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Aim: The aim of present study was to compare cyclic fatigue resistance of Twisted files (TF, Sybron Endo, Glendora, CA) instrument used with continuous rotation and the new Motion (TFAdaptive rotating reciprocation), to evaluate if the new reciprocating motion could affect the lifespan of tested instruments. Methodology: 30 new TF instruments were submitted to cyclic fatigue tests. Group 1 instruments were tested using a TFA motion (TFA) while group 2 instruments were used in continuous rotation at 500 rpm (CR). The cyclic fatigue testing device used in the present study has been used for studies on cyclic fatigue resistance previously. The artificial canal was manufactured to provide the instrument with a very challenging trajectory 60° curvature, with a 2 mm radius. All instruments were rotated or reciprocated until fracture occurred. The time to fracture was recorded. All data were subjected to statistical evaluation with analysis of variance test. Results: TFA reciprocating motion showed a significant increase (p

Introduction. Although many studies have reported various advantages of nickel-titanium endodontic instruments, the use of stainless steel endodontic files still presents a standard in everyday practice. The aim of this study was to evaluate ultrastructure of the surface of stainless steel endodontic instruments before and after their use. Material and Methods. Fourteen sets of non-used stainless steel endodontic reamers and files were included in the study. Each set of instruments was used one, three or six times in simulated clinical conditions on extracted maxillary premolars. After their use the instruments were subjected to cleaning and sterilization procedures. Ultrastructure of the surface of instruments was observed under scanning electron microscope (SEM). Surface analysis was performed based on the number of uses and size of instruments. The following characteristics were analyzed: defects of instrument flutes, defects of cutting edges and instrument deformations. Results. SEM analysis showed defects on the surface of non-used instruments as a result of the manufacturing process. Surface defects, defects of cutting edges as well as flutes deformations were observed after a single use and were more often noticed in small sized instruments. After three uses, flutes deformations were observed in all small sized instruments and some of the medium size. After six uses all groups of instruments showed defects of cutting edges. Conclusion. Non-used stainless steel endodontic instruments showed surface defects created by the manufacturing process. Defects of cutting edges and flutes can be observed after a single use. To minimize complications and mistakes during clinical preparation it is recommended to limit the number of instrument uses.

Background: Root canal instrumentation results in accumulation of debris on the instruments. The present study was conducted to assess effectiveness of pre-sterilization cleaning of endodontic instruments before placement in glass bead sterilizer. Materials & Methods: The present study was conducted on 60 K files used in patients and were divided into 3 groups of 20 each. Group I had contaminated files were without any cleaning protocol, group II had files which underwent manual brushing + 3% H2O2 and group III files underwent manual brushing + ultrasonic bath for 5 min. later on all the instruments were immersed in Van- Gieson's stain for 3 minutes. The instruments were examined for debris based on Linsuwanont et al criteria at 3 levels apical, middle & coronal using a stereomicroscope. Debris was scored as 0, 1, 2, 3 and 4. Results: Score 4 was seen in 4 in group I, and 2 in group II, score 3 was used in 8 in group I and 6 in group II, score 2 was seen in 6 in group I, 8 in group II and 8 in group III, score 1 was seen in 2 in group I, 4 in group II and 12 in group III. The difference was significant (P< 0.05). Conclusion: Manual brushing + ultrasonic bath is better than underwent manual brushing + 3% H2O2 in cleaning of endodontic instruments. [ABSTRACT FROM AUTHOR]

OBJECTIVE: This study identified which regions of ProTaper instruments work during curved root canal instrumentation. MATERIAL AND METHODS: Twelve ProTaper instruments of each type, S1, S2, F1, and F2, were assessed morphometrically by measuring tip angle, tip length, tip diameter, length of each pitch along the cutting blades, and instrument diameter at each millimeter from the tip. Curved canals in resin blocks were explored with manual stainless steel files and prepared with ProTaper instruments until the apical end following four distinct sequences of instrumentation: S1; S1 and S2; S1, S2, and F1; S1, S2, F1, and F2. Image analysis was employed for measuring canal diameters. The diameters of the canals and diameters of the instruments were compared. Data were analyzed by one-way ANOVA and Tukey's test. RESULTS: No statistically significant difference was found between the canals and instrument diameters (p>0.05). The largest diameters in the end-point of the instrumented canals were obtained with F1 and F2 instruments and in the initial and middle thirds with S1 and S2 instruments. CONCLUSIONS: All instruments worked at the tip and along their cutting blades, being susceptible to fail by torsion, fatigue, or the combination of these two mechanisms.

