**Management of Broken Files in the MB Canal of Lower Molars: An Academic Perspective**
**Introduction**
The management of broken files in the mesiobuccal (MB) canal of lower molars is a critical aspect of endodontic
treatment. The fracture of endodontic instruments during root canal procedures can pose significant challenges and
impact the overall prognosis of the treatment. This article aims to provide a comprehensive overview of the causes,
implications, and management strategies for broken files in the MB canal of lower molars.
**Causes of Instrument Fracture**
The fracture of endodontic instruments can occur due to various factors, including flexural and torsional fatigue,
improper use, and manufacturing defects. Nickel-titanium (NiTi) rotary instruments, commonly used in modern
endodontics, are particularly susceptible to fracture due to their high flexibility and cyclic fatigue resistance. The
incidence of instrument fracture ranges from 0.7% to 6% of cases.
**Implications of Broken Files**
The presence of a broken file in the MB canal can hinder the proper cleaning and shaping of the root canal system,
potentially leading to treatment failure. The main prognostic factor in such cases is the existence or non-existence of
preoperative periradicular pathosis. While the fracture of an instrument itself may not cause treatment failure,
fragments present in the root canal can prevent proper preparation and disinfection of the canal space.
**Management Strategies**
The management of broken files in the MB canal involves two primary approaches: bypassing and removal. The
choice of technique depends on the location, length, and engagement of the broken file within the canal.
**Bypassing Technique**
Bypassing the broken instrument is considered a conservative approach that minimizes dentin removal. This
technique involves locating a tiny space behind the broken instrument using precurved small K-files (sizes 6, 8, 10)
in a watch-winding motion, often facilitated by the use of EDTA gel. Once the space is located, the K-file is
engaged, and a picking motion is used to bypass the broken instrument. Multiple radiographs should be taken to
confirm the bypassing after each file size.
**Removal Technique**
The removal of broken files can be achieved using various techniques, including the use of ultrasonic tips, microtube techniques, and grasping techniques. The choice of technique depends on factors such as the length and
engagement of the broken file, as well as its location within the canal.
1. **Ultrasonic Technique**: This technique involves the use of thin ultrasonic tips to expose 1-2 mm of the coronal
part of the fractured instrument. The ultrasonic vibrations help to dislodge the broken file, allowing for its removal.
2. **Micro-Tube Technique**: This technique uses a tube (e.g., flowable composite tip) to engage the exposed part
of the broken file. Dual-cure resin cement or super glue is injected inside the tube, and after a few minutes, the tube
is pulled out, bringing the broken file with it.
3. **Grasping Technique**: This technique involves the use of micro-tweezers, pliers, or forceps to grasp and
remove the broken file. The coronal part of the broken file is exposed using ultrasonic tips or trephine burs, and the
grasping device is used to engage and pull out the file.
**Clinical Decision-Making Algorithm**
The clinical decision-making process for managing broken files involves several steps:
1. **Radiographic Evaluation**: Assess the location, length, and curvature of the broken file using radiographs.
2. **Instrument Exposure**: Create straight-line access to the broken file using Gates-Glidden drills or large rotary
files.
3. **Technique Selection**: Choose the appropriate technique (bypassing or removal) based on the specific case
factors.
4. **Execution**: Perform the selected technique with precision and care to minimize damage to the surrounding
dentin.
5. **Follow-Up**: Monitor the treated tooth for signs of healing or complications, and consider additional
interventions if necessary.
**Conclusion**
The management of broken files in the MB canal of lower molars is a complex and challenging aspect of endodontic
treatment. Understanding the causes, implications, and management strategies is essential for achieving successful
outcomes. By employing appropriate techniques and following a structured clinical decision-making process,
endodontists can effectively manage broken files and improve the prognosis of root canal treatments.
: [Management of broken files - A clinical approach](https://endodontics.styleitaliano.org/management-of-brokenfiles-a-clinical-approach/)
: [Broken Instruments – Clinical Decision Making Algorithm](https://www.aae.org/specialty/broken-instrumentsclinical-decision-making-algorithm/)
: [Management of broken files - A clinical approach - Part 2](https://endodontics.styleitaliano.org/management-ofbroken-files-a-clinical-approach-part-2/)