Efficiency of rotary nickel-titanium K3 instruments compared with stainless steel hand K-Flexofile. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth

Effect of Temperatures on Cyclic Fatigue Resistance of 3 Different Ni-Ti Alloy Files

OBJECTIVE

The aim of this study was to investigate and compare the effect of temperature on the cyclic fatigue resistance of conventional (ProTaper Universal [PTU]), Gold-Wire (ProTaper Gold [PTG]), and Fire-Wire (EdgeTaper Platinum [ETP]) nickel-titanium alloy files.

METHOD

Twenty files from each system were tested for cyclic fatigue resistance in an artificial canal model. The experiments were performed at room temperature and body temperature in controlled temperature water. Magnified videos were recorded using a dental operating microscope integrated camera during testing to detect file fracture. The number of cycles to failure (NCF) was calculated. The type of failure was investigated macroscopically and microscopically with a dental operating microscope and scanning electron microscope, respectively.

RESULT

The NCF at room temperature was significantly higher compared with body temperature in each system (P < .001). Compared at the same temperature, the ETP group demonstrated the highest NCF, followed by the PTG and PTU groups (P < .001). All files demonstrated cyclic fatigue failure macroscopically and microscopically.

CONCLUSIONS

The 3 alloy files were affected by temperature. The cyclic fatigue resistance was reduced at the higher temperature and increased at the lower temperature. If the files are geometrically identical, files made of Fire-Wire are preferred compared with Gold-Wire and conventional nickel-titanium alloys based on cyclic fatigue resistance.

Comparison of apical transportation and centering ability of Mtwo and Reciproc R25 in severely curved canals using cone-beam computed tomography

Background:

Apical transportation (AT) of the root canal moves the physiologic canal terminus to a new location on the external root surface and results in the accumulation of debris and residual microorganisms due to inadequate cleaning and shaping of the canal end. This study aimed to assess the prevalence of AT following canal preparation with Mtwo and Reciproc R25 using cone-beam computed tomographic (CBCT).

Materials and Methods:

In this in vitro study, 40 mesiobuccal root canals of the maxillary molars with 19–22 mm length and (>40°) taper were prepared in two groups using Mtwo and Reciproc R25 rotary systems along with irrigation with 2.5% NaOCl. CBCT scans were obtained of the canals before and after preparation under similar conditions, and the values were measured using the device software. The amount of AT was measured according to Gambill et al. Data were analyzed using SPSS 17 and Chi-square and t-tests. P < 0.05 was considered significant.

Results:

Both systems caused some degrees of AT. No significant difference was found between the two systems in terms of the amount and direction of AT (P > 0.05); overall, the frequency of AT toward the mesial wall was greater than that toward the distal direction. However, this difference was not statistically significant.

Conclusion:

The mean amount of AT and the ability to keep the instruments in severely curved canals were not significantly different in canals prepared by Mtwo and Reciproc rotary systems. Thus, these systems can be used in the clinical setting with the lowest risk of AT.

Comparative evaluation of canal cleaning ability of various rotary endodontic filesin apical third: A scanning electron microscopic study

BACKGROUND

The purpose of this study was to evaluate the canal cleaning ability of three novel endodontic rotary instruments and compare with ProTaper files as a control in apical third of root canals under scanning electron microscopy (SEM).

MATERIALS AND METHODS

Eighty freshly extracted mandibular premolars were selected according to inclusion criteria. Buccal cusp tips were ground to ensure having a flat coronal reference point with a total tooth length of 16 mm for all samples. Teeth were divided equally into four groups: Group I (ProTaper group), Group II (ProTaper next group), Group III (variable taper group), and Group IV (self-adjusting file [SAF] group). Using SEM, the dentinal surfaces were observed and rated at apical thirds with a magnification of ×1000 for the presence/absence of smear layer and debris. Descriptive analysis was performed, and analysis of variance with Bonferroni post hoc test was carried out for comparison between the groups, at a significance level of 0.05.

RESULTS

There was statistically significant difference between Group II and Group IV for debris (P = 0.047) and smear layer (P = 0.037).

CONCLUSION

In apical third of root canal, SAF showed statistically significant canal cleaning ability due to combined effect of continuous streaming irrigation with effectively replacing the irrigant from the apical portion of the root canal, irrigants activation through the creation of turbulence, and its self-adapting design to root canal anatomy with a scrubbing motion on the canal walls.

Comparative analysis of cleaning ability of three nickel-titanium rotary systems: ProTaper universal, K3 and Mtwo: An in vitro scanning electron microscopic study

BACKGROUND

Endodontic instruments including the nickel-titanium (NiTi) instruments produce debris and smear layer during instrumentation. The study was carried out to evaluate and compare the cleaning effectiveness of root canal preparation using three different rotary NiTi instrumentation systems - ProTaper Universal, K3 and Mtwo by means of scanning electron microscopy (SEM).

