Rotary Instrumentation Techniques Research Articles

The evaluation of two rotary instrumentation techniques under "operator-related variables" standardized conditions.

Objective:We aimed here to evaluate the enlargement characteristics of two nickel-titanium rotary instrument systems that use two different preparation techniques, in simulated root canals under “operator-related variables” standardized conditions.Materials and Methods:A total of 40 simulated canals in resin blocks were divided into two groups as the Mtwo group for use with a single-length technique and the ProTaper instrument system group for use with crown down technique. To standardize the operator-related variables, all preparations were carried out with a computer controlled device that was developed and used previously as described in a published study. The pre- and post-operative digital images of the canals were superimposed and measured at 11 levels from the apical tip. The distances between the pre- and post-operative outer lines of the root canals were measured at both the inner and outer sides of the curve. The amount of removed material and the symmetry of the preparations were evaluated. Statistical analyses were performed with Mann-Whitney test.Results:Significantly more material was removed by Mtwo at 9 levels and by ProTaper at 2 levels (P < 0.05) while no significant difference was determined at 11 levels. The preparations made with ProTaper were more symmetrical at 4 levels while no significant difference was determined at 7 levels.Conclusion:Mtwo removed significantly more material than ProTaper at different levels of the curved root canals. Mtwo and ProTaper made symmetrical preparations and maintained the original shape of the root canal at different levels under controlled operator-related variables.

Reciprocating Root Canal Technique Induces Greater Debris Accumulation Than a Continuous Rotary Technique as Assessed by 3-Dimensional Micro–Computed Tomography

IntroductionThe ability of single-file, reciprocating instruments to remove inorganic debris is uncertain. By using micro–computed tomography (microCT), this study compared the 3-dimensional distribution, quantity, and density of remaining inorganic debris in the mesial root of mandibular molars after instrumentation. A single reciprocating file was compared with a multifile rotary instrumentation technique. MethodsTeeth were selected for instrumentation using reciprocating or rotary instruments (n = 19). Teeth were scanned using microCT before and after instrumentation. Through shape recognition and superimposition image analysis techniques, remaining inorganic tissue debris was identified, quantified, and visualized 3-dimensionally, mapping debris to its location. The use of a density phantom enabled the debris density to be calculated, giving a measure of compactness. ResultsAfter single-file instrumentation, an average of 19.5% debris remained in the canal compared with 10.6% with the multifile technique (P = .01) and at an average density of 1.60 g/m3 compared with 1.55 g/m3 for the multifile system (P > .05). Isthmuses, protrusions, and irregularities in the canal wall were repeatedly seen at the locations of debris accumulation. ConclusionsIn canals with a high prevalence of isthmuses and protrusions, using multifile rotary systems may be preferred over reciprocating files because it can yield cleaner canals with less debris accumulation.

Comparison of the Remaining Dentin Thickness in the Root after Hand and Four Rotary Instrumentation Techniques: An in vitro Study

The aim of the present study was to compare the remaining dental thickness (RDT) in the mesiobuccal root of mandibular first molars at 3 and 7 mm from the anatomic apex after instrumentation with ProTaper, light speed LSX, K3 and M2 and to compare with that of K-files. In this study, 60 extracted, untreated human mandibular first molars with fully formed apices, with curvature less than 35° and no root resorption were used. Prepared specimens were cut horizontally at 3 and 7 mm short of anatomic apex. The least dentin thickness from canal to external root surface was observed under 3× magnification and recorded using Clemax measuring tool and the sections were reassembled. Group I-instrumentation with ProTaper, group II-instrumentation with K3, group III-instrumentation with Light Speed LSX, group IV-instrumentation with M2 and group V- instrumentation with K-files and RDT was measured. Results showed that group V removed lesser amount of dentin compared to all other groups while all the three instrumentation techniques removed almost equal amount of dentin apically. Cleaning and shaping of the root canal space involves the elimination of pathogenic contents as well as attaining a uniform specific shape. However, the RDT following the use of various intraradicular procedures is an important factor to be considered as an iatrogenic cause that may result in root fracture. To avoid this, newer rotary instruments are being introduced.

