Post and Cores Flashcards
What aspects of a root treated tooth should be assessed clinically before restoring it?
No sinus
Not TTP
No exposed GP
Coronal seal of restoration following endo
Caries free
Minimum 2mm ferrule that is extending 3/4 around the tooth.
Stable periodontal disease.
Minimum 2mm interocclusal width after core placement for restoration
No toothwear or bruxism habits
What aspects of root treated teeth should be assessed radiographically before restoring them?
Endodontic status
- Well condensed, well tapered, within 1-2mm of radiographic apex, good coronal seal.
Absence of PA radiolucency.
Wide roots
Minimum 1:1 ratio of crown to root
No resorption
Adequate bone levels- post must be able to extend 4mm subcrestal.
No caries, no fracture lines
If GP is exposed, what should you do?
Trim back the GP to the ACJ.
Place RMGIC over the exposed GP.
What are the options for restoration of an anterior tooth that has been root treated?
If marginal ridges intact- could simply do composite.
- If tooth is discoloured, you could bleach and then
If marginal ridges are destroyed
- Need to do a crown- either build up with core or post crown.
What is a post and core and why would you need it?
Gains intraradicular support for a definitive restoration.
- Core provides retention for the crown and the post retains the core.
Inadequate ferrule
What is a ferrule?
Encirclement of 1-2mm of vertical axial tooth structure within walls of a crown.
Prevents tooth fracture- if crown margin is not placed onto solid tooth, root fracture is significantly increased.
Describe the guidelines for post placement?
Tooth type
- Incisors and canines are fine but do not put a post in a molar tooth.
Root filling length
- Must have 4-5mm of GP apically.
Post width
- No more than 1/3 of root width at narrowest point and 1mm of remaining circumferential coronal dentine.
Sufficient alveolar bone support
- At least half of post length into root.
Minimum 1:1 ratio of crown:root
Ferrule
- At least 1.5mm in height and width of remaining coronal dentine.
Length of post should be 1/2 to 2/3 the length of the root.
Describe the ideal post characteristics.
Parallel sided- more retentive than parallel
Non-threaded (smooth)- Incorporates less stress onto the root
Cement retained- less retentive than threaded but cement acts as a buffer between masticatory forces and post/tooth.
What is the difference between direct and indirect posts?
Direct- pre-fabricated posts, only 1 visit required and no impressions or lab work required.
- Chairside core build up.
- Not suitable for wide canals, less accurate fit.
- Fibres posts are harder to retrieve if re-RCT is indicated.
- Low elastic modulus, similar to dentine.
Indirect- fabricated in a lab based off the patient’s impressions that you have taken.
- More costly, requires more appointments.
- Risk of contamination of the root canal space between appointments.
- Can be suitable in wider canals, can be used when not an ideal ferrule is present, more accurate fit.
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What materials are available for posts?
Metal- cast gold, stainless steel
- radiopaque on radiographs, easily retrievable, can cause root fracture, corrosion, poor aesthetics.
Ceramics- alumina, Zirconia
- High flexural strength and fracture toughness, goo aesthetics.
- not as easily retrieved, root fracture common.
Fibre- glass, quarts, carbon
- Flexible, allows light cure through the post, aesthetics, retrievabe, bond to dentine with DBA (hard to get this all the way own the canal).
Under what circumstances would you use threaded post?
Only if high retention is required.
What is a core build up?
Internal structure of the tooth is built up with restorative material to replace the lost tooth tissue
- provides retention and resistance for definitive restorations.
What materials could you use for a core?
Composite- Most commonly used.
- Good aesthetics
- Bonds to tooth structure
- Moisture control is required
- Used for fibre posts.
Amalgam-
- Poor retention
- Poor aesthetics
Core cannot be prepared straightaway- need to leave it for 24 hours to set.
Glass ionomer- Absorbs water and core expands in size.
When designing your post and core restoration for a tooth, what aspects should you be thinking of?
How long will the post be?
- For the parapets system, it must be at least 9mm.
Have you got a ferrule?
- 2mm of coronal dentine.
How wide?
- Must be no wider than 1/3 of the width of the tooth.
3-5mm remaining GP in the apical region of the canal
Is the canal straight?
How much space for the core?
What aspects of the core design are important?
Taper of 6 degrees
Ensure 2mm clearance in the occlusion for an MCC to sit on top
What are your options for provisional restorations if you are doing an indirect post and core?
Provisional post core crown- using temp bond and Protemp (you will have already taken a putty matrix impression for this).
Immediate denture
Dressing
Essex retainer
What problems are there with posts?
Root fracture
Core fracture
Perforation
Post fracture
Infection requiring re-RCT
What factors increase the risk of post fracture?
Deep overbite
Bruxism
Class II div 2
Edge to edge occlusion
What are the contents of a para post system?
Impression posts
Drills
Provisional posts
Burn out posts.
Describe the clinical stages in visit 1 of providing an indirect post using the para post system.
Take putty matrix impression
Administer LA
Apply dental dam
Remove any previous restoration and caries
Refine crown prep depending on the crown you have chosen.
Calculate CWL from the radiograph and determine post width.
Remove 2mm of GP using the GG.
Prepare the post space using the post drills within the parapost system.
Irrigate the post space with sodium hypochlorite or saline.
Prepare the impression tray with appropriate adhesive.
Apply gingival retraction cord- either aluminium chloride or Ferric sulphate as a haemostatic agent.
Insert the impression post and blunt the end to ensure 2mm occlusal space is left.
Remove retraction cord.
Syringe light bodied silicone or medium bodied polyether onto the post and preparation
- Then take impression with medium bodied polyether.
Take an opposing arch alginate.
Bite registration- silicone bite registration paste.
Place temp post inside the canal.
Build up core with composite and then use the sectional putty matrix impression to build up the temporary.
Describe the clinical stages of providing a direct fibre post.
Take putty matrix impression of the tooth incase you need to place a temp.
Administer LA
Apply dental dam
Remove any previous restoration and caries
Refine crown margins
Use a GG size 3 or 4 and remove 2mm of coronal GP
Cut the post.
Prepare the post space up to the correct post size.
Irrigate the post space with sodium hypochlorite.
Try in the fibre post- check it goes fully to WL using a rubber stopper.
- Can also take a PA radiograph with the post in situ to confirm.
Prepare the post space for cementation- may need to etch but some cements are self etching.
- etch, prime the canal, coronal space and also the fibre post and light cure for 20 seconds.
Load the post space with cement and then fully seat the cement
- light cure according to manufacturers instructions.
Build up the composite core.
Make temporary.
Take sectional silicone impression for final crown.
- send to lab with instructions.
What are the temporary crown options for a direct post?
Take a sectional impression prior to prep and make a temporary using pro temp.
Direct composite core.
What are the temporary crown options for a direct post?
Temporary denture
Composite core build up on a temporary post to resemble the tooth structure and then tale a sectional putty matrix impression of this.
