8. Endodontically treated teeth Flashcards
FPD options for endodontically treated teeth?
- large restoration with prefabricated post
- cast post and core
RPD options for endodontically treated teeth?
- over denture
- RPD
Characteristics of ETT? (3)
- Dentin modification
- reduction of structural integrity
- reduction of sensitivity
Properties of dentin?
- Help inhibit crack progression
- Fracture toughening mechanisms
Properties of dentin in ETT? (4)
Increased fragility:
- Dehydration
- collagen fibers reduction and degeneration
Less fatigue resistant
Clinical situations when a tooth has degradation of collagen fibers? (3)
- more minerals
- higher brittleness
- higher fracture risk
When do collagen fibers in a tooth degrade? (2)
- endodontically treated teeth
- older teeth
Why is there a reduction of structural integrity in ETT? (2)
- due to the irrgants over the dentin (NaOCL, EDTA, Ca(OH)2)
- less original structure
What happens to lower molars and upper premolars with MOD restorations and endodontic therapy?
Vertical fracture in 50% of the cases
Reduction of sensitivity in ETT? (5)
• Reduced proprioception.
• Higher pain threshold.
• Lowered capability of recording stimuli.
• Less control of the applied forces over it. Needs twice the forces
to react.
• It leads to inadequate behavior under high occlusal loads.
Assessment of the ETT: When is a tooth considered healthy clinically? (3)
- No fractures that extend beyond the boundaries of the
restoration. - Periodontal health.
- No infection (no fistulas, no oozing, etc).
Assessment of the ETT: When is a tooth considered healthy radiographically? (4)
- no root fractures
- no internal/external resorption
- good apical seal
- no radiolucent periapical areas (at least 6 months after endo treatment)
When do we use a cast post and core?
Great destructions
When do we use a prefabricated post?
Smaller and medium destructions
If the pulp canal is cylindrical what do you place inside?
Cast post and core OR prefabricated post
If the pulp canal is oval what do you place inside?
Cast post and core
Where do you place the post in an upper molar?
Palatal canal
Where do you place the post in multicanal teeth?
Largest, straightest canal
Where do you place the post in a lower molar?
Distal canal
Where do you place the post in a premolar with two canals?
palatal canal
What do you place in the canal if the canal is very inclined relative to the occlusal plane?
prefabricated post
Every posterior ETT will need…
A restoration that covers the cusps : onlay or crown
What is the ferrule effect?
- Crown has to have atleast 1.5-2mm of healthy cervical dentin all around the contour of the tooth (on top and all sides)
Why is the ferrule effect important for teeth? (6)
- to optimize the biomechanical properties
- elevates resistance of the crown
- reduces and transmits stress
- dissipates forces concentrated at tooth circumference
- stabilizes restored tooth
- optimizes the resistance form
The more ferrule height, the …
better the prognosis
The more uniform the ferrule in the whole circumference, the…
better and less risk of fracture
A non-uniform ferrule is…
better than none. More important on the palatal and buccal surface
Incase of no ferrule..
- today many prefer the prefabricated post
- if not viable, extract and restore with implant or bridge
What is the minimally acceptable crown to root ratio? why?
- 1:1
- to resist lateral forces
What crown to root ratio will have a better prognosis?
1:2
What are the solutions for a tooth with subgingival destruction? (3)
- crown lengthening
- orthodontic extrusion
- tooth extraction
What do we need for a ETT tooth?
- 1.5-2mm ferule effect
- respect 3mm biological width
- min 4.5mm of supraalveolar tooth structure
What does surgical crown lengthening do? (4)
- increases crown:root ratio
- reduces volume of root dentine
- good option for molars
- delays treatment 3-6 months
What occurs when orthodontic extrusion occurs?
reduction of bone support
Why should orthodontic extrusion be considered before surgical option? (2)
- more favorable mechanical behavior
- preferable for pm and incisors
ETT patients with excessive occlusal wear or parafunction have a higher risk of…(3)
- fracture
- debonding
- fracture of the composite core
If a ETT tooth has a limited prognosis and has to act as an abutment, we should…
evaluate the higher risk of fracture
If a ETT tooth has a limited prognosis and is in a strategic position in a wider restoration plan, we should…
consider extraction
If a ETT tooth has a limited prognosis and is between two implants, we should…
consider extraction and restore with an implant
What determines a successful clinical outcome of the ETT?
- adequate root canal treatment
- adequate restorative treatment
What characteristics does an adequate restorative treatment have? (3)
- good post and core system
- luting agent and techniques
- restoration type, full or partial coverage crown
Why are posts used?
