Article

Can size 20, .04 taper rotary file reproducibly create a glide path for the self-adjusting file (SAF)? An ex vivo study in MB canals of mandibular molars

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Abstract

AimTo test and compare the effectiveness and safety of two size 20, .04 taper rotary files that were used as glide path preparation files for the self-adjusting file (SAF) in curved canals of mandibular molars.MethodologyForty mandibular molars with curved mesial roots and narrow MB root canals were selected based on a passage of size 15 K-files to WL; size 20 K-files could not reach WL. Only roots with no visible microcracks were included. Two types of size 20 rotary files were used for glide path preparation, the new Pre-SAF size 20, .04 taper file and the ProFile size 20, .04 taper, which served as the reference and control. Both files were used with 3-4 pecking strokes, which brought them to WL. Two parameters were tested: whether the glide path allowed manual insertion of a 1.5-mm SAF file to WL and whether the procedure caused microcracks in the root dentine. Paired t tests were used to compare the groups.ResultsGlide path preparation with both files allowed the manual insertion of the SAF file to WL in all 20 root canals, with no difference between the two groups. No cracks were detected after the procedure in any of the roots in either group.Conclusions Both types of size 20, .04 taper rotary files were effective for glide path preparation for the SAF file in curved canals. Neither file type caused microcracks in root dentine.This article is protected by copyright. All rights reserved.

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... [8,9,16] In the case of the self-adjusting file (SAF) system (ReDent-Nova, Ra'anana, Israel), glide path preparation is especially important because this file, as opposed to most rotary and reciprocating files, has no penetration ability per se. [17] This study was designed to compare the relative axis modification and canal concentricity after a glide path prepared with two types of files such as 20/0.02 hand K-file (NITIFLEX ® , Dentsply Maillefer, Ballaigues, Switzerland) and 20/0.04 rotary file (HyFlex™ CM NiTi File, Coltene-Whaledent, Switzerland) in simulated root canals of resin blocks with 1.5 mm SAF. ...
... The concept of the study design was to test a recently proposed protocol for SAF instrumentation by Kfir et al. (2015), [17] and its effect on the canal geometry. ...
... The concept of the study design was to test a recently proposed protocol for SAF instrumentation by Kfir et al. (2015), [17] and its effect on the canal geometry. ...
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Objectives: To compare the relative axis modification and canal concentricity after glide path preparation with 20/0.02 hand K-file (NITIFLEX®) and 20/0.04 rotary file (HyFlex™ CM) with subsequent instrumentation with 1.5 mm self-adjusting file (SAF). Materials and Methods: One hundred and twenty ISO 15, 0.02 taper, Endo Training Blocks (Dentsply Maillefer, Ballaigues, Switzerland) were acquired and randomly divided into following two groups (n = 60): group 1, establishing glide path till 20/0.02 hand K-file (NITIFLEX®) followed by instrumentation with 1.5 mm SAF; and Group 2, establishing glide path till 20/0.04 rotary file (HyFlex™ CM) followed by instrumentation with 1.5 mm SAF. Pre- and post-instrumentation digital images were processed with MATLAB R 2013 software to identify the central axis, and then superimposed using digital imaging software (Picasa 3.0 software, Google Inc., California, USA) taking five landmarks as reference points. Student's t-test for pairwise comparisons was applied with the level of significance set at 0.05. Results: Training blocks instrumented with 20/0.04 rotary file and SAF were associated less deviation in canal axis (at all the five marked points), representing better canal concentricity compared to those, in which glide path was established by 20/0.02 hand K-files followed by SAF instrumentation. Conclusion: Canal geometry is better maintained after SAF instrumentation with a prior glide path established with 20/0.04 rotary file.
... [9] Establishing a glide path prior motorized instrumentation creates a patent channel from the coronal access cavity to the apical terminus. [10] It also helps in enhancing the Journal of Conservative Dentistry | Volume 20 | Issue 2 | March-April 2017 performance of the rotary nickel-titanium (NiTi) files [11,12] and reduces the extrusion of debris. [13] Most of the NiTi rotary and reciprocating files are flexible and have noncutting tips, [6,10] hence cannot be used for initial negotiation of the root canals. ...
