Simulated Canals Research Articles

Evaluation of the bond strengths of two novel bioceramic cement using a modified thin‐slice push‐out test model

AbstractOrthoMTA (OrthoMTA, BioMTA, Korea) and RetroMTA (OrthoMTA, BioMTA, Korea) have been newly developed bioceramic cements or tricalcium silicate cements (TCSs). The aim of this study was to examine the dislocation resistance of these two novel TCSs from radicular dentin, using a modified thin slice push‐out test design that simulated canal spaces of uniform dimensions. Twenty‐five single‐rooted human canine teeth were used. Longitudinal slabs were obtained from each tooth using a diamond saw. Standardized canal‐like holes were created using size #2 Peeso Reamer along the coronal, middle and apical thirds of longitudinal tooth slabs. The cavities were filled with OrthoMTA or RetroMTA. The slabs were kept at 37°C for 14‐day in 100% humidity before push‐out evaluation (MPa). Failure modes were examined with stereomicroscopy. Data were calculated using unpaired t test (P < 0.05). Location of the TCS‐filled cavities did not affect push‐out strengths. OrthoMTA (9.809 ± 2.176 MPa) had significantly higher push‐out bond strength values than ProRoot MTA (7.103 ± 2.145 MPa) (P < 0.0001). The leaf‐like bodies were seen in the fractured specimens of both TCS groups. Failure modes were predominantly adhesive in both TCS groups. It can be concluded 14‐day push‐out bond strength of OrthoMTA is higher than that of RetroMTA.

Transportation assessment in artificial curved canals after instrumentation with Reciproc, Reciproc Blue, and XP-endo Shaper Systems.

In the present study, we compared the transportation of three different instrumentation systems in different levels of standardized artificial curved canals. Sixty epoxy resin blocks containing simulated canals were divided into three groups (n=20) according to the instrument used for canal preparation: Reciproc (REC), Reciproc Blue (REC Blue), and XP-endo Shaper (XPS). Pre- and post-instrumentation digital images of each specimen were superimposed by Photoshop software to evaluate the different amount of transportation. The Kruskal-Wallis and Wilcoxon were the non-parametric tests applied for the intergroup and intragroup analyses, respectively. The significance level was set at 5%. The XPS showed significantly less canal transportation than REC Blue at five levels (P<0.05) and significantly less canal transportation at seven evaluated levels when compared with the REC (P<0.05). REC Blue showed significant less canal transportation than REC at four of the eight evaluated levels (P<0.05). All evaluated instruments showed a significantly higher amount of resin removal toward the inner wall compared to the outer wall of the curvature (P<0.001). Although the XPS showed significantly less canal transportation than REC and REC Blue, all systems produced transportation from the original canal anatomy.

Canal shaping with a reciprocating system is easy to learn.

To assess progressive learning of root canal shaping in order to define the number of simulated canals in resin blocks needed to reach a level of learning beyond which no further improvement in performance is observed. A total of 216 simulated canals in resin blocks were instrumented by 18 operators without experience in Endodontics and by 18 Endodontists. The R25 file of the Reciproc system (VDW, Munich, Germany) was used to prepare the canals. The blocks were photographed before and after instrumentation. An analysis was made of the variations in the dimensions of the canals at 6 locations and of the instrumentation time. A Student's t-test was used to analyse the data (P<0.05). The group without experience were associated with significant differences in instrumentation time between the first canal and the subsequent canals (P<0.05) but differences in canal dimensions were not significant (P>0.05). In the group with experience, the instrumentation time did not differ significantly after the fifth canal, and no significant variations in canal dimensions were observed (P>0.05). When conducting studies on root canal shaping or educating students with new instruments, a simulated canal sample size of 6 was appropriate to achieve competence.

Comparison of shaping ability of ProTaper Next and 2Shape nickel—titanium files in simulated severe curved canals

Aim: To evaluate the centering ability of ProTaper Next (PTN) and 2Shape (TS) nickel—titanium (NiTi) instruments in terms of maintaining the original root canal configuration in a simulated tooth with severe curvature. Methodology: Twenty standardized simulated curved root canals were prepared to an apical size of 0.25 mm using PTN and TS (n = 10 canal/group) nickel-titanium files. A gig was constructed to enable reproducible image acquisition using a photographic camera. Pre- and post-instrumented images were recorded and superimposed using a computer software. The ability of the instruments to remain centered in the canal was determined by calculating a centering ratio at three independent points of the simulated canal: coronal, middle and apical third of the curvature, using a computer software. Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by independent sample t-test at 5% significance level. Results: No significant difference was found between the two systems (p &gt; 0.05). At the apical third, the mean centering ratio was significantly higher than the centering ratio of the coronal and the middle thirds in both TS and PTN (p &lt; 0.05). Conclusions: There were no significant differences in the centering ability of the ProTaper Next and 2Shape systems in simulated severe curved canals. Both systems exhibited some degree of transportation, especially in the apical third.

