Wizard CD Plus and ProTaper Universal: analysis of apical transportation using new software

Objective

This study has two aims: 1) to evaluate the apical transportation of the Wizard CD Plus and ProTaper Universal after preparation of simulated root canals; 2) to compare, with Adobe Photoshop, the ability of a new software (Regeemy) in superposing and subtracting images.

Material and Methods

Twenty five simulated root canals in acrylic-resin blocks (with 20º curvature) underwent cone beam computed tomography before and after preparation with the rotary systems (70 kVp, 4 mA, 10 s and with the 8×8 cm FoV selection). Canals were prepared up to F2 (ProTaper) and 24.04 (Wizard CD Plus) instruments and the working length was established to 15 mm. The tomographic images were imported into iCAT Vision software and CorelDraw for standardization. The superposition of pre- and post-instrumentation images from both systems was performed using Regeemy and Adobe Photoshop. The apical transportation was measured in millimetres using Image J. Five acrylic resin blocks were used to validate the superposition achieved by the software. Student''s t-test for independent samples was used to evaluate the apical transportation achieved by the rotary systems using each software individually. Student''s t-test for paired samples was used to compare the ability of each software in superposing and subtracting images from one rotary system per time.

Results

The values obtained with Regeemy and Adobe Photoshop were similar to rotary systems (P>0.05). ProTaper Universal and Wizard CD Plus promoted similar apical transportation regardless of the software used for image''s superposition and subtraction (P>0.05).

Conclusion

Wizard CD Plus and ProTaper Universal promoted little apical transportation. Regeemy consists in a feasible software to superpose and subtract images and appears to be an alternative to Adobe Photoshop.     

The Effect of Larger Apical Preparations in the Danger Zone of Lower Molars Prepared Using the Mtwo and Reciproc Systems

Introduction

The aim of this study was to evaluate the effects of large apical preparations in the danger zones of the mesial root canals of mandibular molars instrumented with the Mtwo and Reciproc systems (VDW, Munich, Germany) until reaching apical diameters of 0.25 and 0.40 mm.

Methods

Twelve mandibular molars, the mesial roots of which presented distinct foramens and similar anatomies, were selected using micro–computed tomographic scanning. Mtwo and Reciproc instruments were used to shape the mesiobuccal or mesiolingual canals. The mesial canals were scanned before and after the use of 0.25- and 0.40-mm Mtwo and Reciproc instruments. The analyzed parameters included the root canal volume and remaining dentin thickness at 5 different levels. The obtained data were subjected to paired analysis of variance and Tukey or Friedman and Dunn tests for intragroup analysis and the Mann-Whitney U test for comparison between the mesial and distal walls.

Results

There were no significant differences between the mesial and distal dentin thickness for the points analyzed with both instrumentation techniques (P > .05). The volumetric analysis revealed a significant difference (P < .05) among the initial volume and after the use of the 0.25- and 0.40-mm instruments for both systems. The use of the 0.40-mm instrument increased the root canal volume in comparison to the 0.25-mm instrument (P < .05).

Conclusions

Both systems performed similarly for the preparation of curved root canals with separate apical foramens. The increase of the root canal preparation with the 0.40-mm instrument significantly increased the root canal volume at the apical third without significantly reducing the dentin thickness in the danger zone for both instrument systems.     

Micro–Computed Tomographic Evaluation of Canal Transportation Instrumented by Different Kinematics Rotary Nickel-Titanium Instruments

Introduction

The purpose of this study was to evaluate and compare canal transportation of curved root canals by using 3 nickel-titanium systems: Reciproc, WaveOne, and Twisted Files Adaptive (TF).

Methods

Twenty-four extracted human mandibular molars with 2 separate mesial canals and severe angle of curvature were selected. Individual canals were divided randomly to 1 of the 3 experimental groups: Reciproc group, reciprocating instrumentation with Reciproc R25; WaveOne group, reciprocating instrumentation with the Primary WaveOne file; and TF Adaptive group, Adaptive Rotary Motion with the TF files. Each group consisted of 16 root canals. Specimens were scanned before and after root canal preparation with an isotropic resolution of 20 μm by using micro–computed tomography. The degree of canal transportation, in addition to instruments' centering ability, was recorded.

