Retreatment Flashcards

1
Q

Root canal re treatment outline

A

Non surgical root canal re treatment
Disassembly
GP removal
Treatment outcome

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2
Q

Aims of re treatment

A

To regain access to apical third of RCS and create environment conductive to healing
We need: coronal access (may involve removal or restorations)
Remove all previous obturating materials
Manage any complicating factors like ledges, zips etc
Achieve full working length
Eliminate microbes

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3
Q

Disassembly

A

Right skill set
Right equipment
Luck?

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4
Q

Indirect restoration-removal of it?

A

Yes if defective
If satisfactory - decision making

Advantages of leaving it-avoidance.of cost of replacing, rubber dam isolation is easier, occlusion is preserved and pt is used of the occlusion so no changed to that, aeshetics minimally changed

Disadvantages of leaving it:
Crown removes dentinal core so retention and strength is reduced, increases chance.of iatrogenic mishap, restricted visibility, angulation and anatomy could be misleading, post can obstruct the canal, making more difficult, we can miss hidden caries, fracture, additional canal

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5
Q

Removal of a crown by Wamkey Dentsply set

A
  1. Locating most accessible spot of the crown (at the cement layer, between occlusal surface of the abutment and inner side of the crown itself
    2 drill thin horizontal window in the crown
    3enlarge window until cement underneath can be seen
    4 deepen the hole until it reaches the centre of tooth preparation
    5 extend the hole into horizontal rectangle
    6 introduce Wamkey down to the bottom of the slot and rotate on the handle.
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6
Q

Metalift system

A

For removal of crown

Drilling a small hole in the occlusal surface down to cement layer , then little device is placed through the hole which grips the crown and using forceps supplied, force along the long axis of the tooth, it will break cement.

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7
Q

Post removal-why

A

To gain access to the apical third
Can be fairly predictable with few complications
Ease of removal depends on-type of the post, location in the mouth material used to cement it

Always good to know when the post was cemented, if/when it came out last (can give idea what cement was used to cement it)
Bonded restorations are much more difficult to remove (especially if it is perio involved tooth)

Consider port type and material
-if on radiograph, post is opaque- could be easier to remove
-if on radiographs-cannot see the post- probably fibre glass-hard to remove and time consuming

Considerations:
1. Location in the mouth and which tooth (more posterior-harder)
2. All restoration around the tooth should be removed before removal of the post (if metal restoration-use ultrasonic)

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8
Q

Removal of metal posts

A

Ultrasonics
Eggler post removal
Ruddle/gonon removal
Masseran kit
If metal threathed-unscrew
If quartz fibre post- probably has own kit, or pilot hole and piezo reamer
If zirconia and ceramic post- usually irretrievable

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9
Q

Post removal with ultrasonic

A

Rubber dam
Magnification and illumination
Aim is to reduce the retention using ultrasonic at the interface between the post and the tooth
We should move around the circumference of the post to disrupt the cement along the post/canal wall interface
Due to heat, use copious coolant spray and stop every 15 seconds as too much heat is generated -removal should last at least 10 min with many breaks

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10
Q

Removal of post with other instruments (not ultrasonic)

A

Post puller:
1. Egglers- device with two sets of jaws that work independently of one another, first grips the core, second push away/applies pressure from the tooth in line with the long axis of the tooth
If cast post or large post-use high speed and bur
Eggler not to be used for removal of screw posts(it will take too much extra dentine)

Ganon/ruddle post removal system-highly effective for removal of parallel or tapered posts, especially if non active performed posts.

Masseran kit- hollow tube with cutting edge, find the tube just bigger than the post, it is slipped over the post and use it down through the cement line or through the dentine. Post should loosen and we should be able to grip it.

