Post and Cores Flashcards
What things to check for when assessing whether a RCT’d tooth has been successful?
Lack of symptoms
No pain
Not TTP
No palpation pain
No swelling
Radiographic healing
Functional and aestehtic tooth
Describe radiographically a failed RCT?
Presence of a periradicular radiolucency, unchaned or a new increased rarefraction
When does a RCT’d tooth new re-reatment?
If the GP has been exposed in the mouht for some time
OR
if post-treatment disease has been diagnosed
What factors dictate whether a tooth has a good prosthodontic prognosis?
The quality and quantity of remaining tooth structure is the single most important factor
What to assess in the root filled tooth?
Remove all caries, restorations and assess the quatity distribution and quality of tooth substance remaining
What is the ferrule’s effect?
The remaining coronal tooth tissue offers retention, resistance and a substrate to bond to
What is the defintion of the ferrule?
A metal ring or cap intended to embrace the tooth structure cervically to achieve root strengthing and prevent shattering of the root
2mm H
1mm W (from post hole to margin)
What factors influence the ferrule?
A longer ferrule increases fracture resisatnce significantly
Also resists lateral focres from the posts and leverage from the crown in function
It increases retention and resistance of the restoration
Name the 5 requirements for a successful crown/crown prep?
Ferrule (dentine axial wall height) must be at least 2-3mm
The axial walls must be paralled
Restoration must encircle tooth
Margin is on solid tooth structure
Corwn and prep must not invade the biologic width
What are the clinical complications for missing 1 of the 5 requeirements of the prep?
Root Fracture
Coronal apical leakage
Reccurent caries
Dislodgement or loss of the core
Perio injury - LoA, recession, and bone loss - biologic width invasion
What are the 4 advantages for the Ferrule effect?
Provides anti-rotational features
Increases longevity of post and core
Failure of restoration tends to be retrievable
Increases the fracture resistance of the RCT’d teeth
Is GP antimicrobial?
No
How to remove sealer from pulp chamber?
Alcohol
How to seal the pulp chamber?
Vitrebond - RMGIC
When should we place the post?
Immediately after the prep
WHat are the advantages of placing the post immediateyl?
Familiarity with RCS and WL
Decreased risk of perfs or excessive GP removal
Does NOT disrupt the apical seal
Delayed post space prep does decrease chance of coronal leakage
How does length of post influence success of RCT’d tooth restoration?
More important than width
The longer the post, the better the retention
Siginificant increase in clinical success if longer than the crown height
Shorter posts have poor retention and transmit lateral forces to the remaining root structure compared to longer posts
Need for >4-5mm of GP apically
What is the ideal width of the post?
Adequate width important for post strength and resistance to fracture
Optimum is <1mm width at the tip
but consider root morphology - larger roots can perforate the tooth
Diameter of the post at its tip should be <1/3 of the diameter of the root at the corrsponding depth e.g. lower incisor .6 and upper incisor 1mm
What are the risks of a wider post?
Increased risk of root perf
Increased cervical stresses
Decreased impact resistance
Decreased resistance to root fracture
Explain how to remove the GP for a post?
Chemical - increased apical leakage
Thermal - can distub apical GP
Mechanical - most efficient
GG (Gates Glidden) do not causes the large increases in temperature
Hand or rotary removal of GP?
Hand less change of iatro and temo
Rotary greater change of iatro and temo - high torque and low speed
Explain the process to remove GP and prep the post hole mechanically?
Use non-end cutting bur GG
Cuts GPP preferentially than dentine walls
Then use peeso reamers/parapost reamers to finally comple the prep after GP removed (can lead to increases in temp)
What are the ideal properties for a luting cement?
Insoluble
Prevent microleakage
Adherere to radciaulr dentine - potentially reinforce root
withstand fatigiue froces well
Can risk generation microcrack can culminate in the failure of the restoration
Name 3 types of traditional luting cements?
ZPC - mechanical means no chemical
GIC - depends on resin content - can bond more to dentine
RMGIC - no indicated for posts due to hygroscopy
Name the advantages and disadvantages of resin-based luting cements?
Potentially reinforce tooth
Aid post retention
Require pretreatment with etch and bond
adhesives form hybrid layers allong the post space walls
But bonding to radicular dentine may be affected by NaOCl which is strong oxidising agent
Leaves oxygen rich layer on dentine - inhibits poly of resin
Eugenol diffusing affect retention of bonded post
Explain how to use dual cure resin-based luting cements?
Difficult for moisture control
Use self-etch prposed as an alternative, but hard to penetrate smear layer
Dual cure adhesives developed to ensure better pilymer deeper in root
Contain ternanry catalyst to ofset acid base reaction
Explain how to use self-adhesive resin-based luting cements?
Alternative to conventional resin-based luting cements
React with hydroxyapatite
Does NOT reuire pretreatment of root dentine
Reduces techique sensitivty
Also dual cure, and so need light
adhesion similar to multisetp luting cememnt, not recommended for bonding to enmale without phosphoric etch
Not clinically proven to work
Chemically active resins?
4-META
Don’t use impossible to remove post
Name the advantages of adhesive cementation?
Improved marginal adaptation
Improved apical seal
Increased post retention - even for short posts
Relives stress in root canal
Optimises fracture patterns for re-restoration
Name the disadvantages of adhesive cementation?
