold (Dentsply Tulsa Dental Specialties). MethodsEighty mesial roots of mandibular molars presenting 2 canals were randomly divided into 4 different groups (n = 20) as follows: the control group, no root canal preparation was performed; the ProFile group, root canals were prepared with nickel-titanium ProFile sizes 20.06 and 25.06; the TRUShape group, root canals were prepared with nickel-titanium rotary TRUShape instrument sizes 20.06 and 25.06; and the WaveOne Gold group, root canals were prepared with the reciprocating WaveOne Gold instrument #25.07. The specimens were sliced at 3, 6, and 9 mm from the apex with a low-speed saw under water cooling. Microscopic pictures of the specimens were taken with the aid of LED; the root canal space was masked, and 2 independent evaluators assessed the images for the assessment of dentinal defects. The number of dentinal defects was recorded, and the chi-square test was used for statistical analysis (P < .05). ResultsThe number of specimens presenting dentinal defects was as follows: the control group = 10, the ProFile group = 10, the TRUShape group = 13, and the WaveOne Gold group = 10. ConclusionsUsing the novel LED method, no difference in the visualization of dentinal defects was found among the ProFile, TRUShape, and WaveOne systems and the control group. Previous studies using the traditional sectioning method lack proper control and should be evaluated with caution.

Various heat-treated nickel–titanium rotary instruments evaluated in S-shaped simulated resin canals

Background/purposeHeat treatment of nickel–titanium (NiTi) alloy produces a better arrangement of the crystal structure, thereby leading to increased flexibility and improved fatigue resistance or plastic behavior. This study aimed to assess the performance of various heat-treated NiTi rotary instruments in S-shaped resin canals. Materials and methodsForty S-shaped resin canals were instrumented (10/group) with either Twisted Files (R-phase), WaveOne (M-wire), Hyflex CM, or V Taper 2H (CM-wire) with the same apical size and taper (25/0.08). Each S-shaped resin canal was scanned both before and after instrumentation with microcomputed tomography. Changes in canal volume and transportation were evaluated at regular intervals (0.5 mm). Differences between instruments at the apical curve, coronal curve, and straight portion of the canals were analyzed statistically. ResultsAll tested instruments caused more transportation at the coronal rather than apical curvatures, with the exception of Twisted Files for which apical transportation was the highest for any instrument or location (P<0.05). The transportation was mostly influenced by the alloy type rather than their cross-sectional characteristics (P<0.05). The volumetric increase after instrumentation was similar for all tested instruments at the apical curve (P>0.05), whereas Hyflex CM created the most conservative preparations at the coronal curve (P<0.05). At the straight portion, volumetric changes were largest for Twisted Files and smallest for V Taper 2H (P<0.05). ConclusionAmongst heat-treated NiTi instruments, the CM-wire based instruments created the most favorable preparations in S-shaped resin canals.

Radix Entomolaris: A Case Report

Introduction: During endodontic treatment the variety of mandibular sectorial in the form of an extra lingual (radix entomolaris) or buccal root (radix paramolaris) can often cause difficulties. In other words, awareness and understanding of this unusual root, and its canal morphology, are factors that can affect the outcome of root canal treatment. Case Presentation: A 30-year-old male patient with a history of severe, throbbing, constant pain in the lower mandibular molars was referred to the department of endodontics of Hamedan Dental university. The patient’s medical history was noncontributory. The buccal object rule (same-lingual opposite-buccal technique) confirmed the additional root as a distolingual root (radix entomolaris). Following the evaluation of vitality tests, we began endodontic treatment for this patient, after administration of local anesthesia using 2% lidocaine with 1:80,000 epinephrine (Daroupakhsh, Tehran, Iran) and rubber dam isolation. The working length was determined by a Root ZX apex locator (Dentaport ZX, J Morita) and later confirmed by parallel periapical radiograph. Canals were shaped in a crown down fashion with Protaper Nickel Titanium rotary instruments (Dentsply, Maillefer) under copious irrigation with 2.5% sodium hypochlorite and lubrication with RC-Prep. After drying the canals with paper points, the master gutta-percha points were fitted within the canals and confirmation radiography was taken. The root canal system was obturated with the cold lateral compaction technique. Conclusions: This case is about a mandibular molar with radix entomolaris and the radiographic exploration and endodontic order. Clinicians should be aware of these unusual root morphologies in the mandibular molars. The initial diagnosis of a radix entomolaris or paramolaris before root canal treatment is important to facilitate the endodontic procedure.

