Cyclic fatigue of EndoSequence and K3 rotary files in a dynamic model

The cyclic fatigue resistance of K3 and EndoSequence files was compared by rotating files against a highly polished surface inclined at 15 degrees to the horizontal. For each brand, files with a 25 tip in .04 and .06 taper and files with a 40 tip in .04 and .06 taper were tested at both 300 and 600 rpm. A 3-mm axial movement simulated a clinical pecking motion at 1 cycle per second. The number of rotations to failure was calculated and analyzed by using analysis of variance and Independent Student's t tests, with results confirmed by nonparametric Mann-Whitney U tests with a Bonferroni correction. At both 300 and 600 rpm, K3 files exhibited statistically significantly more cycles to fracture than their EndoSequence counterparts with the same tip size and taper. Scanning electron microscopy images demonstrated surface features consistent with fracture due to cyclic fatigue. In this model, file design appeared to be the most important determinant of cyclic fatigue resistance.     

Comparison of distortion and separation utilizing profile and Pow-R nickel-titanium rotary files.

The purpose of this study was to determine whether there was a difference in the frequency of file distortion and separation between nickel-titanium (Ni-Ti) ProFile 0.04 ISO taper rotary files and Ni-Ti Pow-R 0.04 ISO taper rotary files. For this study, 60 mesial root canals in 30 human mandibular first molars were chosen with the curvature angle of the mesiobuccal and mesiolingual canals of the same tooth within five degrees. ProFile and Pow-R files were randomly assigned to either the mesiobuccal or mesiolingual canal of the same tooth. Instrumentation proceeded per the manufacturer's recommendations, in a crown-down technique, using Gates Glidden burs and rotary files in sizes #50 to #20. Positive and negative controls were used. The instruments were evaluated for signs of distortion or separation by three independent evaluators using magnification under microscope. A total of 420 files were evaluated, 210 files for Pow-R and 210 files for ProFile. There was no statistically significant difference in the incidence of instrument distortion or separation between the two file systems that were studied.     

Comparison of removal times of Thermafil plastic obturators using ProFile rotary instruments at different rotational speeds in moderately curved canals

The purpose of this study was to compare the time required for removal of small Thermafil plastic carriers in moderately curved MB roots of mandibular molars using the ProFile rotary system at 300 and 1,500 rpm. MB roots of 40 mandibular molars were instrumented and obturated with size 30 Thermafil plastic obturators. Teeth were divided into two groups. In group 1, sizes 55 to 25 ProFile 0.04-taper instruments were used in a crown-down manner at 300 rpm. In group 2, size 25 ProFile 0.04-taper instruments were used at 1,500 rpm. Time of carrier removal and the number of instrument separations were recorded. The Student's t test demonstrated a significant difference between groups: 4 minutes 12 seconds for group 1 and 1 minute 28 seconds for group 2 (p < 0.001). However, a trend for greater separation of instruments was found with the higher rpm group.     

Surface analysis of ProFile instruments by scanning electron microscopy and X-ray energy-dispersive spectroscopy: a preliminary study

AIM: The purpose of this preliminary study was to analyze surface irregularities on ProFile nickel-titanium (NiTi) rotary instruments before use, after sterilization by two different methods and after instrumentation of molar root canals. METHODOLOGY: Five new ProFile NiTi rotary instruments with 0.04 taper, size 20, five instruments with 0.04 taper, size 25 and five with 0.06 taper, size 20 were analyzed by scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS). The instruments were then divided into two groups: three of each taper and size were sterilized in a dry heat sterilizer, whilst two of each taper and size were sterilized in an autoclave. After inspection by the same techniques, the files were used to instrument six molar root canals, and again analyzed by SEM/EDS. RESULTS: Together with the usual machining defects, a variable amount of material containing mainly carbon and sulphur was found on the surface of new instruments. This material was not removed by standard cleaning and sterilization procedures. The use of the files for instrumentation of root canals eliminated a considerable amount of the adhered substance, but deposits rich in calcium and phosphorus accumulated on the remaining impurities. CONCLUSIONS: The adherence of dentine on surface deposits found on new ProFile instruments requires special cleaning, prior to sterilization.     