Introduction: There is an increasing awareness of the risk of iatrogenic transmission of prion diseases, since this infective agent has shown resistance to conventional procedures of chemical and thermal decontamination and sterilisation. Aim: The aim of the study was to evaluate the effectiveness of different methods for biological debris removal from the surfaces of endodontic instruments and to suggest an efficient protocol for cleansing prior to sterilization. Materials and Methods: Eighty four new endodontic instruments were used for hand instrumentation of the root canals in extracted teeth in order to accumulate organic debris. The instruments were allocated to four groups and subjected to different methods of decontamination: mechanical cleansing with a brush and sponge, chemical dissolution in sodium hypochlorite (NaOCl) and enzyme cleanser, ultrasonic treatment in water and disinfectant and the combination of the most effective mechanical, chemical and ultrasonic methods. The instruments were stained in the Van Gieson solution which efficiently stains the organic component and then analyzed under a light microscope. Results: Effectiveness was evaluated based on the amount of residual organic material. The analysis of pairs of methods with similar effects showed significant differences between mechanical cleansing with a brush and sponge and ultrasonic treatment in water and disinfectant. No difference was found between treatments in NaOCl and enzyme cleanser. The combined method was significantly more efficient than the other methods. Conclusion: The most efficient protocol for endodontic instrument decontamination consists of mechanical cleansing with a sponge soaked in chlor hexidine, chemical treatment in the enzyme cleanser and ultrasonic treatment in an appropriate disinfectant.

Aim: The purpose of this study was eval Aim: uate the occurrence of displacement on the apical and cervical thirds of artificial curved root canals with 30° of curvature, comparing the use of stainless steel hand and oscillatory files with nickel-titanium (NI-TI) hand, rotary and oscillatory files. Methods: Methods: Seventy artificial curved root Methods: canals were divided into 7 groups (n=10). All canals were prepared with sizes 15 to 40 instruments at the working length according to a crown-down technique. The amount of material removed in the curved portion of the simulated canals at 2 mm level outside and 11 mm inside was measured. Data were analyzed statistically by ANOVA and Tukey’s test (p

Shaping and cleaning of root canal system is one of the most important procedures in endodontic treatment. There has been a constant quest for quicker, safer and more efficient method for cleaning and shaping of root canals. Use of automated Ni-Ti instruments was a logical development to enhance the efficiency of the treatment. Over the past two decades, instrument design has been considerably modified; progress has been made in manufacturing, as well as alloy processing. Clinical procedures and ideal working parameters are still being refined as new instruments continue to be introduced to the market. Separation of instruments while preparing root canals is something that has plagued all practitioners. Therefore, an assessment of effect of speed and torque on the rotary Ni-Ti instruments is of value to the clinician. The purpose of this paper is to discuss the behavioural specific characteristic features and their properties of Ni-Ti rotary instruments. Some guidelines and usage parameters are also detailed. [ABSTRACT FROM AUTHOR]

The purpose of this SEM study was to evaluate the cleaning effects of different manual and mechanical endodontic instruments. Sixty single canal human teeth were selected for this study. The root canals were instrumented by seven types of manual endodontic instruments (K-enlargers, K files Rattail files, K-Flexofiles, K Flex files, Hedstrom and NiTi Flex files) and five different mechanical endodontic instruments (Rispi, Rat tail Hedstrom, NiTi Flex files and K-enlargers). During and after the instrumentation, the canals were irrigated by 2.5% sodium hypochlorit. After splitting the roots longitudinally, the amount of debris and smear layer was quantified on the basis of a numerical evaluation scale, using scanning electron microscope. Results were statistically analysed using the Kruskal-Wallis test and t-test. There were no statistically significant differences between hand instrumentation and machine instrumentation with different endodontic instruments for any of the variables tested. Best instrumentation results in removing the smear layer and dentinal debris from the root canal were obtained with Kerr, NiTi and Hedstrom hand files and with K-enlargers, NiTi and Rat-tail mechanical files. In the apical thirds of root canals prepared using hand and mechanical endodontic instruments the smear layer and dentinal debris were always more abundant when compared with the middle and coronal thirds. In conslusion, cleaning efficacy differed slightly among the techniques and instruments, none of them completely removed smear layer and all left some debris.

The modern concept of endodontic therapy is treatment in one visit. Such an approach is based on the intention to seal the cleaned and disinfected endodontic space as soon as possible apically and coronally, thereby maximally reducing the time in which the endodontic space could be reinfected with bacteria or fungi from the environment. A successfully sealed endodontic space is a prerequisite for healing bone and periodontal tissue defects around the root of the tooth. In order for the selected therapy to be successful, it is important to know where we can make a mistake and at what moment the procedure can go in the wrong direction. The beginning of any therapy is, of course, a diagnosis. A wrong diagnosis can lead to a completely wrong therapeutic plan. In order for the therapeutic plan to be achievable, it is important to know the morphology of the endodontic space, which is specific for individual teeth and also for the patient's age. The specifics of the morphology can change the primary therapy protocol. Knowing the instruments and materials used in treatment is no less important. Their specificities can be crucial for the prognosis and long-term success of the therapy. The cleaned endodontic space must be disinfected. Various disinfectants are avail-able, as well as instruments that increase the quality of disinfection. The treatment does not end only with the sealing of the canal. Coronary sealing is the final stage of treatment. Coronary sealing is achieved by functional and aesthetic reconstruction of the crown part of the tooth, which restores the lost role of the tooth in speech and chewing. [ABSTRACT FROM AUTHOR]

