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Restoration of EndodonticallyTreated Teeth

Selecting the Best Option

Restorative Treatment Planning – First ensure:

Successful obturation of canal(s)No symptoms (sens. to biting pressure)No clinical signs (sens. to percussion)No sens. to palpationNo sinus tractNo perio. probing deeper than 3mmNo radiographic evidence of inflammatory disease

Restorative Treatment Goals

Maintain coronal and apical sealProtect/preserve remaining toothProvide supportive/retentive foundation for definitive restorationRestore function and aesthetics

How does endo. weaken remaining tooth structure?

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FractureIn EndoTreatedTeeth

IatrogenicCauses

Non-Iatrogenic

Causes

ToothStructure

Loss

Intra-canal

Medicaments

RestorativeProcedures

PrimaryCauses

SecondaryCauses

History ofRecurrentPathology

AnatomicalPosition of

tooth

Ageing ofDentalTissues

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2

Inorganic FractionCarbonated Apatite•Stiffness•Ultimate Compressive strength

Water (free & bound)ViscoelasticityStress absorbtionPlasticizing & tougheningDistribution of stress/strain

Organic Fraction (Type 1 collagen)Resistance to crack propagationToughnessUltimate tensile strength

Dentine

The role of different constituents on the mechanical integrity of dentine

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Please see reference 3.

For a thorough discussion of factors in play in the

predisposition of endo. treated teeth to fracture

Endodontic FactorsTooth stiffness

Access cavity preparationRemoval of roof of pulp chamberCanal preparationMedicamentsHeavy obturation forces?(Lateral condensation)

5% reduction in tooth stiffness3

How does previous restorative ₮ weaken teeth?

Isolates cuspsUndermines cuspsBroken cusps –too weak to withstand occlusal forcesSub-gingival margins2

Restorative FactorsTooth Stiffness

Occlusal cavity prep. – 20% reductionLoss of marginal ridge integrity

MOD cavity prep. – 63% reduction 3

Planning Treatment

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Consider1. Amount of remaining tooth

structure2. Anatomic position3. Occlusal/Para-function forces4. Restorative purpose/

requirements5. Aesthetic requirements

1. Remaining Tooth Structure

More tooth structure – better prognosisE.g Crown prep. with even 1 mm dentine above gingival margin

Double the fracture resistance of preps finishing flat & level with gingival margin

Ideally a ferrule effect2

Assessment of Remaining Tooth Structure

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2. Anatomic Position

Canines – Canine Guidance – Sufficient natural dentine to resist lateral forces

Group function –Canine/Pre-molar guidance

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3. Occlusal / Para-functional Forces

Evidence of heavy bruxismThin weak mesio- & disto-buccal cuspsEarly silver-reinforced GIC baseCut back and tooth prepared for full gold inlay/onlay(partial crown)

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4. Restorative purpose?

Single stand alone restoration?Bridge abutment?RPDOverdenture abutment?

4

Stand-alone

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Bridge abutment1

Crown lengthening to obtain sufficient tooth structure for ferrule

Crown/root ratio?

Over-denture Root Filled Anterior teeth

Assessment of Remaining Structure

De-vitalized by TraumaOtherwise intactRestore the access cavity only

Aesthetics?

Minimally restored-The other proximal surface is intact

Restore with composite

Small proximal rest. Small proximal-incisal rest.

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Large mesial and distal cavities plus access cavityRestore with post-core and full coverage crown

Heavily restored

Structurally compromised tooth

Long crown –insufficient remaining stucture

Reduce tooth and

Crown lengthening procedure for the distal & facial –ferrule

Post?

Root Filled Posterior Teeth

Assessment of Remaining Structure Marginal

ridges intact

1.

1

Restore access cavity only

1

Moderately sized cavity

Remove all restoration – any cracks??????

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Marginal ridge undermined?

6

Restoration only

Marginal ridge intact

1

Thin, weak or undermined cusps

Restore with overlay restoration

Cusp reduction

External bevelCast metal overlay

Ceramic and pre-processed resin also possible

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Core Build-ups

Avoid posts wherever possible

Preps. for partial crowns

Grooves for added resistance and retention

Core paste

Core paste

Using the pulp chamber to retain the core

•Shoulder for ceramic or pre-processed resin

•chamfer for cast metal

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7

Margins to finish on sound tooth

Partial crown preparation to finish on sound tooth

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Nayyarcore-for full crown

2mm

2mm

Undercut

Weak sections trimmed down

Ferrule

Crown restoration

Core paste

4

Undercuts in the pulp chamber provide retention and resistance for the core

Use the pulp

chamber Core paste

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Posts?Insufficient tooth to retain the core

