Multimethod analysis of large- and low-tapered single file reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow.

AIM: To compare eight large- and low-tapered heat-treated reciprocating instruments regarding their design, metallurgy, mechanical properties, and irrigation flow through an in silico model. METHODOLOGY: A total of 472 new 25-mm E-Flex Rex (25/.04 and 25/.06), Excalibur (25/.05), Procodile (25/.06), Reciproc Blue R25 (25/.08v), WaveOne Gold Primary (25/.07v), and Univy Sense (25/.04 and 25/.06) instruments were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy (energy-dispersive X-ray spectroscopy and differential scanning calorimetry), and mechanical performance (cyclic fatigue, torsional resistance, cutting ability, bending and buckling resistance). Computational fluid dynamics assessment was also conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparations. Kruskal-Wallis and one-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Instruments presented variations in blade numbers, helical angles, and tip designs, with all featuring non-active tips, symmetrical blades, and equiatomic nickel-titanium ratios. Cross-sectional designs exhibited an S-shaped geometry, except for WaveOne Gold. Univy 25/.04 and Reciproc Blue displayed the smallest and largest core diameters at D3. Univy 25/.04 and E-Flex Rec 25/.04 demonstrated the longest time to fracture (p < .05). Reciproc Blue and Univy 25/.04 exhibited the highest and lowest torque to fracture, respectively (p < .05). Univy 25/.04 and Reciproc Blue had the highest rotation angles, whilst E-Flex Rec 25/.06 showed the lowest angle (p < .05). The better cutting ability was observed with E-Flex Rec 25/.06, Procodile, Excalibur, and Reciproc Blue (p > .05). Reciproc R25 and E-Flex Rec showed the highest buckling resistance values (p < .05), with WaveOne Gold being the least flexible instrument. The impact of instruments' size and taper on wall shear stress and apical pressure did not follow a distinct pattern, although Univy 25/.04 and E-Flex Rec 25/.06 yielded the highest and lowest values for both parameters, respectively. CONCLUSIONS: Low-tapered reciprocating instruments exhibit increased flexibility, higher time to fracture, and greater angles of rotation, coupled with reduced maximum bending loads and buckling strength compared to large-tapered instruments. Nevertheless, low-tapered systems also exhibit lower maximum torque to fracture and inferior cutting ability, contributing to a narrower apical canal enlargement that may compromise the penetration of irrigants in that region.

Characterization of four heat-treated reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow patterns.

AIM: To compare the design, metallurgy, and mechanical properties of four heat-treated reciprocating instruments coupled with the evaluation of the irrigation flow using an in silico model. METHODOLOGY: New EdgeOne Fire Primary, Easy-File Flex Regular 25, WaveOne Gold Primary and Reciproc Blue R25 instruments (n = 124) were initially evaluated regarding their design through stereomicroscopy, scanning electron microscopy and 3D surface scanning. In addition, energy-dispersive X-ray spectroscopy was utilized to determine their elemental composition, and differential scanning calorimetry tests to evaluate their phase transformation temperatures. Their mechanical performance was further assessed through torsional and bending tests. Using scans obtained from a real tooth and the instruments, a computational fluid dynamics assessment was conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparation. Mood's median and One-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Reciproc Blue exhibited a superior number of blades (n = 8), whereas EdgeOne Fire had the highest overall volume (4.38 mm3 ) and surface area (32.32 mm2 ). At the 3-mm axial level, EdgeOne Fire displayed the lowest core diameter (0.13 mm), while Reciproc Blue had the highest (0.16 mm). All blades were symmetrical, and the tips of the instruments were non-active but differed from each other. The most irregular surfaces were observed in EdgeOne Fire and Easy-File Flex. All instruments were manufactured from nickel-titanium alloys and exhibited distinct phase transformation temperatures. WaveOne Gold and Reciproc Blue demonstrated the highest maximum torque values (1.87 and 1.62 N cm, respectively), while the lowest was observed on EdgeOne Fire (1.21 N cm) (p < .05). The most flexible (p < .05) were EdgeOne Fire (angle of rotation: 602.6°; maximum bending load: 251.4 g.f) and Reciproc Blue (533.2° and 235.6 g.f). There were no significant differences observed in the irrigation flow among the four domains generated by the tested instruments. CONCLUSIONS: Despite observing variations in the design, phase transformation temperatures, and in the torsional and bending test outcomes among the four heat-treated reciprocating instruments, no significant differences were found in the irrigation flow pattern among the different groups in the simulated root canal preparations.