Introduction: Presence of surface defects in endodontic instruments can lead to unwanted complications such as instrument fracture and incomplete preparation of the canal. The current study was conducted to evaluate the effect of autoclave cycles on surface characteristics of S-File by scanning electron microscopy (SEM). Methods and Materials: In this experimental study, 17 brand new S-Files (#30) were used. The surface characteristics of the files were examined in four steps (without autoclave, 1 autoclave cycle, 5 autoclave cycles and 10 autoclave cycles) by SEM under 200× and 1000× magnifications. Data were analyzed using the SPSS software and the paired sample t-test, independent sample t-test and multifactorial repeated measures ANOVA. The level of significance was set at 0.05. Results: New files had debris and pitting on their surfaces. When the autoclave cycles were increased, the mean of surface roughness also increased at both magnifications (P<0.05). Moreover, under 1000× magnification the multifactorial repeated measures ANOVA showed more surface roughness (P<0.001). Conclusion: Sterilization by autoclave increased the surface roughness of the files and this had was directly related to the number of autoclave cycles. [ABSTRACT FROM AUTHOR]

The work concerns the analysis of influence of the wear process of endodontic instruments on the mechanical and physico-chemical properties of the materials from which they are made. A detailed study of the microstructure, mechanical properties and corrosion resistance in the environment simulating work of the tool was conducted. The research was done for the new Mtwo endodontic files and after six times of use. In addition, the observations with a scanning electron microscope in order to reveal possible damage caused by the impact of a corrosive environment were carried out. The results showed that use of the tool by six times revealed damage at the edges of the blades and may cause a lack of continuity of the cutting line resulting in the uneven distribution of the resistive force which acts on the tool during operation. [ABSTRACT FROM AUTHOR]

Aim To compare the active dissolution process of K3, ProTaper and Mtwo NiTi endodontic rotary instruments in chloride and fluoride containing solutions. Methods Anodic polarization of K3 size 20, 0.06 taper, ProTaper size F1 and MTwo size 20, 0.06 taper instruments was performed, and anova ( P < 0.05) was used to compare the weight loss, the time of dissolution and the electrical charge generated by the groups of instruments. Fragments of the instruments were polarized in simulated root canals to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify whether the fragment could be bypassed. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution. Results A progressive consumption of the instruments was observed. K3 and ProTaper instruments had significantly greater weight loss than Mtwo instruments after 30 min of polarization. K3 instruments had the highest values of total electrical charge, and MTwo instruments the lowest ( P < 0.05). After 60 min, the anodic polarization of instrument fragments in simulated root canals resulted in their partial dissolution. Conclusion The anodic polarization of K3, ProTaper and MTwo instruments resulted in their progressive consumption with increasing polarization time. Sixty minutes anodic polarization of the various NiTi instrument fragments in simulated root canals resulted in their partial dissolution. [ABSTRACT FROM AUTHOR]

Aim To investigate the effectiveness of the dissolution process when hand stainless steel files are polarized in solutions containing chloride and fluoride to promote their dissolution. Methodology Redox curves and anodic polarization curves were obtained to determine the conditions necessary for the dissolution of stainless steel endodontic files. Anodic polarization of sizes 20 and 30 files was performed, and a t-test ( P < 0.05) was used to compare the weight loss, the time of dissolution and the electrical charge generated by both groups of files. Fragments were polarized in simulated root canals to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify the possibility of bypassing the fragment. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution. Results A progressive consumption of the sizes 20 and 30 files was observed with total polarization times of 7.0 and 9.0 min, respectively. Files with the larger diameters exhibited greater weight loss, longer times of dissolution and generated a greater electrical charge during the active dissolution process ( t-test, P < 0.05). After 60 min, the anodic polarization of file fragments in simulated root canals resulted in their partial dissolution. Conclusion A 60-min anodic polarization of stainless steel K-file fragments in simulated root canals resulted in their partial dissolution. The fragments could be bypassed after the test. [ABSTRACT FROM AUTHOR]

Aim To evaluate the effect of rotational speed on cyclic fatigue of Mtwo nickel-titanium files. Methodology A total of 120 new Mtwo rotary instruments sizes 10, 0.04 taper; 15, 0.05 taper; 20, 0.05 taper; and 25, 0.06 taper were randomly divided into three groups on the basis of the rotational speed used to shape nine standardized simulated canals: group A = 350 rpm; group B = 250 rpm; group C = 150 rpm. Each group consisted of 40 instruments, 10 for every size. The average preparation time (in seconds) and the average correlated numbers of cycles to instrument ( NCI) the nine standardized canals were recorded for each file. The resistance to cyclic fatigue was determined by counting numbers of cycles to failure ( NCF) with a rotational speed of 300 rpm in a 60° curve with a 5-mm radius. Data were analysed by two-way anova. Results Preparation time was significantly longer at 150 rpm than at 250 or 350 rpm. The average number of cycles needed for each file to instrument nine standardized canals was significantly higher at 350 and 250 rpm, than at 150 rpm. There were no significant differences in the NCF ( P > 0.05) between A, B and C groups for instruments of the same size. Conclusions Speed did not affect the cyclic fatigue of Mtwo instruments with the same size and taper. Preparation time was shorter at 350 or 250 rpm rather than at 150 rpm. However, there was no significant difference between 350 and 250 rpm rotational speed, neither in the preparation time of simulated canals nor in the resistance to fatigue fracture. [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]

