Search

Aim To assess and compare the flexibility and torsional resistance of PathFile, Ra Ce ISO 10 and Scout Ra Ce instruments in relation to stainless steel K- File hand instruments. Methodology Rotary Path File (sizes 13, 16 and 19; .02 taper), Race ISO 10 (size 10; 0.02, 0.04 and 0.06 tapers), Scout Ra Ce (sizes 10, 15 and 20; 0.02 taper) and hand K- File (sizes 10, 15 and 20; 0.02 taper) instruments were evaluated. Alloy chemical composition, phases present and transformation temperatures were determined for the Ni Ti instruments. For all instruments, diameters at each millimetre from the tip as well as cross-sectional areas at 3 mm from the tip were measured based on ANSI/ ADA Specification No. 101 using image analysis software. Resistance to bending and torsional resistance were determined according to specification ISO 3630-1. Vickers microhardness measurements were also taken in all instruments to assess their strength. Data were analysed using analysis of variance (α = 0.05). Results The alloys used in the manufacture of the three types of Ni Ti instruments had approximately the same chemical composition, but the Path File instruments had a higher Af transformation temperature and contained a small amount of B19' martensite. All instruments had diameter values within the standard tolerance. The bending and torsional resistance values were significantly increased relative to the instrument diameter and cross-sectional area. Conclusions PathFile instruments were the most flexible and the least torque resistant, whilst the stainless steel instruments were the least flexible although they were more torque resistant than the Ni Ti instruments. [ABSTRACT FROM AUTHOR]

Aim To assess the influence of multiple clinical uses on the torsional behaviour of ProTaper Universal rotary NiTi instruments. Methodology Root canal treatments were performed on patients using the ProTaper Universal rotary system to prepare canals. Ten sets of instruments were used by an experienced endodontist, each set being used in five molar teeth. After clinical use, S1, S2, F1 and F2 instruments were analysed for damage by optical and scanning electron microscopy. The used sets, along with a control group of 10 sets of new instruments, were then torsion tested based on the ISO 3630-1 specification. Data obtained were subjected to a one-way analysis of variance (anova) with α = 0.05. Results The use of the ProTaper Universal rotary instruments by an experienced endodontist allowed for the cleaning and shaping of the root canal system of five molar teeth without fracture. The maximum torque for instruments S2, F1 and F2, and the angular deflection at fracture for instruments S2 and F1 were significantly lower following clinical use. The largest decrease in maximum torque was 18.6% ( P = 0.014) for S2 instruments. The same maximum percent decrease was found for angular deflection at fracture for F1 instruments ( P = 0.009). Conclusions Torsional resistance and angular deflection of used instruments, as compared to that of new instruments, were reduced following clinical use. [ABSTRACT FROM AUTHOR]

Aim To evaluate the influence of cyclic torsional loading on the flexural fatigue resistance and torsional properties of rotary NiTi instruments. Methodology Twelve sets of new K3 instruments, sizes 20, 25 and 30 with an 0.04 taper, and sizes 20 and 25 with an 0.06 taper, were torsion tested until rupture, to establish their mean values of maximum torque and angular deflection. Twelve new K3 instruments of each of the following dimensions, size 30, 0.04 taper and sizes 20 and 25 with 0.06 taper, were tested to failure by rotation bending in a fatigue test device. Cyclic torsional loading was performed in 20 cycles from zero angular deflection to 180° and then return to zero applied torque. After cyclic loading, the same number of instruments were tested until rupture in torsion and flexural fatigue. Data obtained were subjected to a one way analysis of variance (anova) at 95% confidence level. Results Cyclic torsional loading caused no significant differences in maximum torque or in maximum angular deflection of the instruments analysed, but comparative statistical analysis between measured NCF values of new and previously cycled K3 instruments showed significant differences for all tested instrument. Longitudinal cracks, that is, cracks apparently parallel to the long axis of the instruments cycled in torsion was observed. Conclusions Cyclic torsional loading experiments in new K3 rotary endodontic instruments showed that torsional fatigue decreased the resistance of these instruments to flexural fatigue, although it did not affect their torsional resistance. [ABSTRACT FROM AUTHOR]