Does the type of endodontic access influence in the cyclic fatigue resistance of reciprocating instruments?

INTRODUCTION: The aim of the present study was to compare the cyclic fatigue resistance of Reciproc R25 (R25) and Reciproc Blue R25 (R25B) instruments, after simulated clinical use in traditional (TradAC) and ultraconservative (UltraAC) endodontic access cavities. METHODS: Forty mandibular molars were randomly assigned into the following groups, according to the type of access and instrument to be used: TradAC and R25, TradAC and R25B, UltraAC and R25, and UltraAC and R25B. Teeth were accessed accordingly, and the root canals were prepared using "RECIPROC ALL" kinematics. The cyclic fatigue resistance of the forty used instruments was obtained measuring the time to fracture in an artificial stainless-steel canal. Ten brand new R25 and R25B were used as control groups. The fracture surfaces and the side cutting edges of the instruments were examined with a scanning electron microscope. Data were statistically analyzed using one-way ANOVA and post hoc Tukey tests with a significance level of P < 0.05. RESULTS: R25B instruments showed significantly higher cyclic fatigue resistance than R25, regardless of the access cavity type (P < 0.05). No differences were observed in the cyclic fatigue resistance between instruments without simulated clinical use and used in TradAC (P > 0.05). R25 and R25B used in UltraAC showed significantly lower cyclic fatigue resistance compared with the instruments used in TradAC and without simulated clinical use (P < 0.05). CONCLUSIONS: R25B files showed improved cyclic fatigue resistance than R25. The use of R25B and R25 files in mandibular molars with UltraACs decreased their cyclic fatigue resistance, compared with TradAC. CLINICAL RELEVANCE: The use of Reciproc and Reciproc Blue files in mandibular molars with ultra-conservative endodontic access cavities reduced their cyclic fatigue resistance. Clinicians should be aware about the reduced cyclic fatigue resistance of these files when used in mandibular molars with UltraAC, due to the synergistic effect of access angulation and severe curvature induced in the endodontic files.

Torsional behaviour of Reciproc and Reciproc blue instruments associated with their martensitic transformation temperatures.

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.

Torsional fatigue resistance of R-Pilot and WaveOne Gold Glider NiTi glide path reciprocating systems.

AIM: To evaluate the torsional properties of the NiTi glide path reciprocating instruments R-Pilot (VDW, Munich, Germany) and WaveOne Gold Glider (Dentsply Sirona, Ballaigues, Switzerland). METHODOLOGY: Ten R-Pilot (size 12.5, .04 taper) and 10 WaveOne Gold Glider (size 15, .02v taper) instruments were used. The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. The fracture surface of all fragments was examined with a scanning electron microscope. Data were analysed using the Student t-test at a significance level of P < 0.05. RESULTS: The maximum torsional strength of the R-Pilot instruments was greater than the WaveOne Gold Glider (P < 0.05). In contrast, WaveOne Gold Glider instruments had significantly higher angular rotation to fracture than R-Pilot instruments (P < 0.05). The scanning electron microscopy of the fracture surfaces revealed similar and typical features of torsional failure (ductile type) for both brands. The torsional failure displayed two zones: the first with microvoids in the centre of the instruments (core) and the second one represented by plastic deformation around the microvoids; this configuration occurred because of the shear stresses originated during the twisting. CONCLUSIONS: R-Pilot instruments had a lower angle of rotation to fracture but a higher torque to failure than WaveOne Gold Glider instruments.

The impact of using a pneumatic contra-angle device on the lifespan of M-Wire- and Blue-treated instruments.