Effective Establishment of Glide-Path to Reduce Torsional Stress during Nickel-Titanium Rotary Instrumentation.

This study compared the torque generation during canal shaping with a nickel-titanium endodontic instrument according to the extent of glide-path establishment. Seventy-five simulated S-shaped canal blocks were divided into five groups (n = 15) according to the number of repetitive insertions to the working length using a One G glide-path instrument: groups with 5, 10, 15, and 20 insertions as well as group Z without glide-path establishment. When the tip of the One G file reached the working length, the file was moved back and forth repetitively at the working length for the designated number of times for each group. The instrumentation procedure with HyFlex EDM had 15 pecking strokes. During instrumentation, the generated torque was transmitted to a customized data acquisition module and collected using customized software. Data were computed to determine the maximum torque and total stress. The maximum screw-in forces were statistically analyzed using one-way analysis of variance and Tukey’s post hoc comparison test with a significance level of 95%. While the maximum stress did not have significant differences among the five groups (p > 0.05), groups with more than 10 repetitive insertions generated lower total stress during instrumentation than did the group with 5 insertions and group Z (p < 0.05). Under the limitations of this study, repetitive insertions of glide-path establishment files at the working length reduced stress generation during the shaping using nickel-titanium instruments.

Mechanical Properties of Various Glide Path Preparation Nickel-titanium Rotary Instruments

IntroductionThe aim of this study was to compare the cyclic fatigue, torsional resistance, and bending stiffness of single-file glide path preparation nickel-titanium instruments. MethodsProGlider (#16/progressive taper; Dentsply Sirona, Ballaigues, Switzerland), One G (#14/.03; Micro-Mega, Besancon, France), and EdgeGlidePath (#16/progressive taper; Edge Endo, Albuquerque, NM) were tested. For the bending stiffness test, the instrument was bent to a 45° angle along the main axis while 3 mm of the tip was secured. Cyclic fatigue resistance was measured during pecking movement, whereas the file was rotated within a reproducible simulated canal with a 3-mm radius and a 90° angle of curvature. The ultimate torsional strength and toughness were evaluated using a custom device. While tightly holding the end of the file at 3 mm, a rotational load of 2 rpm speed was applied until fracture. The results were analyzed using 1-way analysis of variance and Tukey post hoc comparison. A microscopic inspection was performed on the surface of a separate instrument using a scanning electron microscope. ResultsEdgeGlidePath showed superior cyclic fatigue resistance compared with the other systems. One G showed higher maximum torsional strength than the others. One G showed the largest distortion angle and the highest toughness followed by EdgeGlidePath and ProGlider (P < .05). One G also showed larger bending stiffness than the others, whereas EdgeGlidePath showed a larger residual angle than the others (P < .05). ConclusionsConventional wire showed higher toughness and torsional resistance than M-Wire and heat-treated nickel-titanium instruments. However, heat-treated wire showed higher cyclic resistance than conventional wire and M-Wire.

Evaluation of the efficacy of Er:YAG laser–activated irrigation in a simulated accessory canal

Aim: The aim of this study was to evaluate the effect of laser-activated irrigation (LAI) on the removal of debris-mimicking hydrogel from a simulated accessory canal. Materials and Methods: The simulated accessory canal was located 3 mm from the apex, perpendicular to the straight main canal. Gelatin hydrogel as a substitute of debris was used to fill the simulated accessory canal. The root canals were irrigated for 20 or 40 seconds by LAI using an erbium: yttrium aluminum garnet (Er:YAG) laser (30 mJ, 20 pps) or for 40 seconds by syringe irrigation (SI). During LAI, the cone-shaped tip of the laser was positioned stationary at 3 or 10 mm from the apex. Irrigation was performed using 5% NaOCl. The distance over which the hydrogel was removed from the accessory canal entrance was measured and compared between the irrigation procedures. Results: Using NaOCl as the irrigant, a significant increase was observed in the distance over which the hydrogel was removed by LAI compared with that by SI. A longer irradiation period with LAI resulted in significantly greater amount of hydrogel removal. There was no significant difference in hydrogel removal when the laser tip was positioned at 3 and 10 mm from the apex. Conclusion: Within the limitations of this in vitro model, LAI removed more hydrogel from the accessory canal than SI, when using NaOCl as the irrigant. Furthermore, the irradiation time influenced the cleaning efficacy, but the tip position did not.

