Rotary NiTi Instrument Fracture and its Consequences

Cyclic fatigue life of Tango-Endo, WaveOne GOLD, and Reciproc NiTi instruments

Objectives

To compare the fatigue life of Tango-Endo, WaveOne GOLD, and Reciproc NiTi instruments under static model via artificial canals with different angles of curvature.

Materials and Methods

Reciproc R25, WaveOne GOLD Primary, and Tango-Endo instruments were included in this study (n = 20). All the instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 45°, 60°, and 90° angles of curvatures and a radius of curvature of 5 mm until fracture occurred, and the time to fracture was recorded in seconds using a digital chronometer. The data were analyzed using Kruskal-Wallis and post-hoc Dunn tests were used for the statistical analysis of data in SPSS 21.0 software.

Results

Tango-Endo files were found to have significantly higher values than WaveOne GOLD and Reciproc files in terms of fatigue life (p < 0.05). However, there was no statistically significant difference between fatigue life of Reciproc and WaveOne GOLD files (p > 0.05). It was determined that increasing the angle of curvature of the stainless canals caused significant decreases in fatigue life of all of three files (p < 0.05).

Conclusions

Within the limitations of the present study, the cyclic fatigue life of Tango-Endo in canals having different angles of curvature was statistically higher than Reciproc and WaveOne GOLD.

Detection of Fractured Endodontic Instruments in Root Canals: Comparison between Different Digital Radiography Systems and Cone-beam Computed Tomography

INTRODUCTION

This study compared the detection of fractured instruments in root canals with and without filling by periapical radiographs from 3 digital systems and cone-beam computed tomographic (CBCT) images with different resolutions.

METHODS

Thirty-one human molars (80 canals) were used. Root canals were divided into the following groups: the control group, without fillings; the fracture group, without fillings and with fractured files; the fill group, filled; and the fill/fracture group, filled and with fractured files. Digital radiographs in ortho-, mesio-, and distoradial directions were performed in 2 semidirect systems (VistaScan [Dürr Dental, Beitigheim-Bissinger, Germany] and Express [Instrumentarium Imaging, Tuusula, Finland]) and a direct system (SnapShot [Instrumentarium Imaging]). CBCT images were acquired with 0.085-mm and 0.2-mm voxel sizes. All images were assessed and reassessed by 4 observers for the presence or absence of fractured files on a 5-point scale. The sensitivity, specificity, and accuracy were calculated.

RESULTS

In the absence of filling, accuracy values were high, and there were no statistical differences among the radiographic techniques, different digital systems, or the different CBCT voxels sizes. In the presence of filling, the accuracy of periapical radiographs was significantly higher than CBCT images. In general, SnapShot showed higher accuracy than VistaScan and Express.

CONCLUSIONS

Periapical radiographs in 1 incidence were accurate for the detection of fractured endodontic instruments inside the root canal in the absence or presence of filling, suggesting that this technique should be the first choice as well as the direct digital radiographic system. In the presence of filling, the decision to perform a CBCT examination must take into consideration its low accuracy.

Cone-beam computed tomography assessment of root canal transportation using WaveOne Gold and Neoniti single-file systems

Introduction:

The aim of this study was to compare canal transportation of two single-file systems, WaveOne Gold and Neoniti, using cone-beam computed tomography (CBCT).

Methodology:

A total of 40 mesiobuccal canals of maxillary first molars with curvatures of 15°–30° were chosen and randomly divided into two experimental groups (n = 20). In both groups, glide path was established using ProGlider. In group 1, canals were shaped with WaveOne Gold and in group 2 with Neoniti A1, respectively. According to manufacturer's instructions, canal preparation was made. Canals were scanned before and after instrumentation using CBCT scanner to evaluate root canal transportation at 3, 5, and 7 mm from the apex. Data were statistically analyzed, and significance level was set at P < 0.05.

Results:

Mesiodistal and buccolingual transportation showed a statistically significant difference at 3 mm (P = 0.009) and 7 mm (P = 0.002), respectively, when instrumented with Neoniti than WaveOne Gold.