Endodontic Treatment of Maxillary Premolar with Three Root Canals Using Optical Microscope and NiTi Rotatory Files System

The aim of the study was to report a clinical case of endodontic treatment of a maxillary first premolar with three root canals using an optical microscope and rotary instrumentation technique. The main complaint of the patient, a 16-year-old girl, was pain in tooth 14. After clinical and radiographic examination, irreversible pulpitis was diagnosed. An alteration in the middle third of the pulp chamber radiographically observed suggested the presence of three root canals. Pulp chamber access and initial catheterization using size number 10 K-files were performed. The optical microscope and radiographic examination were used to confirm the presence of three root canals. PathFiles #13, #16, and #19 were used to perform catheterization and ProTaper files S1 and S2 for cervical preparation. Apical preparation was performed using F1 file in the buccal canals and F2 in the palatal canal up to the working length. The root canals were filled with Endofill sealer by thermal compaction technique using McSpadden #50. The case has been receiving follow-up for 12 months and no painful symptomatology or periapical lesions have been found. The use of technological tools was able to assist the endodontic treatment of teeth with complex internal anatomy, such as three-canal premolars.

Assessment of Influence of Flexion Angles of Files in Apical Stop Preparation by Using Manual and Rotary Instrumentation Techniques

IntroductionThis study aimed to evaluate the influence of flexion angles produced by files during root canal instrumentation on the final form of the apical stop. MethodsSixty human lower incisors were divided into 3 groups (n = 20). After access preparation and working length determination, radiographs were taken from a mesiodistal and buccolingual direction with #15 K-file inserted to working length. Teeth from FlexM group were instrumented with stainless steel Flexofiles up to #40 file. For ProM and ProR groups, hand ProTaper Universal and ProTaper Universal rotary files were used, respectively, up to file F4. New radiographs were taken as previously described. After gutta-percha insertion, the apex of each specimen was ground, allowing gutta-percha visualization, and an image of the apex was captured to identify root canal deformation with computer software. The flexion of files was evaluated from both initial and final radiographs as the angle formed between the divergence of the file path and its virtual image represented by the direction taken by the file in the absence of curvature. ResultsFlexM group presented the highest variation in flexion angles compared with ProM (P = .112) and ProR (P = .024) groups. Nickel-titanium rotary system (ProR) reduced apical stop deformation compared with the manual techniques that used nickel-titanium (P = .011) or stainless steel (P = .025) files. ConclusionsForce vectors caused by the flexion angles of the files during the instrumentation of curved canals promoted apical stop deformation. ProTaper Universal rotary files showed less apical deformation than hand ProTaper Universal and stainless steel files.

Comparative evaluation of apical extrusion of bacteria using hand and rotary systems : An in vitro study

Aim:To evaluate the bacteria extruded apically during root canal preparation using two hand and rotary instrumentation techniques.Materials and Methods:Eighty freshly extracted mandibular premolars were mounted in bacteria collection apparatus. Root canals were contaminated with the pure culture of Enterococcus fecalis (ATCC 29212) and dried at 37°C for 24 h. Bacteria extruded were collected, incubated in brain heart infusion agar for 24 h at 36°C and the colony forming units (CFU) were counted.Statistical Analysis:The mean number of colony forming units were calculated by One-way ANOVA and comparison between the groups made by multiple comparison (Dunnet D) test.Results:The step-back technique extruded highest number of bacteria in comparison to other hand and rotary Ni–Ti systems.Conclusion:Under the limitation of this study all hand and rotary instrumentation techniques extruded bacteria. Among all the instrumentation techniques step-back technique extruded more number of bacteria and K-3 system the least. Further in vivo research in this direction could provide more insight into the biologic factors associated and focus on bacterial species that essentially play a major role in post instrumentation flare-ups.

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

To compare the cleaning effectiveness of manual, hybrid and rotary instrumentation techniques in primary molar teeth. 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. 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. The use of NiTi rotary files is an option for root canal instrumentation in primary teeth.

Comparative study of apically extruded debris using one manual and two rotary instrumentation techniques for endodontic retreatment

Background/purposeThe aim of the this study was to compare the amount of debris apically extruded during endodontic retreatment using two rotary nickel–titanium (NiTi) instruments (K3 and R-Endo) and Hedström files. Materials and methodsForty-five extracted human mandibular premolar teeth were used in this study. Root canals of the teeth were filled before being randomly assigned to three groups. In group 1, gutta-percha was removed with K3 (SybronEndo, West Collins, CA, USA) rotary NiTi instruments. In group 2, gutta-percha was removed with R-Endo (Micro-Mega, Besançon, France) rotary NiTi instruments. In group 3, gutta-percha was removed using Hedström files (Dentsply Maillefer, Ballaigues, Switzerland). Debris extruded from the apical foramen was collected into Eppendorf tubes. The liquid inside the tubes was dried, and the debris in each group was weighed and compared. Data were statistically analyzed using one-way analysis of variance, and Kruskal–Wallis test and Mann–Whitney U test. ResultsAlthough all retreatment techniques resulted in apical extrusion, groups 1 and 2 produced significantly less apical extrusion than group 3 (P<0.05). No statistically significant difference was found between groups 1 and 2 (P>0.05). ConclusionAll retreatment techniques produced extruded debris during endodontic retreatment; however, both rotary NiTi systems were associated with less apical extrusion than manual instrumentation with Hedström files.