Comparative evaluation of shaping ability of rotary and reciprocating nickel-titanium single file instruments on simulated root canals

Introduction: Effective cleaning of the root canal system is the primary objective of rotary instrumentation. For three-dimensional obturation of the root canal system, ideal preparation should have a continuously tapering funnel shape from the orifice to the apex. The study aimed to evaluate the shaping ability of two rotary and two reciprocating nickel-titanium (NiTi) single-file instruments on simulated root canals using image analysis software. Materials and Methods: Forty resin blocks with simulated canals of 30° curvature were divided into four experimental groups containing ten samples in each group. The canals were prepared using Reciproc (VDW, Munich, Germany), WaveOne (Dentsply, Maillefer, Ballaigues, Switzerland), OneShape (Micro-Mega, Besancon, France), and F360 (Komet, Brasseler, Lemgo, Germany) size 25 NiTi systems using X Smart Plus (Dentsply). Pre- and post-preparation canals were photographed in a standardized manner and were superimposed. The inner and outer walls of canal curvature were evaluated to determine the most significant change using the image analysis software. Results: The amount of resin removed from the inner walls was less with rotary single-file NiTi systems when compared with reciprocating. Preparation time was less with rotary instruments. No instrument separation was noted. All instrument systems maintained the original canal curvature. Conclusion: Rotary single-file systems maintained the canal curvature better than reciprocating single-file systems.

Shaping effectiveness and surface topography of reciprocating files after multiple simulated uses.

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer's instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals.

Efficacy of passive ultrasonic irrigation, continuous ultrasonic irrigation versus irrigation with reciprocating activation device in penetration into main and simulated lateral canals.

Context:The use of chemicals solutions and means of activation is of utmost importance in endodontic treatment.Aims:This study compared three activation techniques used in the final irrigation of the endodontic treatment.Subjects and Methods:Eighty uniradicular teeth were instrumented with the Protaper Universal system up to F4 file. After decalcification, the teeth had artificial lateral canals created at 2, 4.5 and 6 mm from working length (WL). The groups were randomly divided into four groups (n = 20): control group (C), passive ultrasonic irrigation (PUI) group, continuous ultrasonic irrigation (CUI) group, and easy clean (EC) group. The penetration of the irrigant into the samples was evaluated using image observation using the Image J program.Statistical Analysis Used:The level of agreement among the observers was determined by the Cronbach's alpha test. The likelihood ratio test was used to evaluate possible differences between the groups and the Kendall's W statistic test to verify possible differences between the irrigant penetration levels in the lateral canals. The Fisher's exact test was applied to verify differences by the studied group considering the WL variables and lateral canals.Results:The results showed no statistical difference in the penetration of the irrigator in the main canal when compared to the C, PUI, CUI, and EC groups (P > 0.05).Conclusions:The method using a positive syringe and needle pressure was not able to effectively carry the irrigator to the artificially made lateral canals, whereas PUI, CUI, and EC were equally efficient in this regard (P < 0.01).

Cyclic fatigue resistance of M-Pro and RaCe Ni-Ti rotary endodontic instruments in artificial curved canals: a comparative in vitro study.

ObjectivesTo compare the flexural cyclic fatigue resistance and the length of the fractured segments (FLs) of recently introduced M-Pro rotary files with that of RaCe rotary files in curved canals and to evaluate the fracture surface by scanning electron microscopy (SEM).Materials and MethodsThirty-six endodontic files with the same tip size and taper (size 25, 0.06 taper) were used. The samples were classified into 2 groups (n = 18): the M-Pro group (M-Pro IMD) and the RaCe group (FKG). A custom-made simulated canal model was fabricated to evaluate the total number of cycles to failure and the FL. SEM was used to examine the fracture surfaces of the fragmented segments. The data were statistically analyzed and comparisons between the 2 groups for normally distributed numerical variables were carried out using the independent Student's t-test. A p value less than 0.05 was considered to indicate statistical significance.ResultsThe M-Pro group showed significantly higher resistance to flexural cyclic fatigue than the RaCe group (p < 0.05), but there was no significant difference in the FLs between the 2 groups (p ≥ 0.05).ConclusionsThermal treatment of nickel-titanium instruments can improve the flexural cyclic fatigue resistance of rotary endodontic files, and the M-Pro rotary system seems to be a promising rotary endodontic file.

