Restoration of endodontically treated tooth - posts Flashcards
What are the measurements for post placement? (width and length)
Post needs to be longer than the clinical crown
Need 4-5mm root-filling apically
Post width - has to be no more than 1/3 root width at narrowest point. Will seriously weaken the tooth if not enough dentine either side of the post.
What is a post/ core?
Gains intra-radicular support for a definitive restoration.
CORE provides retention for crown
POST retains the core
What does a post do to strength of tooth?
Post does not strengthen or re-enforce teeth
Preparation of root canal for a post WEAKENS TOOTH
What is a ferrule?
A ferrule is 360 degree collar of circumferential dentine extending 2-3mm above the gingival margin.
What is the primary factor that indicates if an RCT will fail or not?
Having a good coronal seal
What are the 3 factors that make an ideal post?
parallel-sided
Non-threaded (passive) - smooth surface incorporates less stress to remaining tooth
Cement-retained
What is a direct and indirect post?
Direct - comes in a kit and place directly into tooth
Indirect - made in a lab
What are the advantages of a ceramic post?
High flexural strength and fracture toughness, favourable aesthetics
What is a core build-up?
Internal part of tooth is built-up with restorative material to replace the lost tooth tissue.
Core prepared and provides retention.
What is the most commonly used core material?
Composite
Benefits and disadvantages of composite as a core build-up material?
Advantages - Tooth coloured = good aesthetics, bonds to tooth structure
Disadvantages - technique sensitive so moisture control required
Disadvantages of GI as core material?
Absorbs water and core expands in size
Less stable than composite
What problems can occur with post crowns?
Perforation
Core fracture
Root fracture or crack
Post fracture
What is a good prognosis for an endodontically treated tooth?
10 years
When would a post be required?
Insufficient tooth structure to restore without - no walls remaining or if there has been a loss of 3 walls.
What are the appointment stages for a direct post?
- Endo treatment and temporise
- Obturation and temporise
- Para-post kit to drill out GP to size of post you want. Cement post and prepare core. Take impression of cemented post and core to make crown.
- Get final crown made and fit.
What are some stresses that may cause root fracture?
Functional lever forces
Lateral forces exerted during post insertion
Wedging effect of tapered posts
Give 3 potential reasons why a post-core may de-bond?
Secondary caries
Poor moisture control during cementation - poor operator technique
Root fracture
Give 4 reasons why a fracture at the junction of the post and core may occur?
Weakest point - more likely to fracture here
Lack of sufficient ferrule
Trauma
Bio-corrosion
Name 3 ways of receiving a fractured post?
Ultrasonic tip
Moskito forceps
Eggler forceps - specifically for removing posts
Are cast or fibre posts more likely to fracture the root?
Cast posts
Are cast or fibre posts more likely to de-bond coronally (leading to recurrent caries)?
Fibre-posts
Whats advantages of cast metal posts?
Custom made - follows canal shape
Useful in flared canals
Conserve tooth tissue which reduces risk of perforation compared to parallel-sided fibre posts
What are advantages of fibre posts?
Can be placed immediately
Tooth coloured - enhanced aesthetics
Compatible with current adhesive systems
Low elastic modulus similar to dentine - post absorbs/ dissipates stress
What teeth should not have posts placed and why?
Lower incisors - too thin roots would end up hollowing out whole tooth for post prep
Molar teeth
What are some disadvantages of fibre-posts?
Difficult to remove upon re-treatment
What are some disadvantages of cast metal posts?
Direct/ indirect techniques - impression required - lab and extra clinical stages
More room for error
Unfavourable aesthetics if shine through
What are some advantages of tapered posts?
Follows root form ensuring maximal remaining root dentine apically
Less likely to perforate
Stress concentration coronally
Better for small tapered roots
What are some advantages of parallel posts?
Uniform stress distribution along the length
Do not generate as much stress in root canal because wedging effect is less, therefore lower risk of root fracture
What are the disadvantages of parallel posts?
More tooth structure removal - higher risk for perforation
Stress concentrated more apically
What are some disadvantages of tapered posts?
Induce more stress into the root increasing the risk of root fracture
What are disadvantages of a ceramic post?
Difficult retrievability and root fracture common