... [10] It also helps in enhancing the Journal of Conservative Dentistry | Volume 20 | Issue 2 | March-April 2017 performance of the rotary nickel-titanium (NiTi) files [11,12] and reduces the extrusion of debris. [13] Most of the NiTi rotary and reciprocating files are flexible and have noncutting tips, [6,10] hence cannot be used for initial negotiation of the root canals. [14] Therefore, creating a glide path is recommended when using these file systems, especially in curved canals. ...
... [16] The previous manufactures' instructions were to prepare a glide path till #20 K-file. Nevertheless, recently, Kfir et al. [10] reported that creating a glide path to #20 K-file might not be adequate for the SAF to reach the working length (WL) in curved canals. They reported that a glide path with size 20/0.04 ...
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Aim: The aim of this study was to test the effect of new protocol of glide path preparation by 20/0.04 rotary file on apical extrusion of debris when instrumenting fine curved mesial canals in mandibular molars with Self-adjusting File (SAF) and compare it to a glide path prepared by 20/0.02 hand K-file and rotary OneShape (OS) and reciprocating WaveOne (WO) file instrumentation. Materials and Methods: Sixty mandibular molars with curved mesial roots were selected and randomly divided into three groups (n = 20) for instrumentation. In two groups, glide path was prepared using 20/0.02 K-file for instrumentation by OS (size 25/0.06 taper) and WO (size 25/0.08 taper) files; in the remaining group, 20/0.04 rotary file was used for glide path preparation and instrumented by SAF (1.5 mm). The debris extruded during instrumentation was collected in preweighed Eppendorf tubes and stored in an incubator at 70°C for 5 days. Tubes containing the dry extruded debris were then weighed. One-way analysis of variance (ANOVA) was applied to the weights obtained, followed by Tukey's post hoc test for multiple comparison. Results: The mean debris (g) extruded apically was 0.000651 ± 0.000291, 0.000823 ± 0.000319, and 0.000473 ± 0.000238 for Group 1 (20/0.02 + OS), Group 2 (20/0.02 + WO), and Group 3 (20/0.04 + SAF), respectively. The groups exhibited a significant difference (P < 0.01; ANOVA). Group 3 resulted in least debris extrusion compared to Groups 1 and 2 (P < 0.01; Tukey's post hoc test). Conclusion: Glide path prepared to size 20/0.04 and SAF 1.5 mm instrumentation produce less debris in curved mesial canals of mandibular molars, compared to glide path established by 20/0.02 and instrumentation by OS and WO files.
... Therefore, various NiTi rotary instruments are introduced. They are quick, safe and with enhanced flexibility, which lead to less procedural errors during biomechanical preparation (1)(2)(3)(4)(5) . ...
... Vastly available NiTi rotary instruments did not design for initial negotiation of the root canal because they have non-cutting tips. Therefore, preparation of glide path is strongly recommended when using rotary endodontic file systems (1)(2)(3)(4)(5) . ...
... It is aimed to create a smooth radicular tunnel from the coronal orifice of the canal to its physiologic terminus to minimize the incidence of procedural errors and to reduce the amount of apically extruded debris [23]. In the case of the SAF system, this preliminary stage is of most importance, as the SAF is not a penetrating tool and should be allowed to be passively inserted to WL before its activation [29]. Therefore, the essential preliminary stage of glide path preparation should not be ignored when evaluating the total amount of apically extruded debris when using any given procedure, including the SAF. ...
... It is conceivable that a two-file glide path system with bigger sizes and tapers may extrude more debris. However, this does not mean that the ProGlider can be used as part of the SAF sequence because the SAF lacks any penetration capabilities and requires preestablishment of a #20/.04 glide path to allow it to passively reach the WL [29,31]. ...