Aim To evaluate the effect of repeated sterilization cycles in dry oven or autoclave, on the mechanical behaviour and fatigue resistance of rotary endodontic Ni-Ti instruments. Methodology New Ni-Ti instruments were subjected to five consecutive sterilization cycles in a dry oven or steam autoclave. Microhardness was measured in the nonmachined parts of the shanks of instruments using a Vickers indenter. Specimens of Ni-Ti wires were submitted to the same sterilization protocol and tensile tested until rupture. A group of instruments were fatigued to one half of their average fatigue life and then sterilized. New and sterilized instruments were fatigue tested until rupture. ANOVA tests at α = 0.05 were used for statistical analysis. Results Sterilization procedures resulted in no significant changes in Vickers microhardness, nor in the parameters describing the mechanical behaviour of the wires. However, the number of cycles to failure was statistically higher for all instruments after dry heat or autoclave sterilization cycles. In the instruments previously fatigued to one half of their fatigue life, autoclave sterilization gave rise to an increase of 39% in the remaining number of cycles to failure. Conclusions Changes in the mechanical properties of Ni-Ti endodontic instruments after five cycles of commonly used sterilization procedures were insignificant. The sterilization procedures are safe as they produced a significant increase in the fatigue resistance of the instruments. [ABSTRACT FROM AUTHOR]

Endodontic files made of nickel–titanium (NiTi) superelastic wires can be employed in rotary techniques for cleaning and shaping curved root canals, suffering tensile–compressive strain cycles with maximum amplitudes between 3 and 5%. The aim of this work was to study the fatigue behaviour of this material under such high deformation conditions, using NiTi instruments and superelastic wires taken from their production line. One hundred load–unload tensile cycles in the superelastic regime (4% elongation) were applied to NiTi wires. New endodontic instruments were fatigue-tested simulating the geometrical conditions found in their clinical use. It was found that only small changes took place in the parameters describing the mechanical behaviour of the cycled wires. The measured average number of cycles to failure varies inversely with the maximum tensile strain amplitude in the fatigue tests ( r= 0.993). [ABSTRACT FROM AUTHOR]

Aim: To compare the martensitic transformation temperatures and torsional resistance behaviour of classic M‐Wire Reciproc and Reciproc blue files (VDW, Munich, Germany). Methodology: M‐Wire classic Reciproc R25 and Reciproc blue R25 instruments were used. Transformation temperatures were determined by differential scanning calorimetry (DSC‐DSC 60, Shimadzu, Kyoto, Japan). Three samples with approximately 20 mg of each system were cooled to −120 °C and then heated to 100 °C and then cooled to –100 °C at a rate of 10 °C min−1. The maximum torque values and angular deflection until fracture of new instruments (n = 10) were measured according to ISO 3630‐1. Results were analysed statistically using the Student's t‐test at a significance level of P < 0.05. Results: DSC results revealed the absence of martensitic transformation for Reciproc instruments in the temperature range analysed. In both systems, the instruments were composed of a mixture of R‐phase and austenite at room temperature. After torsional tests, Reciproc blue had significantly lower values for mean maximum torque at rupture (P < 0.05), although the angular deflection values were significantly higher than the Reciproc classic group (P < 0.05). Conclusions: Both Reciproc and Reciproc blue instruments were composed of a mixture of R‐phase and austenite. Reciproc Blue instruments had a greater angle of rotation to fracture but a lower torque to failure than M‐Wire Reciproc instruments. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To investigate the surface morphology and electrochemical potential of superelastic (SE), M‐Wire (MW) and shape memory technology (SMT) NiTi instruments before and after single clinical use in vivo. Methodology: A total of 60 ProTaper Universal F2 (PTU‐SE), ProTaper Next X2 (PTN‐MW), Typhoon (TYP), Hyflex (HF) and Vortex Blue (VB), the last three SMT, and size 25, .06 taper (n = 6 of each type) files were examined. Scanning electron microscopy (SEM), X‐ray energy‐dispersive spectroscopy (EDS) and electrochemical potential analysis were employed before and after clinical use. Statistical analysis was performed with one‐way analysis of variance and Bonferroni's post hoc test. Significance was determined at the 95% confidence level for both tests. Results: SEM observations of new instruments indicated the presence of marks left by the machining process during manufacturing and EDS revealed the existence of an oxide coating on shape memory instruments. After clinical use, the five types were associated with propagation of transverse cracks 3 mm from the tip. The surface oxide layer of TYP, HF and VB instruments had microcracks in multiple directions, whilst TYP and HF had fragmentation in chip form of the oxide layer. EDS analysis demonstrated a significant reduction of the oxide layer in shape memory instruments, except for VB. Electrochemical potentials were higher for shape memory instruments than for M‐Wire and superelastic NiTi instruments, respectively (P < 0.05). Conclusions: It appears that shape memory technology NiTi instruments have a dysfunctional oxide layer after clinical use. Additionally, they featured higher electrochemical potential relative to NiTi instruments manufactured from M‐Wire, and conventional superelastic NiTi alloy. [ABSTRACT FROM AUTHOR]