Aim To develop analytical models and analyse the stress distribution and flexibility of nickel-titanium ( NiTi) instruments subject to bending forces. Methodology The analytical method was used to analyse the behaviours of NiTi instruments under bending forces. Two NiTi instruments ( Ra Ce and Mani NRT) with different cross-sections and geometries were considered. Analytical results were derived using Euler- Bernoulli nonlinear differential equations that took into account the screw pitch variation of these NiTi instruments. In addition, the nonlinear deformation analysis based on the analytical model and the finite element nonlinear analysis was carried out. Numerical results are obtained by carrying out a finite element method. Results According to analytical results, the maximum curvature of the instrument occurs near the instrument tip. Results of the finite element analysis revealed that the position of maximum von Mises stress was near the instrument tip. Therefore, the proposed analytical model can be used to predict the position of maximum curvature in the instrument where fracture may occur. Finally, results of analytical and numerical models were compatible. Conclusion The proposed analytical model was validated by numerical results in analysing bending deformation of NiTi instruments. The analytical model is useful in the design and analysis of instruments. The proposed theoretical model is effective in studying the flexibility of NiTi instruments. Compared with the finite element method, the analytical model can deal conveniently and effectively with the subject of bending behaviour of rotary NiTi endodontic instruments. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: This study compared the mechanical properties of endodontic instruments made of conventional nickel-titanium (NiTi) wire (K3 and Revo-S SU), M-Wire (ProFile Vortex), or NiTi alloy in R-phase (K3XF). Methods: The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. Results: In the bending resistance test, flexibility decreased in the following order: K3XF > Revo-S SU > ProFile Vortex > K3. The ranking in the fatigue resistance test was the following: K3XF > K3 > ProFile Vortex > Revo-S SU. In the torsional assay, the angular deflection at failure decreased in the following order: K3XF > Revo-S SU > K3 > ProFile Vortex. For the maximum torque values, the ranking was K3 > K3XF > ProFile Vortex > Revo-S SU. Conclusions: The results showed that the K3XF instrument, which is made of NiTi alloy in R-phase, had the overall best performance in terms of flexibility, angular deflection at failure, and cyclic fatigue resistance. In addition to the alloy from which the instrument is manufactured, the design and dimensions are important determinants of the mechanical performance of endodontic instruments. [Copyright &y& Elsevier]

Abstract: Introduction: The aim of this study was to compare the cyclic fatigue resistance of 3 nickel-titanium (NiTi) endodontic instruments from ProTaper, WaveOne (WO), and Twisted Files (TF). Methods: Cyclic fatigue testing was conducted by operating instruments from ProTaper F2, WO 25 .08, and TF 25 .08. A total of 184 instruments were rotated in 4 curved artificial canals with different angles and radius of curvature. The time and cycles to failure were calculated. The data were compared for differences by using 2-way analysis of variance (P < .05). Results: In general, WO was the most resistant to fatigue failure of the tested instruments, and TF showed a higher number of cycles to failure than ProTaper. Conclusions: Reciprocating movement of WO showed a longer cyclic fatigue life than conventional rotary movement of TF and ProTaper. The new manufacturing twisting process of TF produced NiTi rotary instruments more resistant to fatigue than ProTaper instruments produced with the traditional NiTi grinding process. [Copyright &y& Elsevier]

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]

Abstract: Introduction: The aim of this study was to evaluate, by static and dynamic cyclic fatigue tests, the number of cycles to fracture (NCF) 2 types of rotary NiTi instruments: Twisted File (SybronEndo, Orange, CA), which is manufactured by a proprietary twisting process, and RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland), which are manufactured by grinding. Methods: Twenty Twisted Files (TFs) and 20 RaCe files #25/.006 taper instruments were allowed to rotate freely in an artificial curved canal at 310 rpm in a static or a dynamic model until fracture occurred. Results: Measurements of the fractured fragments showed that fracture occurred at the point of maximum flexure in the midpoint of the curved segment. The NCF was significantly lower for RaCe instruments compared with TFs. The NCF was also lower for instruments subjected to the static test compared with the dynamic model in both groups. Scanning electron microscopic analysis revealed ductile morphologic characteristics on the fractured surfaces of all instruments and no plastic deformation in their helical shafts. Conclusions: Rotary NiTi endodontic instruments manufactured by twisting present greater resistance to cyclic fatigue compared with instruments manufactured by grinding. The fracture mode observed in all instruments was of the ductile type. [Copyright &y& Elsevier]