Article
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Objectives: The purpose of this study was to assess the amount of apically extruded debris during the preparation of oval canals with either a rotary file system supplemented by the XP-endo Finisher file or a full-sequence self-adjusting file (SAF) system. Materials and methods: Sixty mandibular incisors were randomly assigned to two groups: group A: stage 1-glide path preparation with Pre-SAF instruments. Stage 2-cleaning and shaping with SAF. Group B: stage 1-glide path preparation with ProGlider file. Stage 2-cleaning and shaping with ProTaper Next system. Stage 3-Final cleaning with XP-endo Finisher file. The debris extruded during each of the stages was collected, and the debris weights were compared between the groups and between the stages within the groups using t tests with a significance level set at P < 0.05. Results: The complete procedure for group B resulted in significantly more extruded debris compared to group A. There was no significant difference between the stages in group A, while there was a significant difference between stage 2 and stages 1 and 3 in group B, but no significant difference between stages 1 and 3. Conclusions: Both instrumentation protocols resulted in extruded debris. Rotary file followed by XP-endo Finisher file extruded significantly more debris than a full-sequence SAF system. Each stage, in either procedure, had its own contribution to the extrusion of debris. Clinical relevance: Final preparation with XP-endo Finisher file contributes to the total amount of extruded debris, but the clinical relevance of the relative difference in the amount of apically extruded debris remains unclear.
... For the SAF system group, following patency filing, glide path preparation was achieved using Profile size 20, .04 taper, as per the manufacturer's instruction (Kfir et al. 2016) until working length was achieved. Irrigation with 3 mL of 3% sodium hypochlorite was performed using side vented needles (Maxi-I-probe; Dentsply) at 1 mm short of working length. ...
Article
Aim: This randomized controlled trial compared the incidence of post-instrumentation pain associated with Mtwo rotary NiTi files and the Self-Adjusting file system following canal shaping and cleaning. Methodology: Following sample size estimation, a total of 130 patients were randomized into two groups based on selection criteria [Group Mtwo; and Group SAF (Self-Adjusting File)]. Root canal treatment was carried out in two appointments. The teeth were endodontically treated with the appropriate allotted systems following similar clinical parameters. Participants were asked to rate the intensity of pre-instrumentation and post-instrumentation pain (at 2,4,6,8,24,48 hours) using the VAS score. The Kruskal- wallis test was done for overall comparisons of the two systems. The Friedman test was used to compare between time points with each system. Sub-group analyses for independent variables (gender, pulp status and diagnosis) used the Mann-Whitney test and Wilcoxon Signed Ranks test (P < 0.05). Results: No significant difference was found between the two groups in relation to post instrumentation pain. Teeth with pulpal necrosis had significant pain at 8 hours compared to teeth with vital pulps (P = 0.04). Teeth with vital pulps in the SAF group had significantly less post-instrumentation pain compared to the Mtwo group at 6 hours (P = 0.042). Patients with teeth with non-vital pulps in the SAF group experienced more post-instrumentation pain at 8 hours (P = 0.017) and 24 hours (P = 0.005) CONCLUSION: The incidence of post-instrumentation pain at different time intervals in patients undergoing root canal treatment was similar for both the Self-Adjusting file and Mtwo file systems. This article is protected by copyright. All rights reserved.
Article
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Introduction Negotiation, glide path, and preflaring are essential steps in root canal shaping procedures. This report aimed to discuss the terminology, basic concepts, and clinical considerations of negotiation, glide path, and preflaring procedures and the influence of these steps on root canal shaping. Methods This systematic review was undertaken following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol has been registered with the International Prospective Register of Systematic Reviews (number CRD42019127021). A comprehensive literature search was performed by 2 independent reviewers using a selected search strategy in 2 electronic databases (PubMed and Scopus) until January 28, 2019. A further search was performed manually in endodontic journals. Studies investigating or comparing at least 1 shaping property resulting from root canal instrumentation with a glide path or preflaring in human extracted teeth or clinical studies were included. Results The literature shows that the definition of glide path and preflaring procedures remains controversial, which requires an elaboration in the American Association of Endodontists’ Glossary of Endodontic Terms. After the removal of irrelevant and duplicated articles, 98 articles were included. The impact of glide path preparation and preflaring on working length determination, apical file size determination, canal transportation, separation of endodontic files, shaping time, dentinal microcrack formation, and extrusion of debris was discussed. Because of heterogeneity among the included studies, quantitative synthesis was not performed for most of the parameters. Conclusions An evidence-based guideline is needed to define and correlate the basic concepts and current applications of each step of contemporary advancements in root canal instruments. Glide path preparation reduces the risk of debris extrusion, has no influence on the incidence of dentinal crack formation, and improves the preservation of the original canal anatomy. The creation of a glide path may have no impact on Reciproc files (VDW, Munich, Germany) in reaching the full working length. Preflaring increases the accuracy of working length determination. Further randomized clinical trials are required to evaluate the effect of a glide path and preflaring on root canal treatment outcomes.
