Navigating Ledges with a Microscope
Failed RCT LR6
There is apical pathology associated with the inadequate endodontic treatment in the LR6. The mesial canals are obturated short of the working length.
The patient is to undergo orthodontic treatment. It was decided to attempt initially to revise the existing root canal treatment rather than extract LR6, followed by space closure and uprighting of the LR8.
Notice how thin the intraradicular dentine is.
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Access To Pulp Space
The crown is removed intact with a pneumatic crown remover.
Access is made through the existing glass ionomer core to the root canal material.
Care is taken not to disturb the remaining natural morphology of the pulp walls.
The access cavity is disinfected for one minute with hypochlorous acid to reduce the bacterial load [Sterilox]. |
Access To Existing Root Canal Material
The core material is broken down with ultrasound.
Under high magnification, diamond coated restorative ultrasonic tips are used. This allows for precise removal of core material only. This avoids damage and unnecessary removal of further dentine from the already thin floor of the pulp chamber.
Perforation of the floor of the pulp chamber will reduce prognosis
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Removal of Existing Root Canal Material
The existing root canal material [gutta percha] is removed with a combination of rotary instruments and heat.
Rotary instruments are taken to within 2mm of the apical extent of the exiting root canal. Taking rotary instruments closer than this may compound any existing deviation in the previous attempt at preparing the root canal.
When obturation is seen to be well short of the ideal working length, consideration should be given to the presence of ledges.
This is the view of the mesio-lingual root canal. |
Assessment Of Ledge in Mesio-Lingual Root Canal
The last 2mm of gutta percha is removed with NiTi micro-openers and micro-debriders [Maillefer].
The blind use of hand instruments will exacerbate the ledge and make its successful navigation improbable. In such situations the very highest powers of magnification [X24] afforded by the microscope become invaluable. Any small pieces of gutta percha remaining can be removed with a solvent.
A - Ledge with remaining gutta percha
B - Root canal proper. Notice its deviation towards the buccal. |
Ledge Elimination And Final Canal Preparation
The ledge in the mesio-lingual root canal has been navigated successfully. Safe access has been established to the remaining root canal morphology.
Prior to further canal preparation, it is important to consider removal of the ledge. Failure to do this may result in further procedural errors. The easiest and most successful manner in which to do this is with NiTi hand GT files [Dentsply]
A - Ledge incorporated into canal preparation
B - Root canal proper. |
 Final Radiograph
Following complete disinfection of the entire root canal space; the root canals are obturated.
The dentine pin is removed and the root canals are sealed with MTA. A new provisional core is placed and the original crown is recemented. Following orthodontic treatment this will be replaced.
Notice that the remaining dentine thickness in the floor of the pulp is identical to that prior to treatment.
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