Endodontic Failure Re-root Canal Treatment

Question 1

What is the aim of root canal-retreatment?

Answer 1

Regain access into apical1/3 of the root canal system and create an environment conductive to healing.

Question 2

For root canal re-treatment, what are the aims? (5)

Answer 2

• Coronal access (may need to remove direct and indirect restorations)
• once in canal system, remove all previous obturating materials
• manage any complicating factors e.g. ledges, zips
• achieve full working length
• eliminate microbes

Question 3

What are the advantages of retaining a restoration (i.e. crown)? (4)

Answer 3

• cost for replacement avoided
• isolation is easier
• occlusion is preserved in a stable format that the patient is already use to
• patient’s aesthetics are minimally changed

Question 4

What are the disadvantages of retaining restorations in root canal re-treatment (i.e. crown)? (4)

Answer 4

• removes denintal core: reduce retention and strength
• increases chance of iatrogenic mishap as restricted visibility (tooth may of rotated, may have had corrections done to the crown- the anatomy of crown may not follow the anatomy of the tooth)
• removal of canal obstructions such as posts are more difficult
• may miss something important e.g. hidden recurrent caries, a fracture or additional canal

Question 5

What is a Wamkey and how is a wamkey used?

Answer 5

Wamkey is used to remove a crown
1- locate the most accessible spot on the crown
2- drill a thin horizontal window in the crown
3- enlarge this window until you see the cement layer through the window
4- after checking slot is at cement level, deepen the hole until it reaches the centre of the tooth prep
5- slightly extend the hole to form a horizontal rectangle
6- finally introduce the key down to the bottom of the slot and make a simple rotation on the handle. The crown is then removed.

Question 6

How is the metalift system used and when should it be used?

Answer 6

The Metalift system should be used when the Wamkey system is not available.
Involves drilling a small hole in the occlusal surface down to cement layer. Little device is placed through the hole, which grips the crown, and using some forceps supplied and forcing it along the axis of the tooth- breaks the cement.

Question 7

When planning to remove posts, what should you ask the patient and why? (2)

Answer 7

Ask pt when it was cemented.

Ask pt if it came out, if so when.

Question 8

What kind of restoration is more difficult to remove and when should this be particularly important?

Answer 8

Bonded restorations are more difficult to remove- keep in mind especially when dismantling perio-involved teeth.

Question 9

What is present in images 1 and 2? How easy is their removal?

Answer 9

Image 1: quartz fibre posts in teeth will be removed, but more time consuming. It has a paleness of the post, meaning it’s a quartz fibre post.

Image 2: this dentatus screw is unscrew and be removed relatively quickly.

Question 10

When removing a post, what should be considered? (3)

Answer 10

• consider the location in the arch of the tooth that requires post removal
• the more posterior in the arch, the more difficult the post is to remove due to accessibility
• to remove a post, first remove all restorative materials around it. For all metal posts, first use ultrasonics

Question 11

How do you remove posts with ultrasonics?

Answer 11

• Put on rubber dam
• Use magnification and illumination
• Aim to reduce the retention using ultrasonics at the interface between the post and the tooth i.e. the cement line
• constantly move the ultrasonic around the circumference of the post to disrupt cement along the post/canal wall interference
• it will heat up the post, so use copious coolant spray
• owing to the heat that can be generated from this procedure, stop every 15 seconds
• use for at least 10 mins with many breaks

Question 12

When ultrasonics fail to remove a post, what can be used?

Answer 12

Post pullers are required i.e.

• Egglers
• Ganon/ruddle removal system

Question 13

What kind of post puller is image 3?

What kind of posts should these not be used on?

Answer 13

Device consists of 2 sets of jaws that work independently of one another.
- first set of jaws grip the core
- other set of jaws push away from the tooth in line with long axis of tooth
Then can unscrew it and forces pressure on long axis in line with long axis of tooth.