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Introduction: This study aimed to evaluate the frequency of dentinal microcracks observed after root canal preparation with 2 reciprocating and a conventional fullsequence rotary system using micro–computed tomographic analysis. Methods:Thirty mesial roots of mandibular molars presenting a type II Vertucci canal configuration were scanned at an isotropic resolution of 14.16mm. The sample was randomly assigned to 3 experimental groups (n= 10) according to the system used for the root canal preparation: group A—Reciproc (VDW, Munich, Germany), group B—WaveOne (Dentsply Maillefer, Baillagues, Switzerland), and group C—BioRaCe (FKG Dentaire, La-Chaux-de-Fonds,Switzerland). Second and third scans were taken after the root canals were prepared with instruments sizes 25 and 40, respectively. Then, pre- and postoperative cross-section images of the roots (N= 65,340) were screened to identify the presence of dentinal defects. Results: Dentinal microcracks were observed in 8.72% (n= 5697), 11.01% (n= 7197), and 7.91% (n= 5169) of the cross-sections from groups A (Reciproc), B (WaveOne), and C (BioRaCe), respectively. All dentinal defects identified in the postoperative cross-sections were also observed in the corresponding preoperative images. Conclusions: No causal relationship between dentinal microcrack formation and canal preparation procedures with Reciproc, WaveOne, and BioRaCe systems was observed.
Article
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The purpose of this study was to compare dentinal microcrack formation while using hand files (HFs), 4 brands of nickel-titanium (NiTi) rotary files and the self-adjusting file. One hundred forty mandibular first molars were selected: 20 teeth were left unprepared and served as control, and the remaining 120 teeth were divided into 6 groups. HFs, HERO Shaper (HS; Micro-Mega, Besancon, France), Revo-S (RS, Micro-Mega), Twisted File (TF; SybronEndo, Orange, CA), ProTaper (PT, Dentsply Maillefer), and SAFs were used to prepare the 2 mesial canals. Roots were then sectioned 3, 6, and 9 mm from the apex, and the cut surface was observed under a microscope and checked for the presence of dentinal microcracks. The control, HF, and SAF groups did not show any microcracks. In roots prepared with the HS, RS, TF, and PT, dentinal microcracks were observed in 60%, 25%, 44%, and 30% of teeth, respectively. There was a significant difference between the control/HF/SAF group and the 4 NiTi rotary instrument groups (P < .0001). However, no significant difference was found among the 4 NiTi rotary instruments (P > .005). All rotary files created microcracks in the root dentin, whereas the SAF file and hand instrumentation presented with satisfactory results with no dentinal microcracks.
Article
Current rotary file systems are effective tools. Nevertheless, they have two main shortcomings: They are unable to effectively clean and shape oval canals and depend too much on the irrigant to do the cleaning, which is an unrealistic illusionThey may jeopardize the long-term survival of the tooth via unnecessary, excessive removal of sound dentin and creation of micro-cracks in the remaining root dentin. The new Self-adjusting File (SAF) technology uses a hollow, compressible NiTi file, with no central metal core, through which a continuous flow of irrigant is provided throughout the procedure. The SAF technology allows for effective cleaning of all root canals including oval canals, thus allowing for the effective disinfection and obturation of all canal morphologies. This technology uses a new concept of cleaning and shaping in which a uniform layer of dentin is removed from around the entire perimeter of the root canal, thus avoiding unnecessary excessive removal of sound dentin. Furthermore, the mode of action used by this file system does not apply the machining of all root canals to a circular bore, as do all other rotary file systems, and does not cause micro-cracks in the remaining root dentin. The new SAF technology allows for a new concept in cleaning and shaping root canals: Minimally Invasive 3D Endodontics.