Disinfecting Effects of Rotary Instrumentation with Either 2.5% Sodium Hypochlorite or 2% Chlorhexidine as the Main Irrigant: A Randomized Clinical Study

IntroductionThis randomized clinical study compared the antibacterial effects of irrigation with either 2.5% sodium hypochlorite (NaOCl) or 2% chlorhexidine (CHX) during the preparation of infected root canals with rotary nickel-titanium instruments. MethodsThe root canals of 50 single-rooted teeth with apical periodontitis were prepared by using BioRaCe rotary instruments (FKG Dentaire, La Chaux-de-Fonds, Switzerland) and irrigation with either 2.5% NaOCl (n = 25) or 2% CHX (n = 25). Samples were taken from the canal at baseline (S1) and after (S2) chemomechanical preparation. DNA was extracted from the clinical samples, and the reduction of the levels of total bacteria and streptococci was evaluated by means of a 16S ribosomal RNA gene-based quantitative polymerase chain reaction assay. ResultsAll S1 samples were positive for the presence of bacteria. After chemomechanical preparation using either 2.5% NaOCl or 2% CHX, 44% and 40% of the root canals still had detectable bacteria, respectively. As for total bacterial counts, a mean number of 3.7 × 105 bacterial cell equivalents was present in S1 samples from the NaOCl group, with a substantial reduction in S2 to a mean of 5.49 × 102 cell equivalents (P < .001). In the CHX group, a mean bacterial load of 8.77 × 104 cell equivalents occurred in S1, with a significant reduction in S2 to a mean of 2.81 × 103 cells (P < .001). The differences in both the presence/absence and quantitative data were not statistically significant (P > .05). Both irrigation protocols were highly effective in reducing the levels of Streptococcus species (P < .001). ConclusionsNo significant difference was observed for the clinical antibacterial effectiveness of rotary preparation using either 2.5% NaOCl or 2% CHX as the main irrigant.

Mechanical behavior of deep cryogenically treated martensitic shape memory nickel-titanium rotary endodontic instruments.

Objectives:The aim of this study was to investigate the role of deep cryogenic treatment (DCT) on the cyclic fatigue resistance and cutting efficiency of martensitic shape memory (SM) nickel–titanium (NiTi) rotary endodontic instruments.Materials and Methods:Seventy-five HyFlex® CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (–185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.Results:Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.Materials and Methods:Seventy-five HyFlex® CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (–185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.Results:Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.

Comparison of Surface Characteristics of Apical Third of Rotary NiTi Files Manufactured from Different Phases of NiTi before and after Use: an Sem Analysis

AbstractClinically, there is a real potential for rotary NiTi instruments to separate in the canal; hence increasing the resistance to fracture has been a focus in the designing of new NiTi rotary systems. NiTi alloys go through various transitional phases and these have been utilized by manufacturers in different file systems. Aim: To evaluate and compare the surface changes of rotary nickel-titanium instruments manufactured from the Austenite phase, M-wire technology and R- phase before and after multiple uses. Materials and Methodology: 60 freshly extracted human mandibular premolars with a single, straight canal were selected. They were divided into 3 groups of 20 teeth each. Cleaning and Shaping was carried out using the crown down technique. All instruments were evaluated for defects under Scanning Electron Microscope (SEM) before and after multiple uses and scored for the defects. Results were statistically analyzed using Kruskal Wallis and Mann Whitney U test. Results: The p-value was &lt;0.0001, indicating a statistically significant difference between the three groups in terms of resistance to surface defects. Conclusion: R-phase technology had superior resistance to surface defects, followed by M-wire and the austenitic phase.