METHODS

Thirty-six freshly extracted permanent mandibular molars were randomly divided into four groups: ProTaper Universal, K3, Mtwo system and control group. The mesiobuccal canal was cleaned and shaped with rotary instruments. The intracanal irrigant used after each instrument was 3 mL of 3% sodium hypochlorite (NaOCl). After the cleaning and shaping was completed, a 1-min 17% ethylenediaminetetraacetic acid rinse was followed by a final NaOCl rinse. All samples were decoronated. Mesial roots were sectioned buccolingually and examined under SEM at 500× magnification in three areas of root canal. Canal walls were quantitatively evaluated using a five-score evaluation scale. Statistical analysis was done using Kruskal-Wallis test, Fisher's exact test and weighted kappa.

RESULTS

Completely clean canals were not found in any of the groups. The mean value of debris score for ProTaper, K3 and Mtwo was 2.35, 2.41 and 2.22 respectively. There was no statistically significant difference between the three tested groups (P = 0.237). The apical thirds of the canal was found to be significantly less clean than coronal and middle thirds irrespective of the system used.

CONCLUSIONS

There was no statistically significant difference between the three tested groups - ProTaper, K3 and Mtwo in cleaning different regions of the canal - coronal, middle and apical.

Computed Tomographic Evaluation of K3 Rotary and Stainless Steel K File Instrumentation in Primary Teeth

INTRODUCTION

The intention of root canal preparation is to reduce infected content and create a root canal shape allowing for a well condensed root filling. Therefore, it is not necessary to remove excessive dentine for successful root canal preparation and concern must be taken not to over instrument as perforations can occur in the thin dentinal walls of primary molars.

AIM

This study was done to evaluate the time preparation, the risk of lateral perforation and dentine removal of the stainless steel K file and K3 rotary instrumentation in primary teeth.

MATERIALS AND METHODS

Seventy-five primary molars were selected and divided into three groups. Using spiral computed tomography the teeth were scanned before instrumentation. Teeth were prepared using a stainless steel K file for manual technique. All the canals were prepared up to file size 35. In K3 rotary files (.02 taper) instrumentation was done up to 35 size file. In K3 rotary files (.04 taper) the instrumentation was done up to 25 size file and simultaneously the instrumentation time was recorded. The instrumented teeth were once again scanned and the images were compared with the images of the uninstrumented canals.

STATISTICAL ANALYSIS

Data was statistically analysed using Kruskal Wallis One-way ANOVA, Mann-Whitney U-Test and Pearson's Chi-square Test.

RESULTS

K3 rotary files (.02 taper) removed a significantly less amount of dentine, required less instrumentation time than a stainless steel K file.

CONCLUSION

K3 files (.02 taper) generated less dentine removal than the stainless steel K file and K3 files (.04 taper). K3 rotary files (.02 taper) were more effective for root canal instrumentation in primary teeth.

Comparing the Coronal Flaring Efficacy of Five Different Instruments Using Cone-Beam Computed Tomography

INTRODUCTION

Fearless removal of tooth structure during canal preparation and shaping has negative effects on the prognosis of treatment. On the other hand, sufficient pre-enlargement facilitates exact measurement of the apical size. The present in vitro study aimed to compare the efficacy of Gates-Glidden drills, K3, ProTaper, FlexMaster and RaCe instruments in dentin removal during coronal flaring using cone-beam computed tomography (CBCT).

METHODS AND MATERIALS

A total of 40 mandibular molars were selected and the coronal areas of their mesiobuccal and mesiolingual root canals were randomly prepared with either mentioned instruments. Pre- and post-instrumentation CBCT images were taken and the thickness of canal walls was measured in 1.5- and 3-mm distances from the furcation area. Data were analyzed using the one-way ANOVA. Tukey's post hoc tests were used for two-by-two comparisons.

RESULTS

At 1.5-mm distance, there was no significant difference between different instruments. However, at 3-mm distances, Gates-Glidden drills removed significantly more dentin compared to FlexMaster files (mean=0.18 mm) (P<0.02); however, two-by-two comparisons did not reveal any significant differences between the other groups.

CONCLUSION

All tested instruments can be effectively used in clinical settings for coronal pre-enlargement.

Evaluation of Root Canal Preparation Using Rotary System and Hand Instruments Assessed by Micro-Computed Tomography

Background

Complete mechanical preparation of the root canal system is rarely achieved. Therefore, the purpose of this study was to evaluate and compare the root canal shaping efficacy of ProTaper rotary files and standard stainless steel K-files using micro-computed tomography.

