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» Articles -> Smile Magazine Issue 2 May 2006-> Endodontic Management of Broken Instruments
Dated : 2006-05-01
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Endodontic Management of  Broken Instruments

     » By: Dr.Moh’d Hammo
 
                BDS, DESE.
                Endodontist / Private Practice

      E-mail: dentist_h@yahoo.com 

 

Broken, separated, or “disarticulated” instruments can occur during the day-to-day practice of endodontics. No dentist should have a particular tolerance for broken instruments; however, it is important to know how to prevent and treat these incidents and how to explain the situation to the patient.
In fact, broken instruments are not the direct cause of endodontic therapy failure; rather, they may lead to accompanying uncleaned and unfilled spaces within the root canal system. The broken instruments impede the mechanical instrumentation of the infected root canal apical to the instrument (Fig.1), and that is the primary cause of treatment failure (1).
Breaking files is not malpractice; however, failing to inform a patient that a separation has occurred is. Here’s how to best manage this situation: Calmly inform the patient that, during treatment, a sterile piece of the instrument separated from the file and will be removed or bypassed and incorporated into the final fill. Patient should know that a separated file does not mean that the tooth will fail. 

» (Fig. 1): Fractured instruments will impair complete, thorough débridement of the root canal system. 

 

How to prevent instruments breakage?

- The condition of files should be monitored before usage: when you see evidence of unwinding (shiny mark on the file) (Fig.2), discard the file immediately (2). Dental assistant should have alcohol gauze pads to wipe off the file after every use in canal. Ni-Ti files are more susceptible to breakage than stainless steel files. They can be broken without any visible signs that indicate the deformation (Fig.3), so they should be discarded before visual signs of untwisting are seen (3).  Prevention of Ni-Ti files breakage may be greatly facilitated by thinking of negotiating and shaping files as disposable items. Simply discarding all instruments after the completion of each endodontic case will reduce breakage, lost clinical time, and upsets. 

» (Fig. 2): Do check the flutes of files before every use. If it is bent, stretched, or has a shiny spot, discard it immediately. 

 

 

  

» (Fig. 3): After 4 canals preparation, stainless steel file showed signs of untwisting (arrows), while Ni-Ti files did not. This means it might break without warning. 

- The files should never run dry, instead they should be kept in a moist environment (NaOCl or EDTA) while preparing root canals (4). At the beginning, coat the file with lubricant like RC Prep® (15% EDTA, 10% urea peroxide: Premier Dental Products, Philadelphia, USA), or File-eze® (Ultradent).The lubricant will help the file function in a smooth manner, and it will emulsify the tissue in the canal.

- The creation of straight line access and a glide path will help files to perform at maximum capability (5). Incomplete access will increase the stress on the file and causes files breakage (Fig.4). 

» (Fig. 4): Failing to have direct and complete Access (upper arrow) has hindered endodontic treatment and caused breakage of file (lower arrow). 

 

 

- Leaning on the file and forcing it to “work” will only result in fracture. One should be gentle and takes his time while preparing root canal system.

- Preparing the canal in a crown-down sequence (6) , which means preparing the coronal one third first, the middle one third second, and finally the apical third last, will decrease the stress over the files, and improve the tactile sensation (Fig.5). 

 » (Fig. 5): One of the paradigm shifts occurring in endodontics today is the concept of doing the apical preparation last instead of first. By creating shape from coronal to apical direction, the canal is predictably and safely prepared.

 

 

 

 

 

How to treat a canal with broken instruments?

There are basically three possible approaches that may be encountered when treating these cases: (I) Retrieval, (II) Bypass and sealing the fragment within the root canal space, (III) True blockage.


Factors Influencing Broken Instrument Removal

Success of retrieval depends on the canal anatomy, what type of metal the piece is made out of (stainless steel files tend to be easier to remove), the location in the canal of the fragment, the plane in which the canal curves, the length of the separated fragment, and the diameter of the canal itself (7). In general, if one third of the overall length of an obstruction can be exposed, it can usually be removed.
Instruments that lie in the straightaway portions of a canal can typically be removed. More challenging are separated instruments that lie partially around canal curvatures, but these can often be removed if straight-line access can be established to their most coronal extents. If the broken instrument segment is apical to the curvature of the canal and safe access cannot be accomplished, then removal is usually not possible.


Techniques for Broken Instrument Removal

Prior to commencing retrieval efforts, special attention is directed toward preoperative radiographs and working films to better appreciate the thickness of the dentinal walls. Coronal access is the first step in the removal of broken instruments, where straight-line access to all canal orifices should be created, and special attention should be directed toward flaring the axial wall that approximates the canal holding the broken instrument.
Radicular access is the second step required in the successful removal of a broken instrument. Hand files are used serially small to large, coronal to the obstruction, to create sufficient space to safely introduce GG drills (8). They are used like “brushes” to create a smooth-flowing funnel that is largest at the orifice and narrowest at the obstruction.
When the canal, coronal to fractured instrument, has been optimally shaped, then bypass techniques may be employed to remove a broken file segment. Prior to performing any radicular removal techniques, it is wise to place cotton pellets over other exposed orifices, if present, to prevent the nuisance re-entry of the fragment into another canal system. In combination with lubricants, a precurved no.10 stainless file is used to bypass the fractured instrument. If this is successful, Hedstr?m files are used to try to grasp and remove the segment (Fig.6). Then the canal is cleaned, shaped and obturated to its new working length (9).
  