Results

Less transportation occurred with TF Adaptive rotary instruments (P < .0001). The mean degree of canal transportation in the apical third was significantly lower with TF Adaptive group (P < .0001). No significant difference was found between Reciproc and WaveOne systems (P = 1.000). Mean centering ratio was the highest statistically with TF Adaptive (P < .0001), followed by WaveOne, and was minimal with Reciproc (P < .05).

Conclusions

The TF Adaptive system was found to have less canal transportation and better centering ability when compared with the reciprocating groups.     

Apical transportation associated with ProTaper? Universal F1, F2 and F3 instruments in curved canals prepared by undergraduate students

Objective

This study evaluated apical transportation associated with ProTaper^® Universal Fl, F2 and F3 rotary files in curved canais prepared by undergraduate students.

Material and Methods

Twenty mesial roots of mandibular molars with curvatures ranging between 25° and 35° were selected. Mesiobuccal canals were instrumented by twenty students with the ProTaper^® system (Dentsply-Maillefer, Ballaigues, Switzerland) according to the manufacturer''s instructions. Pre-fiaring was performed with Sl and SX files. A #15 K-file was inserted into the root canal up to the working length (WL), and an initial digital radiograph was taken in a buccolingual direction (baseline). Afterwards, the S1, S2, F1, F2, and F3 files were employed up to the WL. Other radiographies were taken in the same orientation of the baseline after the use of the Fl, F2, and F3 files, with each file inserted into the root canal. The radiographic images were overlapped, and the Image J software was used to measure the distance between the rotary files'' ends and the #15 K-file''s end, characterizing the apical transportation. Data were analyzed by Repeated Measure ANOVA and by the SNK post hoc test (P<0.05).

Results

It was verified that file size affected apical transportation significantly (P<0.001). The F3 file showed higher apical transportation than Fl and F2, while between these last files there was no difference.

Conclusion

The undergraduate students produced lower apical transportation in curved canals when they did not use the F3 rotary file.     

Qualitative SEM/EDS analysis of microleakage and apical gap formation of adhesive root-filling materials

Objective

The aim of this study was to compare the correspondence between gap formation and apical microleakage in root canals filled with epoxy resin-based (AH Plus) combined or not with resinous primer or with a dimethacrylate-based root canal sealer (Epiphany).

Material and Methods

Thirty-nine lower single-rooted human premolars were filled by the lateral condensation technique (LC) and immersed in a 50-wt% aqueous silver nitrate solution at 37ºC (24 h). After longitudinal sectioning, epoxy resin replicas were made from the tooth specimens. Both the replicas and the specimens were prepared for scanning electron microscopy (SEM). The gaps were observed in the replicas. Apical microleakage was detected in the specimens by SEM/energy dispersive spectroscopy (SEM/EDS). The data were analyzed statistically using an Ordinal Logistic Regression model and Analysis of Correspondence (α=0.05).

Results

Epiphany presented more regions containing gaps between dentin and sealer (p<0.05). There was correspondence between the presence of gaps and microleakage (p<0.05). Microleakage was similar among the root-filling materials (p>0.05).

Conclusions

The resinous primer did not improve the sealing ability of AH Plus sealer and the presence of gaps had an effect on apical microleakage for all materials.     

Lack of correlation between tubular dentine cement penetration, adhesiveness and leakage in roots filled with gutta percha and an endodontic cement based on epoxy amine resin

Objective

To analyze possible correlations among tubular dentine cement penetration, adhesiveness and apical leakage in fillings performed with gutta percha and an endodontic cement based on epoxy amine resin.

Material and Methods

Sixty similar, extracted human mandibular central incisors were irrigated, instrumented and filled following the same protocol. First, apical leakage was quantified by fluid filtration tests. Then, these same specimens were sectioned for analysis of tubular dentine cement penetration and the middle thirds were submitted to push-out tests to analyze the adhesiveness of the fillings.

Results

In brief, the means and standard deviations with a confidence interval of 95% were as follows: tubular dentine cement penetration (8.875±4.540), adhesiveness (4.441±2.683) and apical leakage (0.318±0.215). The data were confronted using the Pearson''s test (P>0.05), and it was possible to prove that there was no correlation between (1) tubular dentine cement penetration and apical leakage (r²: 0.08276), (2) tubular dentine cement penetration and adhesiveness (r²: -0.2412) and (3) adhesiveness and apical leakage (r²: 0.1340).