Conclusion:

WaveOne Gold single reciprocation file respected original canal anatomy better than Neoniti single continuous file

Alternating versus continuous rotation: Root canal transportation and centering ratio with the ProTaper Next

Background:

The technique of alternating rotation has been used with NiTi rotary instruments to increase the resistance to fracture compared with conventional continuous rotation. However, it is still not clear what type of instrumentation could provide better results in the preservation of the original canal anatomy.

Aim:

The aim of this study is to determine the influence of the type of rotation on canal transportation and centering ability using cone-beam computed tomography (CBCT) imaging.

Materials and Methods:

In total, 50 mesial canals of mandibular molars with curvatures between 30° and 60° were divided into two experimental groups (n = 25 each) according to the type of movement employed with the ProTaper Next (PTN) instruments: Group A (alternating rotation) and Group B (continuous rotation). Canals were scanned before and after instrumentation using a CBCT scanner to evaluate root canal transportation and the centering ratio at 3, 5, and 7 mm from the apex. Data were analyzed statistically using Student's t-test; the significance level was set at P < 0.05.

Results:

There was no significant difference between the groups in canal transportation or the centering ratio at any of the three studied cross sections (3, 5, and 7 mm).

Conclusions:

PTN instruments promoted minimal apical transportation and remained relatively centered within the root canal, with no significant difference between alternating and continuous rotation.

The Effects of Torsional Preloading on the Torsional Resistance of Nickel-titanium Instruments

INTRODUCTION

This study evaluated the effect of torsional preloading on the torsional resistance of nickel-titanium (NiTi) endodontic instruments.

METHODS

WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper Universal F2 (Dentsply Maillefer) files were used. The ultimate torsional strength until fracture was determined for each instrument. In the phase 1 experiment, the ProTaper and WaveOne files were loaded to have a maximum load from 2.0 up to 2.7 or 2.8 Ncm, respectively. In the phase 2 experiment, the number of repetitions of preloading for each file was increased from 50 to 200, whereas the preloading torque was fixed at 2.4 Ncm. Using torsionally preloaded specimens from phase 1 and 2, the torsional resistances were calculated to determine the ultimate strength, distortion angle, and toughness. The results were analyzed using 1-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of 5 specimens per group were examined under a scanning electron microscope.

RESULTS

All preloaded groups showed significantly higher ultimate strength than the unpreloaded groups (P < .05). There was no significant difference among all groups for distortion angle and toughness. Although WaveOne had no significant difference between the repetition groups for ultimate strength, fracture angle, and toughness, ProTaper had a higher distortion angle and toughness in the 50-repetition group compared with the other repetition groups (P < .05). Scanning electron microscopic examinations of the fractured surface showed typical features of torsional fracture.

CONCLUSIONS

Torsional preloading within the ultimate values could enhance the torsional strength of NiTi instruments. The total energy until fracture was maintained constantly, regardless of the alloy type.

Removal of Separated Endodontic K-File with the Aid of Hypodermic Needle and Cyanoacrylate

A wide range of accidents might happen during the treatment of the root canal system, where the instrument separation is one of the most unpleasant occurrences. Several techniques have been developed to facilitate the removal of the fragments; however, they generally require specific devices that not always are available to the clinician. The aim of this case report is to present a simple alternative technique to remove from the root canals manual instruments fractured during the treatment. The case has its outline based on a 31-year-old patient who sought the clinic to have her maxillary first left premolar rehabilitated. The clinic and radiographic examinations revealed the need of endodontic retreatment and the presence of a fragment of a K-file instrument localized at the apical third of the palatine canal. The retreatment was initiated by the removal of the obturation materials followed by several unsuccessful attempts to take out the fractured instrument. Hence, it was chosen to perform the fragment removal using a hypodermic needle and cyanoacrylate adhesive. The fragment easily came out, which reinforces the technique adopted as a safe, simple, and low cost mean to solve the problem of fractured instruments using only items already present in the endodontic arsenal.

