Retreatment (Archer) Flashcards
What is the problem with a tooth that is previously endodontically treated that requires retreatment?
Bacteria
What can cause problems with an existing root canal?
Pre-existing or introduction of new bacteria into the canal
What is the only way to know if a previously endo treated tooth requires retreatment?
Accurate diagnostic testing
Is the radiograph enough to determine if a previously endo treated tooth requires retreatment?
No
Can a patient be sensitive to percussion without the presence of a periapical radiolucency (PARL)?
Yes
What is indicated for a tooth that has no periapical radiolucency, but is sensitive to percussion and it has not had recent restorative work done on it?
Evaluate for NSRCT
What 4 factors can lead to retreatment?
- Leaking coronal restoration
- Leaking apical seal
- Remaining bacterial irritants from initial therapy
- Missed or untreated canals
If a PARL stays the same size or gets smaller on a previously NSRCT tooth, is retreatment (RETX) indicated?
No
If the PARL gets larger after NSRCT, should RETX be done, even if the patient does not have symptoms?
Yes
What are 3 times RETX is indicated in the absence of symptom?
- Caries extending into pulp chamber
- Lack of permanent restorations for months after initial NSRCT
- Existing NSRCT is short, thread, or canal is missed
What are 4 obstacles that complicate RETX?
- Siilver points
- Thermafill
- Posts
- Separated instruments
What corrode rapidly from the apical and coronal aspects of the tooth to form toxic silver amine sulfate amide hydrate?
Silver points
Why are Thermafills poor for NSRCT and why do they make RETX difficult?
Stiff plastic carrier allows the obturators to be seated to length in poorly instrumented canals
These can trap bacteria in canal if separate early in cleaning and shaping, and also obscure entry into apical portion of root?
Separated instruments
What must be done to a post in an endo treated tooth before it is loosened and removed?
All core material around post above and below orifice must be removed
What is used to loosen and remove a post and how long will the post normally take to come loose during this process?
- Ultrasonic in circumferential rotation w/ continuous irrigation
- 10 minutes
What can be used to remove a separated instrument in a canal?
- Long thin ultrasonic tip
2. Instrument retrieval system to engage and remove
What is done during RETX if unable to remove a separated instrument?
Attempt to bypass segment with a smaller file
What are 3 instances when the RETX of a tooth is not indicated?
- Clinically unrestorable
- Extensive resorption
- Vertical root fracture
Working around existing materials in the canals requires what 2 things?
- Light
2. Magnification
Why is magnification and light needed to remove NSRCT materials in a RETX?
Must be able to see fine detail
Ultrasonics used for RETX can do what?
- Discreet dentin removal
- Remove core material
- Remove cements
- Vibrate out posts
- Vibrate out instruments
- Vibrate out silver points
What is a small beaked forceps that can be used to remove materials during RETX?
Stieglitz
What is a threaded tube system used to engage the visible part of a separated instrument?
Instrument removal system
What consists of trephine burs and taps used to extract tight posts?
Post removal system
What is a Trephine?
Cylindrical or crown saw for the removal of a disk of bone or other firm tissues
A small amount of this chemical can be used to initiate the softening of hard gutta percha during a RETX?
Chloroform (solvent)
Why are the past concerns about chloroform not relevant?
Amount of chloroform found past apex is several orders of magnitude less than permissible dose
How does Dr. Perry Jones retreat previous endodontically treated teeth?
Invisalign
What can be used to irrigate?
- NaOCl
- EDTA(ethylenediamine tetraacetic acid)
- CHX
What is a medicament for RETX?
Ca(OH)2
What are 2 good things about 2.5% and 5.25% NaOCl?
- Dissolves vital and necrotic tissue
2. Antimicrobial
What does using EDTA do for irrigation?
17% EDTA for 1 minute removes inorganic smear layer and leaves organic tissue components
What must be used after irrigating for 1 minute with EDTA and why?
Irrigate w/ NaOCl to get rid of organic debris
What is a use of Chlorhexidine as an irrigant?
- Broad spectrum antimicrobial
- Substantive
- 2% CHX has approximately the same properties as 5.25% NaOCl, but 2% CHX is more effective against Enterococcus faecalis
Can Chlorhexidine dissolve necrotic tissue or remove the smear layer?
No
Why is Calcium Hydroxide a medicament?
- Antimicrobial due to alkaline pH
2. May aide in dissolving necrotic tissue remnants, bacteria, and their byproducts
What % of root canals done by general dentists and endodontists that fail?
10%
RETX is an option that should always be evaluated by whom?
Endodontist (don’t EXT until consult)
What is the healed rate of endodontic retreatment cases when the cause of failure is identified and corrected?
81%
