The Ability of Different Nickel-Titanium Rotary Instruments To Induce Dentinal Damage During Canal Preparation

The purpose of this study was to compare the incidence of dentinal defects (fractures and craze lines) after canal preparation with different nickel-titanium rotary files. Two hundred sixty mandibular premolars were selected. Forty teeth were left unprepared (n = 40). The other teeth were prepared either with manual Flexofiles (n = 20) or with different rotary files systems: ProTaper (Dentsply-Maillefer, Ballaigues, Switzerland), ProFile (Dentsply-Maillefer), SystemGT (Dentsply-Maillefer), or S-ApeX (FKG Dentaire, La Chaux-de-Fonds, Switzerland) (n = 50 each). Roots were then sectioned 3, 6, and 9 mm from the apex and observed under a microscope. The presence of dentinal defects was noted. There was a significant difference in the appearance of defects between the groups (p < 0.05). No defects were found in the unprepared roots and those prepared with hand files and S-ApeX. ProTaper, ProFile, and GT preparations resulted in dentinal defects in 16%, 8%, and 4% of teeth, respectively. Some endodontic preparation methods might damage the root and induce dentinal defects. (J Endod 2009;35:236-238)

Cyclic Fatigue Resistance of Rotary Nickel-Titanium Instruments Submitted to Nitrogen Ion Implantation

Introduction: The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments submitted to nitrogen ion implantation by using a custom-made cyclic fatigue testing apparatus. Methods: Thirty K3 files, size #25, taper 0.04, were divided into 3 experimental groups as follows: group A, 12 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), accelerating voltage of 200 kV, currents of 1 mu A/cm(2), 130 degrees C temperature, and vacuum conditions of 10 x 10(-6) torr for 6 hours; group B, 12 nonimplanted files; and group C, 6 files submitted to thermal annealing for 6 hours at 130 degrees C. One extra file was used for process control. All files were submitted to a cyclic fatigue test that was performed with an apparatus that allowed the instruments to rotate freely, simulating rotary instrumentation of a curved canal (40-degree, 5-mm radius curve). An electric motor handpiece was used with a contra-angle of 16:1 at an operating speed of 300 rpm and a torque of 2 N-cm. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. Data were analyzed with the Student t test (P < .05). Results: Ion-implanted instruments reached significantly higher cycle numbers before fracture (mean, 510 cycles) when compared with annealed (mean, 428 cycles) and nonimplanted files (mean, 381 cycles). Conclusions: Our results showed that nitrogen ion implantation improves cyclic fatigue resistance in rotary nickel-titanium instruments. Industrial implementation. of this surface modification technique would produce rotary nickel-titanium instruments with a longer working life. (J Endod 2010;36:1183-1186)

Influence of shaft design on the shaping ability of 3 nickel-titanium rotary systems by means of spiral computerized tomography

Objective. To evaluate the influence of shaft design on the shaping ability of 3 rotary nickel-titanium (NiTi) systems. Study design. Sixty curved mesial canals of mandibular molars were used. Specimens were scanned by spiral tomography before and after canal preparation using ProTaper, ProFile, and ProSystem GT rotary instruments. One-millimeter-thick slices were scanned from the apical end point to the pulp chamber. The cross-sectional images from the slices taken earlier and after canal preparation at the apical, coronal, and midroot levels were compared. Results. The mean working time was 137.22 +/- 5.15 s. Mean transportation, mean centering ratio, and percentage of area increase were 0.022 +/- 0.131 mm, 0.21 +/- 0.11, and 76.90 +/- 42.27%, respectively, with no statistical differences (P > .05). Conclusions. All instruments were able to shape curved mesial canals in mandibular molars to size 30 without significant errors. The differences in shaft designs seemed not to affect their shaping capabilities.