Material/Methods

Sixty extracted upper second premolars were selected and divided into 2 groups of 30 teeth each. Before preparation, all samples were scanned by micro-computed tomography. Thirty teeth were prepared with the ProTaper system and the other 30 with stainless steel files. After preparation, the untouched surface and root canal straightening were evaluated with micro-computed tomography. The percentage of untouched root canal surface was calculated in the coronal, middle, and apical parts of the canal. We also calculated straightening of the canal after root canal preparation. Results from the 2 groups were statistically compared using the Minitab statistical package.

Results

ProTaper rotary files left less untouched root canal surface compared with manual preparation in coronal, middle, and apical sector (p<0.001). Similarly, there was a statistically significant difference in root canal straightening after preparation between the techniques (p<0.001).

Conclusions

Neither manual nor rotary techniques completely prepared the root canal, and both techniques caused slight straightening of the root canal.

Evaluation of canal transportation and centering ability of K 3 (0.02%) and K 3 (0.04%) with hand K files in primary teeth using spiral computed tomography

BACKGROUND

One of the objectives of root canal preparation is to clean and shape the root canal system while maintaining the original configuration. Therefore, it is important to keep the instruments centered to provide a correct enlargement, without excessive weakening of the root structure.

AIM

The aim of the study was to compare canal transportation and centering ability of K 3 (0.02% taper) and K 3 (0.04% taper) with stainless steel hand K files in primary teeth using a spiral computed tomography (SCT) scan.

MATERIALS AND METHODS

A total of 75 extracted mandibular primary second molars was collected. Canals were divided randomly into three groups of 25 teeth each. Group I: K 3 files (0.02% taper), Group II: K 3 (0.04% taper), and Group III: Stainless steel hand K files. Three regions from apical, mid-root, and coronal levels of the canal were recorded. All the teeth were scanned before and after instrumentation by using SCT.

RESULTS

K 3 (0.02% taper) showed less canal transportation and a better centering ratio than K 3 (0.04% taper) and stainless steel hand K files.

STATISTICAL ANALYSIS

The mean values were compared between different study groups and the P-value was calculated by using Kruskal-Wallis one-way ANOVA. The Mann-Whitney U-test followed by the Bonferroni correction method was employed to identify the significant groups at the 5% level.

CONCLUSION

K 3 (0.02% taper) shaped root canals without significant shaping errors when compared to K 3 (0.04% taper) and stainless steel hand K files in primary teeth.

Comparison of Hero 642 and K3 rotary nickel-titanium files in curved canals of molars and a systematic review of the literature

The aim of the present study was to compare the root canal preparation ability of rotary nickel-titanium (NiTi) Hero 642 and K3 files in curved mandibular or maxillary molars. A total of 40 extracted mandibular molars with two separate mesial canals, an apical width of approximately size ≤15 and a root canal curvature of 15–30° were randomly divided into two groups and instrumented using Hero 642 (n=20) or K3 files (n=20). Canal straightening, working length, transportation, cross-sectional area, minimum dentin thickness and the canal angle curvature degree were examined, and a systematic review of the literature was conducted. No statistically significant differences were observed between the two groups with regard to the mean degree of straightening, mean change in working length, mean transportation, amount of dentin removed or remaining minimum dentin thickness (P>0.05). The canal angle curvature decreased in the two groups postoperatively. The systematic review identified six studies, and overall the two files performed similarly in the majority of categories examined. Therefore, the rotary NiTi Hero 642 and K3 files demonstrated comparable shaping abilities and maintenance of working length.

Scanning electron microscopy comparison of the cleaning efficacy of a root canal system by Nd:YAG laser and rotary instruments

This study evaluated the cleaning efficacy of a root canal system by Nd:YAG laser and rotary instruments. Sixty single-rooted human teeth were divided into four experimental groups (n=15). In the first group the teeth were prepared with a step-back technique using conventional K-files. In the second and third groups, tooth preparation was carried out using Nd:YAG laser and rotary NiTi instruments, respectively. Teeth in the fourth group were prepared by combined laser and rotary methods. The smear layer remaining on canal walls was then assessed by scanning electron microscopy in the coronal, middle, and apical portions. The comparison of smear layer removal efficacy between groups was carried out by Kruskal-Wallis and Mann-Whitney U tests. The mean grades of smear layer removal in rotary-laser, rotary, laser and step-back techniques were 1.34 ± 0.18, 2.2 ± 0.28, 1.91 ± 0.25, and 2.42 ± 0.19, respectively. On the whole, differences between rotary-laser and rotary groups, step-back, and the three other techniques (rotary, laser, and rotary-laser) were significant at p=0.034. Based on the findings of this study, the cleaning efficacy of rotary, laser, and rotary-laser techniques were better than the step-back technique and the combined laser and rotary technique was the most efficient method.