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Aim: The aim of the present study was to investigate the incidence of cracks in root dentin after root canal preparation with ProTaper Next, HyFlex, and ProTaper Universal rotary instruments. Methodology: One-hundred mandibular premolars were selected. Twenty-five teeth were left unprepared and served as a negative control; another 25 teeth were instrumented with the ProTaper Universal system up to size F4 as a positive control, and the remaining 50 teeth were shaped with the following experimental groups with an apical size 40 file: ProTaper Next X4 and HyFlex 40/0.4. After the root canal preparation, all of the roots were sectioned perpendicular to the long axis at 2, 4, 6, and 8 mm from the apex, and the sections were then observed under a stereomicroscope. The absence/presence of cracks was recorded, and the data were analyzed with a chi-square test. The significance level was set at p = .05. Results: No cracks were observed in the negative control group. Vertical root fractures were not observed in any of the groups. The ProTaper Next and HyFlex instruments caused fewer cracks (28%) than the ProTaper Universal instrument (56%) (p < .05). However, there were no significant differences in crack formation between the ProTaper Next and HyFlex groups (p > .05). Conclusion: Within the limitations of this in vitro study, all of the instrumentation systems used in this study created cracks in the root dentin. The ProTaper Next and HyFlex instruments tended to cause fewer dentinal cracks compared with the ProTaper Universal instrument.
Article
Introduction The purpose of this pilot study in a cadaver model was to compare 2 different shaping techniques regarding the induction of dentinal microcracks. Methods Three lower incisors from each of 6 adult human cadaver skulls were randomly distributed into 3 groups: the control group (CG, no instrumentation), the GT group (GT Profile hand files; Dentsply Tulsa Dental, Tulsa, OK), and the WO group (WaveOne; Dentsply Tulsa Dental). In the GT group, manual shaping in a crown-down sequence with GT Profile hand files was performed. In the WO group, Primary WaveOne files were used to the working length. Teeth were separated from the mandibles by careful removal of soft tissue and bone under magnification. Roots were sectioned horizontally at 3, 6, and 9 mm from the apex using a low-speed saw. Color photographs at 2 magnifications (25× and 40×) were obtained. Three blinded examiners registered the presence of microcracks (yes/no), extension (incomplete/complete), direction (buccolingual/mesiodistal), and location. Data were analyzed with chi-square tests at P < .05. Results Microcracks were found in 50% (CG and GT) and 66% (WO) of teeth at 3 mm, 16.6% (CG) and 33.3% (GT and WO) at 6 mm, and 16.6% in all 3 groups at 9 mm from the apex. There were no significant differences in the incidence of microcracks between all groups at 3 (P = .8), 6 (P = .8), or 9 mm (P = 1). All microcracks were incomplete, started at the pulpal wall, and had a buccolingual direction. Conclusions Within the limitations of this pilot study, a relationship between the shaping techniques (GT hand and WaveOne) and the incidence of microcracks could not be shown compared with uninstrumented controls.
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The purpose of this study was to evaluate the incidence of dentinal defects after root canal preparation with reciprocating instruments (Reciproc and WaveOne) and rotary instruments. One hundred human central mandibular incisors were randomly assigned to 5 groups (n = 20 teeth per group). The root canals were instrumented by using the reciprocating single-file systems Reciproc and WaveOne and the full-sequence rotary Mtwo and ProTaper instruments. One group was left unprepared as control. Roots were sectioned horizontally at 3, 6, and 9 mm from the apex and evaluated under a microscope by using 25-fold magnification. The presence of dentinal defects (complete/incomplete cracks and craze lines) was noted and analyzed by using the chi-square test. No defects were observed in the controls. All canal preparation created dentinal defects. Overall, instrumentation with Reciproc was associated with more complete cracks than the full-sequence files (P = .021). Although both reciprocating files produced more incomplete cracks apically (3 mm) compared with the rotary files (P = .001), no statistically significant differences were obtained concerning the summarized values of all cross sections (P > .05). Under the conditions of this study, root canal preparation with both rotary and reciprocating instruments resulted in dentinal defects. At the apical level of the canals, reciprocating files produced significantly more incomplete dentinal cracks than full-sequence rotary systems (P < .05).
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The purpose of this study was to compare the rates of separation of 0.04 taper nickel titanium (NiTi) rotary instruments using two different instrumentation techniques. Twenty sets of 0.04 taper Profile Series 29 rotary instruments, sizes 2 to 6 were used in the mesial (mandibular) or buccal (maxillary) canals of extracted human molars with a 20 to 30 degree root curvature according to the Schneider classification. The rotary instruments were used up to 20 times either with the crown-down technique recommended by the manufacturer or with a combination of preflaring with hand files in a passive step-back technique followed by rotary instrumentation. Statistical analysis of the data showed that the combination technique allowed more uses before separation compared with the crown-down technique recommended by the manufacturer p < 0.0001.