OBJECTIVES: To evaluate the cyclic fatigue resistance of Reciproc M-Wire R25 (VDW, Munich, Germany) and Reciproc R25 Blue instruments (VDW) driven by Direct® (VDW) contra-angle connected to an ordinary an air-driven motor or an electric motor and compare the results with those obtained by the Reciproc M-Wire R25 or Reciproc Blue R25 instruments driven by an electric torque-controlled motor using "RECIPROC ALL" preset program. MATERIALS AND METHODS: Thirty Reciproc M-Wire R25 (25/0.08v) and 30 Reciproc Blue R25 (25/0.08v) instruments were used. Cyclic fatigue resistance was tested measuring the time to fracture and the number of cycles to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The Reciproc M-Wire and Reciproc Blue instruments were activated with a 6:1 reduction handpiece powered by a torque-controlled motor using "RECIPROC ALL" preset program, with Reciproc Direct® contra-angle powered by an ordinary air-driven motor or with Direct® contra-angle powered by an electric motor (n = 10). The fracture surface of all fragments was examined with a scanning electron microscope. The results were statistically analyzed using Student's t test and one-way ANOVA at a significance level of P < 0.05. RESULTS: Cyclic fatigue life and number of cycles to fracture were significantly higher for Reciproc Blue instruments than for Reciproc M-Wire instruments regardless of the activation mode (P < 0.05). Instruments driven by Direct® contra-angle powered by an electric or by an ordinary air-driven motor revealed significantly longer cyclic fatigue life and number of cycles to fracture than instruments driven by an electric torque-controlled motor using "RECIPROC ALL" preset program (P < 0.05). CONCLUSIONS: Reciproc Blue instruments showed improved performance regarding fatigue resistance when compared to Reciproc M-Wire instruments. Instruments driven by Reciproc Direct® contra-angle showed higher cyclic fatigue life and number of cycles to fracture than instruments driven by an electric torque-controlled motor. CLINICAL RELEVANCE: Recently, Reciproc Direct®, the world's first contra-angle handpiece with integrated reciprocating motion, has been launched in endodontic market. The present study showed improved cyclic fatigue life of endodontic instruments when activated by Reciproc Direct®.

Impact of a modified motion on the fatigue life of NiTi reciprocating instruments: a Weibull analysis.

OBJECTIVES: To evaluate the impact of a modified motion on the fatigue life of four brands of nickel-titanium (NiTi) reciprocating instruments. MATERIALS AND METHODS: Cyclic fatigue (CF) resistance of 160 instruments was evaluated in an artificial stainless-steel canal (90° angle, 5-mm radius of curvature). WaveOne and WaveOne Gold (Denstply Maillefer, Baillagues, Switzerland) and Reciproc and Reciproc Blue (VDW, Munich, Germany) were tested with two different motions: (1) X-Smart Plus (Denstply Maillefer) endodontic motor and (2) a 4:1 contra-angle with an experimental motion (EVO) with different rotation angles and based on a sinusoidal acceleration. Motions with X-Smart Plus and EVO were recorded and analyzed at a reduced speed with VLC Media Player software for a more accurate analysis. Mean half-life, beta, and eta Weibull parameters were determined and compared. RESULTS: Reciproc Blue resulted the most resistant instruments either with EVO or X-Smart. WaveOne Gold lasted significantly longer than WaveOne with EVO (probability of 91%) while no significant differences were found with X-Smart. Considering NCF, Reciproc, WaveOne Gold, and Reciproc Blue lasted significantly longer with EVO (probabilities of 66%, 80%, and 89% respectively). WaveOne Gold showed the highest beta parameter. CONCLUSIONS: The experimental motion was found to have a positive impact on fatigue lifetime of reciprocating instruments. CLINICAL RELEVANCE: Current findings provide insight for future improvements in the clinical use of reciprocating files. Experimental motions may be considered when searching for additional strategies in order to increase the safer use of NiTi files during endodontic procedures.

Cyclic fatigue using severely curved canals and torsional resistance of thermally treated reciprocating instruments.

