Lesson 16 – Part 1 : Bypass a Broken File

What is a Broken File?

A broken file refers to separation of an endodontic instrument inside the root canal system.

Also called “separated file”.

It usually involves:

• Ni-Ti rotary files
  

  
• Stainless-steel hand files
  

  

Why it concerns us?

The fragment becomes lodged within the canal path and obstructs further cleaning, shaping, and disinfection.

Why is it Clinically Important?

• Compromises prognosis if located in an infected canal.
• Prevents access to the canal portion below the fragment.
• Reduces effectiveness of canal disinfection.

Quick Quiz

Prognosis Depends On

1. Location (coronal / middle / apical third)
2. Canal anatomy
3. Presence of infection before breakage
4. Operator skill
5. Length of fractured segment
6. Type of instrument

Factor	Favorable	Unfavorable	Scientific Rationale
Location	Coronal > Middle third	Apical third	Apical fragments block disinfection and harbor bacteria.
Canal Anatomy	Straight canal	Sharp curvature	Curved canals increase risk of perforation and transportation.
Infection	No apical periodontitis	Pre-existing infection	Infected canals cannot be disinfected apically.
Operator Skill	Microscope + ultrasonics	Limited equipment	Better equipment improves bypass or retrieval.
Fragment Length	Short fragment	Long fragment	Long fragments lock mechanically.
Instrument Type	Stainless steel	Ni-Ti rotary	NiTi fractures without unwinding.

Causes of Instrument Separation

Instrument Factors

• Cyclic fatigue — repeated flexing in curved canals leading to fracture.
• Torsional stress — when file tip locks but shaft keeps rotating.
• Manufacturing defects
• Corrosion or chemical weakening

Operator Factors

• Inadequate glide path
• Improper file use
• Reusing files excessively
• High rotational speed
• Inadequate lubrication
• Failure to irrigate frequently

Quick Quiz

How to Prevent Instrument Separation

Pre-operative prevention

• Study preoperative radiographs or CBCT.
• Achieve straight-line access.

Proper Use of Rotary Files

• Use short light pecking motions
• Do not force files
• Clean file flutes frequently
  

  
• Replace files early
• Use torque-controlled motors.
• Irrigate frequently with NaOCl.
• Use EDTA lubrication.
• Track number of file uses
• Inspect files for unwinding or cracks
  

  

Management of Broken Files

Two major approaches:

• Bypass the fragment
• Retrieve the fragment

If both fail → surgical removal or extraction.

Bypassing the Broken Instrument

Sometimes the safest approach is not removing the fragment but bypassing it.

Bypass means sliding a small hand file beside the fragment until reaching working length.

Once the path is regained, the fragment becomes part of the obturation.

When do we choose to bypass?

• Fragment in apical third
• Curved canals
• Long fragment
• When removal may cause perforation or dentin loss.

Clinical rule: If removing the fragment is risky → bypass it.

Instruments Needed for Bypass

• Dental operating microscope
• Small SS files (#6 #8 #10 #12 #15)
• EDTA gel
• NaOCl irrigation
• Ultrasonic tips

Step-by-Step Bypass Procedure

Step 1 — Improve access

Create straight-line access

Step 2 — Create space coronally

Use ultrasonic tips to create a 0.5–1 mm cuff around fragment.

Step 3 — Pre-bend small file

Use #10 K-file with sharp bend at the last 2–3 mm.

A straight file will not find the pathway.

Step 4 — Watch-winding motion

Use gentle watch-winding movement beside the fragment.

Never apply pushing pressure.

Step 5 — Enlarge pathway

Once #10 passes the fragment:

• #10 → #15 → #20
  

  
  

  
• Then rotary shaping

Step 6 — Confirm patency

When a #15 K-file reaches working length → patency restored.

Step 7 — Complete treatment

• Clean and shape normally
• Fragment remains inside canal.
• Considered part of obturation.

Final Quiz