Evidence for Reduced Fatigue Resistance of Contemporary Rotary Instruments Exposed to Body Temperature

IntroductionThe purpose of this study was to evaluate the effect of 2 different temperatures (20°C and 37°C) on the cyclic fatigue life of rotary instruments and correlate the results with martensitic transformation temperatures. MethodsContemporary nickel-titanium rotary instruments (n = 20 each and tip size #25, including Hyflex CM [Coltene, Cuyahoga Falls, OH], TRUShape [Dentsply Tulsa Dental Specialties, Tulsa, OK], Vortex Blue [Dentsply Tulsa Dental Specialties], and ProTaper Universal [Dentsply Tulsa Dental Specialties]) were tested for cyclic fatigue at room temperature (20°C ± 1°C) and at body temperature (37°C ± 1°C). Instruments were rotated until fracture occurred in a simulated canal with an angle curvature of about 60° and a radius curvature of 3 mm; the center of the curvature was 4.5 mm from the instrument tip. The number of cycles to fracture was measured. Phase transformation temperatures for 2 instruments of each brand were analyzed by differential scanning calorimetry. Data were analyzed using the t test and 1-way analysis of variance with the significance level set at 0.05. ResultsFor the tested size and at 20°C, Hyflex CM showed the highest resistance to fracture; no significant difference was found between TRUShape and Vortex Blue, whereas ProTaper Universal showed the lowest resistance to fracture. At 37°C, resistance to fatigue fracture was significantly reduced, up to 85%, for the tested instruments (P < .001); at that temperature, Hyflex CM and Vortex Blue had similar and higher fatigue resistance compared with TRUShape and ProTaper Universal. ConclusionsUnder the conditions of this study, using a novel testing design, immersion in water at simulated body temperature was associated with a marked decrease in the fatigue life of all rotary instruments tested.

Efficacy of passive ultrasonic irrigation in removing root filling material during endodontic retreatment

Abstract Introduction The aim of endodontic retreatment is to remove the previous root filling materials completely to allow for the subsequent steps of cleaning, canal shaping and filling replacement. Objective To evaluate the efficacy of passive ultrasonic irrigation (PUI) in the removal of residual root filling material after removing the bulk of the root filling with nickel-titanium rotary instruments. Material and method Eighteen mesial isthmus-containing roots of human mandibular molars were prepared and filled. The root canal filling was removed with the ProTaper Retreatment system and K-files. The specimens were randomized into 2 groups (n = 9), both irrigated with 2.5% NaOCl and 17% EDTA. In the conventional group, an irrigation syringe was used. In the PUI group, the PUI technique was used. The roots were sectioned longitudinally and evaluated under stereomicroscopy. Student’s t test was used to compare groups and the general linear model was used to compare the apical, cervical, and middle root thirds within each group, in regard to the percentages of remaining residual filling material. Result There was no statistically significant intergroup difference, irrespective of which root third was evaluated (P &gt; 0.05). In the PUI group, the apical third showed a significantly higher percentage of residual filling material, in comparison with the cervical (P = 0.038) and middle (P = 0.029) thirds. Conclusion The PUI technique was not more effective than the conventional irrigation technique in removing residual root filling material during endodontic retreatment in root canals with a complex anatomy.

Cyclic fatigue resistance of two nickel-titanium rotary instruments in interrupted rotation.

To investigate the influence of interrupted rotation on cyclic fatigue of two nickel-titanium rotary instruments. Cyclic fatigue of 300 new ProTaper Next size X1; X2 and Mtwo size 10, .04 taper; size 15, .05 taper; size 20, .06 taper and size 25, .06 taper instruments was tested in continuous or interrupted rotation. Fifty files of the same brand and size were randomly assigned to five groups (n=10). Group 1 instruments were tested in continuous rotation; groups 2 and 3 in paused rotation for 1s every 10 or 20s, respectively; groups 4 and 5 in interrupted rotation for 5s every 10 or 20s, respectively. Cyclic fatigue was expressed in time to fracture (TtF) in an artificial canal with 60° angle and 5mm radius of curvature. The fracture surface was examined with a scanning electron microscope (SEM). Data were evaluated by two-way analysis of variance. Cyclic fatigue of groups 2 and 4 of ProTaper Next X2 and Mtwo size 25, .06 taper was significantly lower than that of group 1 of the same instruments (P<0.01). ProTaper Next X2 had significantly reduced cyclic fatigue in groups 3 and 5 (P<0.05). No differences were found by interrupting the rotation for 1 or 5s in all instruments (P>0.05). Fatigue of other instruments was not affected by interrupted rotation (P>0.05). Interrupted rotation reduced cyclic fatigue resistance of ProTaper Next X2 and Mtwo size 25, .06 taper, especially when a higher number of interruptions was performed.