Aim To validate torsional analysis, based on finite elements, of WaveOne instruments against in vitro tests and to model the effects of different nickel-titanium (NiTi) materials. Methodology WaveOne reciprocating instruments (Small, Primary and Large, n = 8 each, M-Wire) were tested under torsion according to standard ISO 3630-1. Torsional profiles including torque and angle at fracture were determined. Test conditions were reproduced through Finite Element Analysis (FEA) simulations based on micro-CT scans at 10-lm resolution; results were compared to experimental data using analysis of variance and two-sided one sample t-tests. The same simulation was performed on virtual instruments with identical geometry and load condition, based on M-Wire or conventional NiTi alloy. Results Torsional profiles from FEA simulations were in significant agreement with the in vitro results. Therefore, the models developed in this study were accurate and able to provide reliable simulation of the torsional performance. Stock NiTi files under torsional tests had up to 44.9%, 44.9% and 44.1% less flexibility than virtual M-Wire files at small deflections for Small, Primary and Large instruments, respectively. As deflection levels increased, the differences in flexibility between the two sets of simulated instruments decreased until fracture. Stock NiTi instruments had a torsional fracture resistance up to 10.3%, 8.0% and 7.4% lower than the M-Wire instruments, for the Small, Primary and Large file, respectively. Conclusion M-Wire instruments benefitted primarily through higher material flexibility while still at low deflection levels, compared with conventional NiTi alloy. At fracture, the instruments did not take complete advantage of the enhanced fractural resistance of the M-Wire material, which determines only limited improvements of the torsional performance. [ABSTRACT FROM AUTHOR]

Aim To investigate the influence of cyclic flexural and torsional loading on the flexibility of ProTaper Universal, K3 and EndoSequence nickel-titanium instruments, in view of the hypothesis that these types of loading would decrease the flexibility of the selected NiTi rotary files. Methodology The instruments evaluated were S2 and F1 ProTaper Universal, sizes 20 and 25, .06 taper K3, and sizes 20 and 25, .06 taper EndoSequence. Flexibility was determined by 45° bending tests according to ISO 3630-1 specification. Values of the bending moment ( MB) obtained with new instruments were considered as the control group ( CG). Bending tests were then conducted in instruments previously fatigued to one-fourth and three-fourths of their average fatigue life (fatigue groups, FG¼ and FG¾), as well as after cyclic torsional loading (torsional group, TG). Fatigue tests were carried out in a bench device that allowed the files to rotate freely inside an artificial canal with an angle of curvature of 45° and a radius of 5 mm. Cyclic torsional loading tests were performed that entailed rotating the instrument from zero angular deflection to 180° and then returning to zero applied torque in 20 cycles. Data were analysed using one-way analysis of variance at a significance level of 5%. Results Simulated clinical use by means of flexural fatigue tests did not affect the flexibility of the instruments, except for a significant increase in flexibility observed in a few instruments ( P < 0.05). In addition, comparative statistical analyses between the values of MB measured in new instruments and after cyclic torsional loading showed no significant differences between them ( P > 0.05). Conclusions The flexibility of rotary ProTaper Universal, K3 and EndoSequence NiTi instruments, measured in bending tests, was not adversely affected by simulated clinical use in curved root canals. [ABSTRACT FROM AUTHOR]