OBJECTIVES: To evaluate the cyclic fatigue using severely curved canals and torsional resistance of ProDesign R (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil), Reciproc Blue (VDW, Munich, Germany), and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating instruments MATERIALS AND METHODS: Twenty instruments of the ProDesign R (25/0.06) system, 20 instruments of the Reciproc Blue (25/0.08v) system, and 20 instrument of the WaveOne Gold (25/0.07v) system were used. Cyclic fatigue resistance was tested measuring the time to fracture and the number of cycles to fracture in an artificial stainless steel severely curved canal with 80° angle and a 3-mm radius of curvature (n = 10). Torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. The fracture surfaces of all fragments were examined with a scanning electron microscope. Results were statistically analyzed using one-way ANOVA and Tukey's test at a significance level of p < 0.05. RESULTS: ProDesign R instruments showed a significantly longer cyclic fatigue life than the other tested instruments (p < 0.05). Reciproc Blue showed longer cyclic life than WaveOne Gold (p < 0.05). Reciproc Blue showed the higher torsional strength, followed by WaveOne Gold and ProDesign R instruments (p < 0.05). Moreover, Reciproc Blue showed significantly higher angular rotation to fracture than ProDesign R (p < 0.05). WaveOne Gold showed intermediary results regarding angular rotation to fracture with no differences when compared to Reciproc Blue or ProDesign R instruments (p < 0.05). CONCLUSIONS: ProDesign R presented the highest cyclic fatigue resistance in severely curved canals when compared with Reciproc Blue and WaveOne Gold. However, Reciproc Blue showed the higher torsional strength overall and higher angular rotation to fracture when compared to ProDesign R. CLINICAL RELEVANCE: Despite the numerous advantages of reciprocating instruments, these instruments still have some risk of fracture during its use, especially in severely curved canals. The present study evaluated the cyclic fatigue and torsional resistance of thermally treated reciprocating instruments.

Presence of Metallic Microfragments on Dentinal Walls and Instrument Defects following Root Canal Preparation.

AIM: To determine the presence of metallic microfragments and their elemental composition in the dentinal walls of root canals following preparation using different endodontic instruments and to assess the active cutting edges of instruments with regard to structural defects. MATERIALS AND METHODS: A total of 108 molar teeth were selected and prepared using different endodontic instruments. Teeth were randomly divided into nine groups of 12 teeth each, according to the instruments employed: Manual systems -K-FlexoFile, K-File, and Hedstroem; rotary systems - ProTaper Next, Mtwo, BioRaCe; and reciprocating systems - Reciproc, Unicone, and WaveOne. Both root canals and instruments were assessed using scanning electron microscopy, and the elemental composition of metallic microfragments was determined using energy-dispersive X-ray spectroscopy. RESULTS: Metallic microfragments were found in the groups prepared with both manual and reciprocating instruments, with no statistically significant differences between groups, thirds, or presence of metallic microfragments (p ≥ 0.05). Moreover, all groups presented structural defects in both new and used instruments; however, rotary instruments (ProTaper Next, Mtwo 702, BioRaCe) were the ones with the lowest number of defects, at statistically significant differences in comparison with other instruments (p < 0.05). CONCLUSION: The presence of metallic microfragments on dentinal walls following root canal preparation was associated with manual and reciprocating instrumentation. Furthermore, rotary instruments were the ones with the lowest number of defects. Considering the outcomes measured in this study, rotary instruments performed better than the other two groups, as they were associated with the lowest number of metallic microfragments and structural defects. CLINICAL SIGNIFICANCE: During root canal preparation, operative procedures may induce changes to the root canal shape, as well as the release of metallic fragments resulting from the action of instruments on dentinal walls. Therefore, it is important to determine, among the different techniques used for this purpose, which ones are least susceptible to this occurrence.

Flute and Shank Dimensions of Reciprocating Instruments before and after Simulated Root Canal shaping.

