An ultrasonic tip of appropriate size must be selected, which will be long enough to reach the fragment and thin enough to allow good visibility while working under the microscope. The tip can stay in contact with the obstacle, at minimum power, and a dry canal, so that the clinician has constant visualization of the energized tip against the broken instrument. To maintain visibility, remove the dentinal dust, and cool the ultrasonic tip, the assistant is to constantly blow air using the Stropko three-way adapter with an appropriate Luer-lock tip. The ultrasonic tip is guided counterclockwise around the obstruction to remove the dentin and expose the coronal few millimeters of the fragment. During ultrasonic use, the broken instrument begins to loosen, unwind, then spin, and oftentimes it “jumps” out of the canal.
Microtube Removal Methods
Sometimes, in spite of creating good coronal and radicular access, exposing 2/3 mm of the broken instrument and ultrasonic trephining, a fragment cannot be removed. In these cases, microtube removal methods should be employed to remove the fragment, a strategy [43,46, 51] already mentioned for the removal of silver points. The most popular products are the IRS kit, which is a microtube designed to mechanically engage the broken instrument, and the Cancellier kit, which is designed to engage the fragment using cyanocrylate glue or self-curing dental resin. Clinically, it is important to allow sufficient curing time to promote a secure grip of the fragment.
As an alternative, the fragment can be bypassed using small hand files, perhaps aided by an aqueous chelator, to partially or completely loosen and, hopefully, remove it. As already stated, bypassing the fragment into the root canal apical to it may allow adequate disinfection. If a clinician is unable to bypass the fractured instrument, one should treat it as though a ledge could not be overcome.
The canal may be filled with warm plastified gutta-percha up to that point; sometimes, the portion of canal that was not reached fills automatically during the obturation phase. Naturally, the patient must be advised of the situation and the importance of regular checkups. Depending on whether a lesion or clinical symptoms are present, apicoectomy and retrofill, with or without surgical removal of the instrument, can be considered (see Chap. 10 in this book).
Once again, the rule that prevention is the best therapy holds true. A clinician must adhere to the following guidelines to prevent fracture of instruments in the root canal:
- • One must be familiar with the physical properties and limitations of each instrument.
- • The instruments must work in root canals flooded with irrigating solutions, never in dry canals.
- • Hand instruments should be precurved and used in the proper sequence.
- • Instruments must be worked delicately and preferably on withdrawal from the canal, not on entry.
- • Rotary or reciprocating instruments must never be forced into a tight canal; a sufficient glide path created by preceding hand instruments must be present.
- • Files must be replaced as soon as they are bent or their cutting edges are deformed, and they should always be considered single use.
- • Rarely instruments may have manufacturing defects, which increase the probability of fracture.
The diagnosis of instrument fracture is suggested by the observation of sudden inability to probe a canal from which the last instrument has emerged slightly shorter. A radiograph may confirm the presence of an instrument fragment.
If attempts to remove the fragment are successful, it is advisable to obtain another radiograph to document the removal. For legal reasons, if an instrument fractures, it is essential that the patient be informed .
In cases when the broken file segment is unable to be retrieved, and in the presence of signs and/or symptoms, surgery or extraction may be the best treatment option.