Insufficient core length to retain crown

Post

Core paste22

Varying amounts of loss of tooth structure

***** ***?

Prognosis

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2 mm of remaining coronal tooth allows for preparation creating ferrule effect4

Types of Posts

Pre-fabricated and Cast

Prefabricated(*)and Cast/Custom Posts(#)

Uniformly distributed through cement layer

Little or noneSimilar to parallel, serrated

#Cast post – parallel, serrated

Wedging effectLittle or noneLow#Cast post – smooth tapered

Wedging effect at the tapered end

Little or noneSimilar to parallel serrated

*Parallel, serrated -tapered end

Relatively low –distributed by individual threads

Low after counter rotation

Highest*Parallel threaded

High stresses -accentuating installation stress

Very high – wedging stressIntermediate*Tapered self-tapping

Uniformly distributed through cement layerLittle or noneHigher*Parallel serrated

(cemented vented)

Wedging effectLittle or noneLow*Tapered smooth

Functional StressInstallation stressRetentionType

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Post Materials

Pre-fabricatedStainless steel *Titanium *Glass-fibre reinforced resin (bondable) #Carbon-fibre reinforced resin (bondable) #

Cast/customMetallic

Gold *Semi/Non-precious C+B alloys *

Zirconia *

Rigid * Non-rigid #

Stress of Self Threading Posts1. Threaded post after placement1.

2. Increased stress after tightening by ¼turn

2.1

Cemented Posts

Stress

upon

cementation

Stress in function

+-

- +

1

9

Cast Posts

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Post lengthPost should be at least as long as the desired clinical crown

Mitigating factorsCurved canalsTaper of the rootMaintaining apical seal (4-5mm of GP)

Post diameterChoice of post diameter is based on canal/root sizeAvoid unnecessary removal of internal dentine (weakens root)Post should fit canal dentine walls snugly

Other FeaturesPositive stop of the core on coronal tooth structure to prevent the post/ core unit from being forced apically1.5 – 2.0mm of tooth structure for 360°to receive the crown ferruleMaintain no less than 1mm wall thickness of radicular dentine (preferably 2-3mm)

Risk of root fracture Core•Material

Crown•Loading angle

•Ferrule

Remaining

Structure•Dentine

•Water content

Post•Length

•Shape

•Adhesion

•Diameter

•Elastic modulus3

Fracture predisposing factors in post-core restorations

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3

Post length

What type of post is best?

Studies have shownBonded posts, parallel-sided posts - less dentine stressNon-bonded and tapered posts – more dentine stressIncrease mod. of elasticity (stiffer) and increased diameter of bonded post – less dentine stressDecreased post length – more dentine stress3

Anterior tooth with little coronal structure

Cast post/coreSerrated, parallel-sided post with tapered or rounded tip

Posterior tooth with some coronal structure

One or two pre-fabricated posts and core paste build-up

Posterior tooth with little coronal structure

Cast post/core unit with secondary insertion of a wrought post/s through the core

The final crown restoration

The reinforcement effect of cementation of a full crown with ferrule effect will make the difference between stiff and elastic posts less obvious

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Tooth anatomy

Considerations for post placement

Maxillary first molarsDeep concavities on furcal surfaces

94% mesio-buccal roots31% disto-buccal roots17% palatal roots

Mandibular first molars

Concavities on furcal surfaces of

All mesial roots99% of distal roots

Maxillary first premolars

Deep mesial concavitiesSlender roots with thin dentine

Maxillary first premolarIn this situation the palatal root would be the ideal candidate for the postThe buccal root is highly irregular in form

Buccal

Palatal

CEJ 2mm

4mm 6mm

2

How to tell from x-ray?

Root formCurvature and post placement

2

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Post CementationZinc Phosphate

Mechanical retentionNo chemical adhesion

Resin-modified GIC (auto- or dual cure)

Adhesion to dentine

Resin Cement (dual cure)

Adhesion to dentineIn-soluble when setMoisture sensitive prior to setDifficult to place the bond apically

References1: Endodontics – 3rd Ed. Stock, Walker, Gulabivala2:Pathways of the Pulp 9th Ed. Cohen & Hargreaves3. “Mechanisms an Risk Factors for Fracture Predilection in Endodontically Treated Teeth” Anil Kishen Endodontic Topics 2006, 13, 57-834. Colour Atlas of Endodontics William T Johnson5. Problem Solving in Endodontics 4th Ed. Gutman, Dumsha, Lovdahl6. “Restoration of Endodontically Treated Teeth” Morgano, Rodrigues, SabrosaDental Clinics of North America 48 (2004) 397-416