Micro‐CT analyses of apical enlargement and molar root canal complexity

To compare the effectiveness of two rotary hybrid instrumentation techniques with focus on apical enlargement in molar teeth and to quantify and visualize spatial details of instrumentation efficacy in root canals of different complexity. Maxillary and mandibular molar teeth were scanned using X-ray microcomputed tomography. Root canals were prepared using either a GT/Profile protocol or a RaCe/NiTi protocol. Variables used for evaluation were the following: distance between root canal surfaces before and after preparation (distance after preparation, DAP), percentage of root canal area remaining unprepared and increase in canal volume after preparation. Root canals were classified according to size and complexity, and consequences of unprepared portions of narrow root canals and intraradicular connections/isthmuses were included in the analyses. One- and two-way anova were used in the statistical analyses. No difference was found between the two techniques: DAP(apical-third) (P = 0.590), area unprepared(apical-third) (P = 0.126) and volume increase(apical-third) (P = 0.821). Unprepared root canal area became larger in relation to root canal size and complexity, irrespective of the technique used. Percentage of root canal area remaining unprepared was significantly lower in small root canals and complex systems compared to large root canals. The isthmus area per se contributed with a mean of 17.6%, and with a mean of 25.7%, when a narrow root canal remained unprepared. The addition of isthmuses did not significantly alter the ratio of instrumented to unprepared areas at total root canal level. Distal and palatal root canals had the highest level of unprepared area irrespective of the two instrumentation techniques examined.

Bending Properties of a New Nickel-Titanium Alloy with a Lower Percent by Weight of Nickel

Introduction The aim of the present study was to evaluate the bending properties of Hyflex instruments, which exhibit a lower percent in weight of nickel (52 Ni %wt) and compare them with other commercially available nickel-titanium (NiTi) rotary instruments. Methods Ten instruments with tip size 25, 0.06 taper of each of the following NiTi rotary instrumentation techniques were selected for the study: Hyflex, EndoSequence, ProFile, Hero, and Flexmasters. All instruments from each group were tested for stiffness by comparing their bending moment when they attained a 45-degree bend. Experimental procedures strictly followed testing methodology described in ISO 3630-1. All data were recorded and subjected to statistical evaluation by using analysis of variance test. Statistical significance was set at P < .05). Results Statistical analysis of the data revealed that Hyflex files were found to be the most flexible instruments, with a significant difference ( P < .05) in comparison with the other instruments. Among the other files, a significant difference has been reported for EndoSequence instruments compared with ProFile, Hero, and FlexMaster ( P < .05), whereas no significant differences have been reported among those 3 files ( P > .05). Conclusions Results of the present study have illustrated an increased flexibility of the new NiTi alloy over conventional NiTi alloy, and they highlight the potential of the new manufacturing process.

Comparison Between Rotary and Manual Techniques on Duration of Instrumentation and Obturation Times in Primary Teeth

The aim of this study was to compare the duration of instrumentation and obturation times and quality of root canal filling between rotary and manual instrumentation techniques in primary teeth. A randomized, controlled clinical trial was performed that included deciduous teeth with pulp necrotic. Forty necrotic teeth were included; 20 were instrumented with a rotary technique (experimental group) and 20 with a manual technique (control group). The time taken for instrumentation and for obturation were recorded in minutes, and the quality of the root canal filling was recorded as optimal, under-filled, or overfilled. The use of the rotary technique diminished the time of instrumentation to 63% and time of obturation to 68%, and it improved the quality of the root canalfilling. The use of rotary instruments in the pulpectomy of primary molars represents a promising technique; the time is significantly reduced.