Conclusion

After analysis of these data, it could be observed that there exists no correlation among the variables analyzed in this study.     

The sealing ability of MTA apical plugs exposed to a phosphate-buffered saline

Objective

The aim of this study was to evaluate the influence of exposure of the mineral trioxide aggregate (MTA) - with and without calcium chloride (CaCl₂) - to phosphate-buffered saline (PBS) on the apical microleakage using a glucose leakage system.

Material and Methods

Sixty root segments were randomly divided into 4 experimental groups (n=15). After resecting the apical segments and enlarging the canals with Gates-Glidden drills, the apical cavities were filled with MTA with or without CaCl₂ and the root canals were dressed with a moistened cotton pellet or PBS, as follows: 1) MTA/cotton pellet; 2) MTA/PBS; 3) MTA+10%CaCl₂/cotton pellet; 4) MTA+10%CaCl₂/PBS. All root segments were introduced in floral foams moistened with PBS. After 2 months, all root segments were prepared to evaluate the glucose leakage along the apical plugs. The amount of glucose leakage was measured following an enzymatic reaction and quantified by a spectrophotometer. Four roots were used as controls. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests (p<0.05).

Results

There were no differences between groups 1 and 2 (p>0.05), and 3 and 4 (p>0.05). The addition of CaCl₂ to the MTA significantly decreased its sealing ability (p<0.05).

Conclusion

The interaction with PBS did not improve the MTA sealing ability. The addition of CaCl₂ to the MTA negatively influenced the apical seal.     

WEAR PROMOTED IN THE APICAL THIRD OF SIMULATED CANALS AFTER INSTRUMENTATION WITH PROTAPER UNIVERSAL SYSTEM

Objective:

This study evaluated the wear in the apical third of simulate canals after preparation with ProTaper Universal Rotary System.

Material and Methods:

24 sets of instruments were used in 24 simulated canals in transparent epoxy resin blocks with degree of curvature of either 20°or 40°. The canals were photographed preoperatively and after preparation of the apical stop with ProTaper F3, F4 and F5 instruments. The initial and final images were exported to Adobe Photoshop^® software and superimposed to detect the root canal wall differences (in mm) between them, in two points located 1 (A) and 5 (B) mm from the point where the working length was established. Data were subjected to analysis of variance to verify the existence of interaction among the factors: canal curvature, instrument size and curve location. Significant level was set at 5%.

Results:

Regardless of the location and the canal curvature, F4 and F5 instruments produced the greatest wear (p<0.05).

Conclusions:

There was a deviation from the original pathway towards the outside of the root curvature in both analyzed points. All instruments produced canal transportation, but the F4 and F5 instruments produced more than the other instruments, and should thus be used with care in curved canals.     

Cyclic Fatigue Resistance of Reciproc Blue and Reciproc Files in an S-shaped Canal

Introduction

This study evaluated the cyclic fatigue resistance (CFR) of Reciproc (R25 and R40; VDW, Munich, Germany) and Reciproc Blue (R25 and R40, VDW) instruments used in an artificial S-shaped canal.

Effect of pre-flaring and file size on the accuracy of two electronic apex locators

Objective

This ex vivo study evaluated the effect of pre-flaring and file size on the accuracy of the Root ZX and Novapex electronic apex locators (EALs).

Material and methods

The actual working length (WL) was set 1 mm short of the apical foramen in the palatal root canals of 24 extracted maxillary molars. The teeth were embedded in an alginate mold, and two examiners performed the electronic measurements using #10, #15, and #20 K-files. The files were inserted into the root canals until the "0.0" or ''''APEX'''' signals were observed on the LED or display screens for the Novapex and Root ZX, respectively, retracting to the 1.0 mark. The measurements were repeated after the pre-flaring using the S1 and SX Pro-Taper instruments. Two measurements were performed for each condition and the means were used. Intra-class correlation coefficients (ICCs) were calculated to verify the intra- and inter-examiner agreement. The mean differences between the WL and electronic length values were analyzed by the three-way ANOVA test (p<0.05).