Stereomicroscopic evaluation of defects caused by torsional fatigue in used hand and rotary nickel-titanium instruments

Objective:

The aim of this study was to evaluate defects caused by torsional fatigue in used hand and rotary nickel-titanium (Ni-Ti) instruments by stereomicroscopic examination.

Materials and Methods:

One hundred five greater taper Ni-Ti instruments were used including Protaper universal hand (Dentsply Maillefer, Ballaigues, Switzerland), Protaper universal rotary (Dentsply Maillefer, Ballaigues, Switzerland), and Revo-S rotary (MicroMega, Besançon, France) files. Files were used on lower anterior teeth. After every use, the files were observed with both naked eyes and stereomicroscope at 20× magnification (Olympus, Shinjuku, Tokyo, Japan) to evaluate defects caused by torsional fatigue. Scoring was assigned to each file according to the degree of damage.

Statistics:

The results were statistically analyzed using the Mann-Whitney U test and the Kruskal-Wallis test.

Results:

A greater number of defects were seen under the stereomicroscope than on examining with naked eyes. However, the difference in methods of evaluation was not statistically significant. Revo-S files showed minimum defects, while Protaper universal hand showed maximum defects. The intergroup comparison of defects showed that the bend in Protaper universal hand instruments was statistically significant.

Conclusion:

Visible defects in Ni-Ti files due to torsional fatigue were seen by naked eyes as well as by stereomicroscope. This study emphasizes that all the files should be observed before and after every instrument cycle to minimize the risk of separation.

Electrochemical dissolution of fractured nickel-titanium instruments in human extracted teeth

AIM

To assess the effect of sodium chloride concentration in fluoridated solutions during the electrochemical dissolution of fractured rotary endodontic instruments.

METHODOLOGY

Two solutions were assessed (solution 1: NaF 12 g L^-1  + NaCl 1 g L^-1 , pH = 5.0; and solution 2: NaF 12 g L^-1  + NaCl 180 g L^-1 , pH = 5.0) using two tests: the ProTaper Universal F1 (PTU F1) instrument polarization test and the polarization test for intracanal PTU F1 fragments fractured in mandibular incisors. In the first test, two sets of five instruments were separately and partially immersed in each solution, and the electrical current was evaluated over 30 min. In the second test, 45 PTU F1 instruments were fractured within the root canals of mandibular incisors and subjected to potentiodynamic polarization for 30 min. The electrical current and the variations in the length of PTU F1 fragments were measured. The data were analysed statistically (anova and Wilcoxon and Mann-Whitney tests, respectively).

RESULTS

Solution 2 was associated with more corrosive effects in both tests. In the first test, the PTU F1 instruments immersed in solution 2 had a higher electrical current (P < 0.001) and had a total dissolution time of approximately 540 s. In the second test, a larger difference between the baseline and final lengths of the fragments was noted in solution 2 (P = 0.011).

CONCLUSION

Saturation of fluoridated solution with sodium chloride led to an increase in electrical current and microscopic reductions in the length of fractured instrument fragments subjected to electrochemical dissolution.

Mechanical behavior of deep cryogenically treated martensitic shape memory nickel-titanium rotary endodontic instruments

OBJECTIVES

The aim of this study was to investigate the role of deep cryogenic treatment (DCT) on the cyclic fatigue resistance and cutting efficiency of martensitic shape memory (SM) nickel-titanium (NiTi) rotary endodontic instruments.

MATERIALS AND METHODS

Seventy-five HyFlex(®) CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (-185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.

RESULTS

Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.

MATERIALS AND METHODS

Seventy-five HyFlex(®) CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (-185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.

RESULTS

Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.

Micro-CT evaluation of several glide path techniques and ProTaper Next shaping outcomes in maxillary first molar curved canals

AIM

To evaluate the ability of ProGlider instruments, PathFiles and K-files to maintain canal anatomy during glide path preparation using X-ray computed micro-tomography (micro-CT).

