RESTORATION OF ENDODONTICALLY TREATED TEETH

BYANISH AMIN

CONTENTS • INTRODUCTION

• HISTORIC BACKGROUND

• CHARACTERISTICS OF ENDODONTICALLY TREATED TEETH

• DIAGNOSIS AND TREATMENT PLANNING

• DEFINITION

• INDICATIONS FOR POST AND CORE

• PRINCIPLES OF POST AND CORE

• METHODOLOGY

• Post selection• Removal of endodontic filling• Post space preparation• Preparation of coronal structure• Post fabrication• Core fabrication• Temporization• Try-in & cementation

• FAILURES IN POST AND CORE

• POST REMOVAL TECHNIQUES

• CONCLUSION

• REFERENCES

INTRODUCTION

• Endodontic treatment is largely performed on teeth significantly

affected by caries, multiple repeat restorations and/or fracture.

• Already structurally weakened, such teeth are often further weakened

by the endodontic procedures designed to provide optimal access and

by the restorative procedures necessary to rebuild the tooth.

• Hence it is accepted that these teeth tend to have a lower lifetime

prognosis.

• They require special considerations for the final restoration, particularly where

there has been extensive loss of tooth structure.

• The special needs involve ensuring both adequate retention for the final

restoration and maximum resistance to tooth fracture. Which can be collectively

termed as anchorage

• Ensuring optimal anchorage while maintaining adequate root strength for the

particular clinical situation can be challenging and the problems encountered

have resulted in the development of many different materials and techniques.

• As early as 1728, Pierre Fauchard described the use of “tenons,” which were metal posts screwed into the roots of teeth to retain bridges.

• In the mid-1800s, wood replaced metal as the post material, and the “pivot crown,” a wooden post fitted to an artificial crown and to the canal of the root, was popular among dentists. Often, these wooden posts would absorb fluids and expand, frequently causing root fractures

• In 1869 Black introduced the metal posts in which a porcelain-faced crown was secured by a screw passing into a gold-lined root canal.

Historical perspective

• Clark in the mid-1800s developed a

device that was extremely practical for

its time because it included a tube that

allowed drainage from the apical area or

the canal (Prothero JH; 1921).

• The Richmond crown was introduced in

1878 and incorporated a threaded tube

in the canal with screw retained crown.

• It was later modified to eliminate the

threaded tube and was redesigned as a

1-piece dowel and crown (Hampson EL

et al; 1958, and Demas NC et al; 1957),

which lost its popularity quickly because

they were not practical.

• During the 1930s, the custom cast post-and-core was

developed to replace the one-piece post crowns. This

procedure required casting a post-and-core as a

separate component from the crown.2 This 2-step

technique improved marginal adaptation and allowed

for a variation in the path of insertion of the crown.

Changes occurring in an endodontically treated teeth

• The loss of tooth structure from caries, trauma or both

• The moisture content of dentine from ET teeth is reported to be about

9% less than teeth with vital pulp (GV Black, Helfer et al ). But this was

contradicted by Huang et al who reported that neither dehydration , nor

endodontic treatment – caused any degradation of physical or

mechanical properties of dentin .

• The dentine undergoes changes in the collagen cross linking

• Loss of structural integrity of tooth due to access preparation which may

increase cuspal deflection during function

• Loss of proprioception

• Alteration in the light refraction of dentin as well as discolouration of tooth

due to the ill effects of microbial action, endodontic irrigants and

medicaments, old restorations on dentine

Diagnosis and treatment planning

Endodontic Considerations

1.Good apical seal

2. No sensitivity to pressure

3. No exudate

4. No fistula

5. No apical sensitivity

6. No active inflammation

7. Retreatment should occur if there are

signs or symptoms indicating failure

Periodontal Considerations

1. Extent of underlying periodontal

disease

2. Adequate biologic width

3. In cases with extensive coronal

destruction crown lengthening can be

considered

4. Presence of enough coronal tooth

structure to incorporate ferrule into

cast restoration

Prosthetic Considerations1. Extent of coronal destruction

2.Tooth type (anterior vs. posterior)

3.Position in arch, Morphology, Circumference of tooth, Occlusal and prosthetic

forces applied to tooth, Periodontal support

Esthetic consideration•Thin gingiva may transmit a dark shadow of the root through the tissue

