Post and Core Fabrication Techniques Flashcards
What are the techniques used for fabrication of post and cores?
Direct: Pre-fabricated post + core (composite or amalgam)
Indirect (Impression technique)
Direct-indirect: Burnout resin technique
How should coronal structure be prepared for post core and crown?
Removal of existing restorations.
Eliminate undesirable undercuts (cast post and core only)
Crown preparation to create ferrule
What is the tradeoff that should be considered when choosing post length?
Retention vs seal of the root canal.
What are the steps taken in the direct technique?
Select pre-fabricated post
Check if antirotational features are needed
Cement post
Core build up
Crown preparation
Temporary crown
What are the steps taken in the impression technique?
Select impression post (plastic and smooth surface)
Impression using the impression post
Pour p
Burn-out post and core
Cast the post and core
Cast post and core cementation
Refinement of the crown preparation
Temporary crown
What are the steps taken for the burn-out resin technique?
Select burn-out post (plastic and serrated surface)
Separator (canal and coronal surface)
Copy the shape of the canal using duralay resin (bead-brush technique)
Core build-up using duralay resin (bead-brush technique)
Crown preparation on the burn out post and core (rough prep)
Temp post-crown
How is length of the post space determined?
At least 5mm apical seal
Very short roots and high crowns = 4mm apical seal.
Post length at least equal to the crown length (2/3rd of remaining tooth length, 1.2 of the clinical root, 3.4 of the root canal length)
What steps should be taken for post space preparation?
Determine post length based on PA.
Rubber dam
Remove the GP
Take PA to verify if WL has been reached.
Post space preparation (using parapost system)
Why is rubber dam used?
Avoid bacterial contamination (saliva/blood)
Avoid inhalation of instruments
Avoid contact of sodium hypochlorite with mucosa
How is GP removed?
Start with heated plugger and use a rubber stop to mark the WL
Use a Gates Glidden bur to reach the WL
How can perforation be avoided while removign GP with GG bur?
Use bur parallel with the path of insertion with light vertical forces.
Start with smaller bur and increase size.
Should see red GP coming out not white dentin.
Take PA if you aren’t sure if the bur is following the root canal.
How is post space preparation done?
Use parapost drills
Create parallel walls (let the drill make the work do not tilt the drill)
Remove undercuts inside the canal
Establish the width and shape of the post
Take PA after all this to ensure there is no GP still in the walls prior to placing the post in
How can width of the post be established?
1/3rd of the total width of the root.
What factors should be considered when thinking about placing a post?
Increased post width = increased retention and resistance
Wide post weaken the root (removal of tooth structure)
No more than 1/3rd of the width of the root
Preserve buccal wall in upper incisors.
What is the minimum size for a pre-fabricated post?
0.9mm
1555
1555
How can the post space be made anti-rotational?
The post space should have an elliptical shape to have an antirotational feature.
If the canal is circular, create a small groove in the root canal followign the path of insertion on the thickest wall
In multi-canal teeth, using more than one canal can provide the antirotational feature to improve retention.
How is the small groove made in the post space to provide antirotational support?
It should be 3 - 4mm deep
Should existing temporary restorations be removed and the crown prep done before or after the post space preparation?
Can be either:
If before you get better visualization of the canal, you know how much tooth structure remains so you can plan the post space preparation accordingly (length, shape, antirotational), but the issue is you can sometimes lose the reference point for the post space preparation meaning a new PA would be needed and a new reference point.
If done after, you can maintain the reference point that was established using the PA that was taken after the RCT which is easier to temporize using multi-appointment post space preparation
How should the coronal tooth structure be prepared for the final restoration?
Remove all existing restorations
Eliminate undesirable undercuts
Make the full crown preparation
Eliminate unsupported tooth structure (<2mm)
Preparation of margins (create ferrule)
Positive horizontal stop
How much width should be present when restoring tooth structure?
Minimum of 2mm of enamel width and 1.5 - 2mm of enamel height for ferrule.
What are the indications for the impression technique?
Multiple post and cores
Abutments of bridges (easier to establish parallelism)
Posterior teeth with divergent canals
What are the advantages of the impression technique?
Faster clinical procedure compared to burn-out resin
Lab will manufacture the post
What are the disadvantages of the impression technique?
May introduce errors
May need more adjustments during the try in
What should be done prior to the impression technique?
Use full arch stock tray or custom tray
Dry the canal (air and paper points)
Verify the impression post seating
Apply the light body PVS
Seat the impression post
Apply medium/heavy body on the tray
Insert the tray
Remove the tray with a snap movement
Which post should be used for the impression technique?
Smooth surface round post.
What are the indications and contraindications for the burn-out resin technique?
Indication: Uniradicular or multiradicular teeth without divergent root canals.
Contraindications:
Patients allergic to monomer
Patients who cannot stay with the mouth open for a long period of time.
Divergent roots
What are the advantages and disadvantages of the burn-out resin technique?
Advantages:
You have control of the shape of the post and core
Less adjustment usually during try in
Disadvantages:
More difficult method
More clinical time is necessary.
What is the technique for using burn-out resin technique?
Dry the canal (air and paper points)
Select the size of the burn-out post
Apply separator in the canal and coronal structure
Apply acrylic resin (Duralay or pattern resin) inside the canal and around the burn-out post (bead-brush technique) - PASSIVE FIT.
Insert the burnout post in the canal
Wait until the acrylic starts to set, then make in and out movements until the acrylic polymerize
Use water based lubricant in the canal and around the coronal tooth structure to avoid adherence between the resin and the tooth.
Build up the core after the modeling of the post
Apply duralay to reestablish missing coronal structure (do not overbuild)
Make the crown preparation
Remove the handle and check occlusal clearane (MIP and excursion)
Send acrylic post and core to the lab for cast
What should be done in posterior teeth when there isn’t much coronal structure to support the core material?
Use more than one post
What should be done if the roots are divergent?
Multipiece cast post and core
More retention
Impression technique
Where should the main post be in upper molars?
Palatal root
Where should the main post be in lower molars?
Distal root
How is the burn-out resin technique done in teeth with divergent roots?
Copy with one post one of the canals (main canal)
Adjust first post with disc
Seat the second post in and when fully seated seat the first post (with vaseline)
Create the core attaching it to the second post but not the first.
Remove the first post while leaving the second post and the core intact.
Remove the second post and core.
Lab creates cast
Place the second post and core in followed by first post
Which posts should be used for direct technique?
Stainless steel post or titanium post
How can core retention be improved with the direct technique?
Leave undercuts
Add pins if necessary
Use amalgam tags in other canals (amalgam core in posterior teeth)
How can core retention be improved with the direct technique?
Leave undercuts
Add pins if necessary
Use amalgam tags in other canals (amalgam core in posterior teeth)
Use pins if needed to retain the core.
Ensure that the canals are dried with paper points prior to placement of the core.
What are the steps used in order to place the pre-fabricated posts in the canals?
Dry the canal (air + paper points) Important to prevent secondary infection
Select size of pre-fabricated post that fits tight in the post space (same as the last parapost drill used)
Check length of the post according to the interarch space (3 - 4 mm from the occlusal plane)
Adjust length by cutting apical end if needed (post completely embedded in the core material
Clean the post space and dry very well
Cement the post with resin (metal and fiber posts) or GIC and RMGIC (for metal posts)
Wait at least 10 minutes for complete setting
Place core and crown prep