Difficult to access without magnification
Remnats of acid and debris from prep
Bondign areas decreased by GP remnants, smear or sealer
Voids and gaps in cement interface
Name the 4 main aims for resotorative management of root filled teeth?
Presevre tooth structure
Protect tooth structure
Maintain seal in canal
Allow for re-tretment
What is the function of a post?
Retain the core when the reamining tooth structure is considerably reduced
Stress distribution to radicular dentine and alveolar bone
No strengthening effect excepts for fibre posts
What infleunce the difficulty of a root filled tooth restoration?
Quantity and location of remaining tooth structure
Location of access cavity
Consider the quantity of remaining dentine - coronally, pulp chambers and RCs
Indications for a post?
Primary aim is retention for the core when little detine and little useful pulp chamber remain
How to choose a post?
Passive
Parallel sided
Roughened surface
Easy to use
How long should the post be?
As long as the crown
2/3rd of the length of the too
50% of the root length surrounded by bond
As long as possible
Name the 2 function of the post?
Core retention
Stress distribution
Name 5 factors that determine the dimensions of the post?
Root length
Root diameter - <1/3 diameter of root
Extention of root filling - 5mm min to maintain apical seal
Clinical crown height
Alveolar bone levels
Give an example staging for a cast post and core?
Review RCT
Post space prep
Crown prep
Review anti-rotation
Coronal finishing
Temporary restorations for the cast post and core?
Indirect - imps + cast
Direct - resin pattern
Comapre the indirect versus direct techniques for temproary restoration?
Indirect:
- less surgery time
- working imos
- opposing cast
- shaape of core technician determined
Direct:
- increased surgery time
- direct pattern
- no opposing acst
- core shape by operator
Name the 3 tools for the parapost?
Temp post
Imps post (smooth)
Pattern post (serrated)
Describe the indirect technique for post creation?
Elastomeic impression (wash imps) + lab fabrication
Using smooth imps post
Describe the direct technique for post creation?
Colours relate to parapost diameter
Using serrated burn-out post + DuraLay
Describe the Nealon Incremental Technique
Lub canal with DuraLay - bead brush
Force down canal to express trapped air
Record intra-radicular anti-rotation feature
Trim with turbine + diamon + waterspray
What to do before trying in post-retained core?
Inspect and remove any casting blebs
Name the potential problems for metal posts and cast etal cores?
Radicul;ar fracture
Coronal leakage
Retriveability
Name 3 types of fibre posts?
Carbon
Glass
Quartz
Explain the clinical technique for fibre post placement?
Evaluate pre-Op radio
Determine post length + width
Create post prep and anti-rotation - before refining coronal prep
Extra-coronal prep
Eval H:W of axial walls
Post length
Finial finish
Self-etching composite luting cement - Rely X Unicem
Name the disadvantages of fibre posts?
Post fracture
Loss of retention
Bond of composite resin to dentine
Bond to post
What will determine the success?
Amount and location of the remaining tooth structure
Why do we need a core?
Provide retention and resistance form
Restoration of coronal tissue
Durable coronal seal
How can we increase retention and resistance using a core?
Use of adhesive materials to bond to tooth
tissues (crown and core)
Use of undercuts and grooves in remaining
tooth tissue (core)
Use of ferrule (crown)
How do we assess the need for a core?
- Can the tooth provide retention for its extra-coronal
restoration without additional material being added? - Do we need to add material that will aid resistance and
retention, or do we just need to block out irregularities? - Is there sufficient remaining tooth tissue to retain and
support a core? - Can a ferrule be achieved?
Advantages of the coronal seal? vital and nonvital?
Vital:
➢Provides increased pulpal protection
➢Prevents caries at and beneath restoration margin
Non-vital:
➢Provides additional line of defence to endodontic seal
➢Prevents caries at and beneath restoration margin
Describe amalgam as a core material? Adv and Dis?
Advantages
- Not especially technique sensitive
- Strong in bulk section
- Sealed by corrosion products
- Can be bonded into place with
cements and resins
Disadvantages
- Best left to set for 24 hours before tooth preparation
- Weak in thin section
- Potential electrolytic action between
core and metal crown
- Not intrinsically adhesive
- Poor aesthetics under ceramic
restorations
Indications for amalgam as a core material?
Excellent core build-up material for posterior teeth
Excellent interim restoration for posterior teeth
Adhesives and preparation features can often substitute for pin
retention
Describe composite as a core material? Adv and Dis?
Advantages
- Strong
- Can be used in a thinner section than
amalgam
- Fast setting (either light or chemically
cured)
- Does not always need a matrix
during placement
Disadvantages
- Highly technique sensitive
- Relies on multi-stage dentine
bonding requiring effective isolation
- Dentine bond can be ruptured by
polymerisation contraction
- Can be difficult to distinguish
between tooth and core during
preparation
Indications of composite for core build up?
Excellent build-up material for posterior and anterior teeth if isolation
assured
Aesthetic interim restoration, but takes far longer to place than amalgam
Should we remove the exisiting restoration?
Removal of existing
restorations allows proper
assessment of:
➢The tooth’s structural integrity
➢Pulpal exposure
➢Underlying caries
Describe the Nayyar core?
“Postless” preparation
Retention from coronal and radicular tooth
tissue
Uses pulp chamber as retention and resistance form
Advantages of the Nayyar core?
Can be placed immediately after endo –
reducing risk of coronal leakage
Utilises coronal tooth structure to increase
retention
Reduces stresses created by post placement
Usually easily retrievable