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11
Q

Removal of fibre posts

A

Often come with its own kit
Need magnification

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12
Q

Post removal complications

A

Inability to remove
If post is removed and tooth is unrestorable
Heat damage to the PDL from ultrasonic
Tooth/root fracture
Perforation of root
Fracture of post and inability to remove it

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13
Q

When access is gained

A

Remove any residual cement (with ultrasonic) that are blocking the access into RCS/GP

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14
Q

What is limited access

A

Consider periradicular surgery
Not all teeth are suitable (upper 1-6(mb,dB), lower 1-3)
Operator dependant

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15
Q

Removal of gutta percha

A
  1. Solvents-oil of turpentine (very small amount, in luer lock syringe, toxic to tissue, left for 1 min and then use C + file (high carbon steel, brittle, stiff) or 15,20 Hedstorm,.once GP removed, fill again with the oil and clean with paper points), chloroform, halothene, xylene-disolve the GP, but very messy
  2. Thermal-ultrasonoic, system B
    Can generate too much heat, affect tooth/tissue an cause cell death
  3. Mechanical- rotary NITI files (Protaper D (3 files, d1- shortest, d2- middle, d3- longest, use to reach apex, Mtwo Re-treatment files)
    Both used in 600 rpm, always crown down, active top is penetrating the GP
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16
Q

Removing carrier based system and silver cones

A

Much more difficult
More chance for error
Grip the carrier, moves it around
Guttacore- new carrier system- cross link between GP and core- great but difficult to remove
Once bulk of the GP is removed-last bits are removed by solvents
Then paper points are used to remove all remaining GP and sealer
Use Hedstorm but do not cut further dentine

17
Q

Irrigant protocol

A

NaOCl-sodium hypochlorite first
EDTA or citric acid secondly,
Then povidone iodine soak (effective against E. Faecalis)
Final wash with NaOCl
Then prep the canal as usual-proTaper hand or rotary
Once working length is reached, use progressively larger diameter hand files and rotate in a passive, non binding, clockwise direction to remove remaining GP until files come out of the canal clean (no pink material on them)

18
Q

Silver points

A

Poor success rate of RCT obturated with silver points
They are not adaptable to the canal, have a limited seal, and produce toxic products due to corrosion
Do not re-treat in single visit! -do in multiple as there is 13% more chance of flare up if in single visit

Removing- never use ultrasonic directly on silver cone-will disintegrate into many pieces. Hard to get hold off
Don’t twist them!
When we grip them with forceps-apply ultrasonic to the forceps and it will vibrate out

19
Q

Retreatment option depending on the post material

A

Insoluble resin-ultrasonics
GP -proTaper D
Silver points-Steiglitz tweezers
Soluble pastes-solvent and Protaper D series

20
Q

EAL (electronic apex locator) use in re treatment

A

Very accurate in new RCT
In re treatment -often inacurate readings misreading working length

Accurate if using a brand new, clean file once all GP is removed

21
Q

Why is coronal restoration required for endo treated teeth

A

Due to structural changes
Due to aesthetics (discolouration)

22
Q

If molar is to receive a post, which canal should be prepared for post?

A

In maxillary terth- palatal
In mandibular teeth,- distal

Those usually straight canals and largest ones

23
Q

K files and headstorm

A

Have standard 2%taper
Stainless steel

Headstorm- more aggressive, useful for removal of GP
Should be used in push-pull motion, not rotational as might fracture

24
Q

Gates Glidden drills

A

Rotary stainless steel to enlarge the straight coronal portion
Long shank aids visibility
Non cutting end to reduce risk of ledge formation
Larges used first - to smaller

25
Q

Preparation and obturation should end where?

A

At the apical constriction which is 2 mm from radiographic apex

Working length is up to apical constriction

26
Q

What files is used for guide path

A

Precurved, size 10 to EWL

27
Q

Reasons we cannot reach EWL

A
  1. Canal is clogged- blocked by dense collagen or necrotic tissue
    - solution: irrigate thoroughly with sodium hypochlorite, use precurved small file(8 or 10) and gently touch the blockage, irrigate and repeat until file reaches EWL.
  2. Angulation of access and curved file is not the same
    - solution: try making different curvatures of the file to allow same canal and file curvature and reaching EWL
  3. Too wide diameter of the file
    -Solution: choose smaller file
  4. Shaft of the file is too wide for the canal ( too thick coronally
    -solution: smaller file that has narrower diameter will help. Or use ProTaper in brushing motion
28
Q

Most common problems during canal preparation

A

Loss of working length/blockage
Deviation from normal canal anatomy/ledge, zip
Inadequate preparation
Perforation
Separation of files in canal

29
Q

Apicectomy

A

Indications:
Unable to obturate apical third due to anatomy or calcification
Perforation of the root
Biopsy for a lesion that is there( radicular cyst)
If separated file in canal with residual infection
Persistent apical pathology