Abstract: Introduction: This study compared the torsional resistance of two brands of rotary nickel-titanium (NiTi) instruments indicated for endodontic retreatment. Methods: Mtwo retreatment instruments #15 and #25 (VDW, Munich, Germany) and ProTaper Universal retreatment instruments D2 and D3 (Maillefer/Dentsply, Ballaigues, Switzerland) were subjected to a torsional assay in clockwise rotation. The two parameters evaluated were maximum torque and angular deflection at failure. Fractured instruments had their fractured surfaces and helical shafts examined by scanning electron microscopy. Results: The results indicated that the angular deflection at fracture decreased in the following order: Mtwo retreatment file #15 > Mtwo retreatment file #25 > ProTaper Universal retreatment file D2 > ProTaper Universal retreatment file D3. As for the maximum torque values, the results revealed the following descending order: ProTaper Universal file D2 > Mtwo retreatment file #25 > ProTaper Universal file D3 > Mtwo retreatment file #15. Scanning electron microscopic analysis revealed that plastic deformation occurred along the helical shaft of the fractured instruments. Fractured surfaces were of the ductile type. Conclusions: The instruments tested showed different torsional behavior depending on the parameter evaluated. If one considers that high angular deflection values may serve as a safety factor, then the Mtwo retreatment instruments showed significantly better results. [Copyright &y& Elsevier]

Aim To investigate whether flexibility and cyclic fatigue resistance was increased for nickel-titanium instruments produced by a new manufacturing technique. Methodology Forty K3 tip size 25, 0.06 taper (SybronEndo) nickel-titanium rotary instruments were randomly selected and divided into two groups (n = 20). One group served as control, being the commercially available instruments produced with a traditional grinding process (K3). The second group of instruments (K4 prototypes) were then subjected to a proprietary thermal treatment after the grinding process. Finally, each group was randomly divided into two subgroups of 10 instruments each, to perform the stiffness test and the cyclic fatigue test. All data were recorded and subjected to statistical evaluation using Student's t-test. Significance was set at the 95% confidence level. Results For the stiffness test, a statistically significant difference (P < 0.05) was noted between K3 and K4 prototype instruments. K4 prototype instruments were significantly more flexible when compared to K3 instruments (59.3 ± 4.3 vs. 98.1 ± 6.4 g cm-1). For the cyclic fatigue test, a significant difference (P < 0.05) was noted between K3 and K4 prototype instruments. K4 prototype instruments demonstrated a significant increase in the mean number of cycles to failure (NCF) when compared to K3 instruments (1198 ± 279 vs. 542 ± 81 NCF). Conclusions The new manufacturing technique resulted in the K4 prototype instruments having enhanced mechanical properties, compared to K3 instruments, manufactured with a traditional grinding process. [ABSTRACT FROM AUTHOR]

Aim: The purpose of this study was evaluate the occurrence of displacement on the apical and cervical thirds of artificial curved root canals with 30° of curvature, comparing the use of stainless steel hand and oscillatory files with nickel-titanium (NI-TI) hand, rotary and oscillatory files. Methods: Seventy artificial curved root canals were divided into 7 groups (n=10). All canals were prepared with sizes 15 to 40 instruments at the working length according to a crown-down technique. The amount of material removed in the curved portion of the simulated canals at 2 mm level outside and 11 mm inside was measured. Data were analyzed statistically by ANOVA and Tukey's test (p<0.05). Results: There was statistically significant differences (p<0.05) at 2 mm level between NI-TI and steel stainless groups. At 11 mm, statistically significant differences (p<0.05) were observed between the groups that used rotary systems (5 and 6) and the remaining groups. Conclusions: The most centered preparations were those belonging to groups 5 and 6, at both levels. Root canal preparation with NI-TI files yielded better results than the stainless steel files especially when mechanically activated. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: This study evaluated the influence of electropolishing surface treatment on the number of cycles to fracture of BioRace rotary nickel-titanium endodontic instruments. Methods: BioRace size BR5C instruments with or without electropolishing surface treatment were used in an artificial curved canal under rotational speed of 300 rpm until fracture. Fractured surfaces and the helical shafts of fractured instruments were analyzed by scanning electron microscopy (SEM). Results: Polished instruments displayed a significantly higher number of cycles to fracture when compared with nonpolished instruments (P < .001). Actually, the number of cycles to fracture of a polished BR5C instrument was 124% higher than that of a nonpolished instrument. SEM analysis showed that the fractured surface of both polished and nonpolished BR5C instruments had ductile morphologic characteristics. Evaluation of the separated fragments after cyclic fatigue testing showed the presence of microcracks near the fracture surface. Polished instruments exhibited fine cracks that assumed an irregular path (zigzag crack pattern), whereas nonpolished instruments showed cracks running along the machining grooves. Conclusions: Electropolishing surface treatment of BioRace endodontic instruments significantly increased the cyclic fatigue resistance. [ABSTRACT FROM AUTHOR]