SEM analysis of defects and wear on Ni-Ti rotary instruments

SEM analysis of endodontic instruments from a Ni-Ti rotary system was assessed, before and after using them, considering their defects and deformations. Twenty Twisted File®, BioRąCe®, Mtwo®, and EndoWave® instruments were micrographed at 190× magnification. The files were washed and micrographed again to view alterations as to the presence or absence of irregular edges, grooves, microcavities, and scraping. Simulated root canal preparations were performed using these instruments. The instruments were cleaned and received a microscopic analysis after being used five times. After analysis tests were tested using Fisher's exact test and Kappa to evaluate the concordance among examiners. There was a statistically significant difference with respect to deformations between Twisted File® and other instruments (p < 0.05). There was no statistically significant difference in strains between the other groups (p > 0.05). All Twisted File® instruments showed the same defects; however damage were lower than those found in BioRace® and Mtwo®. The Endowave® did not show the same defects. In accordance with the data we conclude that the presence of defects was higher in Twisted File® instruments as the instruments and BioRace® Mtwo® brand, the defect rate was smaller and Endowave® instruments had no defects. Regarding the presence of wear after five uses among the groups all instruments showed changes in their cutting blades.

Radiographic technical quality of root canal treatment performed ex vivo by dental students at Valencia University Medical and Dental School, Spain

Objectives: To evaluate radiographically the quality of root canal fillings and compare manual and rotary preparation performed on extracted teeth by undergraduate dental students. Study Design: A total of 561 premolars and molars extracted teeth were prepared using nickel-titanium rotary files or manual instrumentation and filled with gutta-percha using a cold lateral condensation technique, by 4th grade undergraduate students. Periapical radiographs were used to assess the technical quality of the root canal filling, evaluating three variables: length, density and taper. These data were recorded, scored and used to study the “technical success rate” and the “overall score”. The length of each root canal filling was classified as acceptable, short and overfilled, based on their relationship with the radiographic apex. Density and taper of filling were evaluated based on the presence of voids and the uniform tapering of the filling, respectively. Statistical analysis was used to evaluate the quality of root canal treatment, considering p < 0.05 as a statistical significant level. Results: The percentage of technical success was 44% and the overall score was 7.8 out of 10. Technical success and overall score were greater with rotary instruments (52% against 28% with a manual one, p < 0.001; 8.3 against 6.7 respectively, p < 0.001). Conclusions: It appears that inexperienced operators perform better root canal treatment (RCT) with the use of rotary instrumentation.

Key words:Dental education, endodontics, rotary instrumentation, radiographs, root canal treatment, undergraduate students.

Effects of preparation techniques on root canal shaping assessed by micro-computed tomography

Background

Root canal shaping without any procedural error is of the utmost preference. Therefore, the purpose of this study was to use micro-computed tomography to evaluate and compare the root canal shaping efficacy of ProTaper rotary files and standard stainless steel K-files.

Material/Methods

Sixty extracted upper second premolars were selected and were divided into 2 groups of 30. Before preparation, all samples were scanned by micro-CT. Then, 30 teeth were prepared with stainless steel files and the remaining 30 with ProTaper rotary files. Canal transportation and centering ability before and after root canal shaping were assessed using micro-CT. The amount and direction of canal transportation and the centering ratio of each instrument were determined in the coronal, middle, and apical parts of the canal. The 2 groups were statistically compared using one-way ANOVA.

Results

ProTaper rotary files gave less transportation (p<0.001) and better centering ability (p<0.00001) compared with stainless steel files.

Conclusions

The manual technique for preparation of root canals with stainless steel files produces more canal transportation, whereas rotary files remain more centered in the canal.

Effects of sodium hypochlorite associated with EDTA and etidronate on apical root transportation

AIM

To evaluate the influence of sodium hypochlorite associated with EDTA and etidronate on apical root transportation.

METHODOLOGY

Forty-five roots of human mandibular molars with curvatures of 15-25° were embedded in acrylic resin to allow standardized angulation of the initial and final radiographs. The pre-instrumentation radiographs of the mesiobuccal canal of each root were taken using a radiograph digital sensor with a size 15 K-file in the canal. The canals were prepared with the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland), using one of the following irrigation regimens during the instrumentation (n = 15): G1 - irrigation with 20 mL of saline solution (control); G2 - alternating irrigation with 2.5% hypochlorite solution (NaOCl) (15 mL); and 17% ethylenediaminetetraacetic acid (EDTA) (5 mL). During instrumentation, the canal was filled with NaOCl and then between each exchange of instrument filled with EDTA for 1 min, and G3 - irrigation with 20 mL of 5% NaOCl and 18% etidronate solution (HEBP) mixed in equal parts. The postinstrumentation radiographs were made with a F3 instrument in the canal. The images were magnified and superposed with Adobe Photoshop software (Adobe Systems, Mountain View, CA, USA). Apical transportation was determined with AutoCAD 2012 software (Autodesk Inc., San Rafael, CA, USA) by measuring the distance in millimetres between the tips of the instruments. The results were subjected to the nonparametric statistical Kruskal-Wallis test (α < 0.05).