Results

ICCs were high (>0.8) and the results demonstrated a similar accuracy for both EALs (p>0.05). Statistically significant accurate measurements were verified in the pre-flared canals, except for the Novapex using a #20 K-file.

Conclusions

The tested EALs showed acceptable accuracy, whereas the pre-flaring procedure revealed a more significant effect than the used file size.     

Shaping Ability of Different Nickel-Titanium Systems in Simulated S-shaped Canals with and without Glide Path

Introduction

The objective of this study was to compare the shaping ability of different rotary and reciprocating nickel-titanium file systems with and without previous glide path preparation in simulated S-shaped canals.

Methods

One hundred twenty S-shaped canals in resin blocks were prepared to an apical size 25 by using Reciproc, WaveOne, HyflexCM, F360, and OneShape systems either with or without previous glide path preparation (Pathfile) (12 canals/group). Material removal was measured at 20 measuring points, beginning 1 mm from the end point of preparation. Incidence of canal aberrations (zip/elbow, ledge formation), preparation time, and instrument failures were also recorded. Statistical analyses were performed by using analysis of variance and Tukey and χ² tests.

Results

For all systems, glide path preparation exerted no significant effect on preparation times (P > .05). Glide path preparation had no influence on the incidence of canal aberrations and instrument fractures (P > .05), with no significant differences between the 5 systems (P > .05). Glide path preparation had no influence on the centering ability of all systems (P > .05). On average, canals prepared with F360, OneShape, and HyflexCM remained better centered compared with those enlarged with WaveOne and Reciproc.

Conclusions

Under the conditions of this study, glide path preparation had no significant impact on canal straightening. Less tapered instruments maintained the original canal curvature better than instruments having greater tapers.     

Importance of a distal proximal contact on load transfer by implant-supported single adjacent crowns in posterior region of the mandible: a photoelastic study

Objective

This study aimed to evaluate the importance of a distal proximal contact on the load transfer to the posterior region of the mandible by non-splinted adjacent implant-supported crowns using photoelastic stress analysis.

Material and Methods

A rectangular model (68x30x15 mm) was made of polymethylmethacrylate resin to simulate half of the mandibular arch. One model was completed with resin replicas representing the first premolar and second molar and with two 3.75 mm dia.x11 mm internal hexagon threaded implants replacing the second premolar and first molar. The other model was manufactured in the same way but without the second molar. Both models were duplicated using photoelastic resin. The roots of the teeth replicas were covered with a layer of polyether impression material to simulate the periodontal ligament. Two different vertical loads were applied to the crowns as follows: 1 - single static point load alternately applied to the crowns replacing the second premolar and first molar (50 N); 2 - simultaneous static point loads applied to both of the crowns replacing the second premolar and first molar (100 N). The resulting isochromatic fringe pattern in the photoelastic model was monitored and photographed.

Results

All loading conditions studied showed that the presence of the second molar has changed the load transmission and the pattern of stresses.

Conclusion

Results showed that the presence of a second molar proximal contact can help minimize the stresses around the implants.     

Evaluation of the resin cement thicknesses and push-out bond strengths of circular and oval fiber posts in oval-shapes canals

PURPOSE

The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts.

MATERIALS AND METHODS

Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done.

RESULTS

No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05).

CONCLUSION

In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.     

The adhesive system and root canal region do not influence the degree of conversion of dual resin cement

Objectives

The aim of this study was to evaluate the influence of two adhesive systems and the post space region on the degree of conversion of dual resin cement and its bond strength to root dentin.

Material and Methods

One three-step etch-andrinse (All-bond 2, Bisco) and another one-step self-etch (Xeno III, Dentsply) adhesive systems were applied on 20 (n=10) crownless bovine incisors, at 12-mm-deep post space preparation, and a fiber post (DT Light Post, Bisco) was cemented using a dual cure resin cement (Duo-Link, Bisco). Three transverse sections (3 mm) were obtained, being one from each study region (cervical, middle and apical). The degree of conversion of the dual cure resin cement was determined by a micro-Raman spectrometer. The data (%) were submitted to repeated-measures analysis of variance and Tukey''s test (p<0.05).

Results

For both groups, the degree of conversion means (%) (All bond 2_cervical = 69.3; All bond 2_middle = 55.1; All bond 2_apical= 56; Xeno III_cervical = 68.7; Xeno III_middle = 68.8; Xeno III_apical = 54.3) were not significantly different along the post space regions (p<0.05).

