Core Restorations Post-Core Systems Flashcards by sophie rosen

Core Restorations
(also known as foundations)

Replace missing tooth structure prior
to crown preparation

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When is a core necessary?
1. “No preparation should be extended farther
into the tooth than – mm at the cervical
line or down – mm from the central fossa.”
2. “No wall of dentin should be reduced to a
thickness less than …”
3. If –% or more of the coronal tooth
structure remains, sufficient retention for a
single crown can be achieved by adding
retentive features to the preparation

1.5, 1.5
its height for sake of
retention.
50

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Materials for Core Restorations
(3)

*Dental Amalgam Alloy
*Composite Resin
*Glass Ionomer/Resionomer

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Amalgam Alloys
Advantages
(5)

*Easy to manipulate
*Favorable mechanical
properties (high compressive
strength, wear resistance, and
dimensional stability)
*Corrosion products
*Acceptable for areas difficult to
isolate
*Relatively inexpensive

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Amalgam Alloys
Limitations
(4)

*Relatively slow setting amalgam alloys (set 15 min)
*Corrosion
*Do not adhere to tooth structure
*Require a certain thickness for strength
*Color

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*Relatively slow setting
(2)

*Usually cannot be prepared at the same visit
*High copper spherical amalgam alloys (set 15 min)

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*Corrosion

*May cause discoloration of tooth structure

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Composite Resin Core
(5)

*Bond to tooth structure
(however the bond strength
to dentin is weak)
*Can be used in thickness
<1mm
*Rapid polymerization
- can be prepared the same visit
*Time efficient, economical
*Relatively easy to manipulate

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Composite Resin Core
Limitations
(4)

*Bond strength to dentin is
weak, require mechanical
retention
*Very susceptible to
moisture contamination
*Require good isolation, the
core margins must be
supragingival (2 mm tooth
structure to provide a
ferrule)
* Polymerization shrinkage (microleakage)

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Composite Resin Core
(3)

*Light polymerized composite resins (Hybrids)
*Chemically polymerized (i.e. ParaCore)
*Dual polymerized (light activated and
chemically polymerized)
i.e. FluoroCore (Dentsply Sirona)

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Glass Ionomer Cements
& Resin Ionomers
(5)

*Glass Ionomer cements (also available Metal reinforced
glass ionomers)
*Resionomers/Hybrid Ionomers
Hybrid of traditional glass ionomer and composite resin
*Significantly inferior strength compared to
amalgam alloys or composite resins
*Water imbibition
*Recommended only for low stress bearing areas or
as block-out materials for undercuts

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Retention of Core Restorations

“A core must be anchored firmly to the
tooth and not just placed to fill the void”
Retention is achieved most times with the
use of pins whether an amalgam alloy or
resin core is used.

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SKIPPED
Threaded pins (TMS)
(3)

*Minuta (0.0135 inch)
*Minikin (0.017 inch)
*Minim (0.021 inch)

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Pin Retention
*One pin per

missing cups/marginal ridge
*4 maximum

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Pin Retention
*Location
*Ideally on —
*– mm inside DEJ for vital teeth
*No closer than – mm from the axial wall

line angles
0.5-1
0.5

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SKIPPED
Amalgam Bonding
(5)

*Increase in retention is minimal
*Sealing of the dentinal tubules
*Decreases post operative sensitivity
*Increases tooth reinforcement
*Technique sensitive, little working time,
added cost

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Core Restorations
(2)

*Preserve tooth structure where possible

*Maintain vitality of tooth where possible

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Core Restorations

*Preserve tooth structure where possible
*Natural tooth is the strongest core material

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*Maintain vitality of tooth where possible

*Success rates of vital teeth are significantly
greater than on endodontically treated
teeth

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Core Restorations
*– mm of natural tooth height to provide
a ferrule
*Understand limitations associated with
each material and technique

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Dowels - Posts
Dowel:

a post, usually made of metal
that is fitted into a prepared root
canal of a natural tooth. When
combined with an artificial crown or
core, it provides retention and
resistance for the restoration.

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Dowels - Posts
FUNCTION of a POST
(3)

➢Anchor the core material with a
stable post
➢Restore missing tooth structure
➢Reinforce the tooth-restoration

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Which endo-treated teeth should
receive a Post?
When there is not adequate tooth
structure to retain a core
*often single rooted teeth since the
anatomy of the pulp chamber does
not offer mechanical retention
*teeth that have lost more than –% of
the coronal tooth structure
FPD and RPD abutment teeth?