Popovic J, Gasic J, Zivkovic S, Petrovic A, Radicevic G. Evaluation of biological debris on endodontic instruments after cleaning and sterilization procedures. International Endodontic Journal, 43, 336–341, 2010. Aim To examine the presence of biological debris and the level of contamination on reusable endodontic instruments those were subjected to different cleaning methods prior to sterilization. Methodology One hundred and eighty endodontic instruments from eighteen dental practices were analysed. These practices used different decontamination protocols for reusable instruments. The presence of organic debris was detected by the use of Van Gieson’s stain. Forty-eight new stainless steel hand instruments were used as controls. The samples were examined by light microscopy. Results Residual biological debris was observed in 96% of the samples. The mean value of maximum biological contamination was 34% in the group in which the instruments were brushed manually and immersed in alcohol, 25% in the group in which commercially available disinfectants were used and 5% in the group in which the instruments were cleaned ultrasonically. There was a statistically significant difference in the mean values with respect to the cleaning protocol applied ( P < 0.001). Conclusions The methods used to clean endodontic instruments appear to be generally ineffective for the removal of biological debris. The best method was the one that included mechanical, chemical and ultrasonic cleaning of instruments. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: This study compared three techniques for preparing oval-shaped root canals: Anatomic Endodontic Technology (AET), hand instruments (Hedström files; Dentsply Maillefer, Ballaigues, Switzerland), and rotary nickel-titanium (EndoWave; Morita, Osaka, Japan) instruments with regard to cleaning ability and final canal shape. Methods: Three groups each of 13 extracted human mandibular premolars with oval-shaped canals were used. After canal preparation, teeth were sectioned at three levels (coronal, middle, and apical), photographed to assess cross-sectional canal shape, and processed for histologic evaluation of canal wall planing and the presence of debris. Results: None of the techniques resulted in completely prepared and cleaned canals. No significant difference was found among the three techniques with regard to untouched surface, cross-sectional area, remaining fins, and canal shape at the three levels. Rotary NiTi instruments resulted in significantly less debris in the apical third compared with AET and hand instrumentation. Conclusions: AET did not perform better than rotary NiTi or hand instruments in oval-shaped canals. [Copyright &y& Elsevier]

Zinelis S, Eliades T, Eliades G. A metallurgical characterization of ten endodontic Ni-Ti instruments: assessing the clinical relevance of shape memory and superelastic properties of Ni-Ti endodontic instruments. International Endodontic Journal, 43, 125–134, 2010. Aim To evaluate the elemental composition, microstructure and hardness of Ni-Ti endodontic instruments and to assess the relevance of shape memory and superelastic properties. Methodology Ten brands of Ni-Ti endodontic instrument were evaluated (EndoSequence, Ergoflex K, FlexMaster, Hero 642, Hyflex X-File, K3 Endo, Liberator, NRT, Profile and ProTaper). After embedding in resin and metallographic preparation the elemental composition, structure and hardness were evaluated employing SEM/energy-dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD) and microhardness measurements. The results of elemental composition and hardness were analysed statistically by one-wayanova followed by SNK test (α : 0.05). The correlation between Ni content and microhardness was examined by the Pearson test. Results The instruments comprised of Ni (52.1–56.2%wt) and Ti (43.8 to 47.9%wt) and were classified in four different Ni content groups: ProTaper, Liberator, ProFile and K3 demonstrated higher Ni content than Hylfex X-File but lower than Hero 642, NRT and Ergoflex. EndoSequence and FlexMaster had the highest Ni content. XRD analysis revealed the presence of the austenitic structure in all instruments. Vickers hardness values ranged from 312 (K3) to 376 VHN (Endosequence). No correlation ( r2 = 0.026) was found between Ni content and hardness among the instruments tested. Microstructural and hardness data confirm that the Ni-Ti instruments were manufactured by cold worked Ni-Ti and do not posses shape memory or superelastic properties. Conclusions The endodontic instruments tested were manufactured from cold worked Ni-Ti wires and thus have neither shape memory nor superelastic properties. [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 in-depth hardness profiles of Stainless Steel (SS) and nickel titanium (Ni-Ti) endodontic instrument cross-sections using a nano-indentation technique. Methodology Three SS (Reamer, K and Hedström) and three Ni-Ti (ProFile, NRT and Liberator) instruments were studied. After embedding and metallographic preparation the in-depth hardness profiles of instrument cross-sections were measured starting from the cutting surface towards the centre to a depth of 2000 nm using an MTS XP nanoindenter with a Berkovich diamond indenter. The results of hardness measurements of outer (near to cutting edge) and inner locations were statistically analyzed by two-wayanova followed by SNK test (α = 0.05). Results For all instrument cross-sections the maximum hardness was obtained at the outer surface followed by hardness attenuation towards the centre of the cross section. The statistical analysis of hardness classified the instruments, for both outer and innermost locations, to the following decreasing order: Reamer > K > Hedström > Profile > NRT shank (without thermal treatment) > NRT tip (with thermal treatment) > Liberator. The maximal hardness, at the outer surface of endodontic instruments, can be attributed to the residual stresses developed due to cutting and thermal effects during the manufacturing process. The increased outer layer hardness may have a beneficial effect on the cutting ability and wear resistance of endodontic instruments. Conclusions All endodontic instruments had a decrease in hardness towards their centre. This implies that the surface hardness of contemporary endodontic instruments is significantly enhanced by the consequences of manufacturing processes. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to evaluate the surface of rotary nickel-titanium (Ni-Ti) files after multiple autoclave cycles. Two different types of rotary Ni-Ti (Greater Taper and ProFile) were attached to a glass base. After 1, 5, and 10 autoclave cycles the files were positioned in the atomic force microscope. The analyses were performed on 15 different points. The same files were used as control before any autoclave cycle. The following vertical topographic parameters were measured: arithmetic mean roughness, maximum height, and root mean square. The differences were tested by analysis of variance with Tukey test. All topographic parameters were higher for both Greater Taper and ProFile after 10 cycles compared with the control (P < .05). ProFile also showed higher topographic parameters after 5 cycles compared with the control (P < .05). The results indicated that multiple autoclave cycles increase the depth of surface irregularities located on rotary Ni-Ti files. [Copyright &y& Elsevier]