RESULTS

The median transportation and interquartile range values were 0.00 ± 0.05 for G1, 0.08 ± 0.23 for G2 and 0.13 ± 0.14 for G3. Comparison between groups showed that apical transportation in G3 was significantly greater than in G1 (P < 0.05).

CONCLUSION

The use of NaOCl associated with etidronate increased apical transportation in the canals of extracted teeth.

Comparison of influence of different manufacturing methods on the cleaning efficiency of rotary nickel-titanium files

The purpose of this study was to evaluate and compare cleaning effectiveness of TwistedFile, GT series X, Revo-S, RaCe, Mtwo, and ProTaper Universal rotary files in curved canals. Seventy mesiobuccal canals of extracted human first maxillary molars were divided into seven groups of 10 samples each. Canals were prepared with six nickel-titanium (NiTi) rotary systems and manual K-Flexofile. Irrigation was performed with 2 mL 2.5% NaOCl solution after each file, and 5 mL 2.5% NaOCl was used for the final flush. After the roots were split longitudinally, the presence of debris and smear layer was visualized using scanning electron microscopic photomicrographs taken at coronal, middle, and apical third. Mean scores for debris and the smear layer were calculated and statistically analyzed for significance between groups using the Kruskal-Wallis nonparametric analysis of variance (P < 0.05) and Mann-Whitney U test (P < 0.001). There was no significant difference among the groups in terms of debris and smear layer scores (P > 0.05). Without considering the preparation method used, while no statistically significant difference was found between the coronal third and the middle third (P > 0.05), higher amount of debris and smear layer were found in apical third (P = 0.001). The new generation of NiTi rotary files including the Twisted File and GT Series X presented similar cleaning effectiveness compared with traditionally ground NiTi rotary files.

Comparison of the cleaning capacity of Mtwo and Pro Taper rotary systems and manual instruments in primary teeth

Background:

Root canal cleaning is an important step in endodontic therapy. In order to develop better techniques, a new generation of endodontic instruments has been designed. The aim of this study was to compare the effectiveness of manual K-files (Mani Co, Tokyo, Japan) and two rotary systems–Mtwo (Dentsply-Maillefer, Ballaigues, Switzerland) and ProTaper (VDW, Munich, Germany)–for root canal preparation in primary molars.

Materials and Methods:

India ink was injected to 160 mesiobuccal and distal root canals of mandibular primary molars. The teeth were randomly divided into three experimental groups and one control group. In each experimental group, either manual instruments (K-files) or rotary instruments (Mtwo or ProTaper) were used to prepare root canals. After cleaning the canals and clearing the teeth, ink removal was evaluated with a stereomicroscope. Statistical analysis was done with Kruskal–Wallis and Friedman tests.

Results:

There were no significant differences in cleaning efficiency between manual and rotary instruments. Only ProTaper files performed significantly better in the coronal and middle thirds than in the apical third of the root canal.

Conclusion:

Manual K-files and the Mtwo and ProTaper rotary systems showed equally acceptable cleaning ability in primary molar root canals.

Evaluation of cleaning capacity and instrumentation time of manual, hybrid and rotary instrumentation techniques in primary molars

AIM

To compare the cleaning effectiveness of manual, hybrid and rotary instrumentation techniques in primary molar teeth.

METHODOLOGY

Fifteen primary molars were selected. After endodontic access, the teeth were immersed in a medium containing Enterococcus faecalis and divided into three groups, according to the root canal instrumentation technique: group 1 - manual, group 2 - hybrid and group 3 - nickel-titanium (NiTi) rotary files. For microbiological evaluation, comparisons before and after instrumentation were performed using the paired Student's t-test. One-way anova complemented with the Student's t-test was used to compare the percentage of microbial reduction. Instrumentation time was evaluated by Kruskal-Wallis and Student-Newman-Keuls tests. Images obtained under scanning electron microscopy were analysed by three blinded examiners, and kappa statistics was used to evaluate calibration among examiners. The most frequent results among examiners were analysed using Kruskal-Wallis and Student-Newman-Keuls tests.

RESULTS

The hybrid technique required a significantly longer instrumentation time than the manual and rotary techniques (P < 0.05). All techniques tested were able to significantly reduce the number of E. faecalis (P < 0.05). The hybrid technique was associated with the highest intracanal bacterial reduction, with a statistically significant difference compared with manual instrumentation (P = 0.01). Manual instrumentation resulted in the lowest amount of debris and the highest amount of smear layer when compared with the rotary and hybrid techniques (P < 0.05). There was no difference between rotary and hybrid instrumentation in the removal of debris and smear layer.

CONCLUSION

The use of NiTi rotary files is an option for root canal instrumentation in primary teeth.