Cyclic Fatigue Analysis of a New Generation of Nickel Titanium Rotary Instruments

Recently, a new generation of nickel-titanium (NiTi) rotary instruments including the Twisted File (TF; Sybron Dental Specialties, Orange, CA) and ProFile GT Series X (GTX; Denstply, Tulsa Dental Specialties, Tulsa, OK) was introduced to the market. The purpose of this study was to determine if these new NiTi instruments were more resistant to cyclic fatigue compared with traditionally ground NiTi rotary instruments such as EndoSequence (ES; Brasseler, Savannah, GA) and ProFile (PF; Dentsply, Tulsa Dental Specialties). Size #25 TF, ES, and PF and size #20 GTX with .04 and .06 tapers were tested in a simulated canal with 60° angle of curvature and a 3-mm radius. The number of rotations until fracture was recorded for each instrument. Among both .04 and .06 tapered files, #20 GTX files performed significantly better than all other files tested with tip sizes of #25 (p < 0.001); this may be because of the increased flexibility in the #20 files compared with #25 files. TF was significantly more resistant to cyclic fatigue than ES (p < 0.05) but not different from PF (p > 0.05) with the same tip size. The new manufacturing processes appeared to offer greater resistance to cyclic fatigue in a simulated canal model.     

A Comparison of Three Nickel Titanium Rotary Systems,EndoSequence, ProTaper Universal,and Profile GT,for Canal-cleaning Ability

Canal preparation is a major step in root canal treatment and is directly related to subsequent disinfection and obturation. In recent years, nickel-titanium rotary systems such as the EndoSequence (Brassler USA, Savannah, GA), the ProTaper Universal (Dentsply/Maillefer, Ballagigues, Switzerland), and the ProFile GT (Dentsply/Maillefer, Ballagigues, Switzerland) have significantly altered root canal instrumentation. EndoSequence has become a very popular system among general practitioners but has not been scientifically tested or compared with other rotary systems that are commonly used by both specialists and general practitioners. The purpose of this study was to compare cleaning effectiveness under scanning electron microscopy (SEM) using three different rotary nickel-titanium instruments: the ProTaper variable taper, the ProFile GT .04 taper, and the EndoSequence .04 taper. Thirty-six extracted mandibular molars were selected for this study. The teeth were randomly divided into three groups. Each group had two noninstrumented teeth that served as controls. All teeth were prepared to a #40 final apical file after manufacturers' instructions. All three systems were used in the traditional “crown-down technique.” Teeth were sectioned buccolingually and examined under SEM at 20.0 kV and 500× magnification in the middle third of the canal. Debris was defined as dentin chips, pulp remnants, and particles loosely attached to the root canal wall. Analysis of the SEM images was performed by using a five-score index. Results indicated that there was no difference in cleansing ability of the three file types.     

Hero 642对弯曲根管根管成形能力的评价

目的：评价机用镍钛锉Hero 642预备弯曲根管时的根管成形能力。方法：利用自主研制的《牙齿模拟根管辅助分析测量系统》软件,定量检测8个模拟根管在用Hero 642以冠下法预备前后的形态变化,并进行统计学分析。结果：机用镍钛锉Hero 642能够很好地保持根管的原始弯曲度。在预备至0.02锥度25#銼和30#锉时,Hero 642对弯曲根管的各部位切割均衡,根管几何中心线基本不移位。结论：机用镍钛锉Hero 642具有良好的根管成形能力。对于高度弯曲的根管,预备主锉仍可选择0.02锥度30^#锉。     

Histologic analysis of the cleaning capacity of mechanical endodontic instruments activated by the ENDOflash system

