Posts Flashcards
What is a post and its purpose
Foundation for indirect restoration
The main purpose of a post is to provide anchorage for a core upon which a restoration can be placed
Indications for posts
When the crown of a tooth has been damaged to the extent that a conventional restoration to restore it is not attainable
When the coronal portion of a root filled tooth has been lost
What are the different types of posts?
Metal (nickel/ chrome alloy)
Prefabricated post (stainless steel/titanium alloy/nickel-chrome)
Cast post (gold alloys)
NON-METAL
Fibre posts
What are the advantages of metal posts? Not on LO
Adaptability- can compensate for between the angulation of the root and the planned crown
Core retention- cast posts don’t have the potential for separation like a prefabricated post and its core
Strength- in comparison to the non-metal counterparts
What are the disadvantages of metal posts?
Root fracture- have a higher incidence of root fracture than non-metal
Aesthetics- when an all ceramic crown is to be used the metal post can alter the optical properties
Biocompatibility- Corrosion?
Preparation of metal posts?
During prep- need to retain as much coronal dentine as possible
The amount of remaining dentine is determined by caries present and also the required dimensions for a crown
The preparation must allow-
Provision of a ferrule
Increase post retention
Resist post rotation
What is the ferulle effect?
When the supra-marginal dentine of a root filled tooth is engaged by a crown, it may create a stronger tooth/restoration complex. This is termed the ferrule effect”
A ferrule is achieved by the parallel walls of the dentine extending coronal to the shoulder of the preparation
This is a protective effect, reducing the stresses within the tooth
What is the definition of ferulle
A ferrule is a band of metal (of the indirect restoration) which totally encircles the tooth, extending 1 to 2 mm onto sound tooth tissue to guard against longitudinal fracture.
What are the other considerations in radicular preparation?
The width of the post is important and should not be more than 30% of the width of the root-face, measured in a labial-palatal direction
If a post is too narrow, it will have insufficient strength for long term survival
While excessive width increases the risk of perforation and root fracture
Some lower anterior teeth are very slender and unsuitable for para-post technique
Considerations for preparation of post
Post length
Post shape
Surface characteristics
Post space preparation
Guarding against coronal micro leakage
What about the post length
Long posts are more retentive than short posts
Posts can be lengthened by extending as apically as possible and leaving as much coronal tissue as possible
No place for de coronating roof top preps
Leave 4-5mm apical GP to ensure apical seal
Post shape considerations
Parallel sided posts more retentive than tapered posts
Wedging effects of tapered posts leading to root fracture
if its is a wide, flared post but thin walls, this is more prone to fracture
Surface characteristics of metal posts
Dentine - elastic
Self-tapping threads set up stresses
Some are also tapered
Often leading to root fracture
Examples- Radix anchor, Dentatus, Kurer anchor -prefabricated posts
Post-space preparation - Minimising danger
Prepare the post space at the time of obturation
Most familiar with angulation, reference points
Rubber dam still on keeps bacteria out
Guarding against coronal micro leakage
A major cause of root treatment failure
Saliva and microorganisms- poorly adapted restorations, even and well condensed RFS
Leading to periapical reinfection
One type of cast post system is
Parapost XP
This system provides a means with which to obtain an impression for a permanent restoration and produce a temporary replacement for a coronally damaged tooth
Produces a parallel sided cast post
The contents of a parapost kit are…
Colour coded- parapost drills, impression posts (smooth sided plastic), temporary posts (metal posts), burn out posts (serrated plastic posts)
Step by step using a parapost (not in the LO)
Use peeso raemers, size 2-3 to remove GP from the canal ensuring that 4-5mm of GP is left at the apex
Use parapost twist drills to parallel the side walls in colour order as shown in the kit
Only work up to a size that is about 1/3 of the width of the root face
Select temporary parapost and cut it to size
Use this to form the basis of the odus pella temporary crown
Prepare the temporary crown as before
Cementing the cast post
The post and core is cemented using RMGI cement
Place retraction cord and take a PVS impression for the MCC
Choose a shade for your crown
Remember to take an impression of the opposing teeth in alginate
Occlusal record- blue mousse
What are the signs that a cast post might be failing
Debonded restoration?
Pain
Swelling
Sinus formation
Why does a post fail?
Biological
Aetiological
Material design
Biological?
Caries- always need to check around the crown margins, poor marginal fit/contour
Endodontic failure- incomplete disinfection/ inadequate initial endodontic treatment/ coronal leakage
Root fracture- excessive tooth tissue loss during preparation/ no ferrule/ traumatic occlusion
Aitrogenic
Perforation- difficult endodontic treatment (root morphology)/ inappropriate post space preparation
Material/design-
Debonding/decementation- wrong cement choice/ inadequate moisture control/ inadequate post length/ traumatic occlusion
What are fibre posts (made from)
These are now made from silica or quartz fibre strands surrounded by a matrix of polymer resin
There are several manufacturers
Why use non metallic post systems?
A material with a modulus of elasticity similar to dentine would allow for more even distribution of mechanical stresses and reduce the incidence of radicular fractures
Aesthetics
All ceramic crowns
What are the advantages of fibre posts?
The elasticity of fibre posts more closely matches that of dentine than metal posts
They flex under pressure and the stress is distributed more evenly between the post and the dentine
They are less likely to cause tooth fracture
They are managed at chair side and impressions are not necessary
Tooth selection for fibre post preparation
There should always be at least 2 mms of dentine left above the labial face of the root-filled tooth to be restored
How are fibre post restorations used?
The root-filled tooth is prepared coronally, where the canal is then cleaned out using a peeso reamer
Each kit contains twist drills and the diameter of these will match the diameter of the fibre post
The twist drill is used to prepare the canal walls
What is the DT light post clinical procedure?
Post preparation made with universal drill
Final preparation using the appropriate colour coded finishing reamer
What do you do after crown prep and the canal prep?
Seat the post
Cut with a diamond bur to the appropriate length
After that? (Still DT light post clinical procedure)
Apply etch to exposed dentine for 15 seconds
Wash for 10 seconds, remove excess water from canal with paper points but leave the surface moist
Bonding…
Apply 2 coats of the primer in the canal
Remove excess with paper points
Air dry and light cure 10-20 seconds
Apply one coat of the primer onto the post
Air dry
Light cure surface of post for 10-20 seconds outside of the mouth
Cementation…
Completing of core
Cementation…
Place Corecem cement into canal and insert the post
Hold the post steady within the canal and light cure for 40-60 seconds
Completing the core
Some systems will allow the operator to continue to use the resin cement to build up a core. This can then be modified with a diamond bur, and the crown preparation can be completed