•Metal or dark carbon fiber placed in the canal can result in unacceptable gingival

discoloration from the underlying root

•Endodontic and restorative materials in these esthetically critical cases must be

selected so as to provide the best health service with the minimum of esthetic

compromise

DEFINITION Of POST & CORE

o A one-piece foundation restoration

for an endodontically treated tooth

that comprises a post within the

root canal and a core replacing

missing coronal structure to form

the tooth preparation (GPT 8)

Indications for post and core

ANTERIOR TEETH• Anterior teeth with minimal loss of tooth

structure may be restored conservatively with

a bonded restoration in the access opening

• A post and core is only indicated when the

tooth is weakened by the presence of large or

multiple coronal restorations, presence of

undermined marginal ridges, or if they require

form or/and color changes that cannot be

affected by bleaching, resin bonding or

laminate veneers

• Mandibular incisors and maxillary lateral

incisors receiving crown

• Abutments for FPD and RPD INTERNATIONAL DENTAL JOURNAL OF STUDENT’S RESEARCH| Feb 2013-May 2013| Volume 1| Issue

POSTERIOR TEETH:A)MOLAR • Endodontically treated, molar teeth

should receive cuspal coverage, but

in most cases, do not require a post

• Posts are indicated in molars when

large percentage of coronal structure

is missing and teeth are at high risk

of fracture

•  If posts are required, they should be

placed only in the largest and

straightest canals--upper palatal and

lower distal.

INTERNATIONAL DENTAL JOURNAL OF STUDENT’S RESEARCH| Feb 2013-May 2013| Volume 1| Issue

B) PRE MOLAR• Premolars are usually bulkier than anterior teeth, but

often are single-rooted teeth with relatively small pulp

chambers and are more likely than molars to be

subjected to lateral forces during mastication. For

these reasons, they require posts more often than

molars.

•  A post may be indicated if a premolar will function as

an abutment for an RPD or suffers from an attachment

loss

• The canal anatomy of premolars is delicate and in

order to succeed, the post system chosen must require

minimal reshaping and enlargement of the canal

space.

INTERNATIONAL DENTAL JOURNAL OF STUDENT’S RESEARCH| Feb 2013-May 2013| Volume 1| Issue

PRINCIPLES FOR POST AND CORE

1) Preservation of tooth structurea) Preparation of the canal b) Preparation of the coronal

tissue 2) Retention 3) Resistance

1) PRESERVATION OF TOOTH STRUCTURE :

a) Preparation of the canalo Whenever possible, coronal and radicular

tooth structure should be conserved. In most

cases, preparation of a post space should

require minimal removal of additional

radicular dentin beyond the requirements for

root-canal treatment. Further enlargement

only weakens the root .

6 important features for a successful design

o Adequate apical seal

o Minimal canal enlargement

o Adequate post length,

o Positive horizontal stop (to minimize

wedging),

o Vertical walls to prevent rotation and

o Extension of the final restoration margin

onto sound tooth structure

b) Preparation of coronal tissue:o The amount of remaining tooth structure is

probably the single most important predictor

of clinical success.

o If more than 2 mm of the coronal tooth

structure remains, then the post and design

plays little role in the fracture resistance of

the restored tooth.

o Extension of the axial wall of the crown apical

to the missing tooth structure provides what

is known as a ferrule and helps to bind the

remaining tooth structure together,

preventing root fracture during function

2) RETENTION: • Post retention refers to the ability of a post to resist vertical dislodging forces.

• Retention is influenced by the

Canal shape & preparation of canal space

post’s length

Post diameter and taper

post design

Tooth location in the dental arch

the luting agent and luting method

3) RESISTANCE • Resistance refers to the ability of the post and tooth to withstand

lateral and rotational forces.

• It is influenced by the

o remaining tooth structure

o the post’s length and rigidity

o the presence of antirotation features

o the presence of a ferrule.

Rotational Resistance :

• In areas where coronal dentin has

been completely lost, a small

groove placed in the canal can

serve as an anti rotational element.

• The groove is normally located

where the root is bulkiest, usually

on the lingual aspect

The ferrule effect:• A ferrule is defined as a vertical band of tooth structure at the gingival aspect of

a crown preparation.

• The ferrule should be a minimum of 1 – 2 mm high, have parallel axial walls,

completely encircle the tooth, end on sound tooth structure and not invade the

attachment apparatus of the tooth.