Shaping Ability of ProTaper Universal, ProTaper NEXT and WaveOne Primary in Severely Curved Resin Blocks

Complex anatomy of roots requires endodontic rotary instruments that respect and follow that anatomy. The purpose of this study was to compare the shaping ability of three engine-driven nickel-titanium instruments in severely curved simulated canals. Forty-eight severely curved simulated canals in resin blocks were prepared to an apical size of 25 using the following systems (n = 16 per group): ProTaper Universal (PTU), ProTaper NEXT (PTN), and WaveOne Primary (WO) (all Dentsply Maillefer, Ballaigues, Switzerland). Composite images were made from the superimposition of pre- and post-instrumentation images. The amount of resin removed by each system was measured by using a digital template and image analysis software. Shaping ability of each system was compared using different parameters: total resin removal, centering ability, canal transportation in the apical, middle and coronal third of canal. Preparation times were also recorded. The data were statistically analyzed by using analysis of variance, paired t-test, and Tukey's post hoc test. Canals prepared with PTN were better centered in the apical part than those prepared with WO and PTU (p < 0.05). WO removed significantly more resin at the outer aspect of the maximum point of curvature. WO and PTU caused similar canal transportations at 7 points out of 11 measuring points. At measuring points 3, 4, and 5 WO caused more canal straightening than PTU. Instrumentation with PTU required more time than with the two other instruments (p <0.05). No preparation error or instrument separation occurred. In the apical part of the canals PTN obtained the best results with regard to canal transportation. All of the rotary instruments were safe in preparing severely curved canals and PTN showed better preparation of apical part of the canal.

Effect of Different Speeds of Up-and-down Motion on Canal Centering Ability and Vertical Force and Torque Generation of Nickel-titanium Rotary Instruments

IntroductionThis study was performed to evaluate how the speed of up-and-down motion affects the canal centering ability and torque/force generation of ProTaper Next rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland). MethodsTwenty-one simulated resin canal blocks with a J-shaped canal were prepared with ProTaper Next X1, X2, and X3 instruments using an original automated root canal instrumentation and torque/force analyzing device with up-and-down speed settings of 10, 50, and 100 mm/min (low-, medium-, and high-speed groups, respectively). Pre- and postinstrumentation images were superimposed, and centering ratios were calculated at 0–3 mm from the apex. The maximum vertical force and torque were also recorded. The results were statistically analyzed using 1-way analysis of variance and the Tukey test. ResultsAt 0, 0.5, 1, and 2 mm from the apex, the high-speed group showed the lowest centering ratio (ie, least deviation) followed by the medium-speed and low-speed groups (P < .05). Force values (downward and upward) tended to increase as the up-and-down speed increased; with the X2 and X3 instruments, the high-speed and/or medium-speed groups generated significantly larger values than the low-speed group (P < .05). With all instruments, the high-speed and/or medium-speed groups generated significantly larger clockwise torque than the low-speed group (P < .05). One and 2 X2 instruments fractured in the low- and high-speed groups, respectively. ConclusionsThe up-and-down speed affected the canal centering ability and stress generation of ProTaper Next instruments. The high-speed group showed the best centering ability but tended to generate larger vertical force and torque than the medium- and low-speed groups.

Shaping ability of the profile 25/0.06 and protaper F2 in rotary motion, and reciproc in simulated canals.

