30 June 2020
The prognosis of initial endodontic treatment is mostly favorable . Nevertheless, failure can occur due to the persistence of bacteria following initial treatment or due to inadequate disinfection, shaping and obturation of the root canal system. The possibility of a secondary infection is also not to be excluded, especially when a defective coronary reconstruction leads to percolation.
In such cases non surgical retreatment is required.
The success of the retreatment will depend amongst other criteria on the complete removal of all filling material debris, such as gutta-percha or sealer. In fact, the old filling material can contain necrotic tissues and bacteria often assembled in biofilm. These bacteria and their toxins can diffuse into the peri-radicular tissues and cause symptomatic or asymptomatic apical periodontitis.
A lower mandibular molar shows a large peri-apical periodontitis after first root canal therapy with poor obturation. After retreatment, removal of all the filling material, cleaning, shaping and filling, a post and core and a temporary crown was placed on the tooth by the referring dentist. A 6 months Follow up shows healing.
Traditionally obturation material was removed with hand files, but since many years rotary and reciprocating files are used in retreatment cases. Some exclusive retreatment systems exists, but many clinicians also use shaping system to remove old filling material.
Instruments combining good cutting efficiency, flexibility, resistance to fracture and a safe tip are more likely to remove old filling material without harming the original anatomy of the root canal system.
The case of a lower right first mandibular molar with short obturations in all canals and a ledge in the mesial root.
The obturation material is removed without the use of any solvent with the a rotary instrument and activation with Ultra X (Eighteeth, Changzhou, China)
The final X ray after shaping, cleaning and obturation in one session.
Exclusive retreatment instruments are designed specifically for the removal of filling material. This case was managed with these instruments.
Initial periapical Xray showing a large periapical periodontitis. Clinically, the tooth was asymptomatic and no probing was noticed.
During the the retreatment procedure gutta-Percha was removed with an exclusive retreatment instrument.
Final Peri-apical X ray after one session retreatment.
Clinical case retreatment of an upper molar by Dr. Calogero Bugea
The complete elimination of the material can be assessed clinically, by observing the canals under high magnification or radiographically by taking a peri-apical X ray confirming the working length determined with an apex locator
Nevertheless, in many cases, the remaining material can’t be detected neither with the microscope nor with the radiograph, because it can be hidden by anatomical obstacles such as curvatures or anastomosis. According to many studies, the removal of filling material from the apical third is very challenging.
A 20 microns micro CT image reconstructed from an extracted mesial root of mandibular molar after material removal, shows material remnants in the isthmus area and in the apical part of the canals.
This 3D animation after micro CT 3D reconstruction showing the presence of material remnants after retreatment on an extracted tooth.
Until now, almost all publications confirmed the impossibility to completely eliminate all the filling material during retreatment. The usage of a supplementary approach such as ultrasonic activation (UAI) or sonic activation (SI) seems to enhance the removal of remaining material.
Micro CT images confirming the effectiveness of the UAI EndoUltra (Vista Dental Products, Racine, WI,USA) in removing more remnants.
A case of a mandibular symptomatic molar retreated through the bridge.
Removal of carrier based obturation with Reciproc Blue (VDW) from a C shaped canal.
Final X ray after filling material removal, shaping, cleaning and 3D filling.
No clinical protocol has yet shown the possibility of eliminating the filling material entirely. However the usage of an instrument combining a high cutting efficiency, a non-active point, a high resistance to cyclic fatigue and a flexibility necessary to respect the canal anatomy optimizes the elimination of filling material in difficult anatomical areas.
Supplementary approach methods must also be used with to achieve a rapid, simple and effective filling material removal protocol.