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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]

Summary: The aim of this study was to compare the amount of residual organic debris on endodontic instruments that had been cleaned in either an ultrasonic bath or a washer disinfector prior to sterilisation. A total of 90 endodontic files of varying sizes were used to clean and shape root canals in extracted teeth and were then placed in endodontic file holders. Test group 1 (36 files) were ultrasonically cleaned for 10min and test group 2 (36 files) were cleaned in a washer disinfector. A control group (18 files) were not cleaned at all. Following sterilisation, all the files were visually inspected under a light microscope and scored using an established scale. The results showed that both test groups had significantly less residual debris than the control group. Comparing the test groups, the files that had been cleaned ultrasonically had significantly less debris than those cleaned in the washer disinfector. The design of the instrument holder may have been a factor in this result. More research is needed into the use of washer disinfectors in the cleaning of small dental instruments that have a complex surface structure. [Copyright &y& Elsevier]

Abstract: Because no scientific literature exists regarding endodontic pathfinders, the aim of this study was to compare such instruments. Ten different pathfinder-type files were analyzed with respect to dimensional characteristics, pitch, and rigidity; efficiency, wear, and distortion were assessed by using an in vitro simulation exercise. SEM cross-sections and tip images were obtained and analyzed. To assess efficacy and distortion, 10 operators attempted to achieve patency with the files in small, S-shaped canals in acrylic blocks. Trends in canal negotiation efficiency and file distortion were recorded. Results showed that the Hi-5 (Miltex, York, PA) and C+ files (Dentsply/Maillefer, Johnson City, TN) were the least flexible, whereas the Pathfinder CS (SybronEndo, Glendora, CA) and Pathfinder SS (SybronEndo) files were the most. Pathfinder SS, S finder (JSDental/Sendoline, Ridgefield, CT), and D finder (Mani, Tochigi-ken, Japan) were the most efficient during the simulation exercise. Within the parameters of this study, pitch, taper, cross-section, heat tempering, metal type, tip geometry, and operator skills all influenced pathfinder efficiency. [Copyright &y& Elsevier]

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]

Aims To assess whether pre-soaking files in an enzymatic cleaner prior to ultrasonic cleaning had any effect on cleanliness and also to assess the effect of the time that endodontic files spend in an ultrasonic bath prior to sterilization on their overall cleanliness. Methodology Twenty root canals in a total of ten patients were cleaned and shaped using conventional techniques. Following use, some of the files were pre- soaked and then ultrasonically cleaned for either 5, 10, 30 or 60 mm. Other files had no pre-soaking and were then ultrasonically cleaned. There were two control groups, one where the files were pre-soaked and not ultrasonically cleaned and the other where the files were neither pre-soaked nor ultrasonically cleaned. All files were then subjected to a standard packing and autoclaving process. Following autoclaving, the files were examined using a light microscope at a magnification of 40x. The cutting section of each file was divided into two parts, the tip and the shaft, for visualization under the microscope. Any debris or cement on the files was scored using a modification of the scale used by Smith et al. (Journal of Hospital Infection, 51, 2002, 233). The data were analysed using one-way analysis of variance. Results Pre-soaking had no significant effect on the cleanliness of the files (P = 0.18 at the tip, P = 0.93 at the shaft). Ultrasonic cleaning had a significant effect on the cleanliness of the files (P < 0.00) but there was not a linear relationship between cleanliness and the ultrasonic cleaning time. There was little benefit in extending the ultrasonic cleaning time beyond 5 mm. Calcium hydroxide deposits on two files were resistant to ultrasonic cleaning. Conclusions There is no benefit in pre-soaking endodontic files prior to ultrasonic cleaning. The optimum time for ultrasonic cleaning was between 5 and 10 min. Further ultrasonic exposure, up to 60 mm, did not improve cleanliness. Although a majority of files were free from debris following ultrasonic cleaning, a substantial minority still retained debris. This supports the case for endodontic files being single-use only. [ABSTRACT FROM AUTHOR]