Not recommended to use egglers for removal of screw posts as it will take far too much dentine

Question 14

What is the name for the post removal system in image 4?

When should it be used?

Answer 14

Ganon/Ruddle removal system.

Effective for removing parallel or tapered, non-active preformed posts.

Question 15

What are potential complications of post removal? (6)

Answer 15

• inability to remove
• tooth is unrestorable after removal
• heat transmission to PDL from ultrasonics
• tooth/root fracture
• perforation of root
• fracture the post/inability to remove all

Question 16

When the post cannot be removed, what can be done?

Answer 16

Periradicular surgery can often be performed

Question 17

Which teeth are suitable for periradicular surgery to remove a post when it cannot be removed otherwise?

Answer 17

UR: 6 (DB&MB), 5, 4, 3, 2, 1
UL: 6 (DB&MB), 5, 4, 3, 2, 1
LL and LR: 1, 2, 3

Question 18

What are the 3 ways to remove GP? And give examples of each

Answer 18

-Solvents
oil of turpentine, chloroform.

-Thermal
ultrasonics
system B

-Mechanical
Rotary nickel titanium files
I.e. protaper D series

Question 19

How do you use oil of turpetine?

Answer 19

Use in very small amounts in a luer lock syringe.
If overflows- will breakdown the rubberdam.
Leave in canal for a minute then work into GP with a C+ file or a no 15, 20 hedstrom
Once all GP seems removed, fill canal with solvent again, and ‘wick’ out the pink solution with paper points until solution is clear.

Question 20

What is C+ files?

Answer 20

Used in the chemical removal via oil of turpentine.
High carbon steel.
Very stiff and brittle and good for pushing through GP.

Question 21

What issues can thermal removal of GP cause?

Answer 21

These melt the GP by increasing temperature.

The thermal energy can transfer through the tooth onto the PDL and cause injury or cell death.

Question 22

In the mechanical removal of GP, what should always be remembered i.e. what systems are available, speed wise, and direction of removal?

Answer 22

Protaper D series
Use at 600rpm
Always a crown down technique

Question 23

In the Protaper D series for mechanical removal of the GP, what files are there and how long are they?

Answer 23

There are 3.
16mm
18mm
22mm.

Question 24

What are the ways to remove silver cones?

Answer 24

Brading- putting 3 small files down around the file, and twisting and moving the heads/handles of the file. Will brade and bind to the carrier- allowing extraction.

Question 25

What is the irrigant protocol used after the GP is removed to disinfect the canal?

Answer 25

NaOCl —> EDTA or citric acid —> providone iodone soak —> NaOCl

Question 26

After the GP is removed, and irrigation has been used to disinfect the canal, what is the next step?

Answer 26

Once the WL is reached, progressively larger diameter hand files are rotaated in a passive, non-binding clockwise direction to remove remaining GP until the files come out clean i.e. no pink material on them

Question 27

What are the issues with silver points?

Answer 27

• poor success rate of RCT with silver cones
• not adaptable to canal, limited seal
• produce toxic products due to corrosion
• do not re-treat in single visit where silver points removed
• either very difficult to remove, or very easy
• never apply ultrasonic energy directly on silver cone- will disintegrate into many pieces

Question 28

If the silverpoint is grippable, what can be used to remove it?

Answer 28

Stielglitz

Question 29

How would you remove: 
1- insoluble resin 
2-GP 
3- silver points 
4- soluble pastes

Answer 29

1- ultrasonics
2- protaper D series
3- Steiglitz tweezers
4- solvent and protaper D series

Question 30

What issues can be faced when using electronic apex locators in re-treatment cases and how can these be overcome?

Answer 30

In re-rx cases, they frequently misread the working length.

They regain accuracy if a clean (brand new) file is used following GP removal.

Question 31

In image 5, in terms of survival is the tx a success? In terms of bony infill, is it a success?

Answer 31

If survival is used- success.

If bony infill- there is post treatment disease.