Canal-centering ability: An endodontic challenge

During instrumentation of the root canal, it is important to develop a continuously tapered form and to maintain the original shape and position of the apical foramen. However, the presence of curvatures may cause difficulty in root canal instrumentation. The ability to keep the instruments centered is essential to provide a correct enlargement, without excessive weakening of the root structure. Several studies have shown that Ni-Ti instruments remain significantly more centered and demonstrated less canal transportation than stainless steel files. Considerable research has been undertaken to understand the several factors related to an instrument's canal-centering ability. In this article, we have discussed the influence of various parameters such as alloys used in the manufacture of instruments, instrument cross-section, taper, and have given tips on canal-centering ability.

Histological analysis of cleaning efficacy of hand and rotary instruments in the apical third of the root canal: A comparative study

AIM

To compare the cleaning efficiency of manual and rotary instrumentation in the apical third of the root canal system.

MATERIALS AND METHODS

In group 1 (n=10), instrumentation was performed with stainless steel K-file; in group 2 (n=10), it was done with hand ProTaper files; and in group 3 (n=10), instrumentation was done with ProTaper rotary. Distilled water was used for irrigation. The apical third was sectioned transversally and histologically processed. The cross sections were examined under optic microscope and debris was measured using Motic software.

RESULTS

Instrumentation with stainless steel K-files showed minimum amount of debris, followed by ProTaper hand files, and rotary ProTaper files were least effective with maximum amount of debris; however, there were no significant differences between the three experimental groups.

CONCLUSIONS

Both the manual and rotary instrumentation are relatively efficient in cleaning the apical third of the root canal system and the choice between manual and rotary instrumentation should depend on case to case basis.

Comparison of dentine removal using V-taper and K-Flexofile instruments

AIM

To compare the dentine removal ability of V-Taper and K-Flexofile instruments in mesiobuccal canals of extracted mandibular first molar teeth.

METHODOLOGY

Preoperative images of 40 mesiobuccal canals of mandibular first molars (with a curvature between 20° and 35°) were obtained at 2, 4.5, and 7 mm from the root apices by CT-scan and divided into two groups. Group F was prepared with K-Flexofiles and Gates Glidden drills and Group V with V-Taper Ni-Ti rotary and stainless steel hand instruments. Post-instrumentation images were then obtained and compared with the preoperative images. The ratio of dentine removal based on pre- and postoperative images was calculated, and data was analysed by anova and Tukey post hoc test.

RESULTS

In group F in the coronal sections, the least ratio of the dentine removal to the initial root thickness was on the buccal aspect (15.14% ± 6.72), and the greatest ratio was found on the distolingual (29.38% ± 8.19). In group V in the coronal, the least ratio of the dentine removal to the initial root thickness was on the buccal aspect (9.81% ± 3.26); the greatest ratio was found on the distolingual surface in the coronal sections (34.38% ± 10.51). In the middle sections, the least ratio was on the buccal (10.51% ± 3.39) and the greatest on the distolingual aspects (27.46% ± 12.34) of the roots. In the apical sections, the amount of the dentine removed from the mesial and distal surfaces in group V was significantly more than group F (P < 0.01).

CONCLUSION

The distolingual aspect of the root canal is a danger zone for the mesiobuccal canal of the mesial root in mandibular molar teeth, and preparation of that area should be performed with caution. Except the apical part of the canal, no significant difference was found between the two preparation files or techniques used. Apart from the apical part of the canal, neither instrument maintained the original shape of the coronal and middle parts of the canal.

[Scanning electron microscopy investigation of canal cleaning after canal preparation with nickel titanium files]

INTRODUCTION

Root canal preparation is the most important phase of endodontic procedure and it consists of adequate canal space cleaning and shaping. In recent years, rotary instruments and techniques have gained importance because of the great efficacy, speed and safety of the preparation procedure.

OBJECTIVE

The aim of this research was to investigate the influence of different NiTi files on the canal wall cleaning quality, residual dentine debris and smear layer.

METHODS

The research was conducted on extracted human teeth in vitro conditions. Teeth were divided in 7 main groups depending on the kind of instruments used for root canal preparation: ProTaper, GT, ProFile, K-3, FlexMaster, hand ProTaper and hand GT. Root canal preparation was accomplished by crown-down technique. Prepared samples were assessed on scanning electron microscopy JEOL, JSM-6460 LV. The evaluation of dentine debris was done with 500x magnification, and the evaluation of smear layer with 1,000 times magnification. Quantitive assessment of dentine debris and smear layer was done according to the criteria of Hulsmann.

RESULTS

The least amount of debris and smear layer has been found in canals shaped with ProFile instruments, and the largest amount in canals shaped with FlexMaster instruments. Canal cleaning efficacy of hand GTand ProTaperfiles has been similar to cleaning efficacy of rotary NiTi files. Statistic analysis has shown a significant difference in amount of dentine debris and smear layer on the canal walls between sample groups. shaped with different instruments.