METHODOLOGY

Forty-five extracted maxillary first permanent molars were selected. Mesio-buccal canals were randomly assigned (n = 15) to manual K-file, PathFile or ProGlider groups for glide path preparation. Irrigation was achieved with 5% NaOCl and 10% EDTA. After glide path preparation, each canal was shaped with ProTaper Next X1 and X2 to working length. Specimens were scanned (isotropic voxel size 9.1 μm) for matching volumes and surface areas and post-treatment analyses. Canal volume, surface area, centroid shift, canal geometry variation through ratio of diameter ratios and ratio of cross-sectional areas were assessed in the apical and coronal levels and at the point of maximum canal curvature. One-way factorial anovas were used to evaluate the significance of instrument in the various canal regions.

RESULTS

Post-glide path analysis revealed that instrument factor was significant at the apical level for both the ratio of diameter ratios and the ratio of cross-sectional areas (P < 0.001), with an improved maintenance of root canal geometry by ProGlider and PathFile. At the coronal level and point of maximum canal curvature, ProGlider demonstrated a tendency to pre-flare the root canal compared with K-file and PathFile. PathFile and ProGlider demonstrated a significantly lower centroid shift compared with K-file at the apical level (P = 0.023). Post-shaping analysis demonstrated a more centred preparation of ProGlider, compared with PathFile and K-files, with no significant differences for other parameters.

CONCLUSIONS

Use of ProGlider instruments led to less canal transportation than PathFiles and K-files.

Cone-Beam Computed Tomography Assessment of Root Canal Transportation by Neoniti and Reciproc Single-File Systems

Introduction:

The aim of this in vitro study was to compare the canal transportation of two single-file engine-driven systems, Neoniti and Reciproc, using cone-beam computed tomography (CBCT).

Methods and Materials:

Forty-five non-calcified roots with mature apices and apical curvature of 15-30 degrees were selected from extracted human maxillary molars for this study. Samples were randomly divided into two groups (n=20) and a control group (n=5) and canal preparation with either system was performed according to manufacturers' instructions. Pre- and post-instrumentation CBCT images were captured and the amount of canal transportation within the files was calculated at levels of 3, 4, and 5 mm from the apex. The independent sample t-test was used to analyze the statistical significance between the two groups. The level of significance was defined at 0.05.

Results:

Reciproc created more canal transportation compared to Neoniti in both mesiodistal and buccolingual directions. The difference between the two systems was statistically significant in all evaluated distances from the apex (P<0.001). During this study fracture of one file (25/0.08) in the Neoniti group occurred.

Conclusion:

Neoniti and Reciproc systems have significant difference in terms of creating canal transportation. Reciproc created more canal transportation in buccolingual and mesiodistal dimensions.

Effect of dry cryogenic treatment on Vickers hardness and wear resistance of new martensitic shape memory nickel-titanium alloy

OBJECTIVES

The aim of this study is to investigate the role of dry cryogenic treatment (CT) temperature and time on the Vickers hardness and wear resistance of new martensitic shape memory (SM) nickel-titanium (NiTi) alloy. The null hypothesis tested was that there is no difference in Vickers hardness and wear resistance between SM NiTi alloys following CT under two soaking temperatures and times.

MATERIALS AND METHODS

The composition and the phase transformation behavior of the alloy were examined by X-ray energy dispersive spectroscopy and differential scanning calorimetry, respectively. Fifteen cylindrical specimens and 50 sheet specimens were subjected to different CT conditions: Deep cryogenic treatment (DCT) 24 group: -185°C, 24 h; DCT six group: -185°C, 6 h; shallow cryogenic treatment (SCT) 24 group: -80°C, 24 h; SCT six group: -80°C, 6 h; and control group. Wear resistance was assessed from weight loss before and after reciprocatory wet sliding wear.