- The retention of the core
- Optimization of the resistance
- Transfer and dispersion of the loads into the root
*strengthens tooth and restoration overall
Indications for placing a post (4)
- Large defects requiring crowning
- Large defects requiring partial coverage
- Narrow abutment diameter
- Immature root with a large root canal
Which materials do not have a reinforcing effect over the tooth or restoration? (3)
- gutta percha
- MTA
- composite
Posts and upper central incisors?
Three times tougher if it doesnt have a cast post and core
Why is a post sometimes beneficial in anterior teeth? (2)
- anterior teeth suffer more from flexural stress
- helps increasing the rigidity and biomechanical properties
What must you always take into consideration with anterior tooth with loss of tooth structure?
the translucency of the final restoration to choose the restorative material
Recommended treatment plan for anterior tooth with loss of tooth structure?
- endo
- prefabricated post and composite resin restoration
- CP&C
Recommended treatment plan for posterior teeth with minor tooth structure loss? (3)
- crown
- onlay
- endocrown
Recommended treatment plan for posterior teeth with moderate (<50%) tooth structure loss? (2)
- increased seveirty if there are also cervical lesions
- prefabricated post and composite resin restoration and crown/onlay
Recommended treatment plan for posterior teeth with severe (>50%) tooth structure loss? (3)
- Post is recommended
- CP&C and crown
- prefabricated post and crown
What is considered moderate (<50%) tooth structure loss? (2)
big occlusal or proximal caries
What is considered severe (>50%) tooth structure loss? (3)
- two or less walls left
- MOD caries
- Cusp loss
If there is no ferrule effect in the posterior ETT, the treatment plan is…
- crown lengthening + CP&C + crown
- CP&C with additional post
ETT premolars? (4)
• Smaller teeth means less structure.
• Smaller pulp chamber to use to increase retention and
adhesion
• Subject to lateral forces during mastication
• The post is usually indicated
ETT when is a post is more indicated in molars? (4)
- coronal structure is totally missing
- small pulp chamber that will not allow us to gain retention and adhesion
Why can an ETT not be the abutment of a free ended RPD?
Four times more risk of fracture
Why cant an ETT be used in a cantilever bridge?
High risk of fracture or failure
In which situations can a ETT NOT be used? (2)
- free ended RPD
- cantilever bridge
What happens to ETT used as abutments of bridges?
Suffer fractures twice as often as teeth without endodontic treatment or single tooth FPDs even with furrule efect
The use of ETT as abutments for bridges with more than one pontic is…
questionable
The clinical preformance of the restored ETT will depend on… (5)
- The post and core material
- The luting agent and technique
- The overlying crown
- The ferrule effect
- The functional occlusal loads
What are posts classified by? (3)
- material
- shape
- surfae
What are the different post materials? (2)
- metal
- esthetic
What are the different post shapes? (2)
- cylindrical
- tapered
What are the different post surfaces? (2)
threaded
unthreaded
What are the different metal posts? (3)
- stainless steel
- Ni-Cr alloy
- Titanium alloy
What are the different esthetic posts? (4)
- carbon fiber
- glass fiber
- quartz fiber
- zirconia
Metal post rigidity?
Very rigid
Metal post indications?
indicated more for posterior teeth and / or crowns
Titanium post characteristics? (3)
- Appeared to avoid corrosion.
- Low radioopacity.
- Low toughness when small diameter.
Stainless steel post characteristics?
Still used successfully
Carbon fiber post characterisitcs? (5)
◦ 8 µm fibers parallel to the axis of the post.
◦ Epoxy resin matrix.
◦ Radiolucent.
◦ Biocompatible
Carbon fiber post elasticity?
◦ Elasticity 21 GPa (dentin 18 GPa)
Carbon fiber post disadvantage?
Dark color
Glass fiber post characteristics? (4)
◦ Translucent.
◦ Favorable color.
◦ Transmit light (cements).
◦ Similar elasticity to the dentin.
Fiber post characteristics?
Flexibility can lead to microleakage and fracture is there isnt adequate ferrule effect
Zirconia post characteristics? (3)
◦ Prefabricated or custom-fitted.
◦ High compression strength.
◦ Very rigid.
Cons of zirconia posts? (4)
◦ Almost impossible to remove.
◦ Require more pulp canal preparation.
◦ Cannot be etched.
◦ Better not to be used.
Cylindrical post characteristics? (2)
- greater retention (more friction)
- create a weaker area of the root at the tip of the post
Tapered post characteristics? (3)
◦ Fit better the pulp canal.
◦ Lower retention.
◦ “Wedge effect” if not deep
enough.
Threaded post characteristics? (3)
◦ Risk of fracture.
◦ Creates high tension
over the residual walls
◦ Don’t use.
Unthreaded post characterisitcs?
Lower risk of fracture of the
root
Prefabricated post purpose?