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To investigate physical parameters for ProTaper nickel-titanium (NiTi) rotary instruments whilst preparing curved canals in maxillary molars in vitro. A novel torque-testing platform was used to prepare root canals in 15 extracted human maxillary molars with ProTaper rotary instruments. Peak torque and force was registered along with numbers of rotations required to shape the canals. Canals were divided into 'wide' and 'constricted' groups depending on canal volumes assessed by micro computed tomography. Mean scores for each instrument type were calculated and statistically compared using anova and Scheffé posthoc tests. Mean torque varied between 0.8 +/- 0.5 and 2.2 +/- 1.4 N cm whilst mean force ranged from 4.6 +/- 2.6 to 6.2 +/- 2.7 N. Mean numbers of rotations totalled up to 21. All three variables registered were significantly correlated to preoperative canal volumes (P < 0.001) and differed significantly between 'wide' and 'constricted' canals (P < 0.001). Whilst high forces were used in some cases, no ProTaper instrument fractured when a patent glide path was present. There were significant positive correlations between canal geometry and physical parameters during shaping.
Article
The purpose of this study was to apply the Endographe to analyze the vertical forces and torque developed during mechanical preparations in extracted teeth. The data collected in this study may be used to calculate the safety quotient (SQ) as proposed by J.T. McSpadden. The SQ formula is defined as the torque required to break a file at D3 divided by the mean working torque required to cut dentin. The Endographe is a unique force-analyzer device equipped to measure, record, and generate graphs of the vertical forces and torque exerted during root canal preparation. All preparations were performed by endodontists in roots with narrow, more restrictive canals, larger, more open canals, or in roots sectioned in two halves. All canals, including the sectioned canals, were prepared with ProTaper files in accordance with the manufacturer's guidelines for use. For narrow canals, the mean values of the generated vertical forces (g) and torque (g.cm) varied from 80 (+/- 20) g (SX) to 232 (+/- 60) g (F2) and from 80 (+/- 24) g x cm (F1) to 150 (+/- 45) g x cm (S2), respectively. For large canals, the mean values of the generated vertical forces (g) and torque (g x cm) varied from 80 (+/- 20) g (SX) to 340 (+/- 20) g (F1) and from 31 (+/- 9) g x cm (S2) to 96 (+/- 35) g x cm (SX), respectively. The SQ varied from 0.93 to 7.95 for narrow canals and from 1.58 to 14.50 for large canals. The SQ is intended to provide values that can be analyzed to predict whether a rotary file will have a tendency to break or will work safely during clinical use. However, if the formula is going to provide useful information, it must index the "rotation to failure torque" with the "mean working torque" at a specific location along the cutting blades of a file. Additionally, this mathematical formula does not account for factors such as the concentration of forces, the way the instruments are used, or the wear of the instruments. A precise protocol for canal preparation should emphasize using small flexible stainless steel hand files to create or verify that within any portion of a root canal there is sufficient space for rotary instruments to follow. When there is a confirmed smooth, reproducible glide path, then a "secured" space exists to safely guide the more flexible terminal extent of a rotary NiTi file. Endogrammes provide an innovative approach to the analysis of mechanical preparations and suggest that the ProTaper shaping files are best used with lateral forces to decrease the coronal screwing effect. The ProTaper finishing files should be used with slow penetration and be introduced only into canals that have a confirmed smooth and reproducible glide path. When any part of the overall length of a canal has been secured, then the number of instruments, the time spent utilizing each instrument, and the overall time progressing through a sequence of instruments to shape this region of the canal is reduced.