 

(Fig. 6): A. Fractured instrument at the mesial root of the upper 1st molar.
                B. Bypassing the broken segment with no. 10 K-file
                C. Retrieval of broken file
                D. Obturation.

On occasions, the clinician may create excellent coronal and radicular accesses, bypass the fractured instrument, but could not retrieve the fractured instrument. In this case, the canal is cleaned and shaped, and the segment is incorporated into the obturation (10) (Fig.7).
If the fractured instrument cannot be bypassed, then microsonic techniques may be employed to remove a broken file segment. Dental microscope, which allows clinicians to visualize most broken instruments, and ultrasonic instrumentation have dramatically improved the potential and safety of removing broken instruments
(11)
(Fig.8) 

» (Fig. 7):      

 A. Fractured instrument at the apical portion of the distal canal of the upper 2nd molar.

 B. Bypassing the broken segment with no. 10 K-file, and failed to retrieve the broken file. 

 C. Incorporation of the broken file into the obturation.

(Fig. 8): A. Dental microscope. / B. Microscopes, with its different magnification power, are of utmost important for visualization of fractured instruments. / C. The use of Ultrasonic instruments have revolutionized the art of endodontic .They have multiple uses and have become an integral part of the endodontic instruments. 

Attempting to remove a fragment without adequate visualization highly risks perforation, as root curvatures can easily mislead the clinician to remove dentin where it will have little benefit toward file removal.
An appropriately sized ultrasonic instrument is selected, such that its length will reach the broken obstruction and its diameter will passively fit into the previously shaped canal. The tip of this ultrasonically selected instrument is placed in intimate contact against the obstruction and typically activated within the lower power settings. The selected instrument is moved lightly in a counter clockwise direction around the obstruction. This ultrasonic action trephines, sands away dentin, and exposes the coronal few millimetres of the obstruction. Typically, during ultrasonic use the obstruction begins to loosen, unwind, and then spin (12,13). Gently wedging the energized tip between the tapered file and the canal wall often causes the broken instrument to abruptly “jump out” of the canal
(Fig.9).

 » (Fig. 9):

A. Fractured instrument at the middle third of the distal canal of the upper 2nd molar.
 B. Broken file was visualized by dental microscope.
 C. Retrieval of the fractured file using ultrasonic tips.
 D. Complete cleaning and shaping was done.
 E. obturation of all root canals.

True blockage also does not mean automatic failure. If the bulk of the canal space has been soaking in full strength sodium hypochlorite, and the critical concentration of bacterial contaminants within the canal are sufficiently reduced, the body may heal around this root as well (14).

Conclusion

Prevention of file separation is always more desirable than attempted removal. Adhering to proven concepts, integrating best strategies, and utilizing safe techniques during root canal preparation procedures will virtually eliminate the broken instrument procedural accident.


References

1-  Louis M.: Do procedural errors cause endodontic treatment failure? JADA, Vol. 136, 2005.
2- Richard Mounce. : The heartache of separation, Dentistry Today, April, 2003.
3- Rbeiez R.: Profile®, Guide lines for safe use and predictable results, Arab Dent.J, Vol.3:6, 1998.
4- Robert Frank. : Endodontic Mishaps, Endodontics, 5th ed., 785, 2002.
5- Schilder H.: Cleaning and Shaping the Root Canal , Dent. Clinic of N. Am., 18:269, 1974.
6- Marshall et al.: A crown-down pressurless preparation, Oregon Un., 1980 .
7- Ruddle CJ.: Broken Instrument Removal: The Endodontic Challenge, Dentistry Today, July 2002.
8- Ruddle CJ. : Nonsurgical endodontic retreatment. In: Cohen S, Burns RC, eds. Pathways of the Pulp. 8th ed. St Louis, Mo:   Mosby; 2002:875-929, chapter 25.
9- Gilbert Bo. : Retreatment in Endodontics, Oral Surg. 64:333-8, 1987.
10- Ralan Wong : Microscopic management of procedural errors, Dent. Clinic of N. Am., 41:455, 1997.
11- David Clark: The Operating Microscope and Ultrasonics; a Perfect Marriage, Dentistry Today, June, 2004.
12- Mian Iqbal: Non surgical ultrasonic endodontic instruments, Dent. Clinic of  N. Am., 48:19-34, 2004.
13- Ruddle CJ.: Microendodontic nonsurgical retreatment  in endodontics, Dent Clin of North Am. 1997; 41:429-454.
14- Steven J. Cohen, Rips, Strips and Broken Tips: Handling the Endodontic Mishap, Oral Health, May 2005.
 

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