- intraradicular retention
- doesnt reinforce tooth perse
- helps reinforcement of the tooth (new literature)
*crown really reinforces the tooth
The post’s design will depend on (4)
◦ Length.
◦ Shape.
◦ Surface.
◦ Diameter.
The posts retention depends on… (2)
- design of post
- cement
Characteristics of the post’s length for retention? (4)
- Minimum: crown height.
- Minimum: +/- 8 mm.
- 2/3 of the length of the tooth.
- Leave at least 4-5 mm of apical seal.
Best shape for a post?
cylinder/tapered.
Most retentive surface for a post?
Threaded but high risk
Prefabricated posts are usually…
FLUTED
Characteristics of the diameter of the post?
- The greater the diameter, the greater the retention.
- Not greater than 1/3 of the diameter of the root.
- At least 1 mm of root wall thickness.
- Always try not to weaken the tooth.
Prefabricated post procedure? (12)
- radiograph
- Confirm apical seal and performance of the endodontic treatment
- Calculate working length (4-5 mm of apical seal)
- Remove gutta-percha with GatesGlidden drills.
- Shape canal
- Put post into canal and take xray
- Cement post
- Build up core
- Crown prep
- impression
- provisional restoration
- cementation of crown
How do we shape the pulp canal with drills? (3)
- Increasing diameter.
- Contra-angle hand piece.
- Up to the desired width.
Why do we take an xray of the post in the canal? (2)
- check the fit
- Confirm all gutta percha has been removed
How do you cement fiber posts? (3)
- composite resins
- translucent post: dual-cure
- opaque post: self cure
How do you cement metal posts? (2)
- zinc phosphate cements
- glass ionomer cements
What is a CP&C
Cast posts and cores
Cast in one piece (core and post joined)
CP&C requires a ___ afterwards
Crown placement
CP&Cs are independent from… (2)
- the final restoration
- the fit of the restoration
CP&Cs must be made of… (2)
- a noble alloy
- the same alloy as the final restoration
How long should the post of CP&Cs be?
Into the root below bone level to prevent fractures
What is the minimum diameter for a CP&C?
1mm
What type of surface is needed for a CP&C?
Flat supporting surface
Margin of CP&C restoration must …
end over healthy dentin
Crown of CP&C must..
surround the CP&C completely to double its strength
How do you prepare the pulp canal for CP&C? (3)
- Same as for prefabricated posts.
- Conical drills should be used after GatesGlidden drills.
- Width of no more than 1/3 of the diameter of the root.
How do you prepare do the coronal prep for CP&C? (3)
- A small slot must be made to prevent rotation.
- Surface must be flat to provide support.
- Remove any undercuts in the coronal area (check direction of the pulp canal)
Indirect procedure for CP&C? (5)
- manufacturing at lab
- LBS poured in pulp canal
- bolt placed right after
- rest of impression taken
- wax pattern made over cast with shape of final abutment
What characteristic is needed for the bolt in the direct impression pattern?
Must have a retentive end
Direct pattern clinical procedure? (9)
- Pattern of the CP&C is made in the patient mouth.
- Made of acrylic resin.
- Sent to the lab for casting.
- canal lubricated with petroleum jelly
- plastic bolt used as support for resin
- resin prepared and pushed into canal
- acrylic core built
- when set, prepared for crown
- dental tech casts the CP&C
how is the acrylic resin prepared and pushed into the canal in the direct pattern?
With lentulo and bolt
How is the acrylic resin core built in the direct pattern ?
With a brush and plastic instrument
What is the overstable post procedure for CP&C?
- A noble alloy prefabricated post is put into the canal.
- The rest of the core is built with acrylic resin.
- The dental technician overcasts the CP&C.
What is the multiple canal post procedure for CP&C? (3)
- A second canal is used to increase retention.
- The widest pulp canal is prepared in the usual way.
- The preparation of the second canal is shallower
What is the multiple canal post procedure for telescopic CP&C? (4)
- Overcastable post in the main canal.
- Prefabricated post in the secondary canal.
- Core build with acrylic resin.
- The abutment preparation can also be designed at the
laboratory
When do we have no post and composite core building?
- Molars and small destructions. -
It is enough taking advantage of the anatomy of the pulp chamber
When do we use a fiber post? (5)
- When at least 50% of the structure is lost
- Two surfaces or less are present.
- Incisors and premolars.
- Studies on pm demonstrated less fractures when
posts are placed - Molars, if crown structure is missing and insufficient
pulp chamber
When are the pre-restorative treatments for ETT?
- crown lengthening
- ortho extrusion
When do we need a cast post and core? (4)
- Big destruction
- No ferrule
- Patients insisting on trying to save the tooth
- Acceptable results
When do we do an extraction? (2)
- When the tooth has no viability
- Because of the planification the extraction makes more
sense
