Post and core and re-rct Flashcards
5 possible problems after Rct/reRCT
- inadequate tooth structure left
- Lack or no ferrule
- Fractured instruments
- Perforations
- Inadequate root fillings
- Wide post holes
Are teeth more brittle after RCT?
no
What is one of the most important causes of RCT failure?
- Coronal micro-leakage
- more problematic in multi-rooted teeth
When should an unrestored root filled teeth be reroot treated?
if unrestored for 3 months
Ideal restoration for anterior teeth with intact marginal ridges? (root treated)
Composite veneer
Ideal restoration for discoloured anterior teeth with intact marginal ridges?
Bleaching / composite veneer
Ideal restoration for anterior teeth with marginal ridges destroyed?
- Post crown
- Core build up with crown
What is the function of a post/core?
- Gains intraradicular support for a definitive restoration
- Core provides retention for crown
- Post retain core
Where is a post placed?
in the root canal
When would you not place a post in incisors and canines?
When there is sufficient coronal dentine
Why would you avoid post placement in mandibular incisors?
due to thin/tapering and narrow mesiodistal roots
Why would you avoid post placement in premolars, and where should you place the post if indicated?
- due to small pulp chambers and tapering roots
- Place in widest root canal
Why would you avoid placing a post in curved canals?
To avoid perforations
What is the root filling length that should be left when placing a post?
4-5mm root filling apically
How should the post width be?
- no more than 1/3 of root width at narrowest point
- 1mm of remaining circumferential coronal dentine
How much of the post should go into the root?
At least half of the root length
What is the minimum post/crown length ratio?
1:1
What is ferrule?
Dentine collar
* which is an encirclement of 1-2mm of vertical axial tooth structure within the walls of a crown
What is the function of the ferrule?
Prevent tooth fracture when placing a post
What is the dimensions of the ferrule ?
At least 1.5mm height and width of remaing coronal dentine
2 methods of making a ferrule if there is lack of it?
- Orthodontic extrusion
- Crown lengthening
3 features of an ideal post?
- Parallel
- non threaded (passive)
- Cement retained
Why is parallel sided post better than tapered?
- more retentive than tapered
- avoids wedging
Why is non threaded post better than threaded?
less stress on tooth - less risk of fracture
Which post is more retentive , threaded or cement retained (parallel) ?
- Threaded
Why is cement retained better than threaded although threaded is more retentive?
because cement act as a buffer between masticatory forces and post/tooth
Name A - F
- Tapered smooth
- Tapered serrated
- Tapered threaded
- Parallel smooth
- Parallel serrated
- Parallel threaded
3 advantages of prefabricated posts ?
- only 1 visit required
- no impression and laboratory visit required
- large selection of designs and materials
What are 3 materials of posts?
- Metal - gold, SS , brass, titanium
- Ceramics - alumina and zirconia
- Fibre - glass, quartz and carbon
advantages of metal posts?
Radiopaque on radiographs
4 disadvantages of metal posts?
- poor aesthetics
- root fracture
- corrosion
- nickel sensitivity
3 advantages of ceramic posts?
- good aesthetics
- high flexural strength
- Good fracture toughness
2 disadvantages of ceramic posts
- difficult to retrieve
- root fracture
4 advantages of fibre posts?
- retrievable
- flexible
- similar properties to dentine
- bond to dentine with DBA
What is a core buildup?
Internal part of tooth is built up with restorative material to provide retention and resistance for definitive restorations
2 reasons why posts is not a good idea in posterior teeth?
- high occlusal forces
- have multiple roots
3 core materials ?
- composite
- amalgam
- glass ionomer
2 reasons why composite is the most commonly used material for cores?
- Good aesthetics
- Bonds to tooth structure
What core material is used with fibre posts?
Composite
1 disadvantage of composite as a core material?
Technique sensitive and requires good moisture control
3 disadvantages of using amalgam as a core material?
- not aesthetic
- need 24h to set
- needs retention
What is the disadvantage with using GI as a core material?
- absorbs water and expands
What is a Nayyar core ?
A core of amalgam where root filling is removed from coronal part and amalgam is packed into the root canals and tooth built up which provides retention
5 methods to remove a post?
- Ultrasonic
- Masseran kit - Trephan
- Eggler device
- Moskito forceps
- Sliding hammer
- Anthogyr - safe relax
4 problems you would encounter when removing a post?
- Post fracture
- Root fracture
- Tooth becomes unrestorable
- Post space becomes too wide
4 problems with posts ?
- Perforation
- Core fracture
- Root fracture
- Post fracture
2 management options for post perforation?
- Repair - internal or external (periradicular surgery)
- Extraction
Post failure rate due to restorative reasons?
60%
What is the ideal taper of a core?
6 degrees
Why is length of core important ?
Important to allow clearance for definitive restoration
2mm for MCC
What material would you use for a provisional post core and crown?
Temp bond
3 provisional restorations for post and core ?
- provisional post core crown
- immediate denture
- Essex retainer
- Dressing
4 Steps to remove gutta percha?
- Dental dam
- soften using heat or solvent
- Use gates glidden to minimum size 3 ( straight part of canal only)
- Use working length and rubber stopper on gates glidden
Write a prescription for a post and core to the lab
- Please construct post and core
- Para post (colour)
- Core 6 degree taper
- Please leave 2mm space in occlusion for crown
Provide the lab with registration and impressions with shade
4 treatment options when RCT fails?
- Monitor if asymptomatic
- Orthograde treatment
- Periradicular surgery
- Extract ± implant
3 indication of non surgical root canal retreatment?
- intra-radicular infection
- New restoration with poor RCT
- Loss of coronal seal
6 principles of retreatment?
- remove restoration
- assess restorability
- remove all root filling
- assess anatomy
- refine and modify preparation
- complete treatment as de novo case
How would you remove insoluble resins from the root canal?
Ultrasonics
How would you remove gutta percha and soluble paste from the canal ? (generally)
- Handfiles and solvents
- then reciproc
Which files will you use to remove poorly condensed GP?
Hedstroem files
What is the problem with removing well condensed GP?
- Harder as need to create space
What reciproc files GP for reroot treatment? and why?
Reciproc (r25, R40, R50) , to avoid loss of tooth substance as these files are regressively tapered
What solvent would you use
- chloroform
- eucalyptus
What is the difference between using a solvent and not using a solvent on the on root canal walls according to Horvath et el 2009 ?
Using solvents lead to more gutta percha and sealer remnants on root canal wall and inside dentinal tubules
What are the 4 steps in retreatment using GP?
- Remove GP from coronal third using Ultrasonics, GG or heat carrier
- Remove GP from Mid third using Reciproc 25 (set stopper to 2/3 of EWL) in slow pecking motions , can use eucalyptus to soften GP
- Determine working length with K files size 10/15
- Complete apical third using R25/R25 blue to CWL
2 advantages of using reciproc for retreatment?
very efficient
removes bulk of GP