CONCLUSION

Completely clean canals have not been found in any tested group of instruments. The largest amount of debris and smear layer has been found in the apical third of all canals. The design and the type of endodontic instruments influence the efficacy of the canal cleaning.

Comparative evaluation of surface characteristics of dentinal walls with and without using plastic finishing file

Aim:

The aim of this in vitro research is to evaluate the debris present on the dentinal walls after instrumentation in mesiobuccal root of maxillary molar with Hand Protapers, Hand Profiles, Hand Hero Shapers, and finishing the dentinal walls with and without rotary plastic files using stereomicroscope.

Materials and Methods:

Sixty freshly extracted human maxillary first molar teeth were divided into two groups of 30 teeth each (group A and B). Both the groups were divided into three subgroups of 10 teeth each (group A had subgroups A1, A2, and A3) and (group B had subgroups B1, B2 and B3). In group A, all the 30 canals were subjected to cleaning and shaping with three different instruments system and kept unfinished. This group was named as unfinished group. In group B, all the 30 canals were subjected to cleaning and shaping with three different instruments system followed by finishing with plastic files. This group was named as finished group. The crown of each tooth was sectioned at the cementoenamel junction. Canals were prepared following conventional principles of crown down technique. After splitting the roots longitudinally, the dentinal debris of each root canal was evaluated in three areas (coronal, middle and apical thirds of the root) by means of numerical evaluation scale, using a stereomicroscope.

Results:

Stereomicroscopic evaluations showed that there was no significant difference in the debris scores between the subgroups when the canals were instrumented with hand Protaper, hand Profile and hand Hero Shaper in all the thirds. There was no significant difference in scores between the unfinished group and the finished group in the coronal third but significant differences were seen in middle third and apical third.

Conclusions:

After instrumentation with different hand instruments, the use of plastic finishing files showed cleaner canal walls.

Evaluation of apical deviation in root canals instrumented with K3 and ProTaper systems

Objectives:

this study evaluated the apical deviation of curved root canals instrumented with K3 and ProTaper systems.

Material and methods:

twenty root canals of human maxillary and mandibular first molars were employed, which were divided into 2 groups: group A (10 teeth) was instrumented with the K3 system, and group B (10 teeth) with the ProTaper system. Evaluation of deviation was performed by double radiographic exposure. Radiographs were achieved before and after instrumentation, with 0.3-second, thus allowing superimposition of images. Three-dimensional computerized tomograph was performed in 3 specimens in each group, as an additional means to evaluate the apical deviation.

Results:

were evaluated by the parametric test Student-Newman-Keuls at 5%, which did not reveal significance between groups concerning the apical deviation. The results of computerized tomograph images demonstrated that the larger deviation of the root canal occurred at the distolingual area for both systems.

Conclusions:

both techniques produced a mild apical deviation. Computerized microtomography was shown to be accurate for experimental endodontics studies.

Scanning electron microscopic evaluation of debris and smear layer remaining following use of ProTaper and Hero Shaper instruments in combination with NaOCl and EDTA irrigation

OBJECTIVE

The purpose of this study was to evaluate the amounts of debris and smear layer remaining on canal walls after preparation with ProTaper and Hero Shaper instruments in combination with NaOCl and EDTA irrigation in curved root canals.

STUDY DESIGN

A total of 55 root canals were randomly divided into 2 instrumentation groups of 20 canals each and 1 negative control group of 15 canals. The canals in each of the 2 instrumentation groups were prepared with ProTaper or Hero Shaper instruments. Irrigation was performed with 5% NaOCl and 17% EDTA solutions. The control group was not instrumented. The remaining debris and smear layer were evaluated from scanning electron photomicrographs at x200 and x1,000 magnification taken in the coronal, middle, and apical thirds of the canals at both inner and outer canal walls. A 5-category scoring system for debris and smear layer was used. Statistical analysis was carried out using the Kruskal-Wallis and Mann-Whitney rank sum tests.

RESULTS

Completely clean root canals were not found in either instrumentation group. In the coronal and middle thirds, the canal walls of both instrumentation groups were clean, with no or only small areas of debris and smear layer. In the apical region, there were higher scores in terms of debris and smear layer in both instrumentation groups. No significant difference was found at the inner wall of the 2 instrumentation groups in terms of debris mean score. However, the outer canal walls prepared with ProTaper showed lower debris score compared with those prepared with Hero Shaper (P < 0.001). Concerning the smear layer, both the inner and outer canal walls prepared with ProTaper showed lower mean scores compared with those prepared with Hero Shaper (P < 0.001).

CONCLUSIONS

Within the limitations of this study, both instruments in combination with NaOCl and EDTA irrigation produced a clean and debris-free canal surface in the coronal and middle thirds, but were unable to produce a canal surface free from debris and smear layer in the apical third. However, the canals prepared with ProTaper instruments showed smaller amounts of debris and smear layer remaining in the apical region.