Abstract: Atomic force microscopy (AFM) is a well established and documented tool for materials investigation. The aim of this study was to evaluate the topography of conventional stainless-steel files and both hand and rotary nickel-titanium (NiTi) files by using AFM. One endodontic file of each of the following was selected: stainless-steel K-file Dentsply, stainless-steel K-file Moyco, hand NiTi K-file Nitiflex, hand NiTi Greater Taper, rotary NiTi Greater Taper, and rotary NiTi Quantec. The analyses were performed on twenty different points located along a 3-mm section starting at the tip of each file. Root mean square (RMS) parameters for contact mode imaging microscopy variations were measured. The differences between RMS values were tested by ANOVA with Fisher''s protected LSD test for multiple comparisons (p < 0.05). RMS of depth profile data was used to determine any statistically significant difference in vertical amplitude. According to results, all instruments showed topographic irregularities distributed on surface. Endodontic files manufactured by the same method and alloy demonstrated significant differences, whereas no significant differences were found for instruments produced by different alloys and methods (p < 0.05). The hand NiTi Greater Taper, rotary NiTi Greater Taper, and rotary NiTi Quantec showed greater values of vertical amplitude topography compared to K-Dentsply and Nitiflex files (p < 0.05). The AFM technique proved to be a valuable research tool in the investigation of endodontic files topography. [Copyright &y& Elsevier]

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]

Riitano F. Anatomic Endodontic Technology (AET) – a crown-down root canal preparation technique: basic concepts, operative procedure and instruments. International Endodontic Journal, 38, 575–587, 2005. To illustrate the conceptual basis and the operative procedure of the Anatomic Endodontic TechnologyTM (AET) technique and to illustrate the specific instruments used in each phase. The basic characteristics of the AETTM technique are reported. The instruments and procedure are described in three phases: coronal access, coronal-middle preparation and apical preparation. In the first phase, correct cavity design is described. In the coronal-middle phase, the use of four stainless steel shaping instruments, powered by a reciprocating handpiece is described, incorporating a brushing-milling action against canal walls. During the apical phase, dedicated apical stainless steel and NiTi hand instruments are used to complete the preparation. The stainless steel apical files are used with a 1/4 turn and withdrawal movement whilst the NiTi are used in 360° rotary motion. • Most current canal shaping techniques do not prepare all the canal walls and can result in over-enlargement in some areas. • AETTM defines three regions of the canal: coronal (from the cavo-surface of the access cavity), coronal-middle, and apical. • Coronal-middle instrumentation is undertaken with four mechanically driven stainless steel shaping instrument used in brushing-milling action against canal walls. • Apical preparation is completed by hand and with the formation of a stop. [ABSTRACT FROM AUTHOR]

Linsuwanont P, Parashos P, Messer HH. Cleaning of rotary nickel–titanium endodontic instruments. International Endodontic Journal, 37, 19–28, 2004. To develop and evaluate an effective cleaning procedure for rotary nickel–titanium (NiTi) endodontic instruments. New rotary instruments (ProFile size 25/.04) were contaminated by preparing canals of extracted teeth. Three factors were evaluated to develop an effective cleaning sequence: dry or moist storage before cleaning; mechanical removal (brushing); and chemical dissolution in 1% NaOCl with ultrasonication. Debris on flutes was scored after staining in situ with Van Gieson's solution at ×45 magnification. Debris was classified as stained or unstained particulate debris and organic film, and rated as none, slight, moderate or heavy. The effectiveness of a recommended cleaning sequence was tested on different instrument types and in private endodontic practices. All new instruments showed metallic spurs and fine particulate debris on the surfaces. After contamination, brushing alone removed most particulate debris, but did not remove organic film. NaOCl effectively removed organic film. Under laboratory conditions, the sequential cleaning procedures (moist storage, brushing followed by immersion in 1% NaOCl and ultrasonic cleaning) totally removed organic debris. Dry storage before cleaning or autoclaving with debris present reduced cleaning effectiveness ( P < 0.001, one-way anova). In three private practices, the cleaning protocol substantially reduced biological contamination, but complete cleaning was not always achieved (87% clean). Complete removal of organic debris from instruments is feasible using a combination of mechanical removal and chemical dissolution, but requires meticulous attention to details. [ABSTRACT FROM AUTHOR]