BackgroundSince the introduction of nickel–titanium (Ni–Ti) instruments to dentistry, a wide variety of Ni–Ti instruments have become commercially available. These Ni–Ti instruments are expensive, which limits their usage in developing countries and forces practitioners to use instruments repeatedly. Another problem is the possible prion cross-contamination associated with the multiple usage of endodontic instruments. In addition, the use of these instruments requires new skills and experience. In this article, the shaping capacities of two conventional rotary file systems, ProFile 25/0.06 and ProTaper F2, were reviewed and compared with the Reciproc single-file system.MethodsA total of 45 simulated canals with 40° curvature, in clear resin blocks, were prepared using conventional rotary systems consisting of ProFile orifice shaping (OS) #3 and final flaring #25/.06, Reciproc R25, and ProTaper shaping file SX and finishing file F2. Pre-and post-instrumentation images were analyzed at ten different levels, using AutoCAD 2007 software. The measurement positions were defined in 1-mm intervals: positions 0–3 established the apical part, positions 4–6 constituted the middle part, and positions 7–10 established the coronal part of the canal. The amount of removed resin, the transportation, instrumentation time, change in working length (WL), instrumentation fractures, and the presence of ledge were evaluated. Data were analyzed using ANOVA, Kruskal–Wallis and independent t-test (p < 0.001).ResultsProFile removed the least resin (p < 0.001) and caused less transportation than Reciproc and ProTaper, in total (p < 0.001). ProTaper caused more transportation ProFile and Reciproc in the apical part (p < 0.000). Reciproc caused more transportation than ProTaper and ProFile (p < 0.001), and the transportation tendency toward the inner aspect of the curvature in the middle part. Reciproc caused the less transportation than ProFile and ProTaper in the coronal part. The transportations tended to occur toward the outside of the curvature, except the middle part with Reciproc and at points 5 and 6 with ProTaper. There were no significant differences among the groups in terms of maintaining the original WL. Reciproc was significantly faster than the others group (p < 0.001). Only one instrument fracture (25/0.06 ProFile) was noted. All groups showed one ledge each.DiscussionThe results of the present study showed that both ProFile 25/06 and ProTaper F2, combined with a file used for coronal enlargement (OS3 and SX), have the potential to create satisfactory canal shape in the curved root canals. Further studies using real human teeth are needed to confirm our results.

Comparison of the Shaping Ability of Endowave and K3 Rotary Nickel-Titanium Instruments in Simulated Canals

Abstract Objectives The aim of this study was to compare canal aberrations and transportation of Endowave and K3 rotary nickel-titanium files in simulated canals with 40-degree curvature. Materials and Methods Twenty simulated canals with 40-degree curvature were divided into two groups (each of 10). In one group, canals were instrumented with Endowave and in the other group with K3. Both systems were used in crown-down manner, and canals were prepared till apical size # 25/0.06 taper. The pre- and post-instrumentation radiographic scanned images were superimposed on each other using software movements and viewed for canal aberrations and transportation. Results are statistically analyzed using Student's t-test. Results In the canals prepared with Endowave files, one (10%) ledge was created whereas in the canals prepared with K3 files, one (10%) apical zip and elbow, one (10%) ledge, and two (20%) perforations were created. When two groups were compared, results were statistically insignificant (p &gt; 0.05) for the amount of resin removed from inner and outer aspect of the canal. Conclusions Endowave files revealed better results in terms of the canal aberrations compared to K3 files. The direction of transportation was generally toward the outer aspect with both files.

Effect of the irrigation protocols on the elimination of dentin debris from simulated lateral canals

Objective: Computed microtomography was used to evaluate the capacity of debris removal from simulated lateral canals, in conventional irrigation, passive ultrasonic irrigation (PUI), continuous passive irrigation (CUI), Endoactivator and EasyClean, for both types of motion (continuous and reciprocating). Material and Methods: Sixty acrylic incisors with 3 simulated lateral canals per tooth (cervical, middle and apical third) were instrumented with Reciproc 40/06 and then filled with dentin debris. The teeth were scanned and divided into 6 groups (n = 10) according to the irrigation protocol: G1 - conventional, G2 - PUI, G3 - CUI, G4 - Endoactivator, G5 - EasyClean continuous rotation and G6 - EasyClean reciprocating. After the irrigation protocols, the samples were scanned again. The initial and final volume images were analyzed and the percentage of debris removal were found for each group in all levels. Results: There were significant differences between the initial and final volume of debris after the protocols, with the exception of conventional irrigation group in the apical and cervical thirds, EasyClean reciprocating in the middle and cervical thirds, and CUI in the middle third. In the analysis between the groups: in the apical third, Endoactivator and PUI removed more debris than CUI (p &lt; 0.05); in the middle and cervical thirds, PUI was more efficient than conventional irrigation, EasyClean reciprocating and CUI (p &lt; 0.05). Conclusion: No method completely removed the debris. PUI was the method that showed greater effectiveness in cleaning the lateral canals.KeywordsRoot canal therapy; Microct; Dentin; Ultrasonic therapy.

Evanescent waves in simulated ear canals: Experimental demonstration and method for compensation.