Article
We evaluated the influence of manual preflaring and torque on the failure rate of rotary nickel-titanium ProTaper instruments Shaping 1 (S1), Shaping 2 (S2), Finishing 1 (F1), and Finishing 2 (F2). These factors were evaluated using an in vitro method by calculating the mean number of Endo-Training-Blocks shaped before file breakage under different conditions. Group A (S1 on simulators with no preflaring) shaped 10 blocks before failure, group B (S1 on manually preflared simulators) shaped 59 blocks (p<0.01 versus group A), group C (S2 with low torque) shaped 28 blocks, group D (S2 with high torque) shaped 48 blocks (p<0.01 versus group C), group E (F1 with low torque) shaped eight blocks, group F (F1 with high torque) shaped 23 blocks (p<0.01 versus group E), group G (F2 with low torque) shaped four blocks, and group H (F2 with high torque) shaped 11 blocks (p<0.01 versus group G). Manual preflaring creates a glide path for the instrument tip and is a major determinant in reducing the failure rate of these rotary nickel-titanium files. All instruments worked better at high torque.
Article
The dual purpose of this study was, to evaluate the fracture rate of Ni-Ti rotary instruments when following a manual glide path and using stainless steel hand files before carrying out instrumentation by means of rotary files and, to compare the results in this study with those obtained in two previous analyses, in which the glide path technique was not used. A total of 208 canals obtained from a pool of freshly extracted human mandibular and maxillary molars was divided into three groups corresponding to; K3, ProFile and ProTaper. The coronal 2/3 of each tooth were used. In all three groups the apical portion of the samples was prepared with size 10-20 stainless steel K-type hand files. The apical stops were prepared using K3, ProFile and ProTaper rotary instruments. Logistic regression model analysis indicated that breakage was significantly associated with the angle of curvature of the canal (OR = 1.078; 95% CI = 1.032-1.12; p = 0.001), and with the number of clinical uses (files used more than eight times broke more frequently that those used 1 or 2 times; OR: 22.686; 95% CI: 2.6-191.3; p = 0.004). The breakage rate obtained in the present study is significantly lower than in our previous studies, in which the angle of curvature was also greater than 30 degrees and rotational speed a constant 350 rpm, but in which the canals were not first prepared with hand files (25/205 = 12% versus 16/61 = 26%, p = 0.007). Based on the results of this study, we recommend the use of stainless steel hand files to prepare the apical 1/3 of curved canals before introducing rotary files.
Article
Chemomechanical preparation of the root canal includes both mechanical instrumentation and antibacterial irrigation, and is principally directed toward the elimination of micro-organisms from the root canal system. A variety of instruments and techniques have been developed and described for this critical stage of root canal treatment. Since their introduction in 1988, nickel-titanium (NiTi) rotary instruments have become a mainstay in clinical endodontics because of their exceptional ability to shape root canals with potentially fewer procedural complications. Safe clinical usage of NiTi instruments requires an understanding of basic metallurgy of the alloy including fracture mechanisms and their correlation to canal anatomy. This paper reviews the biologic principles of preparing root canals with an emphasis on correct use of current rotary NiTi instrumentation techniques and systems. The role and properties of contemporary root canal irrigants is also discussed.
Article
Failure to grasp the rationale behind cleaning and shaping concepts can increase the occurrence of needless complications, such as ledges. A ledge is created when the working length can no longer be negotiated and the original pathway of the canal has been lost. Extension of the access cavity to provide unobstructed access to the root canals, precurving and not forcing instruments, using NiTi files, using passive step-back and balanced force techniques, and instrumenting the canal to its full length will all help to prevent ledge formation. Initial negotiation and bypassing the ledge can be achieved using a small file with a distinct curve at the tip, whereas a slight rotation motion of the file combined with a ''picking'' motion can often help advance the instrument. A review of the literature and a discussion of the options for prevention, recognition and managing the ledge are presented.
New clinical protocol for the SAF System The effect of preflaring on the rates of separation for 0.04 taper nickel titanium rotary instruments
  • Redent-Nova Roland
  • Dd Andelin
  • We Browning
  • Df Hsu
  • Gh Torabinejad
ReDent-Nova (2014) New clinical protocol for the SAF System. http://www.redent.co.il/clinical_principles Roland DD, Andelin WE, Browning DF, Hsu GH, Torabinejad M (2002) The effect of preflaring on the rates of separation for 0.04 taper nickel titanium rotary instruments. Journal of Endodontics 28, 543–5.
New clinical protocol for the SAF System
  • Redent-Nova
ReDent-Nova (2014) New clinical protocol for the SAF System. http://www.redent.co.il/clinical_principles
The endodontic glide path
  • J West
West J (2010) The endodontic glide path: "Secret to rotary safety". Dentistry Today 29, 86-93.