Effect of Nitrogen Ion Implantation on the Flexibility of Rotary Nickel-Titanium Instruments

Introduction: The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30 degrees angle. Methods: Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), voltage 200 KeV, current density 1 mu A/cm(2), temperature 130 degrees C, and vacuum conditions of 10 x 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30 degrees. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. Results: The mean load required to bend instruments at a 30 degrees angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. Conclusions: Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments. (J Endod 2012;38:673-675)

Wear resistance of nickel-titanium endodontic files after surface treatment

Objectives The purpose of this work was to submit the Nitinol files to plasma immersion ion implantation (PIII) and evaluate the effects of the surface treatment. Materials and Methods Wear resistance was determined in vitro by using an equipment for the application of horizontal movements on previously prepared notched plates made of resin. Vickers microhardness was measured in plates and files, before and after surface treatment and the surface chemical composition of the instruments was determined by X-rays photoelectron spectroscopy. Results The hardness values found for the treated Nitinol files were significantly lower than the hardness values measured before the implantation process. The comparison of commercially available instruments shows that the wear resistance of the stainless steel file is higher than the resistance of the Nitinol. Conclusions The results found led to the conclusion that the surface treatment significantly increased the Nitinol files wear resistance.

Cutting Ability of Nickel-titanium rotary systems protaper, mtwo and k3

Nickel-titanium rotatory systems should remove dentin during the root canal preparation to promote the enlargement and tapered shape with continuously narrowing towards the apex. Objective: The aim of this study was to analyze the cutting ability of three NiTi rotatory systems (n = 12): ProTaper (group 1), Mtwo (group 2), and K3 (group 3). Material and methods: Thirty six maxillary molar teeth were weighted on an analytical balance before and after the rotatory preparation of the mesio-buccal root canal. Data was statistically analyzed by ANOVA and Tukey s test with a significance level of 5%. Results: The results revealed the following mass differences (g) before and after the root canal preparation: ProTaper (group 1 – 0.0159 ± 0.004), Mtwo (group 2 – 0.0125 ± 0.002), and K3 (group 3 – 0.007 ± 0.003). Conclusion: ProTaper showed the highest cutting ability among the three tested nickel-titanium rotatory systems followed by Mtwo and K3.

Resistance to Flexural Fatigue of Reciproc R25 Files under Continuous Rotation and Reciprocating Movement

Introduction: The aim of the present work was to evaluate the resistance to flexural fatigue of Reciproc R25 nickel-titanium files, 25 mm, used in continuous rotation motion or reciprocation motion, in dynamic assays device. Methods: Thirty-six Reciproc R25 files were divided into 2 groups (n = 18) according to kinematics applied, continuous rotary (group CR) and reciprocation motion (group RM). The files were submitted to dynamic assays device moved by an electric engine with 300 rpm of speed that permitted the reproduction of pecking motion. The files run on a ring's groove of temperate steel, simulating instrumentation of a curved root canal with 400 and 5 mm of curvature radius. The fracture of file was detected by sensor of device, and the time was marked. The data were analyzed statistically by Student's t test, with level of significance of 95%. Results: The instruments moved by reciprocating movement reached significantly higher numbers of cycles before fracture (mean, 1787.78 cycles) when compared with instruments moved by continuous rotary (mean, 816.39 cycles). Conclusions: The results showed that the reciprocation motion improves flexural fatigue resistance in nickel-titanium instrument Reciproc R25 when compared with continuous rotation movement. (J Endod 2012;38:684-687)

Root Canal Area Increase Promoted by the EndoSequence and ProTaper Systems: Comparison by Computed Tomography

Introduction: The aim of this study was to compare the increase of the root canal area after instrumentation with EndoSequence or ProTaper rotary systems. Methods: Twenty-two mesial root canals from mandibular molars were instrumented. Teeth were mounted on a base, numbered, and divided into 2 groups; teeth from 1-11 (PT group) were instrumented by using the ProTaper system, and teeth from 12-22 (ES group) were instrumented by using the EndoSequence system. Cone beam computed tomography was performed on all teeth before and after instrumentation. Measurements at 3,5, and 7 mm as well as differences in instrument performance were statistically compared by the Student t test at 5% significance level. Results: Both systems increased significantly the root canal area (P < .05) at all levels. Comparison between the rotary systems showed significantly greater increase (P < .05) for EndoSequence at 3 mm, with no statistically significant difference (P < .05) at the other levels. Conclusions: Both rotary systems increased significantly the root canal area. (J Endod 2010;36:1179-1182)