The technical quality of nonsurgical root canal treatment performed by a selected cohort of Australian endodontists

AIM

To investigate the technical quality of nonsurgical root canal treatment performed by endodontists in Melbourne, Australia.

METHODOLOGY

Clinical and radiographic records of 100 sequential nonsurgical patients were obtained from each of six endodontists working in private practice. The following variables were analysed: proximity of root filling to radiographic apex; homogeneity and radiodensity of root filling; lateral adaptation of the root filling to the canal walls; taper; extrusion of material; small, appropriate or excessive apical enlargement; presence of lateral canals; transportation; procedural errors. The radiographs were assessed by three independent evaluators. Exploratory data analysis was undertaken using simple frequencies and cross-tabulations. A generalised linear mixed model (GLMM) was used for the formal statistical modelling.

RESULTS

Of the 1351 canals that were examined, 91.7% were filled within 2 mm of the radiographic apex and 74% were within 1 mm. Homogeneity and adequate density were found along the entire length of the canal in 86.1% and 88.6% of cases respectively. Lateral adaptation was adequate in 95.6% of cases and the taper was 'smooth and continuous' in 83.8% of roots. No and/or small extrusion of sealer was noted in 98.3% of cases. Apical enlargement was 'appropriate' in 85% of roots. Both transportation (1.1%) and procedural errors (1.3%) were rare occurrences.

CONCLUSIONS

The technical quality of root fillings performed by endodontists in Melbourne, Australia complied with current guidelines in 77.4%-91.0% of roots. All variables examined confirmed high levels of technical proficiency. There were very few instances of canal transportation and/or procedural errors.

Effect of environment on low-cycle fatigue of a nickel-titanium instrument

This study examined the low-cycle fatigue (LCF) behavior of a nickel-titanium (NiTi) engine-file under various environmental conditions. One brand of NiTi instrument was subjected to rotational-bending fatigue in air, deionized water, sodium hypochlorite, or silicone oil. The curvature of each instrument, diameter of the fracture cross-section, and the number of rotations to failure were determined. The strain-life relationship in the LCF region was examined by using one-way analysis of variance, and the number of crack origins with chi2, for differences between groups. The results showed a linear relationship, on logarithmic scales, between the LCF life and the surface strain amplitude; regression line slopes were significantly different between noncorrosive (air, silicone oil) and corrosive (water, hypochlorite) environments (P < .05), as well as number of crack origins (P < .05). Hypochlorite was more detrimental to fatigue life than water. In conclusion, environmental conditions significantly affect the LCF behavior of NiTi rotary instruments. Fatigue testing of NiTi engine-files should be in a service-like environment.

Root canal preparation with the NiTi systems K3, Mtwo and ProTaper

The aim of this paper was to examine the result of rotary root canal preparation with the nickel-titanium (NiTi) systems K3, ProTaper and Mtwo. One hundred and fifty curved artificial root canals and 60 mesial canals of human mandibular molars were selected. In the group of curved artificial canals, all canals were prepared to size 35/0.04 taper with the three systems. In the group of human mandibular molars, the teeth with mature root canals were radiographed with silver points inserted in bucco-lingual and in mesio-distal positions. In the artificial root group, one K3 instrument separated. Mtwo (20%) showed significantly (P = 0.003) less zips than K3 (46.9%) or ProTaper (50%). There were no significant differences in ledge and elbow formation. K3 and Mtwo had the lowest percentage of canal transportation. There was no significant difference regarding the preparation length or the condition of the apical foramina following the preparation. Canals prepared with K3 (26.5%) were significantly (P < 0.001) less tapered than ProTaper (62%) and Mtwo (82%). In the human mandibular molar group, one Mtwo and one ProTaper instrument separated. No significant differences were found in the preparation length, transportation or taper. The three systems tested, K3, Mtwo and ProTaper, achieved good preparation results.

Pulp ablation therapy by inductive heating: heat generation characteristics in the pulp cavity

OBJECTIVE AND METHODS

This study was performed to clarify the usefulness of inductive heating system for the new endodontic therapy. Dextran magnetite complex (DM) suspensions were injected into the root canal of a permanent tooth, and the tooth was heated up to about 55.0 degrees C by alternating-current magnetic field.

RESULTS AND CONCLUSION

The time until the temperature in the pulp cavity reached 55.0 degrees C was 328 +/- 26 s (mean +/- s.d., n = 8) in the 56 mg as Fe ml(-1) of DM concentration. The temperature in the pulp cavity could be maintained at 53.5-59.0 degrees C for 1200 s by changing the magnetic field intensity safely, while temperature elevations of the dental surface on the coronal and apical sides were 4.9 degrees and 3.7 degrees C, respectively. Thus, this inductive heating system, which has the possibility of selective heating, might be useful for eliminating residues of pulp as a new ablation therapy.