Fig. 1

Upon clinical examination, the presence of a good ferrule effect was noticed specially in the buccal aspect of the tooth. Nonetheless, a leaking cast post and core on the lingual limit of the restoration was present. Therefore a Non Surgical root canal retreatment was planned prior to a full coverage crown. 

Fig. 2

After mandibular block anesthesia using Articaine 4 % with epinephrine and a buccal infiltration, the tooth was isolated with W8A wingless clamp and medium rubber dam. An additional isolation was also obtained by injecting the liquid dam around the preparation.

Fig. 3

The core separation was initiated under microscope magnification X10 using a transmetal bur. 

Fig. 4

The metal core aspect after the use of the transmetal bur. 

Fig. 5

A long Surgical round carbide bur was used to separate the 2 parts precisely and completely without touching the tooth structure.

The image shows the exposure of the cement covering the pulpal floor after the 2 parts were partially separated by using the round surgical long carbide bur.

Removal of the mesial part of the metal core.

The removal of the distal part took around 3 minutes. This was done under coolant irrigation with breaks after each cycle of 15 seconds of vibration as suggested by Domenici et al. (2005) to avoid any rase of temperature over 10℃. 

Fig. 6

Post and core removed from the distal root

Fig. 7

After removing the cast post and core, remaining cement should be removed from the pulp chamber using an ultrasonic tip, the ET20, and the decay cleaned. 

Cement remnants cleaned with ultrasonic tip under coolant water irrigation.

Fig. 8

After cleaning the cement, caries control should be performed specially on the lingual wall before starting the retreatment procedure.

Filling material is then retrieved from all the canals using a mechanical technique without dispensing any solvent in that particular case. The video shows as example the removal of the gutta-percha  in the coronal third from the mesio-buccal canal with a rotary instrument.  

The video shows an exemple of the shaping procedure in the mesio-buccal canal with a Ni-Ti instrument.

Fig. 9

The pulp chamber aspect after obturation. 

Fig. 10

final Xray after 3D filling with the warm vertical compaction and backpack using the injecting technique. 

Conclusions

Post removal is mandatory in many cases specially when a non surgical retreatment is indicated with an inadequate coronal restoration. In fact, surgical procedure can only be performed when the coronal restoration is satisfying. Posts can be drilled with burs, pulled out using several devices or vibrated with ultrasonic appliances.  In this case we opted for a combination of grinding for separation  and vibration for retrieval. Studies showed that the smaller was the core structure the better was the transmission of the vibrating technique all along the post. By separating the core in 2 parts, this concept was followed because the distal part of the core containing the long post became smaller.  On the other hand the risks of over enlargement of the post space, or removal of healthy surrounding dentine was avoided by exclusively working on the post thanks to the better visibility given by the high magnification and light provided by the operatory microscope.  

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