Avaliação dos sistemas MTwo Retratamento e ProTaper Universal Retratamento na remoção de guta-percha e novos cimentos endodônticos dos canais radiculares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Topography of four different endodontic rotary systems, before and after being used for the 12th time

Root canal preparation may damage NiTi instruments resulting in wear and deformation. The aim of this study was to make a comparative evaluation of the surface topography of the cervical third of four different rotary systems, before and after being used twelve times, in 1.440 resin blocks with simulated root canals with standardized 45 degrees curvatures, and analyzed by atomic force microscopy AFM. The blocks were divided into four groups and prepared according to the manufacturers recommendations: Group 1 - K3 (R); Group 2 - Protaper Universal (R); Group 3 - Twisted Files (R) and Group 4 - Biorace (R). After each preparation, the instruments were washed and autoclaved. A total of 240 instruments were selected, being 30 new instruments and 30 after having been used for the 12th time, from each group. These instruments were analyzed by AFM and for quantitative evaluation, the mean RMS (Root mean square) values of the cervical third of the specimens from the four groups were used. The result showed that all the rotary files used for the 12th time suffered wear with change in the topography of the cervical region of the active portion of the file (ANOVA p < 0.01). Classifying the specimens in increasing order, from the least to the greatest wear suffered, Group 3 (2.8993 nm) presented the least wear, followed by Group 4 (12.2520 nm), Group 1 (36.0043 nm) and lastly, Group 2 (59.8750 nm) with the largest amount of cervical surface wear. Microsc. Res. Tech. 75:97-102, 2012. (c) 2011 Wiley Periodicals, Inc.

Effect of rotary or manual instrumentation, with or without a calcium hydroxide/1% chlorhexidine intracanal dressing, on the healing of experimentally induced chronic periapical lesions

Objective. To evaluate the healing of experimentally induced chronic periapical lesions in dogs at 30, 75, and 120 days after root canal instrumentation with rotary NiTi files or manual K-files, with or without a calcium hydroxide/1% chlorhexidine paste intracanal dressing.Study design. The second, third, and fourth mandibular premolars and the second and third maxillary premolars of 5 dogs (12 to 18 months of age, weighing 8 to 15 kg) were selected for treatment (a total of 82 root canals). After pulp removal, the root canals were left exposed to the oral cavity for 7 days to allow microbial contamination, after which the root canals were sealed with ZOE cement until periapical lesions were confirmed with radiography. Group I and II teeth were instrumented with manual K-files using the crown-down technique. In group III and IV teeth, NiTi rotary files were used. The apical delta was perforated by using #20 to #30 K-files at the length of the tooth, thus creating a standardized apical opening. The apical stop was enlarged to size 70, with 2.5% sodium hypochlorite irrigation at each file change. Teeth in groups II and IV were dressed with calcium hydroxide (Ca(OH)(2))/1% chlorhexidine (CHX) paste for 15 days before root filling. Group I and III teeth did not receive an intracanal dressing. The access openings of the teeth were permanently restored with silver amalgam condensed on a glass ionomer cement base. Pairs of standardized periapical radiographs were taken at the beginning of the treatment (0 days) and at 30, 75, and 120 days after filling.Results. There was no significant difference in the rate of radiographic healing of the periapical lesions between manual and rotary instrumentation. Radiographs taken at 120 days showed that the treatment with Ca(OH)(2)/1% CHX paste resulted in a significant reduction in mean size of the periapical lesions in comparison to single-session treatment. These findings were also true for histologic observations.Conclusion. The findings support the hypothesis that, regardless of the instrumentation technique (manual or rotary), the use of an intracanal dressing is important in the endodontic treatment of dog's teeth with experimentally induced chronic periapical lesions.

Avaliação da resistência à fratura torcional de diferentes instrumentos rotatórios de níquel-titânio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)