RESULTS

The as-received SM NiTi alloy contained 50.8 wt% nickel and possessed austenite finish temperature (Af) of 45.76°C. Reduction in Vickers hardness of specimens in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference [HSD]). The weight loss was significantly higher in DCT 24 group (P < 0.05; Tukey's HSD).

CONCLUSION

Deep dry CT with 24 h soaking period significantly reduces the hardness and wear resistance of SM NiTi alloy.

Evaluation of Time to Fracture and Vertical Forces Applied by a Novel Gentlefile System for Root Canal Preparation in Simulated Root Canals

INTRODUCTION

A great number of studies performed in the last 3 decades have shown the superior mechanical features of nickel-titanium files as compared with stainless steel files. A novel file system recently developed, Gentlefile, defies these findings and claims to have superior qualities despite the fact it is made from stainless steel.

METHODS

Three file systems were used in this experiment: ProTaper Next (X1, X2, and X3), RevoS (SC2, SC3, and AS30), and Gentlefile (GF1, GF2, and GF3). Time to fracture, rotations to fracture, and vertical forces applied to a simulated root canal, which was fabricated from a metal block with a Plexiglas cover, were measured.

RESULTS

The GF system required significantly longer time and more rotations to fracture compared with the ProTaper and RevoS systems (P < .001). The GF system applied significantly less vertical force to the canal in comparison with the ProTaper and RevoS systems (P < .01).

CONCLUSIONS

Under the limitations of this study the GF system showed better mechanical properties in comparison with the ProTaper and RevoS systems. Further investigation is needed to assess the clinical meaning of these findings.

Modern Endodontic Principles Part 3: Preparation

The purpose of instrumentation is to facilitate irrigation and allow controlled obturation. This article will revisit methods of instrumentation of the root canal system with consideration given to length determination, apical preparation and the concept of patency filing. It will discuss hand instrumentation and rotary preparation looking at emerging technology such as reciprocating systems and the self-adjusting file. CPD/CLINICAL RELEVANCE: Mechanical preparation of the root canal system is of fundamental importance in achieving success, creating a more easily managed environment from a biological perspective.

Nickel-Titanium Single-file System in Endodontics

AIM

This work describes clinical cases treated with a innovative single-use and single-file nickel-titanium (NiTi) system used in continuous rotation.

BACKGROUND

Nickel-titanium files are commonly used for root canal treatment but they tend to break because of bending stresses and torsional stresses. Today new instruments used only for one treatment have been introduced. They help the clinician to make the root canal shaping easier and safer because they do not require sterilization and after use have to be discarded. A new sterile instrument is used for each treatment in order to reduce the possibility of fracture inside the canal. The new One Shape NiTi single-file instrument belongs to this group.

CASE DESCRIPTION

One Shape is used for complete shaping of root canal after an adequate preflaring. Its protocol is simple and some clinical cases are presented. It is helpful for easy cases and reliable for difficult canals.

CONCLUSION

After 2 years of clinical practice, One Shape seems to be helpful for the treatment of most of the root canals, with low risk of separation. After each treatment, the instrument is discarded and not sterilized in autoclave or re-used.

CLINICAL SIGNIFICANCE

This single-use file simplifies the endodontic therapy, because only one instrument is required for canal shaping of many cases. The respect of clinical protocol guarantees predictable good results.

Retained dental needle migration across the skull base to the cochlea presenting as hearing loss

OBJECTIVES

Long-term retained foreign bodies in the human body have been reported across many specialties, but relatively few exist in the ENT literature.

PATIENTS

We present a case report of a patient with a broken dental needle fragment in the posterior oral cavity with subsequent migration to the cochlea over the course of 4 years, eventually leading to hearing loss. CT scan and middle ear exploration demonstrated a 4-cm metallic fragment abutting the base of the cochlea, immediately adjacent to the internal carotid artery.

INTERVENTIONS

The needle segment was removed through an endaural approach without complication.

RESULTS

Postoperatively, the patient had improvements in PTA and speech discrimination, as well as the resolution of chronic otalgia and jaw pain. Imaging, audiologic results, and surgical details and pictures are presented herein.