The cleaning capacity of mechanical endodontic instruments activated by the ENDOflash system was evaluated by means of histologic and morphometric analyses. Twenty-two distobuccal roots of human maxillary molars from laboratory stock were randomly separated into four groups. Group 1 was instrumented with ENDOflash files, group 2 with ProFile taper .04 files, group 3 received instrumentation with Pow-R taper .04 files, and group 4 (positive control) was instrumented with Nitiflex files. After instrumentation, teeth were sectioned transversally and processed for microscopic evaluation to determine the amount of debris on root canal walls. Results obtained by morphometric analysis indicated significant statistical differences (p < 0.01) between groups. ProFile taper .04 files were significantly more efficient in cleaning the root canal, followed by Pow-R files, Nitiflex, and ENDOflash, which had the lowest levels for cleaning the root canals.     

Efficiency of the 0.04 taper ProFile during the re-treatment of gutta-percha-filled root canals

AIM: The objective of this study was to determine the effectiveness of 0.04 ProFile instruments during the removal of root fillings. METHODOLOGY: A total of 30 single-rooted mandibular canines were divided into three groups. The canals were accessed and then prepared with a reciprocating automated device and nickel-titanium files. Three different techniques of obturation were used: Thermafil system (group I), thermomechanical compaction (group II) and lateral condensation (group III). Sealer 26 was used in all three groups. Two weeks after obturation, the fillings were removed using 0.04 ProFile instruments following standardized sequence of size 90, 60, 45, 40, 35 and 30 at a speed of 300 rpm in a crown-down manner. The teeth were subsequently split with a chisel, photographs were taken with a colour video camera and the removal of filling material was assessed visually (by colour) by two examiners. The time required to achieve the working length was also recorded. RESULTS: ProFile instruments reached the working length in all cases. However, complete removal of gutta-percha occurred in only three specimens (two of group I, and one of group II). Thermafil plastic carriers were removed successfully in all specimens of group I. CONCLUSIONS: ProFile instruments with 0.04 taper were inadequate in completely removing the filling materials from the root canal system. However, the ideal working length was achieved rapidly.     

Influence of rotational speed, torque and operator's proficiency on ProFile failures

AIM: The purpose of this study was to evaluate the influence of rotational speed, torque, and operator experience with a specific Ni-Ti rotary instrumentation technique on the incidence of locking, deformation and separation of instruments. METHODOLOGY: ProFile Ni-Ti rotary instruments (PRI) sizes 40-15 with a 6% taper were used in a crown-down technique. In one group of canals (n = 300) speeds of 150, 250 and 350 rpm (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (n = 300) three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of PRI and 100 canals of extracted human molars. Each set of PRI was used in up to 10 canals and then sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments for the different groups, and within each part of the study was analysed statistically for significance with chi-squared tests. RESULTS: In group 1 only one instrument was deformed in the 150-rpm group and no instruments separated or locked. In the 250-rpm group instrument separation did not occur, however, a high incidence of locking, deformation and separation was noted in the 350-rpm group. In general, instrument sizes 30-15 locked, deformed and separated. Chi-squared statistics showed a significant difference between the 150 and 350 rpm groups but no difference between the 150 and 250 rpm groups with regard to instrument separation. Overall, there was a trend toward a higher incidence of instrument deformation and separation in smaller instruments. Locking and separation occurred during the final passage of the instruments, in the last (tenth) canal in each subgroup. In the second group, neither separation nor deformation and locking occurred during the use of the ProFile instruments, at 150 rpm, and at the different torque values. In the third group, chi-squared analysis demonstrated that significantly more instruments separated with the least experienced operator. Instrument locking, deformation, and separation did not occur with the most experienced operator. CONCLUSIONS: Preclinical training in the use of the PRI technique with crown-down at 150 rpm were crucial in avoiding instrument separation and reducing the incidence of instrument locking and deformation.     