Morphometrical analysis of cleaning capacity of a hybrid instrumentation in mesial flattened root canals

The cleaning capacity of hybrid and rotary instrumentation techniques in mesial flattened canals of mandibular first molars was evaluated by morphometrical analysis in this study. Twenty human mandibular first molars were randomly assigned into two groups, according to instrumentation technique, as follows: group 1, instrumentation with ProTaper Starter Kit (Dentsply/Maillefer) rotary system; group 2, manual instrumentation using K files (Dentsply/Maillefer) by crown-down technique in middle and apical thirds, cervical preparation with Gates-Glidden #1 and #2 (Dentsply/Maillefer) burs, and to finalise the preparation, ProTaper F2 and F3 rotary files. Serial transverse cross-sections (5 µm) of the apical third, stained with hematoxylin and eosin, were analysed at 100× original magnification. The images were submitted to morphometrical analysis with an integration grid to determine the percentage of root canal area with debris. Statiscal analysis (t-Student, P < 0.05) showed significant difference between the techniques (P < 0.05), although neither completely cleaned the root canal.

Effectiveness of rotary or manual techniques for removing a 6-year-old filling material

The aim of this study was to evaluate the effectiveness of manual and rotary instrumentation techniques for removing root fillings after different storage times. Twenty-four canals from palatal roots of human maxillary molars were instrumented and filled with gutta-percha and zinc-oxide eugenol-based sealer (Endofill) , and were stored in saline for 6 years. Non-aged control specimens were treated in the same manner and stored for 1 week. All canals were retreated using hand files or ProTaper Universal NiTi rotary system. Radiographs were taken to determine the amount of remaining material in the canals. The roots were vertically split, the halves were examined with a clinical microscope and the obtained images were digitized. The images were evaluated with AutoCAD software and the percentage of residual material was calculated. Data were analyzed with two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) between the manual and rotary techniques for filling material removal regardless the ageing effect on endodontic sealers. When only the age of the filling material was analyzed microscopically, non-aged fillings that remained on the middle third of the canals presented a higher percentage of material remaining (p<0.05) compared to the aged sealers and to the other thirds of the roots. The apical third showed a higher percentage of residual filling material in both radiographic and microscopic analysis when compared to the other root thirds. In conclusion, all canals presented residual filling material after endodontic retreatment procedures. Microscopic analysis was more effective than radiographs for detection of residual filling material.

A micro‐computed tomographic evaluation of apical root canal preparation using three instrumentation techniques

To investigate the morphological changes in the apical third of the root canal after preparation with three techniques. Forty molar teeth were scanned using micro-computed tomography before and after instrumentation with: Group 1 - stainless steel K-files using the balanced force technique; Group 2 - stainless steel K-files (balanced force) and then refining the apical preparation with the equivalent size 0.04 taper FlexMaster instrument; Group 3 - a hybrid ProTaper/FlexMaster (ProFile for sizes 45 and 60) sequence. Eight canals were excluded because of artefacts in the images or unnegotiable blockages leaving 110 canals that could be analysed. Apical root canal preparation was evaluated with respect to the amount of dentine removed, canal roundness, transportation and how the dimensions of the prepared apical root canal correlated with those of the final instrument used. The median apical preparation sizes for the three groups respectively were: 30, 30 and 40. Despite the larger size and less experienced operator, the volumetric change (the amount of dentine removed) in canals prepared with a hybrid rotary nickel-titanium instrumentation technique remained small and, a more rounded preparation (P < 0.001) that closely matched the final instrument dimensions (P < 0.001) was produced. There was a trend for less canal transportation using rotary nickel-titanium instruments. Stainless steel hand preparation was not conservative of apical dentine. When used correctly, even by less experienced operators, rotary nickel-titanium instruments were able to precisely 'machine' a canal to larger apical sizes with minimal risk of iatrogenic damage.

Comparison of apical debris extrusion using a conventional and two rotary techniques.

Preparation techniques and instruments produce and push debris out of canals. This can induce inflammation within the periapical area. Therefore, instrumentation that causes less extrusion of debris is more desirable. The purpose of this in vitro study was to evaluate the quantity of debris extruded from the apical foramen during root canal preparation by using one hand, and two rotary instrumentation techniques. Three different groups each with 12 mesiobuccal roots of human maxillary first molar were instrumented using either step-back technique with hand instruments, FlexMaster or Mtwo rotary system. Debris extruded from the apical foramen during canal preparation was collected. The mean dry weights of debris were compared using one-way ANOVA. Step-back group had a significantly greater mean weight of debris compared to the other two groups (P<0.05). Mtwo group had the lowest mean weight of debris, though it was not significantly different from FlexMaster group. According to this study, the engine driven techniques were associated with less apical debris extrusion. [Iranian Endodontic Journal 2009;4(4):135-8].

