ETT 1 Flashcards
When is Endodontic Treatment indicated?
- Deep caries
- Trauma
- Primary periodontal infection
- Elective endodontic treatment to facilitate prosthodontic rehabilitation
Reasons for fracture in ETT
- Loss of tooth structure
- Endodontic irrigants and medicaments
- Bacteria-dentine interactions
- Age-related changes in dentine
- Reduced protective response to loading (Loss of pressoreception or elevated pain threshold)
- Restorative factors
Differences between ETT and vital tooth?
- ETT abutments had higher failure rate
- ETT more likely to fracture
Is a crown needed after endo treatment?
Anterior teeth: No significant improvement in success of ETT
Posterior teeth: Significant improvement in success of ETT
Why do posterior teeth need crown after ETT?
Cuspal coverage prevent fracture when occlusal forces attempt to separate the cusp tips
When should we crown posterior ETT?
- Large magnitude of force
- Proximity to terminal hinge axis (Class III lever)
- Vertical path of loading
When do we not need to crown posterior ETT?
1.No opposing dentition
2. Tooth is out of occlusion
3. Enough remaining tooth structure (Dens evaginatus)
When should we crown anterior ETT?
- Plastic restorative materials have limited prognosis
- Extensive loss of tooth structure
- Aesthetic requirement
Definition of Anchorage
Securing of restoration by supporting abutment
Anchorage can be achieved by
- Mechanical (Preferred): Reciprocal locking of 2 opposing surfaces of abutments
- Adhesive means: Bonding between restoration and enamel/dentine
Quality of enamel/dentine is critical
For mechanical anchorage, there should be
3-4 mm of tooth structure available interproximally
What should you do if there is insufficient tooth structure available?
Foundation restoration: Core build-up portion of a tooth that is prepared for an artificial crown (Post+Core)
How should you restore intact and vital teeth?
Direct restorations (TCR)
How should you restore vital teeth with the lingual cusp partly destroyed?
Reconstruct a conical abutment with CR
CR increment should be limited to 1-1.5 mm only
How should you restore vital teeth with buccal and lingual cusps partly destroyed?
More than 1.5mm CR build-up needed to get conical abutment
Elective endodontic treatment is required
1. Core bonded to pulp chamber
2. Post + Core
What is the Nayer’s technique?
Amalgam coronal-radicular dowel(post) and core technique
- 2-4mm of GP removed
- Fast-setting amalgam condensed into canals, pulp chamber, coronal portion of tooth
- Crown preparation
- Cast restoration cemented over amalgam core
How should you restore non-vital teeth with extensive damage + ferrule?
- Endodontic treatment
- Post + Core
How should you restore non-vital teeth with extensive damage + NO ferrule?
- Endodontic treatment
- Crown lengthening
- Post + Core
Function of a Core
The foundation restoration which restores sufficient coronal anatomy of a vital tooth or ETT
Function of Post+Core
Provides retention and resistance for artificial crown
Post and core systems strengthen the root. True or false?
False
Ideal properties for foundation restorations?
Post
1. Distribute occlusal loads to entire surface of post space
2. Adequately retained within root
3. Well-contrasted on radiographs
4. Retrievable whenever needed
5. Light in colour if root/planned restoration is translucent
6. No health hazard
Core
1. Stable relative to root
2. Resist occlusal loads
3. No health-hazard
What is a ferrule?
1.5mm-2mm of dentine protrudes above gingival level
What is the ferrule effect?
Small cone of dentine protects the root against splitting
What is the most-important feature of a post-core design
Ferrule bracing
Criteria for successful Endodontic Treatment
- No pathologic signs and symptoms
- Normal periapical tissue (via radiograph)
- Signs of decreasing radiographic PA lesion
How much GP is needed to maintain apical seal?
As much as possible.
Study shows 5mm of GP can achieve a balance between adequate apical seal of canal and sufficient length of post for retention and resistance
Advantages of immediate post placement?