Stereomicroscopic evaluation of defects caused by torsional fatigue in used hand and rotary nickel-titanium instruments.

Objective:The aim of this study was to evaluate defects caused by torsional fatigue in used hand and rotary nickel-titanium (Ni-Ti) instruments by stereomicroscopic examination.Materials and Methods:One hundred five greater taper Ni-Ti instruments were used including Protaper universal hand (Dentsply Maillefer, Ballaigues, Switzerland), Protaper universal rotary (Dentsply Maillefer, Ballaigues, Switzerland), and Revo-S rotary (MicroMega, Besançon, France) files. Files were used on lower anterior teeth. After every use, the files were observed with both naked eyes and stereomicroscope at 20× magnification (Olympus, Shinjuku, Tokyo, Japan) to evaluate defects caused by torsional fatigue. Scoring was assigned to each file according to the degree of damage.Statistics:The results were statistically analyzed using the Mann-Whitney U test and the Kruskal-Wallis test.Results:A greater number of defects were seen under the stereomicroscope than on examining with naked eyes. However, the difference in methods of evaluation was not statistically significant. Revo-S files showed minimum defects, while Protaper universal hand showed maximum defects. The intergroup comparison of defects showed that the bend in Protaper universal hand instruments was statistically significant.Conclusion:Visible defects in Ni-Ti files due to torsional fatigue were seen by naked eyes as well as by stereomicroscope. This study emphasizes that all the files should be observed before and after every instrument cycle to minimize the risk of separation.

Cleaning efficacy of reciprocal and rotary systems in the removal of root canal filling material.

Aim:The aim of this study was to compare the efficacy of hand file, nickel titanium rotary instrument, and two reciprocating instruments for removing gutta-percha and sealer from the root canals.Materials and Methods:Eighty-eight mandibular premolar teeth were used. The root canals were shaped and filled with gutta-percha and a resin-based sealer. The specimens were divided into four groups according to the technique by which the root filling material was removed: Group 1 — Wave One; Group 2 — Reciproc; Group 3 — ProTaper; and Group 4 — Gates-Glidden burs and stainless steel hand file. Then teeth were split longitudinally and photographed. The images were transferred to a computer. The ratio of remaining filling material to the root canal periphery was calculated with the aid of ImageJ software. Statistical analysis was performed using Kruskal–Wallis and Mann–Whitney tests.Results:A significant difference was found among all groups (P < 0.001). The WaveOne group demonstrated significantly less remaining filling material. The greatest amount of filling material was found in specimens where gutta-percha was removed with Gates-Glidden burs and stainless steel hand file.Conclusion:The reciprocating files were found to be significantly more effective in removing the filling material from the canal walls compared to the rotational file and hand file.

Scanning electron microscopic evaluation of the influence of manual and mechanical glide path on the surface of nickel-titanium rotary instruments in moderately curved root canals: An in-vivo study

Aim:The aim of this study was to evaluate the influence of manual versus mechanical glide path (GP) on the surface changes of two different nickel-titanium rotary instruments used during root canal therapy in a moderately curved root canal.Materials and Methods:Sixty systemically healthy controls were selected for the study. Controls were divided randomly into four groups: Group 1: Manual GP followed by RaCe rotary instruments, Group 2: Manual GP followed by HyFlex rotary instruments, Group 3: Mechanical GP followed by RaCe rotary instruments, Group 4: Mechanical GP followed by HyFlex rotary instruments. After access opening, GP was prepared and rotary instruments were used according to manufacturer's instructions. All instruments were evaluated for defects under standard error mean before their use and after a single use. The scorings for the files were given at apical and middle third.Statistical Analysis Used:Chi-squared test was used.Results:The results showed that there is no statistical difference between any of the groups. Irrespective of the GP and rotary files used, more defects were present in the apical third when compared to middle third of the rotary instrument.Conclusion:Within the limitations of this study, it can be concluded that there was no effect of manual or mechanical GP on surface defects of subsequent rotary file system used.