2 types of ferrule:

• Core ferrule – part of a cast metal core

For cast post & core a contrabevel is given collar of metal that encircles the

tooth and serves as a secondary ferrule – independent of crown ferrule .

• Crown ferrule – the ferrule created by the overlying crown engaging the

tooth structure.

the ferrule must encircle a vertical wall of sound tooth structure above the margin

and must not terminate on restorative material.

In those clinical situations where there is

insufficient ferrule length, even where

margins are placed subgingivally,

surgical crown lengthening or

orthodontic extrusion may be

considered.

• It increases the mechanical resistance of a post/core/crown restoration by

reducing the potential for displacement (labial and axial rotation) and

compressive stresses within labial dentine and the canal wall.

• The purpose of a ferrule is to improve the structural integrity of the pulp less tooth

by counteracting functional lever forces, wedging effect of tapered dowels and

lateral forces exerted during insertion of the dowel.

Consequences of Inadequate Ferrule Catastrophic root fracture Cement failure and post loosening Post fracture

Methodology

1. Post selection2. Removal of endodontic filling3. Post space preparation4. Preparation of coronal structure5. Post fabrication6. Core fabrication7. Temporization8. Try in and cementation

1) POST SELECTION

1. Root length

2. Tooth anatomy

3. Post width

4. Canal configuration

5. Amount of coronal tooth structure

6. Torquing force

7. Stresses

8. Development of hydrostatic pressure

9.Post design

10. Post material

11. Material compatibility

12. Bonding capability

13. Core retention

14. Retrievability

15. Esthetics

16. Crown material

Dent Clin N Am 2002;46:367–384.

Factors influencing Post selection

ROOT LENGTH

o Determines length of post

o Greater the post length, better the retention and

stress distribution

o 3-5 mm of GP in the apical region to maintain apical

seal

o Parallel sided threaded post or Reinforced composite

luting agents can compensate for reduced post

length

o For short rooted molars more than one post will

provide additional retention for core

o The post should equal the incisocervical or

occlusocervical dimension of the crown.

o The post should be longer than the crown.

o The post should be 1 1/3 the length of the

crown.

o The post should be a certain fraction of the

length of the root such as one half, two

thirds, or four fifths.

o The post should end halfway between the

crestal bone and the root apex.

o The post should be as long as possible

without disturbing the apical seal

TOOTH ANATOMY o Root anatomy such as root curvature, mesio-

distal width, and labio-lingual dimension, canal

structure, proximal root concavities, anatomic

variation - all these factors should be considered

inorder to avoid any risk of apical or lateral

perforation

o Gutmann (1992) reviewed the anatomic considerations and

stated that roots of maxillary centrals and laterals, and also

mandibular premolars have sufficient bulk to accommodate

most post systems.

o Clinically, a post in a maxillary anterior tooth is subjected to compressive, tensile,

shear, and torquing forces. At the dentin-post interface, the forces that tend to

dislodge the post are predominately labially inclined shear forces. studies have

suggested resistance form can be increased with the use of a beveled preparation.

POST WIDTH• Post width must be controlled to

preserve radicular dentin reduce the potential for perforationspermit the tooth to resist fracture.

• Stern and Hirshfeld (1973) proportionist approach suggest the post width should not be greater than one third of the root width at its narrowest dimension.

• Halle EB et al ( 1984) preservationist approach suggest that the post should be surrounded by a minimum of 1 mm of sound dentin.

• Pilo and Tamse (2000) conservationist approach advocated minimal canal preparation and maintaining as much residual dentin as possible .

Studies have shown that

• An increase in post width has no significant effect on its retention.

• The tooth restored with larger diameter posts is reported to provide the least

resistance to fracture with a decrease in the width of the remaining dentin.

Recommended post width by Tilk MA et al • 0.6mm –mandibular incisors

• 1mm- maxillary central incisors, maxillary

and mandibular canines, palatal root of

maxillary first molar

• 0.8mm –other teeth

CANAL CONFIGURATION

Post should Fit closely Aptly conform to canal shape & size Less dentin removal Enhance fracture resistance

• Circular canals – prepared to have parallel walls - parallel prefabricated posts .