AIM: This study analyzed the effect of the dimensions of the flute and shank in the first 4 mm of instrument tips on the deformation and dimensional changes of reciprocating instruments after root canal shaping (RCS). MATERIALS AND METHODS: The reciprocating instruments used were Reciproc® R25, R40, and R50; WaveOne® Small, Primary, and Large; and Unicone® #20, #25, and #40. Scanning electron microscopy images of the first 4 mm of the tip were acquired at 30× magnification before and after simulated curved root canals were shaped. Each instrument was used only once. The images were transferred to the AxioVision® software to measure the flute area (µm2), shank area (µm2), flute length (µm), and cross-sectional diameter (µm). Student's t test for paired samples was used to compare differences before and after RCS, and analysis of variance followed by the Tukey test, to compare differences between instruments of similar sizes. The instruments were classified according to deformations after RCS. RESULTS: Reciproc® instruments had larger flutes and smaller shanks. The Reciproc® R40 had significant differences in cross-sectional diameter at 0.5 mm from the tip. Reciproc® had no plastic deformations. Unicone® #20 instruments had significant differences in cross-sectional diameter at 1.5 and 3.0 mm from the tip, and #25 instruments had differences at 1.5 and 3.0 mm and in length of the second and third flutes. One #20 and three #40 instruments had plastic deformations. The differences in length of the first and fourth flutes of WaveOne® Primary and in cross-sectional diameter at 2.0 mm from the tip of WaveOne® Large were significant. Two of three WaveOne® Large instruments had plastic deformations. CONCLUSION: Reciproc® instruments had greater flute areas and lengths and smaller shanks than Unicone® and WaveOne® instruments of similar sizes. Reciproc® instruments had a greater flute-to-shank ratio. WaveOne® instruments had the lowest flute-to-shank ratio. Unicone® instruments had the most plastic deformations. Instruments with larger flutes and smaller shanks had fewer plastic deformations after curved RCS. CLINICAL SIGNIFICANCE: The knowledge of mechanical behavior before choosing the endodontic instrument may avoid fracture, regardless of the clinical condition, and it is essential to the success of root canal treatment.

Evaluation of dentinal defect formation after root canal preparation with two reciprocating systems and hand instruments: an in vitro study.

The purpose of this study was to evaluate the presence of dentinal defects after root canal preparation with hand instruments and two different reciprocating instruments. Sixty freshly extracted mandibular incisor teeth were selected for this in vitro study. On the basis of root length, mesiodistal and buccolingual dimensions, the teeth were allocated into three identical experimental groups (n = 15) and one control group (n = 15). The teeth in the control group were left unprepared. The other groups were: stainless steel hand instruments, WaveOne® Primary instruments and RECIPROC® R25 instruments. The reciprocating instruments were used with a reciprocating gentle in-and-out motion in a torque-limited electric motor at the appropriate preset mode. Horizontal sections were made 3, 6 and 9 mm from the apex. Samples were stained with methylene blue and viewed through a stereomicroscope. The presence of dentinal defects (fractures, incomplete cracks and craze lines) and their locations were investigated by two endodontists. These data were analysed statistically by Fisher's exact and chi-square tests. No defects were observed in the unprepared group. All instruments caused dentinal defects, with no significant differences between the instrument systems. All experimental groups demonstrated significantly more defects at the 3-mm level in comparison with the unprepared group (p = 0.032). At the other levels, there was no significant difference between the experimental groups and the control group. The use of hand or reciprocating instruments could induce the formation of dentinal defects during root canal preparation.

Influence of the Brushing Motions on the Dynamic Cyclic Fatigue Resistance of the Reciproc Blue Instrument: In vitro Study.

INTRODUCTION: This study aimed to evaluate the dynamic cyclic fatigue resistance of Reciproc Blue files subjected to brushing motion. METHODS: Twenty Reciproc Blue files (R25, VDW, Munich, Germany) were employed for chemical-mechanical preparation in root canals of 3D printed replicas of mandibular molars. The instruments were divided into two groups (n = 10): Group brushing motion, instrumentation with brushing motions; Group without brushing motion , instrumentation without brushing motions. Subsequently, the same instruments underwent cyclic fatigue testing using artificial canals consisting of a stainless-steel plate and an apical segment with a 45° curvature. Data regarding the time to fracture, number of cycles to fracture, and length of the fractured fragment were collected and subjected to statistical analysis using the t-test or Mann-Whitney test, with a significance level of 5%. Additionally, the fractured fragments were examined under a scanning electron microscope. RESULTS: No statistical differences were observed between the groups in terms of time to fracture (P < .05), number of cycles to fracture (P < .05) and length of the fractured fragment (P < .05). CONCLUSION: The brushing motion did not affect the dynamic cyclic fatigue resistance of Reciproc Blue files.

Evaluation of the Ability of 3 Reciprocating Instruments to Remove Obturation Material: A Micro-Computed Tomography Study.