- Greater familiarity with root canal morphology (less risk of perforation)
- More precise working length determination
Immediate post space preparation via hot pluggers does not seem to different from delayed preparation with drills. True or False?
True
Why should we decrease time interval between post space preparation and cementation of post?
Temporary restorations and provisional crowns do not provide a tight coronal seal
Function of Post
Retain core and Minimise stress concentration
Considerations when selecting a post
- Custom-cast post-cores (CPC) vs Prefabricated posts
- Shape (Tapered vs parallel-sided
- Material
- Passive vs Active
- Surface texture
- Post length and diameter
What are the ADVANTAGES of CPC (Indirect technique)?
- Optimally conforms to existing canal (More critical for severely-damaged teeth)
- Appropriate for slender roots with small root diameters and small diameter teeth
What are the DISADVANTAGES of CPC (Indirect technique)?
- Increased no. of appointments needed (At least 2 visits)
- More expensive to fabricate
What are the ADVANTAGES of Pre-fabricated post+core (Direct technique)?
- Convenient and straightforward (Only 1 visit required)
- Less expensive
What are the DISADVANTAGES of Pre-fabricated post+core (Direct technique)?
- May not be appropriate for slender roots with small root diameters
(Cannot maintain minimum dentinal thickness of 1mm)
- May not be suitable for small diameter teeth
(Insufficient space for core material to adequately surround the post
Advantages of Tapered/Conical posts?
Better conform to overall contour of root
Disdvantages of Tapered/Conical posts?
- Greater stress concentrations in apical zones of root
- Poorer pull-out strength
Advantages of Parallel-sided/Cylindical posts?
- Less stress concentration in apical zones of root
- Better pull-out strength
Disdvantages of Parallel-sided/Cylindical posts?
Does not conform to overall contour of root, especially slender roots
Which post material is custom-made?
- Noble alloy
- Zirconiun oxide
Which post material is pre-fabricated?
- Stainless steel
- Co-Cr or Co-Ni alloy
- Titanium
- Zirconium oxide
- Fibre-based
Which post material has high strength?
- Noble alloy
- Stainless steel
- Co-Cr or Co-Ni alloy
Which post material is highly biocompatible?
Titanium
Which post material has low toughness and brittle?
Zirconium oxide (Avoid using as post)
Which post material has a mode of failure of debonding?
Fibre-based (resin composite structures)
Which post material is soft and mechanically inferior?
Titanium
Differences between Fibre posts and Metal Posts
- Resins can bond to roots
- Fibre’s post modulus of elasticity is lower, less stress concentration in root
- Fibre posts will not corrode
- Fibre posts are more conveniently removed during re-treatment
Differences between passive and active posts?
Passive posts merely adapt to the inner walls of post space
Active posts have threads that are either self-threading or tapped
Self-threading vs Tapped posts
Self threading: The post cuts its thread during placement
Tapped: Screw thread is formed with special tool before post placement
Advantages of Passive Post
Does not generate stress concentration in dentine walls
Advantages of Active Post
Tremendous pull-out strength
Disadvantages of Active Post
Generate local tensile stresses, magnified when post is loaded during function
Purpose of Serrations on Post
Increase retention
Serrated posts are passive posts. True or False?
True
Considerations for post length?
- At least equal but preferably exceed the clinical crown height
- As long as possible without disturbing apical seal
- > 4mm apical to bone crest or at least 1/2 root length in alveolar bone
Considerations for post diameter?
- Preserve as much root substance as possible
- Does not exceed 1/3 of root width at its apical end
- At least 1mm root dentine around entire post length
What is the core material for amalgam?
Dispersalloy
What is the core material for composite resin?
3M ESPE FIitek Supreme Ultra
LuxaCore Z Dual
What is the Prefabricated Metal Post called?
ParaPost (Titanium alloy or stainless steel)
What is the Prefabricated Fibre Post called?
D.T. Light-post
What is the Metal Custom Cast-Post-Core called
ParaPost system + Noble metal alloy
Prefabricated Metal/Fibre Post + CR core are cemented with?
Resin cement