Conclusion

Neither the adhesive nor the post space region influenced the degree of conversion of the cement layer.     

Comparative Study of Different Novel Nickel-Titanium Rotary Systems for Root Canal Preparation in Severely Curved Root Canals

Introduction

We compared the effects of 6 different rotary systems on transportation, canal curvature, centering ratio, surface area, and volumetric changes of curved mesial root canals of mandibular molar via cone-beam computed tomographic (CBCT) imaging.

Methods

Mesiobuccal root canals of 120 mandibular first molars with an angle of curvature ranging from 20°–40° were divided into 6 groups of 20 canals. Based on CBCT images taken before instrumentation, the groups were balanced with respect to the angle and radius of canal curvature. Root canals were shaped with the following systems with an apical size of 25: OneShape (OS) (MicroMega, Besancon, France), ProTaper Universal (PU) F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Next X2 (Dentsply Maillefer), Reciproc (R) R25 (VDW, Munich, Germany), Twisted File Adaptive (TFA) SM2 (SybronEndo, Orange, CA), and WaveOne primary (Dentsply Tulsa Dental Specialties, Tulsa, OK). After root canal preparation, changes were assessed with CBCT imaging. The significance level was set at P = .05.

Results

The R system removed a significantly higher amount of dentin than the OS, PU, and TFA systems (P < .05). There was no significant difference among the 6 groups in transportation, canal curvature, changes of surface area, and centering ratio after instrumentation.

Conclusions

The 6 different file systems straightened root canal curvature similarly and produced similar canal transportation in the preparation of mesial canals of mandibular molars. R instrumentation exhibited superior performance compared with the OS, TFA, and PU systems with respect to volumetric change.     

Dentine microhardness after different methods for detection and removal of carious dentine tissue

There are several methods for identifying carious dentinal tissue aiming to avoid removal of healthy dentinal tissue.

Objectives

The purpose of this study was to test different methods for the detection of carious dentinal tissue regarding the amount of carious tissue removed and the remaining dentin microhardness after caries removal.

Material and methods

The dentin surfaces of 20 bovine teeth were exposed and half of the surface was protected with nail polish. Cariogenic challenge was performed by immersion in a demineralizing solution for 14 days. After transverse cross-section of the crown, the specimens were divided into four groups (n=10), according to the method used to identify and remove the carious tissue: "Papacárie", Caries-detector dye, DIAGNOdent and Tactile method. After caries removal, the cross-sectional surface was included in acrylic resin and polished. In a microhardness tester, the removed dentin thickness and the Vickers microhardness of the following regions were evaluated: remaining dentin after caries removal and superficial and deep healthy dentin.

Results

ANOVA and Tukey''s test (α=0.05) were performed, except for DIAGNOdent, which did not detect the presence of caries. Results for removed dentin thickness were: "Papacárie" (424.7±105.0; a), Caries-detector dye (370.5±78.3; ab), Tactile method (322.8±51.5; bc). Results for the remaining dentin microhardness were: "Papacárie" (42.2±10.5; bc), Caries-detector dye (44.6±11.8; abc), Tactile method (24.3±9.0; d).

Conclusions

DIAGNOdent did not detect the presence of carious tissue; Tactile method and "Papacárie" resulted in the least and the most dentinal thickness removal, respectively; Tactile method differed significantly from "Papacárie" and Caries-detector dye in terms of the remaining dentin microhardness, and Tactile method was the one which presented the lowest microhardness values.     

SURGICAL CROWN LENGTHENING: A 12-MONTH STUDY - RADIOGRAPHIC RESULTS

Objective

The purpose of this study was to perform a radiographic follow-up evaluation after a 12-month healing period, following crown lengthening surgery.

Material and methods

Twenty-three periodontally healthy subjects (mean age 32.5 years) that required crown lengthening surgery in premolars were recruited. In a total of 30 premolars, full thickness flaps, osseous resection, and flap suturing were performed. The restorative margin was defined in the pre-surgical phase and maintained unaltered during the healing period, serving as a reference point. Standardized bitewing radiographs were taken before and after osseous reduction, and at 2, 3, 6, and 12-month healing periods.