Modeling capacity of ENDOflash files in simulated root canals

With the development of rotary nickel-titanium files and their applications in Endodontics, the concepts of root canal preparation have changed. The objective of this research is to evaluate the transportation of simulated root canals caused by stainless steel ENDOflash rotary files compared to nickel-titanium ProFile files (.04, .06 and Orifice Shapers). Twenty-four simulated root canals with a 30 degrees curvature were randomly divided into 2 groups and prepared with ENDOflash or ProFile files according to manufacturers' instructions. Comparison between the simulated root canals before and after instrumentation showed significant differences (p < 0.001) between the groups, with greater transportation observed with ENDOflash files. One case of deformation was observed with a ProFile instrument (#20/.04) and there were no fractures.     

K3 Endo, ProTaper, and ProFile systems: breakage and distortion in severely curved roots of molars

It was the aim of this study to investigate the incidence of file breakage and distortion when the ProTaper, K3 Endo, and ProFile systems were used to instrument canals in the severely curved roots of extracted molars. Forty-five roots of extracted mandibular and maxillary molars with curvatures between 40 and 75 degrees were chosen for this study. The canals in group 1 were instrumented with the ProFile system. Roots in group 2 were instrumented with the ProTaper system, and those in group 3 were instrumented with the K3 Endo system. The three systems were used according to the manufacturers' instructions. The proportion of files distorted was 15.3% for the ProFile group, 2.4% for the ProTaper group, and 8.3% for the K3 Endo group. There was a statistically significant difference between the ProFile and ProTaper groups (p=0.0079). The percentage of broken files was 1.7% for the ProFile group, 6.0% for the ProTaper group, and 2.1% for the K3 Endo group. No statistically significant differences were found between these three groups (p=0.4243). The results of this study showed that these three rotary tapered systems were not significantly different with regard to breakage. There were significantly more distorted files in the ProFile group when compared with the ProTaper group. With regard to distortion, there was no significant difference between the ProTaper and K3 Endo and the ProFile and K3 Endo groups.     

An In Vitro Comparison of Torsional Stress and Cyclic Fatigue Resistance of ProFile GT and ProFile GT Series X Rotary Nickel-Titanium Files

The purpose of this in vitro study was to compare the torsional stress and cyclic fatigue characteristics of ProFile GT (Dentsply Tulsa Dental, Tulsa, OK) and ProFile GT Series X (Dentsply Tulsa Dental). Files of 0.04 and 0.06 taper, 25 mm in length, and ISO sizes of 20 and 30 tips were compared (n = 25 per test group). Torque stress resistance was evaluated by measuring the torque in gram-centimeters (g-cm) and angle of deflection (degrees of rotation) required for instrument separation with use of a torsiometer instrument. Cyclic fatigue was determined by recording the time until breakage of a file rotating in a simulated canal with an applied 45° or 60° curve. The files were operated in a cyclic fatigue instrument that simulated clinical rotary file usage with a constant cyclical axial motion. There was no statistical difference (p > 0.05) when comparing the torque (g-cm) required to induce a torsional failure of ProFile GT and ProFile GT Series X files of identical file sizes. The angle of deflection (degrees of rotation) of ProFile GT was significantly greater (p ≤ 0.001) before separation than ProFile GT Series X for all file sizes tested except 20/.04 (p > 0.05). There was no statistical difference (p > 0.05) in cyclic fatigue failure for ProFile GT and ProFile GT Series X in a canal with a curvature of 45°. In the 60° canal curvature, ProFile GT was found to be significantly more resistant (p = 0.005) to fracture because of cyclic fatigue than ProFile GT Series X for file size 30/.06 and significant (p ≤ 0.001) for files sizes 20/.06 and 30/.04. There was no difference (p > 0.05) in cyclic fatigue resistance in the 60° canal for ProFile GT and ProFile GT Series X for file size 20/.04.     