Smear layer removal and ultramorphological changes of root canal dentin induced by erbium, chromium: Yttrium-scandium-gallium-garnet laser

Aim: Using SEM & EDX analysis to evaluate: 1. The ability of Er;Cr;YSSG laser irradiation to the remove of smear layer from the root canal walls compared to the conventional EDTA/NaOCl irrigation technique 2. The effect of Er;Cr;YSSG laser irradiation on ultra morphologic characteristics and on the inorganic contents of root canal dentine. Materials and Methods: 18 single rooted freshly extracted human premolars) were chemomechanically prepared using protaper rotary nickel titanium (Ni-Ti) instruments (Dentsply maillefer) up to size 40/60 (F4) between each instruments 2 ml of 2.5% NaOcl were used. Samples were divided into two groups (n=8): Group A: 5 ml of 17% EDTA for 1 minute. Group B: Irradiation with Er;Cr;YSSG laser. Two teeth were used as a positive control (presence of smear layer). Teeth sections were evaluated by using the SEM and the EDX analysis. Results: It has been found that more than 70% of the examined samples in EDTA group showed significant removal of the smear layer in coronal, middle and apical third of the examined teeth. In Er;Cr;YSGG group, the coronal portion showed complete removal of the smear layer but with destruction of the inner wall of the dentin. In apical portion more than 87.5% of the samples showed the persistence of the smear layer in that region after laser treatment. When evaluating the degree of erosion, the highest degree was noted in the samples treated with Er,Cr;YSGG. Laser irradiation has less effect on the mineral contents of the root canal walls. Conclusions: The findings of the present study suggest that the use of Er;Cr;YSGG laser irradiation alone is significantly less effective in removing the apical third smear layer than the golden standard irrigation with 2.5% NaOCl and 17% EDTA.

MICROSONIC RETRIEVABILITY OF INTRACANAL SEPARATED ROTARY NICKEL-TITANIUM INSTRUMENTS HAVING ASYMMETRIC VERSUS SYMMETRIC DESIGNS AND EVALUATION OF REMAINING DENTIN THICKNESS USING CBCT

Objective: This study compared retrievability of two rotary nickel Titanium (NiTi) instruments with symmetric versus asymmetric cross sections; ProTaper Universal® and RevoS®, respectively, with reference to the influence of some anatomic factors, as well as evaluated of the remaining minimum dentin thickness after retrieval using cone beam computed tomography (CBCT). Materials and Methods: Thirty six extracted mandibular first molars with curved mesiobuccal canals were used. The apical 4mm of ProTaper Universal rotary NiTi instrument ® (Dentsply Maillefer, Ballaigues, Switzerland) size F3 (n=18) and RevoS rotary NiTi instrument ® (Micro- Mega, Besanc¸on, France) size A35/06 (n=18) were fractured in the apical region of the canal. Fragments were located at apical or apical-middle and their coronal end were before canal curvature, at or beyond it. Microsonic technique was successful when instrument retrieval occurred without mishaps. Post retrieval CBCT was superimposed on preoperative CBCT to determine changes in distal dentin thickness (at coronal end of instrument (C level) and at furcation level (F level) and in canal width. Chi-square test evaluated success incidence between the two instruments types and effects of influencing anatomic factors. Mann-Whitney U test compared quantitative data, significance was set at P<0.05. Results: Overall success rate for removal of fractured fragments was 72.2% with equal incidence in both instruments types. Retrieval of ProTaper instrument was positively affected by being in the apical-middle location, P=0.047. Retrieval of RevoS instrument was positively affected by being before and at the curvature; P = 0.04. CBCT measurements showed overall minimum distal dentin thickness after retrieval to be approximately 0.67±0.14 mm. Percent of dentin removal was significantly higher at F level, P=0.04, while Canal width was higher at C level P=0.052. In ProTaper group, percent of dentin removal at C level was slightly lower than in RevoS group, P=0.28. Strip perforation occurred in 8 samples and secondary fracture in 2 samples. Conclusions: The successful removal of fractured Ni-Ti instruments is more influenced by anatomical factors namely; the position of the instrument within the root canal, the location of the fractured instrument in relation to the root canal curvature and the remaining dentin thickness. Instrument’s design indirectly affects success by requiring greater amount of dentin removal to disengage it.

Danger zone analysis using cone beam computed tomography after apical enlargement with K3 and K3XF in a manikin model.

