The Use of a Chelating Agent and Ultrasonic Tips in the Retrieval of Broken Rotary Ni-Ti

[drsushant]

Case Report One
Examination of the pre-operative radiographs reveals clearly the calcifying canal space of the two mesial root canals
This represents a contraindication to initiate shaping with Ni-Ti files without first preceeding them with stainless steel files and creating a glide path. Ignoring this point led to separation of two Ni-Ti files, one in each root (Fig. 3). The case seems hopeless at this point.

Each root was treated separately with a lot of attention and time to provide a proper result.

Although patency was finally achieved there were certain risks associated with this success. As seen in this post-operative radiograph the risk of a stripping was very high (Fig. 4). Nonetheless the case may be described as a success if one considers the perfect seal of the root canal system, and a failure if one considers the amount of dentin lost in the retrieval process.

Case Report Two
The second case shows a rotary Ni-Ti file separated in one of the mesial roots (Fig. 5), the location which appears to be impossible to see it under the microscope. Citric acid was placed into the canal and small hand files were used to create a bypass. A Pathfinder™ (Sybron Endo, Orange, CA) was useful in bypassing the separated file. The challenge was to reach working length and achieve patency at the apex and not to create damage in any way, such as ledging or perforation. Figure 6 shows the post treatment result.

Case Report Three
Two rotary Ni-Ti files were separated in this case. One was separated in the distal canal and one in the mesial canal (Fig. 7). The files where very tightly caught between the canal walls and the challenge here was to retrieve them in total from both canals, especially the one in the distal root that was separated beyond the apex. Figure 8 shows the post treatment result.

Conclusions
The most ideal management of separated instruments is to prevent the occurrence in the first place. The mesial root of lower molars often presents a specific challenge. A second curve (buccolingual) not seen on the radiograph combined with the mesio-distal curve offers a perfect trap for Ni-Ti files and 60 to 70% of all file separation occurs in this mesial root.

The irrigation protocol, the delivery and the sequence in which they are delivered is paramount when considering removal of the smear layer as well as the debris caught between the flutes of the files.

Ultra sonic tips are very handy instruments in these clinical situations, but care must be taken as the root canal is a very tiny space and any damage created, such as a perforation, ledging or weakening of the canal walls may be irreversible, leading to the loss of the tooth. The use of the dental operating microscope is not an option when treating the situations as described, but a must!