Aim To compare the flexibility, torsional resistance and structural and dimensional characteristics of instruments produced by twisting with those of a geometrically similar nickel-titanium ( Ni Ti) system produced by a grinding process. Methodology The mean diameters along the flute and the pitch length of size 25, .04 taper, size 25, .06 taper, and size 25, .08 taper Twisted File ( TF) ( SybronEndo, Orange, CA, USA), and size 25, .04 taper, and size 25, .06 taper Ra Ce instruments ( FKG, La Chaux-de-Fonds, Switzerland) ( n = 10 each) were measured according to ANSI/ ADA specification No. 101. Two pairs of instruments were found to have similar diameters at 3 mm from the tip: TF size 25, .06 taper and Ra Ce size 25, .04 taper, and TF size 25, .08 taper and Ra Ce size 25, .06 taper. The cross-sectional areas at 3 mm from the tip were determined. These instruments were then submitted to energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry ( DSC), and Vickers microhardness measurements. Bending moment at 45° and maximum torque at fracture were measured ( n = 10) according to specification ISO 3630-1. Data were analysed using analysis of variance (α = 0.05). Results The two types of instruments had approximately the same chemical composition, phase constitution, and austenite finishing temperatures. TF instruments had significantly ( P ≤ 0.001) lower Vickers microhardness values and were more flexible than Ra Ce instruments ( P = 0.016), but had similar ( TF size 25, .08 taper and Ra Ce size 25, .06 taper, P = 0.916) or significantly higher ( TF size 25, .06 taper and Ra Ce size 25, .04 taper, P ≤ 0.001) torsional resistance. Conclusions Comparison of TF and Ra Ce instruments of similar measured dimensions revealed that the different manufacturing methods employed for producing these instruments gave rise to different mechanical behaviours. [ABSTRACT FROM AUTHOR]

Pereira ESJ, Peixoto IFC, Viana ACD, Oliveira II, Gonzalez BM, Buono VTL, Bahia MGA. Physical and mechanical properties of a thermomechanically treated NiTi wire used in the manufacture of rotary endodontic instruments. International Endodontic Journal, 45, 469-474, 2012. Abstract Aim To compare physical and mechanical properties of one conventional and one thermomechanically treated nickel-titanium (NiTi) wire used to manufacture rotary endodontic instruments. Methodology Two NiTi wires 1.0 mm in diameter were characterized; one of them, C-wire (CW), was processed in the conventional manner, and the other, termed M-Wire (MW), received an additional heat treatment according to the manufacturer. Chemical composition was determined by energy-dispersive X-ray spectroscopy, phase constitution by XRD and the transformation temperatures by DSC. Tensile loading/unloading tests and Vickers microhardness measurements were performed to assess the mechanical behaviour. Data were analysed using analysis of variance (α = 0.05). Results The two wires showed approximately the same chemical composition, close to the 1 : 1 atomic ratio, and the β-phase was the predominant phase present. B19′ martensite and the R-phase were found in MW, in agreement with the higher transformation temperatures found in this wire compared with CW, whose transformation temperatures were below room temperature. Average Vickers microhardness values were similar for MW and CW ( P = 0.91). The stress at the transformation plateau in the tensile load-unload curves was lower and more uniform in the M-Wire, which also showed the smallest stress hysteresis and apparent elastic modulus. Conclusions The M-Wire had physical and mechanical properties that can render endodontic instruments more flexible and fatigue resistant than those made with conventionally processed NiTi wires. [ABSTRACT FROM AUTHOR]