Comparison of the Canal Master endodontic instrument and K-type files for enlargement of curved root canals

Twenty mandibular molars with 40 mesial curved root canals were instrumented with a circumferential technique using K files and the Canal Master instrumentation technique by junior dental students whose only endodontic experience had been completion of a preclinical endodontic course. Preoperative and postoperative radiographs were taken facially and mesially with instruments in place. The canals were evaluated radiographically for transportation 1 mm and 4 mm from the apex. The mesial roots were cross-sectioned at the same level. The sections were evaluated for roundness of the canal preparation. It was concluded that the Canal Master instrumentation technique transported the root canal less and produced rounder preparations than the K file circumferential technique. There appears to be a greater tendency for breakage with the Canal Master.     

A retrospective clinical study of incidence of root canal instrument separation in an endodontics graduate program: a PennEndo database study

This study investigated the incidence of hand and rotary instrument separation (IS) in the endodontics graduate program at the University of Pennsylvania between 2000 and 2004. In 4,865 endodontic resident cases the incidence of hand and rotary IS was 0.25% and 1.68%, respectively. The odds for rotary IS were seven times more than for hand IS. The probability of separating a file in apical third was 33, and 6 times more likely when compared to coronal and middle thirds of the canals. The highest percentage of IS occurred in mandibular (55.5%) and maxillary (33.3%) molars. Furthermore, the odds of separating a file in molars were 2.9 times greater than premolars. Among the ProFile series 29 rotary instruments, the .06 taper # 5 and # 6 files separated the most. There was no significant difference in IS between the use of torque controlled versus nontorque controlled handpieces, nor between first and second year residency.     

Effectiveness of the ProFile.04 Taper Series 29 files in removal of gutta-percha root fillings during curved root canal retreatment.

The purpose of this in vitro study was to evaluate the capacity of ProFile.04 Taper Series 29 files to remove gutta-percha during curved root canal retreatment. Forty-four mandibular molars whose mesial roots presented between 26 and 40 degrees of curvature, determined by Schneider's method, were selected. The root canals were enlarged to ISO size 35 and obturated with laterally condensed gutta-percha using Sealer 26. The teeth were randomly divided into three groups for gutta-percha removal: GI: size 2 Gates Glidden drills; GII: size 6 ProFile.04 Taper Series 29 files; GIII: size 7 ProFile.04 Taper Series 29 files. The penetration of the instruments was measured with millimetered x-rays and clinical observation. The ProFile.04 Taper Series 29 files removed the endodontic filling material better than the Gates Glidden files.     

A comparison of two nickel-titanium instrumentation techniques in teeth using microcomputed tomography

AIM: The aim of the study was to compare the shaping of root canals by two nickel-titanium instrumentation techniques using microcomputed tomography (MCT). METHODOLOGY: Ten mandibular first molar teeth (30 canals) that had intact crowns and fully formed roots were scanned using MCT. Fifteen canals were instrumented using NiTiFlex hand files (Maillefer) using balanced force. The remainder were instrumented using prototype ProFile 0.04 Taper instruments (Dentsply) in a crown-down manner to an apical size ISO 25. The teeth were scanned again following instrumentation. The two instrumentation techniques were compared in a total of 27 canals. The area of dentine removed at predetermined levels (2.0, 3.0, 4.5, 6.0, 7.5 mm) from the apex was measured. Transportation and centring were recorded. Images constructed at these levels were compared with video images of equivalent physical sections created after the second scan. The volume of dentine removed in the apical 7.5 mm of the root canals of each tooth was calculated and the different techniques compared. Rendered three-dimensional images were used to assess the preparations qualitatively. The time taken for preparation was recorded. RESULTS: There was no significant difference between hand instrumentation with NitiFlex files and machine instrumentation with prototype ProFile 0.04 Taper instruments for any of the variables tested. CONCLUSIONS: Both techniques produced well centred and tapered preparations.     

