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Research Articles
Pattern of endodontic instrument separation and factors affecting its retrieval: a 10-year retrospective observational study in a postgraduate institute
Velmurugan Natanasabapathy, Aswathi Varghese, Paul Kevin Abishek Karthikeyan, Srinivasan Narasimhan
Restor Dent Endod 2025;50(1):e7.   Published online February 19, 2025
DOI: https://doi.org/10.5395/rde.2025.50.e7
AbstractAbstract PDFPubReaderePub
Objectives
This study aimed to assess the pattern of endodontic instrument separation, their retrievability, and factors affecting its retrieval, in a postgraduate institute.
Methods
Cases referred for the management of separated endodontic instruments (SEI) from 2013 to 2023 were considered for this study. Data related to demographics, tooth type, file type, and retrieval were documented in an Excel sheet. Eight prognostic factors assumed to influence the retrieval were analyzed in this study. The secondary aim was to compare the pattern of SEI and retrievability between conventional nickel-titanium files and newer generation heat-treated nickel-titanium files. Retrieval was attempted by a senior endodontist under the dental operating microscope. Various ultrasonic tips and a Broken Tool Removal loop system were used during retrieval. Simple descriptive statistics were performed. Binomial logistic regression was done to identify the effect of the eight prognostic factors on the retrieval outcome.
Results
A total of 190 SEI was reported. SEI occurred more often in posterior teeth than anterior teeth, mandibular arch than maxillary arch, and in larger files than smaller files. Separation occurred more often in the apical third compared to the other levels. Retrieval was attempted in 88 cases and successful in 70 cases (79.5%). The larger taper and apical position of the SEI negatively influenced the retrieval by 1.4 and 8.7 times, respectively.
Conclusions
Retrieval of SEI was successful in the majority of the cases. An increase in taper and apically placed SEI negatively impacted the retrieval. There was no difference in the pattern of separation nor retrievability between conventional nickel-titanium files and newer generation heat-treated nickel-titanium files.
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Influence of operator's experience level on lifespan of the WaveOne Primary file in extracted teeth
Abdulrahman Mohammed Saleh, Saeid Tavanafar, Pouyan Vakili-Gilani, Noor Jamal Al Sammerraie, Faahim Rashid
Restor Dent Endod 2013;38(4):222-226.   Published online November 12, 2013
DOI: https://doi.org/10.5395/rde.2013.38.4.222
AbstractAbstract PDFPubReaderePub
Objectives

The aim of this study was to assess the influence of operator experience level on the lifespan of the WaveOne Primary file (Dentsply Maillefer, Ballaigues, Switzerland) in extracted teeth.

Materials and Methods

Moderately curved canals of extracted maxillary and mandibular molars were randomly distributed into 2 groups: experienced and inexperienced operators. Ten files were allocated to each group (n = 10). Each canal was prepared until the working length was reached, and the same file was used to prepare additional canals until it separated. The number of canals prepared before file separation was recorded. The fragment length of each file was measured, and the location of the fragment in the canal was determined. Data were statistically analysed using the independent 2-sample t-test.

Results

The 2 operators prepared a total of 324 moderately curved canals of maxillary and mandibular molars. There was no significant intergroup difference in the mean number of canals prepared (p = 0.27). The average lifespan of the WaveOne Primary file was 17.1 and 15.3 canals, and the longest lifespan was 25 and 20 canals, when used by experienced and inexperienced operators, respectively. There were no statistically significant intergroup differences in separated fragment length and location.

Conclusions

Within the limitations of this study, operator experience level appears to have no effect on the lifespan of the WaveOne Primary file in preparation of moderately curved canals. Single teeth with multiple canals can be prepared safely even by a novice operator by using a single file.

Citations

Citations to this article as recorded by  
  • Microstructural, microchemical, and mechanical changes associated with the clinical reuse of two nickel–titanium endodontic instruments
    Felipe Augusto Restrepo-Restrepo, Viviana Andrea Holguín-Vásquez, Syldana Julieth Cañas-Jiménez, Paula Andrea Villa-Machado, Sara Ochoa-Soto, Claudia Patricia Ossa-Orozco, Sergio Iván Tobón-Arroyave
    Dental Research Journal.2021; 18(1): 48.     CrossRef
  • Fracture incidence of WaveOne Gold files: a prospective clinical study
    C. S. P. Bueno, D. P. Oliveira, R. A. Pelegrine, C. E. Fontana, D. G. P. Rocha, J. L. Gutmann, C. E. S. Bueno
    International Endodontic Journal.2020; 53(9): 1192.     CrossRef
  • Current Assessment of Reciprocation in Endodontic Preparation: A Comprehensive Review—Part II: Properties and Effectiveness
    Gianluca Plotino, Hany Mohamed Aly Ahmed, Nicola Maria Grande, Stephen Cohen, Frédéric Bukiet
    Journal of Endodontics.2015; 41(12): 1939.     CrossRef
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Effect of internal stress on cyclic fatigue failure in .06 taper ProFile
Hye-Rim Jung, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
Restor Dent Endod 2012;37(2):79-83.   Published online May 18, 2012
DOI: https://doi.org/10.5395/rde.2012.37.2.79
AbstractAbstract PDFPubReaderePub
Objectives

The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of .06 taper ProFile.

