REMOVAL OF INSTRUMENT DEBRIS: MEANS AND TECHNIQUES
INTRODUCTION
The fracture of an endodontic instrument is an operative accident, which can occur during canal preparation following its accidental blockage in the canal, this will occur especially in the presence of curvature at the level of the apical third.
The existence of intracanal fragments will prevent access to the entire canal system, thus compromising canal disinfection and obturation procedures.
The risk of instrumental fracture has increased in recent years with the increasing use of rotary instrumentation for canal shaping.
I. PREVALENCE
Several recent studies have shown that the risk of instrumental fracture is 3.5%.
Among the fractured instruments, 78.1% are nickel titanium rotary instruments, 15.9% are steel hand instruments, 4% are lentulos and 2% are lateral compaction rammers.
Most instruments fractured in the apical third of the root (77.1%).
Rotary instruments fracture more often in curved canals than in straight canals, and half of the fractured instruments are found in the mesial roots of mandibular molars.
II. ETIOLOGIES
Instrument fracture means an unbearable increase in the sheath effect produced by the parietal resistance on the blades of the instrument. This effect is due to:
– excessive fatigue of the endocanal instrument (repeated sterilization),
– scraping carried out with the application of excessive force to the instrument,
– unfavorable anatomical factors (angled canal).
-non-compliance with torque or rotation speed.
III. INSTRUMENTAL FRACTURE AND PROGNOSIS
Several studies have shown that there is a weak relationship between the presence of a fractured instrument fragment in the root canal network and endodontic failure.
When an instrumental fracture occurs, the factors that may influence the prognosis are: the initial state before treatment (infected tooth or not), the aseptic conditions, the stage of treatment during which the fracture occurs, the location of the fragment.
In the context of endodontic retreatment, the therapeutic objective is to neutralize the canal space and preserve dental tissue as much as possible and not to eliminate the fragment.
IV. MEANS AND TECHNIQUES
Before any action, it is first necessary to confirm the anatomical situation of the broken fragment, by retroalveolar radiography and to evaluate the possibilities of recovering the fragment remaining in the canal, then the practitioner must choose between several management solutions (removal or not), depending on:
• Of the initial pulp status.
• From the channel in which the fragment is located,
• From the position of the instrument.
• The type of instrument and the size of the fragment.
• Canal anatomy, particularly curvatures.
• Weakening of the tooth caused by tissue loss.
• From the time of occurrence of the fracture in the shaping.
•Technical platform available (microscope, inserts, etc.).
The technical means for removing these fragments have been considerably improved in recent years, mainly thanks to ultrasonic instrumentation and the operating microscope.
The ability to see the fragment greatly facilitates its release and grasping, thus requiring specific micro-instrumentation and adopting a systematic clinical approach.
REMOVAL OF INSTRUMENT DEBRIS: MEANS AND TECHNIQUES
1. IMPROVE CORONARY ACCESS
Instrumental fracture is most often associated with a canal curvature; the first step must be to widen the canal coronally by straightening the curvature, using Gates drills working against the wall opposite the curvature.
It is necessary to advance the Gates drill No. 3 to the coronal portion of the fragment in order to improve access and create a reflux space to evacuate the fragment in a coronal direction.
2. BYPASS ATTEMPT
-The operator must first attempt a By-Pass procedure.
-The coronal part of the canal is filled with a lubricating gel.
-A small diameter hand file passes next to the instrument, if the initial path of the canal is found in this way, the fragment can either be removed using a file mounted on an ultrasonic handpiece, or left in place and embedded in the obturation after manual shaping.
-If the bypass attempt fails, the obturation must be done coronally to the fragment (high risk of root perforation in the event of an attempted removal).
-In all cases, the evolution of symptoms and radiological signs must be monitored.
-The rather favorable prognosis of the tooth, despite the presence of a fractured instrument.
Indications
– Must be attempted in all cases
Benefits
– Simple procedure, requiring no specific equipment
– Dental tissue saver
– Does not require the use of an operating microscope
Disadvantages
– Not always possible
3. TECHNIQUES FOR REMOVING A BROKEN INSTRUMENT
To remove a fractured instrument , it must be possible to free it from its parietal constraints. There are two techniques:
- The ultrasonic technique : using a very fine insert, the practitioner destroys the dentine surrounding the instrument and tries to rotate the fragment to unscrew it or apply the insert directly to the fragment and abrade it until it disappears, taking care not to propel it apically.