Creating a Post Space
Gutta-Percha removal technique
(3)

Peeso Reamers
Gates Glidden drills
Hot Instrument

Gutta-Percha can be removed either

Immediately or Delayed

Custom vs. Prefabricated Posts

*Custom Posts (also known as cast post&cores) *Prefabricated Posts (several systems on the market)

Custom Posts *Usually cast in --- *Are often --- in cross section (builtin anti-rotation) *Rely mostly on the --- for retention * Less than 10% of clinicians use them

Type III gold tapered and ovoid cement

Custom Posts:

Are the only option when the crown and post have different angulations

Ferrule Effect A minimum of --- mm vertical axial wall circumferentially must be present.

Prefabricated Posts *Several materials available on the market *Mostly ---walled (greater retention) and ---shaped in cross section (does not provide anti-rotation) *Greater versatility -immediate (emergency) treatment *Used by the majority of clinicians

parallel round

Prefabricated Posts *Several materials available on the market (2)

*Alloys (titanium or stainless steel) * Fiber-reinforced posts

Cross Section Post Shape *--- post (most custom posts) *---wall post (most prefabricated posts)

Tapered Parallel

The most retention would be provided with a ----walled post

parallel

Anti-rotation Prefabricated posts (1) Cast posts (1)

Lack of anti-rotation (round in cross-section) Built-in (oval in cross-section)

Post Retained Amalgam Core (2)

* Cement prefabricated post in the canal * Condensed amalgam around the post

Critical to have access to

condense amalgam around the post. Root canal morphology dictates post orientation.

Post Retained Composite Resin Core Retention similar to

post retained amalgam and cast post & core

Optimum Post Length (3)

*The greatest the post length, the more retentive the post is (one factor that would cause root fracture is a short post) *The post should be at least as long as the length of the crown/restoration *Retain about 4-5 mm of apical gutta-percha seal

Optimum Post Diameter (2)

➢ The diameter of the post should not be greater than 1/3 of the tooth/root diameter. ➢ Choosing a post is usually based on the optimum diameter.

Most times -- post per tooth is adequate

one

SKIPPED Fiber-reinforced posts Silica-fiber, Glass-fiber, Quartz-fiber Posts (US) (7)

*ParaPost Fiber White & Fiber Lux (Coltene/Whaledent) *Dentflex (Brasseler) *Luscent Anchors(Dentatus) *FibreKor (Jeneric/Pentron) *FRC Postec (Ivoclar/Vivadent) *D. T. Light-Post (BISCo) *Aestetic-Plus(BISCo)

Fiber-reinforced Posts Main advantage:

better esthetics

Fiber-reinforced Posts Main difference from metal posts: (1)

* Modulus of elasticity similar to dentin (however the modulus decrease over time and more critically in the presence of moisture)

Fiber-reinforced Posts Failures: (2)

* Less root fractures than metal posts, fracture usually occurs in the coronal part or the post itself or debonding of the post occurs * Failure rates in the literature range from 0% to as high as 32.2% and most are because the post becomes debonded

Fiber-reinforced Posts Indication for use:

only teeth that have several dentinal walls remaining

Fiber-reinforced Posts Main Clinical Consideration

The majority of failures with these posts occur on teeth that have little natural tooth structure remaining

Ceramic Posts (3)

*Good esthetics *Very rigid (high modulus of elasticity) *High rates of root fracture

Cementation (4)

*Zinc-Phosphate cement *Resin cements *Glass-ionomer cements *Modified resin-glass ionomer cements

Canal(s) should be --- prior to post cementation

cleaned/conditioned (phosphoric acid)

Step by step procedures

* Remove gutta-percha (Peeso #2 and then #3, avoid #4 and 5), evaluate with radiographs periodically for angulation and length (post should be as long as possible and retain 4-5 mm apical guttapercha) * Post diameter not to exceed 1/3 of root diameter * For prefab posts, the final drill should be the drill that corresponds with the correct post diameter * For prefab posts the length should be adjusted so that the head of the post is at the top of the core * Cement post (for prefab posts remove cement from most coronal part of canal to allow core material to help with anti-rotation) * 2 mm of ferrule circumferentially is critical for longevity regardless of post used

Amalgam Radicular Core (3)

*Amalgam is condensed into pulp chamber and 2-3 mm into the pulp canal *If pulp chamber is 4 mm in height: sufficient retention from pulp chamber alone *Reduces number of visits/reduces cost

Are endodontic teeth prone to fracture?

* Endodontic access / Instrumentation results in reduced tooth structure

* Other factors that affect strength? (2)

1. previous/existing caries/restorations 2. amount of root surrounded by alveolar bone

Crown treatment after endo treatment

* Crowns did not significantly improve success rates of endodontically treated anterior teeth when ample tooth structure remains ➢ Crowns significantly improved success rates of endodontically treated posterior teeth

Longevity of endodontically treated teeth (3)

*Endo treated teeth without crowns lost at 6 times the rate of those with crowns *Teeth with 2 proximal contacts had significantly longer survival than teeth with 1 or no proximal contacts *2 nd molars showed sign. reduced longevity compared to all other teeth