A comparative photoelastic stress analysis of internal root stresses between RC Prep and saline when applied to the Profile/GT rotary instrumentation system

The purpose of this study was to measure and compare the amount of stress produced by GT ProFile (GT) and ProFile (PF) rotary files lubricated with either RC Prep (RCP) or saline (S) on the walls of prepared simulated canals. Twenty-four 10-mm long canals with a 10 mm radius of curvature were prepared in PL-2 photoelastic acrylic blocks which were lubricated with either RCP or S. The files were inserted into a Nouvag handpiece mounted to an Instron 4502 universal testing machine and lowered into the canal at a rate of 60 mm/min and a rotational speed of 300 RPM. The following four GTs and four PFs were sequentially introduced into predetermined depths of each canal: 20/.10, 20/.08, 20/.06, 20/.04, 40/.04, 35/.04, 30/.04, and 25/.04. Total areas of stress created by each file were captured by digital video images and measured using Image J software. Statistical analysis of the data was performed using a two-way ANOVA (p < 0.05, n = 24). The GT/RCP group demonstrated a significant average of 64.22% less stress than GT/S group. The PF (25, 30, and 35)/RCP groups demonstrated a significant average of 27.02% less stress than the same S groups. PF (40) produced a negligible amount of stress regardless of the lubricant type. The results reveal that using RCP as a lubricant when instrumenting curved canals with GT and PF results in less stress when compared to saline.     

Shaping ability of ProFile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals

AIM: To compare the shaping ability of ProFile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals with different curvature and radius. METHODOLOGY: ProFile or K3.06 taper instruments were used to prepare simulated canals of 20 degrees curvature and 5 mm radius (n = 10) and 30 degrees curvature and 3 mm radius canals (n = 10) in resin blocks. All canals were prepared to an apical size 40 at 0.5 mm from the canal terminus using a variable tip crown-down sequence. Pre- and postinstrumentation digital images were recorded, and an assessment of the canal shape was determined using a computer image analysis program. The material removal from the inner and outer wall of the canal was measured at 28 measuring points, beginning 0.5 mm from the end-point of the canal and the data compared using the Mann-Whitney U-test. RESULTS: In 20 degrees and 30 degrees canals both instruments significantly removed more (P < 0.05) material on the outer wall than the inner wall in the apical half of the canal. For ProFile files there was no significant difference in the amount of material removed on the outer canal wall between the 20 degrees and 30 degrees canals. However, in the K3 groups significantly more (P < 0.05) outer canal wall was removed in the apical area in 20 degrees canals. When comparing both instruments the results showed that in 20 degrees canals K3 instruments removed more outer and inner canal wall than ProFile instruments (P < 0.05) but that there was no significant difference (P > 0.05) between the instruments in 30 degrees canals. CONCLUSION: Within the limitation of this study, both rotary nickel-titanium instruments prepared a well-shaped root canal with minimal canal transportation.     

Effect of modified Hedstrom files on instrumentation area produced by ProFile instruments in oval canals

OBJECTIVE: To study the effect of a modified Hedstrom file called IqFile on the instrumentation shape of oval canals prepared with ProFile instruments. STUDY DESIGN: Fifty extracted premolars were divided into 3 groups of 16 teeth each. Group 1 was subjected to ProFile 0.04 rotary instrumentation to a size 6. Group 2 followed the same technique, but also received buccolingual hand instrumentation with IqFiles to ISO size 70. Group 3 was instrumented similarly to group 2 but unmodified Hedstrom files were used. Teeth were sectioned at 1 and 3 mm from working length and photographed at 26x magnification. AutoCAD was used for measuring the percentage of instrumented area of the canal. RESULTS: ANOVA revealed that Group 2 was significantly better than Groups 1 (P=.00) and 3 (P=.00) at the 1 mm level. At the 3 mm level Group 2 was significantly better than Group 1 (P=.03), but no differences were found between Groups 2 and 3 (P=.15). CONCLUSION: The combination of ProFile and IqFile was found more effective in instrumenting oval canals at both the 1 and the 3 mm levels. However, at the 3 mm level no difference was detected between the use of IqFiles and the use of unmodified Hedstrom files.