Evanescent waves emerge from a small sound source that radiates into a waveguide with a larger cross-sectional area, but unlike planar waves, do not propagate far from the source. Evanescent waves thus contaminate in-ear calibration of acoustic stimuli. Measurements with an otoacoustic-emission (OAE) probe inserted at the entrance of long tubes of various diameters show a decline in the evanescent wave with distance from the source when advancing a probe tube through the OAE probe and into the long tube. The amplitude of the evanescent pressure increases with frequency and depends strongly on the diameter of the long tube. Modifying the shape of the aperture of the probe's sound source, thus effectively enlarging its diameter and redirecting acoustic flow, greatly reduced evanescent waves. The reduction in evanescent-wave pressure was observed in calibration cavities used to determine the Thévenin-equivalent source pressure and impedance of the probe. Errors in source calibrations were considerably larger in the unmodified configuration. An alternative method is proposed for calculation of acoustic source parameters that models the evanescent-wave pressure and reduces its influence on the calculation. This reduction greatly improves the quality of source calibrations, which should improve the accuracy of ear-canal impedance measurements and related quantities.

Performance of progressive and constant tapered instruments rotary systems at canal preparation

ABSTRACT Objective: The aim of this study was to compare the performance of two nickel-titanium rotary systems regarding the preparation time, final shape of canal, incidence of aberration, transportation, and fracture of instrument. Methods: A total of 40 simulated canals in resin blocks with 30o curves and a length of 17 mm were divided randomly into two groups: preparation with ProTaper and BioRaCe systems up to F5 and BR5 respectively. Pre- and post-operative canal images were taken and superimposed in order to identify aberrations, transportation, and to take measurements of the canal width. In addition, the preparation time and instrument fractures were recorded. The data were analyzed using Student's t test. Results: There is no difference (p&gt;.05) comparing the systems regarding preparation time, canal aberration, and instrument fracture rates. The progressive tapered instruments of ProTaper prepared significantly larger canal widths in the apical third (p&lt;.05). Conclusion: Overall, both systems provided safe canal preparation, associated with few canal aberrations and instrument fractures.

Influence of the calcium hydroxide paste vehicle on penetration into lateral canals

Objective: The aim of this study was to use Micro computed tomography (micro-CT) to evaluate the influence of the type of vehicle associated with calcium hydroxide on its ability to penetrate simulated lateral canals. Material and methods: 30 acrylic blocks with simulated lateral canals comprising apical, middle and cervical thirds were used in the in vitro study. The blocks were divided into 3 groups (n = 10) according to the type of vehicle used (chlorhexidine, distilled water and propylene glycol) in the calcium hydroxide slurry, which was inserted in the respective group of simulated canals with a K# 30 file and then agitated with an ultrasonic tip. The blocks were scanned by micro-computed tomography (micro-CT) before and after insertion of the medication. The images obtained were reconstructed and analyzed to obtain the initial volume of lateral canals and the volume of medication that penetrated into them. Results: In the intragroup analysis, both distilled water and chlorhexidine 2% were observed to present statistical difference in all thirds of the canal. Propylene glycol showed no intragroup difference. In the inter-group analysis, the propylene glycol paste presented higher values of penetration into the simulated lateral canals than the other groups (p &lt;0.05). Conclusion: Propylene glycol used as vehicle of the calcium hydroxide paste provided better penetration results in simulated lateral canals. KeywordsEndodontics; Calcium hydroxide; Propylene glycol.

Characterization of the nucleus, cutting edge and failure detection in NiTi instruments for endodontic retreatment

OBJECTIVE: To characterize the nucleus, cutting edge and to detect defects in surfaces of nickeltitanium (NiTi) instruments for endodontic retreatment.METHODS: The selected endodontic instruments (D-RaCe, ProTaper retreatment and Mtwo retreatment) were evaluated prior to their use in 30- and 50-fold magnification in scanning electron microscopy (SEM), for linear measurements of lateral cut edge areas and of the nucleus and the ratio between these measures. After use in simulated canals, faults in the active surface were analyzed by SEM with 30 and 50 times magnification, and 200 times magnification when faults were found. The images were examined by three evaluators, whose measurements were previously calibrated. The defects analyzed were crack, blunt and barb, and data were tabulated for analysis.RESULTS: The instruments studied differed in results. The D-RaCe system instruments had the highest nucleus:edge ratio, while ProTaper retreatment instruments yielded the lowest ratio. All instruments presented some defect, with the instruments Mtwo retreatment presenting two instruments with defects.CONCLUSION: All analyzed instruments presented some type of failure after using them for removal of the filling material of simulated root canals. The D-RaCe system presented the highest edge measurements and the smallest nucleus measurements, contrary to the ProTaper retreatment system, which presented the smallest edge measurements and the largest core measurements.