INTRODUCTION: The purpose of this study was to evaluate the ability of the Reciproc, Reciproc Blue, and WaveOne Gold systems to remove filling material during endodontic retreatment of extracted human mandibular premolars. METHODS: Thirty-nine teeth were instrumented with the Protaper Universal System to the F3 file and filled with the Tagger hybrid technique using an F3 gutta-percha cone and AH Plus cement. At the end of this period, the teeth were scanned with micro-computed tomography before and after removal of the filling material from the root canals. The teeth were divided into 3 groups (n = 13) based on the apical volume, depending on the systems used to remove the filling material. Group GR: Reciproc 40/.06; Group GRB: Reciproc Blue 40/.06; and Group GWG: WaveOne Gold 35/.06. The results were statistically analyzed using the tests of Kruskal-Wallis, Duncan, and analysis of variance at a significance level of 5%. RESULTS: The results showed that there were no significant differences between the amounts of filling material removed, either for the apical and middle regions alone or in the overall evaluation for the 3 groups (P = .97). The time evaluation statistically showed that the GR and GWG groups required less time to clean the root canals than the GRB group. CONCLUSIONS: Reciproc R40 files and WaveOne Gold Medium files required less time for endodontic treatment than Reciproc Blue R40 files. There was no difference in the ability to remove obturation material between the 3 instruments. No instrument was able to completely remove the filling material from the root canals.

Evaluation of cyclic and torsional fatigue resistance of several heat-treated reciprocating nickel-titanium instruments.

This study investigated the cyclic fatigue and torsional resistance of Unicone Plus (UCP 25.06), Unicone (UC 25.06), Reciproc Blue (RB 25.08) and Wave One Gold (WOG 25.07) performed at body temperature (35° ± 1°C). Time and number of cycles to fracture (NCF), as well as torque and angular deflection were recorded. Fractured surfaces were evaluated by scanning electron microscopy (SEM). Data were analysed using one-way ANOVA and Holm-Sidak's tests for multiple comparison. The RB had a significantly higher time to fracture, followed by the WOG and UCP (p < 0.05). Regarding the NCF, there was no significantly difference between RB and WOG (p > 0.05). UC presented highest torque values and the lowest angular deflection (p < 0.05). SEM analysis demonstrated typical failures features in both cyclic and torsional fatigue tests. Overall, UC had the lowest time, NCF and angular deflection at fracture. RB presented the highest time to fracture and angular deflection values.

Shaping Properties and Outcomes of Nickel-Titanium Reciprocation Systems in Primary Teeth: A Systematic Review and Meta-Analysis of In Vitro Studies.

The aim of this systematic review was to investigate the shaping properties and outcomes of reciprocating instruments in primary teeth. A search was conducted across various electronic databases such as PubMed, Scopus, EBSCO (dentistry and oral health sciences), LILACS, Cochrane, Google Scholar (first 100 hits), Open Grey, Ovid, and Shodhganga. Two authors independently performed data extraction and quality assessment of the selected articles using Rayyan software. A total of 12 studies were included. All 12 included studies qualified for qualitative analysis and five for meta-analysis. The meta-analysis revealed there was no statistical significance between rotary and reciprocating instruments concerning instrumentation time and canal transportation. The rotary and reciprocating instruments showed better shaping outcomes than hand instruments. Randomized controlled trials are required with adequate quality to perform a meta-analysis to provide better and more substantial evidence to use reciprocating instruments.

Quantitative analysis of apically extruded bacteria following preparation of curved canals with three systems.

This study compared the amount of apically extruded bacteria following preparation of curved root canals using two continuously rotating multifile and one reciprocating single-file systems. Mesiobuccal canals from maxillary molars were contaminated with Enterococcus faecalis and divided into three groups according to the instrumentation system: Reciproc (R25 instrument, 25/.08), BT-RaCe (10/.06, 35/.00 and 35/.04), and Mtwo (25/.06, 30/.05 and 35/.04). Apically extruded material was collected by a customized apparatus with 1.5% agarose gel covering the root apex to simulate the periradicular tissues. The extruded material was extracted from the gel and subjected to bacteriological culture for bacterial quantification. The three systems showed a high frequency of bacterial extrusion (>70%). There were no statistically significant differences in the counts of extruded bacteria between groups (P > 0.05). The incidence and amount of apical bacterial extrusion were similar between the three systems. The customized apparatus was effective in collecting apically extruded bacteria.

Torsional Fatigue Resistance of Blue-treated Reciprocating Instruments.