Aim To assess the dimensional characteristics, flexibility and torsional behaviour of nickel-titanium retreatment instruments. Methodology Using image analysis software and high-resolution digital images, the instrument length, tip angle, diameter at 3 mm from the tip and the distance between the blades (pitch length) of the following eight instruments were measured (n = 12 for each measurement parameter): the ProTaper Universal retreatment (PTU-R) D1, D2 and D3 instruments; the R-Endo R1, R2 and R3 retreatment instruments; and the Mtwo retreatment (Mtwo-R) sizes 25 and 15 retreatment instruments. Maximum torque and the angular deflection at fracture as well as the bending moment at 45° were measured (n = 12) according to the International Standards Organisation (ISO) specification number 3630-1. Data were analysed using the analysis of variance (α = 0.05). Results The length of the active part of the instruments was found to vary according to the depth of the canal into which they were designed to reach. The pitch length also increased along the active length. The PTU-R D1 and the Mtwo-R instruments had active tips. Measurements of the bending moment at 45° revealed that the Mtwo-R 15 instrument was the most flexible, whereas the PTU-R D1 was the least flexible. The maximum torque tended to increase as the instrument diameter at 3 mm from the tip increased, whereas the angular deflection at fracture varied in the opposite direction. Conclusions The geometrical characteristics of the retreatment instruments and their flexibility and torsion behaviour were consistent with their intended clinical application. [ABSTRACT FROM AUTHOR]

Aim To correlate the mechanical behaviour in torsion, bending and fatigue tests of K3 instruments with their dimensional characteristics. Methodology Instrument length, tip angle, distance between blades (pitch length) and the diameter at each millimetre from the tip of sizes 20, 25 and 30, 0.04 taper and sizes 20 and 25, 0.06 taper K3 rotary instruments were measured in an optical microscope equipped with digital micrometers. The cross-sectional area at 3 mm from the tip of the same instruments was determined using digital image analysis of scanning electron microscopy images. Maximum torque and angular deflection, as well as bending moment at 45° were measured according to specification of ISO 3630-1. Fatigue resistance of instruments size 30, 0.04 taper, and sizes 20 and 25, 0.06 taper was determined in a fatigue test bench device. Results The analysed instruments presented no uniformity in the distance between adjacent blades, but the measured diameters at each millimetre from the tip were regular, showing compliance with manufacturing standards. Torque and bending moment of the tested instruments increased significantly with diameter and cross-sectional area at 3 mm from the instrument tip. The fatigue resistance of the instruments showed a tendency to decrease as the diameter of the instruments increased. Conclusions The bending moment at 45° and the torsional resistance of K3 instruments can be predicted using instrument diameter and cross-sectional area at 3 mm from the tip. Fatigue resistance decreased as the instrument diameter increased. [ABSTRACT FROM AUTHOR]

Aim To examine the influence of clinical use on the occurrence of deformation and fracture and on the fatigue resistance of ProTaper rotary instruments. Methodology Root canal treatments were performed on patients using the ProTaper rotary system. Ten sets of instruments were used by an experienced endodontist, each set in five molars. Another 10 sets of instruments were used by the same operator, each set in eight molars. In addition, 10 sets of instruments were used, each set in five molars, by undergraduate students with no clinical experience with the system. After clinical use, S1, S2, F1 and F2 instruments were analysed for damage by optical and scanning electron microscopy. The used sets, along with a control group of 12 sets of new instruments, were then tested in a bench device for fatigue resistance. Results The use of the ProTaper rotary instruments by an experienced endodontist allowed for the cleaning and shaping of the root canal system of up to eight molars without fracture. During the students work, six instruments fractured. Fatigue resistance decreased upon clinical use for all instruments analysed. Conclusions Fatigue resistance of used instruments was reduced, but no significant change was observed amongst the instruments used for shaping the canals of five and eight molars. Operator experience affected the occurrence of fracture and plastic deformation during shaping. [ABSTRACT FROM AUTHOR]

