REPROCESSING: MEANS AND TECHNIQUES
INTRODUCTION
Following the anamnesis, clinical and radiographic examination, it is necessary to assess the favorable and unfavorable factors in terms of the prognosis, which will depend essentially on the ability of the operator to improve and correct the inadequacies of the initial treatment.
In our course we will illustrate the operating procedures for the resumption of orthograde treatment which will be done in two stages, a coronal stage and a radicular stage.
CLINICAL PROCEDURES
1. ANALYSIS OF THE CLINICAL SITUATION
Clinical and radiographic examinations allow us to answer several necessary questions before re-intervening:
• Periodontal examination:
-Presence of mobility, fistula, periodontal pocket, etc.
REPROCESSING: MEANS AND TECHNIQUES
• Review of coronal restoration:
-Materials?
-What type of fixed prosthesis? Single or multiple fixed prosthesis?
-Nature of the sealing/bonding cement?
- Root anchorage examination:
– Anchor type? lnlay-core? Monobloc crown?
-Anatomical or preformed tenon?
-How many anchors?
-Material ?
-Axis of the tenon?
– Tenon/root ratio?
-Length of the tenon?
- Examination of residual walls
- X-ray analysis:
– Presence or absence of radiolucent image?
-Quality and level of root canal filling.
-Presence of obstacle (fracture of instrument, stop, calcifications, perforations)
1.2. CORONARY TIME = The access route
To perform orthograde retreatment in the best conditions, the copings and old restorations are removed to ensure marginal cleaning of the infiltrated areas and allow better visibility and easy access to the canal system.
- Removal of plastic coronal restorations
If the restoration is watertight and without root anchorage, its removal is not necessary or even contraindicated. It facilitates obtaining a four-walled access cavity, the placement of the dam and the retention of the temporary dressing between sessions. In the opposite case or the restoration is defective, unobturation is necessary and the restorative materials (amalgams, composites, glass ionomer cements) are removed en bloc with round burs mounted on a turbine under spray.
- Removal of fixed prosthesis
Several systems can be used to remove fixed prostheses. The crown remover and the Furrer® forceps should only be used to remove temporary prostheses and definitive prostheses that are not very retentive or sealed with temporary cement. In fact, the constraints exerted are significant and the extraction forces can cause cracks or even fractures of the underlying tooth. There are several systems for removing fixed prostheses, including:
• The Wam Key ® system 3 different keys are available. The clinical sequence is as follows:
-Create a gutter on the vestibular surface parallel to the occlusal surface and located 1 mm from it.
-The gutter must be deep enough to exceed half of the occlusal surface.
-It is carried out using a diamond cutter for the ceramic part and a transmetallic cutter for the metal part under abundant irrigation.
-The WamKey® is inserted into the orifice thus created, and a 1⁄4 turn is made allowing the fixed prosthesis to rise along the insertion axis. This type of loosening is completely atraumatic.
Removal of fixed plural prosthesis The parachute technique associated with a Kava coronaflex® or easy pneumatic crown and bridge remover® system (Dentco) is the most recommended. The use of long-necked round burs mounted on a low-speed contra-angle cleans the cavity while polishing the angles and walls. Then the entrances of the canals and the untreated canals are actively sought with the systematic use of optical aids (magnifying glasses or operating microscope) and the ultrasound inserts provided for this purpose.
REPROCESSING: MEANS AND TECHNIQUES
1.3. RADICULAR TIME
In the case of a coronradicular restoration that is either crushed or cast, the strategy is as follows:
- Removal of root anchor:
1. Preformed metal posts and restorative material
• The restorative material must be removed to isolate the head of the post.
• Then the post is vibrated using an ultrasonic insert under abundant irrigation in order to disintegrate the sealing cement.
• In the case of screw post®, the ultrasonic inserts are used in counterclockwise rotational motion, to facilitate the unscrewing of the screw.
2. Fibered tenons
The principle is the same as before since the composite restoration material is removed. Then the ultrasonic inserts are applied so as to destroy the bonding resin.
3. lnlay-core
• Reduction of the inlay-core with a trans-metallic bur.
•Use of ultrasonic inserts under irrigation to disintegrate the sealing cement.
•If this fails: use one of the gripping systems:
-Gonon® System:
The principle of the instrument is that of the corkscrew: two perfectly balanced forces will be applied:
– one on the residual dental structure,
– the other on the tenon.
- Unclogging of the canal system
In most clinical situations the root canal system is obturated either:
- Along its entire length: The unclogging will be more or less rapid and complete.
- Along part of its length: Generally the absence of canal permeability is linked to the presence of calcification, blockage or fractured instrument….
In all cases, the unobturation of the canal filling material aims to restore canal permeability. It is based on the combined use of chemical means (solvents) and mechanical means (manual steel or NiTi rotary instruments).
Identification of the obturation material allows the following unobturation strategy to be adapted.
REPROCESSING: MEANS AND TECHNIQUES
1. Gutta percha
– Unobturation of gutta percha can be carried out in the following way:
•The Gates or Largo drill can be useful in creating a reservoir for the solvent, provided that its activity is limited to the canal entrances .
• Manual mechanical unclogging (H file or K file, etc.) or mechanized (ProTaper
Retreatment Kit®).
• Chemical unclogging (solvent: Endosolv E®).
• Thermal unclogging (endotec, system B).
NOTE Special case of unblocking a Thermafil®: use of solvent or heat to remove the gutta percha; an H file is inserted at the level of the groove of the tutor in order to uninsert it.
2. Root canal paste
– The root canal pastes used are most often non-resorbable. The solvent will be chosen according to the material to be removed (its appearance, its radiopacity, its hardness, its density).
- For zinc oxide eugenol pastes: use solvents such as tetrachloroethylene derivatives (Endosolv®), or solvents based on orange essence (Eugenate Desobturator).
- For phenolic or bakelite pastes: Endosolv®, Resosolv® but these resins are insoluble and harder than dentine.
After sufficient softening of the filling material with manual steel files in the canal, NiTi instruments in continuous rotation, with a taper of 6.5 or even 4 depending on the unobturation system, can help to remove the filling material in the coronal 2/3.
The unobturation of the material must be slow, controlled and progressive in the canal in a coronoapical direction.
In the case where the canal is blocked over part of its length, the practitioner must manage each situation (stop, fractured instrument, calcifications) in order to have permeability over the entire canal system:
•In case of a stop: the manual instrument blocks and does not exceed this stop. The management of this type of complication is based on two steps: passage and erasure. These steps are carried out using manual steel instruments with a pre-curved end.
The passage is confirmed using the larger diameter instruments and in a serial manner.
•In case of calcified canal: use of a chelating solution and small diameter K files K 08 or 10, pre-curved in order to negotiate the non-instrumented calcified part associated with abundant irrigation with ClONa.
•In the case of fractured instruments (see the course on the management of fractured instruments ).
Once canal permeability is obtained, the practitioner performs:
•Root shaping combined with disinfection of the root canal network
•Endodontic obturation.
•Permanent waterproof restoration.
PROGNOSIS Several studies have stated that the prognosis of endodontic retreatment is lower than that of initial treatment, the success rate is:
-76% according to De Chevigny et al in 2008),
-76.7% according to the meta-analysis of Ng et al. 2008
Except for Gagliani et al. (2005), if the apical third could be cleaned, the prognosis would be identical to that of initial treatment.
CONCLUSION Coronary retreatment should be able to improve the initial situation with the same objectives of permeability, disinfection, shaping and three-dimensional obturation.
The anatomical complexity of the canal network and, above all, the obstacles related to previous attempts make this orthograde treatment approach more difficult and the result less predictable.