BackgroundThe objective of the study was to evaluate and compare how apical enlargement with K3 and K3XF nickel-titanium (NiTi) rotary instruments reduces the root thickness in the danger zone and affects canal transportation and centering ability in mandibular molar mesial canals in a manikin extracted tooth model. Material and Methods Seventy-two mesial root canals of first mandibular molars were instrumented. Initial and post-instrumentation Cone Beam Computed Tomography scans were performed after root canal preparation up to size 25, 30, 35 and 40 files. Canal transportation, canal centering and remaining root dentin thickness toward the danger zone were calculated in sections 1, 2 and 3 mm under the furcation level. Data were analyzed using non-parametric Kruskal-Wallis analysis of variance at a significance level of P < 0.05. Results K3 instruments removed more dentin toward the danger zone compared with K3XF instruments (P< .05) and significant differences in dentin thickness were found when canal enlargement was performed to a #35-40 with both systems (P< 0.05). No significant differences in canal transportation and centering ability were found between systems, except when canal enlargement was performed to a #40 (P = 0,0136). No differences were observed when comparing the number of uses in both systems (P> 0.05). Conclusions Under the conditions of this study K3 removed a significant amount of dentin at the furcation level compared with the R-Phase K3XF rotary system in curved root canals. Enlargement to a 35-40/04 file removed significantly more dentin with both systems. Key words:K3, K3XF, R-phase, center ability, canal transportation, dentin thickness, increased apical enlargement, danger zone, dentin thickness.

Evaluation of the dentinal wall adaptation ability of MTA Fillapex using stereo electron microscope.

Background:An ideal root canal obturation requires a complete dentinal wall adaptation of sealer and Gutta-percha combinations without any gap formations.Aims:The aim of the study was to evaluate the dentinal wall adaptation ability of MTA Fillapex root canal sealer using stereo electron microscope (SEM).Methods:Twenty-four, single-rooted, human maxillary incisor teeth were used. All canals were prepared with a rotary nickel–titanium (Ni–Ti) instrument to a size F3 file. Teeth divided into two equal groups and one of the experimental groups was filled with AH Plus, and the other group was filled with MTA Fillapex using Gutta-percha single cone as a core material. The roots were prepared for SEM evaluation, and serial scanning electron photomicrographs were taken at ×50, ×100, ×500, and ×1000 magnifications. The gaps between the root canal sealer and canal walls were detected and measured in coronal, middle, and apical thirds. For each section, the highest value among the detected gap formations was recorded.Statistical Analysis:Mann–Whitney U-test, Freidman, and Wilcoxon tests were used.Results:The statistical analysis showed no significant difference between two sealers in terms of gap formation (P > 0.05).Conclusions:MTA Fillapex has a similar dentinal wall adaptation ability as AH Plus does.

Comparison of the shaping ability of RaCe, FlexMaster, and ProFile nickel-titanium instruments in severely curved root canals.

BackgroundThis in vitro study compared the shaping ability of RaCe, FlexMaster, and ProFile rotary nickel-titanium instruments in severely curved root canals of extracted teeth.Material and MethodsSixty maxillary molars with curvatures ranging from 25° to 65° were embedded in a muffle system and portioned into five horizontal sections (thickness 1.2 mm), starting from the apex. Canals were divided into three groups (n = 20, each) and were prepared with RaCe, FlexMaster, or ProFile rotary nickel-titanium instruments and the TriAuto ZX handpiece using a crown-down preparation technique. We evaluated the difference between pre- and postoperative root canal cross-sections, loss of working length, instrument failure, and preparation time. The root canal area before and after the intervention was determined using an area-measuring software. The data were analyzed statistically using a one-way ANOVA followed by a Kruskal-Wallis multiple-comparison Z-value test.ResultsSpecimens treated with FlexMaster showed the greatest change from preoperative cross-sections, followed by RaCe and ProFile. The cross-sectional changes induced by RaCe and FlexMaster preparation differed significantly from those produced by ProFile. Loss of working length, instrument failure, and preparation time did not differ significantly between the groups.ConclusionsRoot canal preparation with the three instruments did not lead to any significant alteration of the original root anatomy or working length. Thus, we conclude that RaCe, FlexMaster, and ProFile instruments are of comparable efficiency and usefulness in the preparation of severely curved root canals. Key words:Endodontics, root canal preparation, rotary, extracted teeth, nickel-titanium.