Materials and Methods

Length 25 mm, .06 taper ProFile (Dentsply Maillefer), and size 20, 25, 30, 35 and 40 were used in this study. To give the internal stress, the rotary NiTi files were put into the .02 taper, Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. Rotary NiTi files were grouped by the number of induced internal stress and randomly distributed among one control group and three experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For cyclic fatigue measurement, time for separation of the rotary NiTi files was recorded. The fractured surfaces were observed by field emission scanning electron microscope (FE-SEM, SU-70, Hitachi). The time for separation was statistically analyzed using two-way ANOVA and post-hoc Scheffe test at 95% level.

Results

In .06 taper ProFile size 20, 25, 30, 35 and 40, there were statistically significant difference on time for separation between control group and the other groups (p < 0.05).

Conclusion

In the limitation of this study, cyclic fatigue failure of .06 taper ProFile is influenced by internal stress accumulated in the files.

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Effect of internal stress on cyclic fatigue failure in K3
Jun-Young Kim, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
Restor Dent Endod 2012;37(2):74-78.   Published online May 18, 2012
DOI: https://doi.org/10.5395/rde.2012.37.2.74
AbstractAbstract PDFPubReaderePub
Objectives

This study aimed to evaluate the relationship between the cyclic fatigue of a K3 file and internal stress intentionally induced until the activation of the auto-stop function of the torque-controlled motor.

Materials and Methods

K3 (Sybron Endo) .04 and .06 taper, size 25, 30, 35, 40 and 45 were used in this study. To give the internal stress, the K3 files were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until the activation of the auto-stop function of the torque-controlled motor. The rotation speed was 300 rpm and torque value was 1.0 N·cm. K3 were grouped by the number of induced internal stress and randomly distributed to 4 experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For measuring the cyclic fatigue failure, the K3 files were worked against a sloped glass block and time for file separation was recorded. Data was statistically analyzed Statistical analyses were performed using two-way ANOVA and Duncan post-hoc test at p < 0.05 level.

Results

Except .04 taper size 30 in Stress 1 group, there were statistically significant differences in time for file separation between control and all experimental groups. K3 with .04 taper showed higher cyclic fatigue resistance than those of .06 taper.

Conclusion

In the limitation of this study, the cyclic fatigue of the K3 file was influenced by the accumulated internal stress from use until the auto-stop function was activated by the torque-controlled motor. Therefore, clinicians should avoid the reuse of the K3 file that has undergone auto-stops.

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Case Report
Management of separated file in the root canal
Hye-Jeong Kim, Hoon-Sang Jang, Se-Hee Park, Kyung-Mo Cho, Jin-Woo Kim
J Korean Acad Conserv Dent 2006;31(3):161-168.   Published online May 31, 2006
DOI: https://doi.org/10.5395/JKACD.2006.31.3.161
AbstractAbstract PDFPubReaderePub

During root canal preparation procedures, the potential for instrument separation is always present. Files, a lentulo, a Gates-Glidden (GG) bur or any manufactured obstruction can be left behind in the canal. Nickel-titanium (NiTi) rotary files are in common usage in these days. Despite their undeniable advantages, there is a potential risk of separation within the canals. It is very rapid, unpredictable, and creates a great deal of stress for the practitioner.

When an endodontic instrument separates, the best option is to remove it. Ultrasonic instruments and microscopes have improved the success rate for removing separated instruments. But it is difficult and not always possible. Therefore prevention is the key.

In this case report, several management methods of separated file in the canal are presented.

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Original Article
Lifetime and fracture patterns of NiTi rotary files in molars
Jin-Woo Kim, Byung-Doo Ahn, Se-Hee Park, Hye-Jin Shin, Kyung-Mo Cho
J Korean Acad Conserv Dent 2005;30(3):184-192.   Published online May 31, 2005
DOI: https://doi.org/10.5395/JKACD.2005.30.3.184
AbstractAbstract PDFPubReaderePub

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth.

Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation.

The results were as follows :

1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups.

2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files

3. Separations of instruments were occurred at the midpoint of curvatures within the canals.

4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples.

Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.

Citations

Citations to this article as recorded by  
  • Developing evidence-based clinical imaging guidelines for the diagnosis of vertically fractured teeth
    Ki-Hong Kim, Jo-Eun Kim, Sam-Sun Lee, Chena Lee, Miyoung Choi, Hwan Seok Yong, Seung Eun Jung, Min-Suk Heo, Kyung-Hoe Huh
    Oral Radiology.2024; 40(4): 471.     CrossRef
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