CONCLUSION

To our knowledge, based on a thorough PubMed and Google Scholar search, there are no reports of such a foreign body migration from the oral cavity to the skull base.

Microstructure of cryogenically treated martensitic shape memory nickel-titanium alloy

Context:

Recent introduction of shape memory (SM) nickel-titanium (NiTi) alloy into endodontics is a major breakthrough. Although the flexibility of these instruments was enhanced, fracture of rotary endodontic instruments during instrumentation is an important challenge for the operator. Implementation of supplementary manufacturing methods that would improve the fatigue life of the instrument is desirable.

Aim:

The purpose of this study was to investigate the role of dry cryogenic treatment (CT) conditions on the microstructure of martensitic SM NiTi alloy.

Materials and Methods:

Experiments were conducted on Ni-51 wt% Ti-49 wt% SM alloy. Five cylindrical specimens and five sheet specimens were subjected to different CT conditions: Deep CT (DCT) 24 group: −185°C; 24 h, DCT 6 group: −185°C; 6 h, shallow CT (SCT) 24 group: −80°C, 24 h, SCT 6 group: −80°C, 6 h and control group. Microstructure of surface was observed on cylindrical specimens with an optical microscope and scanning electron microscope at different magnifications. Subsurface structure was analyzed on sheet specimens using X-ray diffraction (XRD).

Results:

Microstructures of all SM NiTi specimens had equiaxed grains (approximately 25 μm) with well-defined boundaries and precipitates. XRD patterns of cryogenically treated specimens revealed accentuation of austenite and martensite peaks. The volume of martensite and its crystallite size was relatively more in DCT 24 specimen.

Conclusions:

DCT with 24 h soaking period increases the martensite content of the SM NiTi alloy without altering the grain size.

Alternative techniques to remove fractured instrument fragments from the apical third of root canals: report of two cases

This paper describes two cases of instrument fragment removal from the apical thirds of root canals using a customized extractor and a modified needle technique, respectively. In case 1, a customized extractor was manufactured to remove a bur fragment located in the apical root canal of a maxillary central incisor. The use of this extractor enabled successful and conservative removal of the instrument fragment. In case 2, a modified injection needle was used as a trepan to gain access around an instrument fragment located in the curved apical portion of the mesiobuccal canal of a mandibular molar. A segment of steel wire was inserted into the needle lumen to engage the metallic fragment, enabling its removal with counter-clockwise rotation and a simultaneous pull-out motion. Alternative and creative methods are useful for the management of intracanal metallic fragments during root canal treatment.

Obturation over an S1 ProTaper instrument fragment in a mandibular molar with three years of follow-up

This case report describes root canal filling performed over a large S1 ProTaper file fragment in a second mandibular molar with irreversible pulpitis. An S1 ProTaper file was fractured during the instrumentation of the mesiobuccal canal. Approximately 10 mm of file fragment remained in the apical and middle thirds of the canal. The obturation was performed over this fragment using thermomechanically compacted gutta-percha and sealer. Radiographic findings and the absence of clinical signs and symptoms at 3-year follow up indicated successful treatment. Cone-beam computed tomography images revealed absence of periapical lesion and details of intracanal file fragment related to root fillings and apex morphology. In this case, the presence of a large intracanal fractured instrument did not have a negative impact on the endodontic prognosis during the follow up evaluation period.

Calcium hydroxide medication in primary molars using different preparations and placement techniques: an in vitro study

AIM

This was to compare the effectiveness of different preparations and delivery techniques of calcium hydroxide paste as an intracanal medicament in primary molar root canals.