Scanning electron microscopy with energy dispersive X-ray spectrophotometry analysis of reciprocating and continuous rotary nickel-titanium instruments following root canal retreatment.

This study aimed to evaluate superficial defects and the composition of Reciproc R25 and ProTaper Retreatment file systems (Dentsply Maillefer, Ballaigues, Switzerland) used for retreatment. A total of 100 maxillary incisor teeth were randomly divided into the following two groups: Reciproc R25 (n = 25) and ProTaper Retreatment instrument (n = 75) groups. The nickel-titanium (Ni-Ti) compositions of the files before and after use were analyzed using energy dispersive X-ray spectrophotometry (EDX). Chi-square, Mann-Whitney U, and Kruskal-Wallis tests were used to analyze the data. ProTaper Retreatment instrument group showed a significantly higher number of defects than the Reciproc group (P < 0.05). No instrument fracture was detected. The presence of debris was observed in both groups before use, although the level was significantly higher in the ProTaper Retreatment group, which consisted of metals (P < 0.05). There was no significant difference between new and used instruments with regard to Ni-Ti composition (P < 0.05). EDX analysis showed that both the Reciproc and ProTaper Retreatment instruments had a Ni-Ti composition that was within the standards specified by the American Society of Testing and Materials. This study confirmed the use of both the Reciproc R25 file and ProTaper Retreatment file system for root canal filling removal in straight root canals as a safe procedure. (J Oral Sci 58, 401-406, 2016).

Root Canal Surface Strain and Canal Center Transportation Induced by 3 Different Nickel-Titanium Rotary Instrument Systems

IntroductionRoot canal anatomy and canal preparation instruments affect the outcome of endodontic treatment. The purpose of this study was to determine the root surface strain (SS) generated and the extent of canal center transportation during canal shaping using 3 different nickel-titanium instruments. MethodsSimulated root canals in resin blocks (n = 10 per group) were prepared using adaptive rotary motion with twisted files (Twisted File Adaptive [TFA]; SybronEndo, Orange, CA), reciprocating rotary motion with WaveOne (WO; Dentsply Maillefer, Ballaigues, Switzerland) files, and continuous rotary motion with ProTaper Next files (PTN, Dentsply Maillefer). Electrical strain gauges at 3 sites recorded SS real time during canal shaping, and the blocks were scanned by micro–computed tomographic imaging to assess the canal center deviation at 3 sections after root canal instrumentation. The mean maximum SS and the canal center transportation for all groups and sites were derived and analyzed for a possible correlation between them. ResultsAn overall increase in root SS was observed after root canal instrumentation. A significant difference in the induced mean maximum SS between TFA, WO, and PTN at specific sites of curved root canals was observed. A statistically significant difference in the mean distance of canal center transportation was observed among the 3 shaping techniques at the apical section. Finally, the mean maximum SS values induced during canal shaping strongly correlated with canal center transportation in the apical section and the coronal section. ConclusionsThe curved canals prepared using TFA exhibited lower SS and less canal center transportation at the apical section than the WO and PTN systems. SS generated during canal shaping correlated with canal center transportation in a site-specific manner.

Deformation and fracture of K3 rotary nickel-titanium endodontic instruments after clinical use.

The aim was to evaluate the incidence and type of defects that occurred with K3 rotary nickel-titanium instruments during routine clinical use. A total of 2397K3 (G-PACKS, SybronEndo, West Collins, Orange, CA, USA) instruments were collected from a graduate endodontic clinic over 21months. All the instruments were limited to a maximum use of 30 canal preparations. The collected instruments were measured by a digital caliper to determine whether any fractures had occurred and then were visually inspected for deformation and fracture under a stereomicroscope. The surfaces of fractured instruments were further evaluated under a scanning electron microscope. Data were analysed using chi-square test and Kruskal-Wallis test. The incidence of instrument defect was 5.63%, consisting of 3.59% fractures and 2.05% deformations. The defect rates of 0.04 and 0.06 files were statistically higher than the other taper groups (P<0.003) except for 0.08 files (P>0.05). For the fractured instruments, 63.95% failed from flexural fatigue, whilst 36.05% failed from torsion. Flexural fracture was the major mode of fracture for instruments with larger taper. A routine check for instrument integrity particularly for 0.04 and 0.06 files at high magnification is recommended after each clinical use.