INTRODUCTION: The aim of the present study was to evaluate the influence of blue thermal treatment on the torsional resistance behavior of M-Wire Reciproc files (VDW, Munich, Germany). METHODS: Ten M-Wire Reciproc R25 (25/0.08v) and 10 Reciproc Blue R25 (25/0.08v, VDW) instruments were used. The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. Three millimeters of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. The fracture surface of all fragments was examined with a scanning electron microscope. Results were statistically analyzed using the Student t test at a significance level of P < .05. RESULTS: The maximum torsional strength of M-Wire Reciproc was higher than Reciproc Blue instruments (P < .05). Reciproc Blue instruments showed significantly higher angular rotation to fracture than M-Wire Reciproc instruments (P < .05). Scanning electron microscopy of the fracture surface showed similar and typical features of torsional failure for the 2 types of instruments, including concentric abrasion marks and the fibrous dimple marks at the center of rotation. CONCLUSIONS: Reciproc Blue instruments showed a higher angle of rotation to fracture but a lower torque to failure than M-Wire Reciproc instruments.

Comparison of Cyclic Fatigue Resistance of WaveOne and WaveOne Gold Small, Primary, and Large Instruments.

INTRODUCTION: To compare the cyclic fatigue of resistance of WaveOne (WO; Dentsply Maillefer, Ballaigues, Switzerland) and WaveOne Gold (WOG, Dentsply Maillefer) small, primary, and large instruments in simulated root canals. Each instrument was rotated until fracture occurred. METHODS: One hundred twenty nickel-titanium endodontic instruments were tested in two different curved artificial canals with different angles and radii of curvatures. WO and WOG small, primary, and large instruments were evaluated (n = 10 for each curvature). Each instrument was rotated until fracture occurred. The time to failure was recorded, and the length of the fractured tip was measured. An independent Student't test was used to compare the means between the 2 groups. One-way analysis of variance and Tukey' post hoc tests were used for multiple comparisons (P < .05). RESULTS: At all the sizes tested and both curvatures, the cyclic fatigue resistance of the WOG instruments was higher than that of the WO instruments of corresponding sizes (P < .001). The WOG instruments were approximately twice as resistant to failure as the WO instruments were at a 60° angle of curvature, whereas the WOG instruments were 3 times more resistant at a 90° angle of curvature. The length of the fractured part of the instruments was similar among all the groups (P > .05). CONCLUSIONS: Within the limitations of this study, WOG instruments were more resistant to cyclic fatigue than WO instruments.

Cyclic fatigue resistance of nickel-titanium instruments after immersion in irrigant solutions with or without surfactants.

INTRODUCTION: The aim of the study was to assess cyclic fatigue resistance of reciprocating (Reciproc and WaveOne) and continuous rotating (ProTaper) nickel-titanium files after immersion in different irrigation solutions with or without surfactants during several short time periods. METHODS: A total of 270 new Reciproc R25, WaveOne Primary, and ProTaper F2 files were tested. Instruments of each brand were divided into 1 control group (n = 10) formed by new files and 4 test groups (n = 20) formed by instruments dynamically immersed at 37°C for 16 mm in 5.25% sodium hypochlorite (NaOCl), Hypoclean (5.25% NaOCl with surfactant), 17% EDTA, or EDTA Plus (17% EDTA with surfactant). Each test group was subdivided into 2 subgroups (n = 10) on the basis of the time of dynamic immersion in the endodontic irrigant solution (45 seconds or 3 minutes). Resistance to cyclic fatigue was determined by recording time to fracture in a stainless steel artificial canal with a 60° angle of curvature and 5-mm radius of curvature. The fracture surface was examined by using scanning electron microscopy. RESULTS: Immersion in NaOCl did not reduce the cyclic fatigue of reciprocating or continuous nickel-titanium files. The 17% EDTA reduced the fatigue resistance of all instruments after 3 minutes. The immersion in irrigants with surfactants did not influence the cyclic fatigue of instruments except for Reciproc immersed in Hypoclean solution. CONCLUSIONS: EDTA immersion reduced the cyclic fatigue resistance of all instruments after 3 minutes. Addition of surfactants did not influence the cyclic fatigue of files except when added to NaOCl when it contacts Reciproc instruments.