• Elliptical canals/excessively flared canals - cannot be prepared to give parallel walls – taper restricted to 6-8 degrees - custom cast posts or tapered prefabricated posts

Canal configuration determines whether to use custom designed or prefabricated post

AMOUNT OF CORONAL TOOTH STRUCTURE

• The bulk of the tooth above the restorative margin should be at least 1.5mm to

2mm to achieve resistance form

• In case of endodontically treated teeth with moderate to severe coronal tooth

loss cast post and cores were more successful whereas, in cases where

ample coronal dentin remains non-metal posts such as a carbon fiber posts

were deemed successful

TORQUING FORCE

• Torsional forces on the post-core-crown unit

lead to loosening and displacement of the

post from the canal

• Active post designs provide greater torsional

resistance than a passive post

STRESSES

• Post and core–restored endodontically

treated teeth are subjected to various types of

stresses: compression, tensile, and shear.

• Of these stresses, shear stress is most

detrimental to the restored tooth.

• Holmes et al have demonstrated that the

variation in post dimension greatly influences

shear stresses.

• An increase in the post length with diameter

kept to a minimum will help to reduce shear

stresses and preserve tooth structure. Thus,

the vulnerability of the endodontically treated

tooth to fracture is decreased.

DEVELOPMENT OF HYDROSTATIC PRESSURE • During cementation, an increase in stress within the root canal has been reported

because of the development of hydrostatic pressure. This pressure affects the complete seating of the post and may also cause fracture of the root.

• There is evidence that the fitting stresses can be reduced by careful placement of the post and by using a proper post design with a cement vent to permit escape of the luting agent and thus reduce the hydrostatic pressure

• Pressure development is also dependent on the viscosity of the cement. The more viscous the cement, the greater the development of the hydrostatic pressure

POST MATERIALS

• Wagnild et al (2002) summarized the ideal physical properties of a post that include:

(1) Maximum protection of the root.

(2) Adequate retention within the root.

(3) Biocompatible / noncorrosive

(4) Maximum retention of the core and crown.

(5) Maximum protection of the crown margin cement seal.

(6) Pleasing esthetics

(7) Radiopaque

Walton and Torabinejad

According to shape•Parallel •Tapered

According to surface configuration•Smooth •Serrated•Threaded

According to nature of fit•Passive•Active

According to construction•Custom made•Preformed

Custom-cast posts(i) Gold alloys(ii) Chrome-cobalt alloys(iii) Nickel-chromium alloys

CUSTOM CAST POSTS:Indications •When multiple cores are being placed in the same

arch. •It is more cost effective to prepare multiple post spaces, make an impression, and fabricate the posts in the laboratory.

• When post and cores are being placed in small teeth, such as mandibular incisors.

• In this circumstance it is often difficult to retain the core material on the head of the post.

• When the angle of the core must be changed in relation to the post.

• Prefabricated posts should not be bent; therefore, the custom-cast post best fulfills this requirement.

• When an all-ceramic noncore restoration is placed, it is necessary to have a core that approximates the color of natural tooth structure.

• If a large core is being placed in a high-stress situation, resin composite may not be the material of choice due to the fact that it tends to deform under a load

• In this circumstance, the post and core can be cast in metal, and porcelain can be fired to the core to simulate the color of natural tooth structure.

• The core porcelain can then be etched with hydrofluoric acid, and the all-ceramic crown can be bonded to the core.

Disadvantages • Less retentive

• Higher rate of root fracture mainly due to the wedging forces produced by the tapered design

• Time consuming and involves an additional laboratory cost

• Requires two appointments

• Requires temporization between appointments

• The laboratory procedure is technique sensitive

PREFABRICATED POSTS

a) METAL(i) Stainless Steel(ii) Titanium(iii) Brass

b) NON METAL(i) Carbon-fiber(ii) Fiber-reinforced

(1) Glass fiber (2) Quartz fiber (3) Woven Polyethylene

fiber (iii) Ceramic and zirconia

Pre fabricated metal posts• They are very rigid, and with the exception of the titanium

alloys, very strong.

• Titanium posts were introduced in order to compensate

for corrosion

• Titanium alloys are generally weak and therefore not

suitable for thin posts

• Titanium alloys have the same radiodensity as gutta-

percha and are sometimes hard to detect

radiographically.