METHODS

Extracted lower primary second molars roots (72) were randomly assigned to the four experimental groups. After complete root canal preparation with TF rotary nickel titanium up to .06/30 file, a mix of calcium hydroxide/ distilled water was delivered by lentulo spiral (group 1) or a syringe (group 2). UltraCal(®) XS was placed by lentulo spiral (group 3) and a syringe (group 4). Digital radiographs were taken in both buccal and proximal directions before and after calcium hydroxide placement to evaluate the quality of filling. The mean percentages of filled calcium hydroxide area by subtracted digital radiograph, and the quality assessments between four experimental groups, were compared by using Two-way ANOVA and Fisher's exact test respectively. A p value of less than 0.05 was considered statistical significance.

RESULTS

There was no statistically significant difference in the mean percentages of the filled calcium hydroxide area among different preparations and delivery techniques (p ≥ 0.05). The syringe technique had statistically significant fewer of air inclusions than when using the lentulo spiral with the mix of calcium hydroxide group (p < 0.05). The completeness of obturation and the quality of filling at apical part were not different among groups (p ≥ 0.05).

CONCLUSION

Syringe technique was a simpler handling method that presented similar filling quality but fewer porosities than lentulo spiral technique in primary molar root canals.

Effects of NiTi rotary and reciprocating instruments on debris and smear layer scores: an SEM evaluation

PURPOSE

The purpose of the present study was to investigate the cleaning efficacy of 2 different nickel-titanium (NiTi) rotary systems: a new single system Reciproc compared with the rotary full sequence Mtwo. The amount of debris and the morphology of smear layer were the parameters for the evaluation of the cleanliness of root canals. The null hypothesis of the study was that there would be no significant difference in debris scores and smear layer scores between the 2 systems. 


METHODS

Forty single-rooted freshly extracted teeth were selected and divided into 2 groups. For each group, all root canals were shaped with 2 different NiTi instruments (Mtwo and Reciproc) and irrigated with 5.25% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA) solutions by 3 trained operators. Specimens were fractured longitudinally and prepared for scanning electron microscopy (SEM) analysis at a standard magnification of ×5,000. The presence/absence of smear layer and the presence/absence of debris at the coronal, middle and apical third of each canal were evaluated using two 5-step scales for scores. Numeric data were analyzed using the Kruskal-Wallis and Mann-Whitney U statistical tests, and significance was set at a P value <0.05. 


RESULTS

This study revealed significant differences among the various groups. The Mtwo group presented significantly lower smear layer scores than the Reciproc group (P<0.01) in the middle and apical third of the canal. 


CONCLUSIONS

Conventional continuous rotary NiTi instruments associated with 5.25% NaOCl and 17% EDTA solutions seem to be better for obtaining clean dentinal canal walls. Reciprocating instruments leave a higher quantity of smear layer which covers dentinal walls and dentinal tubules.

Comparison of canal transportation and centering ability of rotary protaper, one shape system and wave one system using cone beam computed tomography: An in vitro study

Aim:

The aim of the present study was to compare the canal transportation and centering ability of Rotary ProTaper, One Shape and Wave One systems using cone beam computed tomography (CBCT) in curved root canals to find better instrumentation technique for maintaining root canal geometry.

Materials and Methods:

Total 30 freshly extracted premolars having curved root canals with at least 10 degrees of curvature were divided into three groups of 10 teeth each. All teeth were scanned by CBCT to determine the root canal shape before instrumentation. In Group 1, the canals were prepared with Rotary ProTaper files, in Group 2 the canals were prepared with One Shape files and in Group 3 canals were prepared with Wave One files. After preparation, post-instrumentation scan was performed. Pre-instrumentation and post-instrumentation images were obtained at three levels, 3 mm apical, 3 mm coronal and 8 mm apical above the apical foramen were compared using CBCT software. Amount of transportation and centering ability were assessed. The three groups were statistically compared with analysis of variance and Tukey honestly significant.

Results:

All instruments maintained the original canal curvature with significant differences between the different files. Data suggested that Wave One files presented the best outcomes for both the variables evaluated. Wave One files caused lesser transportation and remained better centered in the canal than One Shape and Rotary ProTaper files.

Conclusion:

The canal preparation with Wave One files showed lesser transportation and better centering ability than One Shape and ProTaper.