Results

Intact lamina dura was observed at both mesial and distal alveolar crests only from the 3rd month. At 12-months, all alveolar crests presented lamina dura. The overall mean distance from the restorative margin to the alveolar crest achieved after osseous resection was 3.28±0.87 mm at mesial and 2.81±0.51 mm at distal sites. No significant radiographic changes in the bone crest were observed during a 12-month healing period.

Conclusion

The findings of this study suggest that the radiographic proximal bone level observed on bitewing radiographs following crown lengthening surgery can be used as a reference to predict the future level of the healed alveolar crest.     

EVALUATION OF APICAL MICROLEAKAGE OF TEETH SEALED WITH FOUR DIFFERENT ROOT CANAL SEALERS

Objectives:

to compare the apical sealing ability of four root canal sealers. Materials and methods: forty extracted human maxillary canines were instrumented 1 mm short of the anatomical apex and randomly assigned to four groups (n=10), according to the root canal sealer used for obturation: Endofill, AH Plus, EndoREZ and Epiphany. Root canals were obturated with guttapercha points, except for the Epiphany group, in which resin points (Resilon) were used. The teeth were immersed in India ink for seven days and clarified using methyl salicylate. The extent of apical dye penetration was measured with a measuroscope in all aspects of the canal.

Results:

AH Plus (0.02 mm ± 0.07), Epiphany (0.00 mm ± 0.00) and EndoREZ (0.32 mm ± 0.62) did not differ statistically to each other (p>0.01). EndoFill presented the highest dye penetration mean (0.83 mm ± 0.73) and was statistically different from the other sealers (p<0.01).

Conclusions:

the resin-based root canal sealers presented lesser apical microleakage than the zinc oxide and eugenol based sealer. No statistical differences were observed among resin based sealers.     

Factors affecting the bond strength of denture base and reline acrylic resins to base metal materials

Objective

The shear bond strengths of two hard chairside reline resin materials and an auto-polymerizing denture base resin material to cast Ti and a Co-Cr alloy treated using four conditioning methods were investigated.

Material and Methods

Disk specimens (diameter 10 mm and thickness 2.5 mm) were cast from pure Ti and Co-Cr alloy. The specimens were wet-ground to a final surface finish of 600 grit, air-dried, and treated with the following bonding systems: 1) air-abraded with 50-70-µm grain alumina (CON); 2) 1) + conditioned with a primer, including an acidic phosphonoacetate monomer (MHPA); 3) 1) + conditioned with a primer including a diphosphate monomer (MDP); 4) treated with a tribochemical system. Three resin materials were applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles.

Results

The strengths decreased after thermocycling for all combinations. Among the resin materials assessed, the denture base material showed significantly (p<0.05) greater shear bond strengths than the two reline materials, except for the CON condition. After 10,000 thermocycles, the bond strengths of two reline materials decreased to less than 10 MPa for both metals. The bond strengths of the denture base material with MDP were sufficient: 34.56 MPa for cast Ti and 38.30 for Co-Cr alloy.

Conclusion

Bonding of reline resin materials to metals assessed was clinically insufficient, regardless of metal type, surface treatment, and resin composition. For the relining of metal denture frameworks, a denture base material should be used.     

ASSESSMENT OF CANAL WALLS AFTER BIOMECHANICAL PREPARATION OF ROOT CANALS INSTRUMENTED WITH PROTAPER UNIVERSAL? ROTARY SYSTEM

Objective:

The aim of this study was to examine the instrumented walls of root canals prepared with the ProTaper Universal™ rotary system.

Material and Methods:

Twenty mesiobuccal canals of human first mandibular molars were divided into 2 groups of 10 specimens each and embedded in a muffle system. The root canals were transversely sectioned 3 mm short of the apex before preparation and remounted in their molds. All root canals were prepared with ProTaper Universal™ rotary system or with Nitiflex™ files. The pre and postoperative images of the apical thirds viewed with a stereoscopic magnifier (×45) were captured digitally for further analysis. Data were analyzed statistically by Fisher''s exact test and Chi-square test at 5% significance level.

Results:

The differences observed between the instrumented and the noninstrumented walls were not statistically significant (p<0.05).

Conclusions:

The Nitiflex™ files and the ProTaper Universal™ rotary system failed to instrument all the root canal walls.