Abstract Martins RC, Bahia MGA, Buono VTL. Surface analysis of ProFile instruments by scanning electron microscopy and X-ray energy-dispersive spectroscopy: a preliminary study. International Endodontic Journal , 35 , 848–853, 2002. 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. [ABSTRACT FROM AUTHOR]

Aim To analyse the influence of cyclic loading on the mechanical behaviour of nickel-titanium (NiTi) wires employed in the manufacture of ProFile rotary endodontic instruments. Methodology Nickel-titanium wires, 1.2 mm in diameter, taken from the production line of ProFile rotary endodontic instruments before the final machining step, were tensile-tested to rupture in the as-received condition and after 100 load–unload cycles in the superelastic plateau (4% elongation). The wires were characterized by X-ray energy-dispersive spectroscopy, X-ray diffraction and by differential scanning calorimetry and compared with new size 30, .06 taper ProFile instruments. The fracture surfaces of the wires were observed by scanning electron microscopy. Results The mechanical properties of the as-received wires, their chemical composition, the phases present and their transformation temperatures were consistent with their final application. Only small changes, which decreased after the first few cycles, took place in the mechanical properties of the cycled wires. The stress at maximum load and the plastic strain at breakage remained the same, while the critical stress for inducing the superelastic behaviour, which is related to the restoring force of the endodontic instruments, decreased by approximately 27%. Conclusions The mechanical behaviour of the NiTi wires was modified slightly by cyclic tensile loading in the superelastic plateau. As the changes tended towards stabilization, the clinical use of rotary NiTi ProFile instruments does not compromise their superelastic properties until they fracture by fatigue or torsional overload, or are otherwise discarded. [ABSTRACT FROM AUTHOR]

Background and purpose: Late‐onset Pompe disease (LOPD) is a rare, multisystem disorder that is well established to mainly impair skeletal muscle function. Systematic studies exploring brain functions in LOPD are lacking. The aim of this study was to detect morphological and functional brain alterations as well as neuropsychological impairment in LOPD. Methods: We studied 21 patients (10 male, mean age 49 ± 18.4 years) with defined diagnosis of LOPD, divided into two groups: one with pre‐symptomatic hyperCKemia with no muscle weakness and the second with limb‐girdle muscle weakness. All patients underwent 3T magnetic resonance imaging (MRI) to obtain morphological/angiographic evaluation as well as normalized cortical brain volume and resting‐state functional MRI. Fazekas score was applied to quantify white matter lesions, whereas Smoker's criteria were used to examine dolichoectasia. A complete neuropsychological assessment was performed. Results: The MRI data showed that 12/21 patients (57%) demonstrated signs of cerebral vasculopathy, with a Fazekas score >2 in 67%. According to Smoker's criteria, 11/21 patients (52%) had a dolichoectasia of the vertebrobasilar system; an intracranial aneurysm was detected in 3/21 patients (14%). Resting‐state functional MRI demonstrated significantly decreased brain connectivity in the salience network with a more relevant reduction in the bilateral middle and superior frontal gyrus. Gray matter atrophy correlated with age and disease duration. A mild impairment in executive functions was also identified. Conclusions: In this LOPD cohort the results showed morphological and functional brain alterations with mild neuropsychological dysfunction, mainly in the limb‐girdle muscle weakness group. Cerebrovascular alterations seemed to be not related to common risk factors, suggesting a major role of enzymatic deficiency in the pathogenesis of brain abnormalities. [ABSTRACT FROM AUTHOR]