This is the least invasive technique, it requires very good visual control (use of an operating microscope), a lot of patience and several replacement inserts.
- Technique called “microtubes”
The principle consists of using a trephine to drill the dentine around the fragment and thus release it from the dentinal walls . Then a tube is placed around the instrument, with the aim of blocking the fragment inside using a punch (Masseran kit, IRS), or by glue.
It is important to know that there is no standardized, safe and step-by-step method for removing a fragment.
First , access to the instrument must be achieved using a Gates drill No. 4 to relocate the orifice, followed by drills No. 2 and 3 positioned in contact with the fragment (coronal or median third).
The next steps involve using an operating microscope to precisely visualize the head of the fractured instrument.
A platform is then arranged around the coronal part of the fragment using a Gates drill No. 3 whose head is cut at its widest part.
In a second step, the dentin around the fragment is removed using either a fine ultrasonic insert (ET 25, Satelec; Pro-Ultra 6, 7, 8, Dentsply; RT3, EMS)( Fig ), or a trephine (Masseran® Kit, Endorescue®,).
The trephine of the Endorescue® kit must be used at a slow speed (300 rpm) and in a counterclockwise direction. Once the fragment has been released over a length of 1 to 2 mm, it can be evacuated in the coronal direction either directly by the trephine of the Endo Rescue® kit, or by the vibrations of the ultrasonic insert, or by an extractor (Masseran ® kit), or by a needle of the appropriate size filled with composite . In the latter case, after the composite has set (4 minutes), the fragment will be unscrewed in a counterclockwise direction.
REMOVAL OF INSTRUMENT DEBRIS: MEANS AND TECHNIQUES
Description of the Masseran box
The system is composed of:
-trephines (The trephine is used to free the coronal part of the fragment at the expense of the dentinal walls ,
– Calibration gauges
-A handle for manual trepanation
-Two calibrated tubes for manual gripping
The use of the Masserann kit ( Fig.4,5 ) is indicated for the extraction of small caliber metal objects, encountered at the level of the straight part of the root canals up to the middle 1/3 of the root canal.
o ADVANTAGES OF TECHNIQUE USING THE MASSERAN SYSTEM
• Effective technique
o DISADVANTAGES
• More mutilating technique
• Requires an operating microscope to properly position the trephine and/or extractor
o INDICATIONS
• Long fragments (length greater than 3mm)
- Other systems from the Masseran system
Several instrument breakage extraction systems such as the Instrument Removal System (IRS) and the Endorescue are particularly inspired by the Masserann extractor, but are much finer.
-IRS System Three sizes have been designed with external diameters measuring 0.60, 0.80 and 1.00 mm. The two finest are specifically intended for use in depth, beyond the coronal third
Endorescue System
It has the particularity of containing small diameter instruments. This kit is composed of 5 instruments: a cylindroconical cutter, 2 Gates drills, 1 pointer and 1 trephine.
The external diameter of the instruments intended to descend into contact with the head of the instrument is 0.90 mm (also available in 0.70 mm), the equivalent of a Gates drill no. 3. This technique is therefore much less damaging than other techniques in its category.
NOTE If the fragment is located beyond a curvature or at the apical third, it is best not to attempt removal.
4. ENDODONTIC SURGERY
Surgical treatment should not be considered as an alternative to attempted removal, but as a complementary treatment.
Surgical solution will be considered in case of failure of the orthograde removal attempt and in the presence of persistence or appearance of a pathology and also in the case where the instrument passes via the apex in the apical region. Current endodontic surgery techniques allow cleaning and disinfecting the portion of the canal located apically to the fragment before retro obturation.
V. PREVENTION OF INSTRUMENTAL FRACTURES
Instrument fracture can be avoided by detecting structural damage to the instrument which is however invisible to the naked eye.
Several solutions are possible:
• Manufacturers suggest disposing of instruments after a certain number of cycles.
• replace instruments already used in curved, calcified or very thin canals.
• Avoid subjecting NiTi instruments to excessive stress from twisting and bending forces.
• Work with low speed and torque: between 300 and 600 rpm.
CONCLUSION
The removal of fractured endodontic instruments is always a challenge, even for the most experienced endodontist. There are a wide variety of techniques proposed, but no miracle method allows to succeed, with certainty, in ridding the canal of the metal fragment that obstructs it. Recent technologies based on the visualization of the intimacy of the endodontic system by the microscope, and on ultrasonic instruments dedicated to endodontics, particularly long and thin, but resistant, made it possible to remove instrument breakage with minimal damage.