Impact of Er,Cr:YSGG Laser Therapy on the Cleanliness of the Root Canal Walls of Primary Teeth

Root canal therapy might be required for primary teeth displaying signs of pulpal inflammation or necrosis. Cleaning and shaping followed by obturation of the canal space with a resorbable paste have been widely performed with remarkable clinical success. However, lengthy endodontic procedures might be contraindicated when treating certain pediatric patients. The aim of this study was to compare the cleanliness of the root canal walls of primary teeth and the time required for the completion of the cleaning and shaping procedures performed by the Er,Cr:YSGG laser, manual or rotary instrumentation techniques. Thirty-five extracted, single-rooted, primary teeth were divided into 4 groups: I, canals were instrumented with Profile .04 rotary instruments to a master apical file size #35; II, the laser was used (parameters: 1.50 W, 20 pps, 30% water and 50% air) with a Z3 laser tip (0.32-mm diameter); III, canals were instrumented with stainless steel K-files; and IV, no instrumentation was performed (control). The teeth were split in 2 halves and prepared for scanning electron microscopy analysis. Images from the coronal, middle, and apical thirds of the roots were analyzed independently by 2 calibrated, blinded evaluators. Statistical analysis revealed significant differences among the groups (Kruskal-Wallis, P = .0001). The techniques were not capable of providing completely clean canals. Treatment with Er,Cr:YSGG laser provided similar cleanliness when compared with rotary instrumentation technique and was superior to manual instrumentation. The laser technique required less time for completion of the cleaning and shaping procedures when compared with both rotary or hand instrumentation.

Ex vivo study of manual and rotary instrumentation techniques in human primary teeth

This study aimed to evaluate, ex vivo, time and dentin removal by manual and rotary instrumentation in human primary teeth. Eighty primary teeth were divided into 2 groups, embedded in resin, and sectioned for evaluation before and after instrumentation. For manual technique, teeth were prepared using K-type files and rotary preparation was performed with Hero 642. All root canals were prepared up to size 40, and the instrumentation time was recorded. Dentin removal was calculated using digital image software. Data was statistically analyzed using chi-squared, Mann-Whitney, and t tests. Manual instrumentation removed more dentin in all groups compared with rotary instrumentation (P < .05). In some specimens, root perforations were observed in areas coinciding with largest root resorption. Rotary technique showed the shortest instrumentation time (P < .05). Deciduous teeth, without significant root resorption, have enough root structure for instrumentation up to size 40. Rotary technique required less time and generated less dentin removal.

A quantitative analysis of rotary, ultrasonic and manual techniques to treat proximally flattened root canals

Objective:The efficiency of rotary, manual and ultrasonic root canal instrumentation techniques was investigated in proximally flattened root canals.Material and Methods:Forty human mandibular left and right central incisors, lateral incisors and premolars were used. The pulp tissue was removed and the root canals were filled with red die. Teeth were instrumented using three techniques: (i) K3 and ProTaper rotary systems; (ii) ultrasonic crown-down technique; and (iii) progressive manual technique. Roots were bisected longitudinally in a buccolingual direction. The instrumented canal walls were digitally captured and the images obtained were analyzed using the Sigma Scan software. Canal walls were evaluated for total canal wall area versus noninstrumented area on which dye remained.Results:No statistically significant difference was found between the instrumentation techniques studied (p<0.05).Conclusion:The findings of this study showed that no instrumentation technique was 100% efficient to remove the dye.

The principles of techniques for cleaning root canals

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.

Bacterial reduction by extensive versus conservative root canal instrumentation in vitro

Objective. This study aimed to test the hypothesis that aggressive dentin removal through greater-tapered instrumentation reduces the intracanal bacteria more effectively than conservative dimension instrumentation. Material and methods. Twenty extracted human lower premolar teeth were used. After extirpation of the pulps, the teeth were autoclaved and immersed in a broth inoculated with Enterococcus faecalis and incubated for 7 days to allow infection of the dentinal tubules. The teeth were divided into 2 experimental groups, each comprising 10 teeth. The teeth were instrumented either with ProTaper or with Hero Shaper nickel-titanium rotary instrumentation techniques. It was calculated that ProTaper theoretically has the potential to remove at least twice the dentin volume compared with Hero Shaper. The apical preparation was standardized to file size 30. Saline solution was used for irrigation. Bacteriological samples were taken before and after instrumentation and plated onto tryptic soy agar, and the reduction in numbers was calculated. Results. Both instrumentation techniques significantly reduced the number of bacteria in the root canal (p<0.05). Reduction in absolute bacterial numbers was up to 98%. There was no statistically significant difference between the two techniques. Conclusions. Preparation with an instrumentation technique removing substantial amounts of dentin did not reduce the intracanal bacteria more effectively than a more conservative instrumentation technique.