• Because they are round, they offer little resistance to

rotational forces

Advantages• Less expensive • less no. of

appointments Disadvantages • Dislodgement • Chemical reaction • Difficult to retrieval of

active post

Prefabricated non metal posts (1) CARBON FIBRE POSTS

Eg: composipost

• The carbon fibre prefabricated post, introduced in the early

1990s, is comprised of longitudinally aligned carbon fibres

embedded in an epoxy resin matrix (approx 36%).

• Studies have shown that the carbon fibre post is “quite stiff

and strong, to a degree comparable to several posts made

of metal” and to have a modulus about ten times higher

than dentine. However these are still controversial

Disadvantages:

• no radiopacity , hence impossible to detect radiographically

• black in colour and are unsuitable for use beneath all

ceramic restorations. J Dent, 1999. 27: p. 275-

278. Int J Prosthod, 2004. 17: p.

369-376.

2)GLASS FIBER- REINFORCED AND COMPOSITE POSTS :

Eg: parapost white

• Largely used for highly esthetic

restorations, these posts

typically are bonded with resin

luting cements and utilize

composite cores.

• These posts should not be used if there is

less than 2-3 mm of supra-gingival tooth

structure present, if there is parafunction or

a deep overbite.

• Glass-fibre reinforced posts have less stiff fibres than carbon fibre posts.

They are therefore more flexible than both metal and carbon-fibre posts and

this has been both cited as an advantage in some reports and a

disadvantage in others

• It is frequently stated that the failure occurs at lower loads, but is less

catastrophic with fibre reinforced posts. such teeth remain re-restorable as

fibre posts will be more readily retrievable from the canal.

Ceramic posts

ADVANTAGES : Esthetic - dentin like shade

Radioopaque , biocompatible

Low solubility

DISADVANTAGES :Low tensile strength – fracture easily – thicker post needed – more dentin removal

Low fracture strength and fracture toughness .

Removed by grinding if retreatment necessary but is a tedious & risky procedure.

1989, Kwaitowski & Geller described clinical application of

glass ceramic posts.

ADVANTAGES : Esthetic

Extremely radioopaque , biocompatible

Low solubility

High flexural strength & fracture toughness

DISADVANTAGES:Zirconia posts cannot be etched - not possible to bond a composite core

material to the post, making core retention a problem.

Grinding is impossible if retrieval necessary for retreatment

Higher incidence of root fracture than fiber posts

Zirconia posts 1994, Sandhaus and Pasche

Metal v. Fiber Reinforced

MetalCoronal impact is transmitted to remaining tooth Fiber reinforcedCoronal impact is dispersed through the post alleviating force on remaining tooth

             

ACTIVE vs PASSIVE posts :• Most active posts are threaded

and are intended to engage the walls of the canal, whereas passive posts are retained strictly by the luting agent.

• Active posts are more retentive than passive posts, but introduce more stress into the root than passive posts

• They can be used safely, however, in substantial roots with maximum remaining dentin

• Active posts should be limited to short roots in which maximum retention is needed.

ACTIVE •Self threaded•Pretapped posts

PASSIVE •Tapered smooth sided•Parallel sided•Parallel with tapered apical ends

SELF THREADED POSTS: • Eg: DENTATUS SCREW, FLEXI-POST

• Self-threading posts have a shank (shaft) that is

fractionally narrower than the post channel that is cut

into the root and has a thread of wider diameter. Thus,

as the post is screwed into place the threads cut their

own counter-channel into the dentine.

• They can be either tapered or parallel in

design of which tapered ones are more

retentive but induce high stresses due to

the wedging effect and may result in

fracture of the tooth

• A novel post type( the Flexi Post) , has been

designed in an attempt to overcome the

stresses that self-threading posts induce into

the root structure .

• This is a parallel-sided threaded post with a

split in its apical half. As the post is screwed in

place, the split closes, transforming into a

tapered post, absorbing some of the potential

stresses

• The coronal half of the post is not split and it is

in this area that the highest strain has been

recorded in the root

PRETAPPED POSTSEg: Kurer Anchor post

• It has a high frequency thread around a parallel-sided shank.

• Once the post space preparation has been carried out the

counter-thread on the internal aspect of the post hole is

prepared with a thread cutter.

• The system also provides a Kurer Root Facer which flattens

the root face onto which the head of the post seats. This

unfortunately removes coronal tissue, which is important in

creating a ferrule for the final restoration.

• During insertion of the post, the threads fit into the counter-

threads. This design creates large stresses in the root which

can lead to catastrophic root fracture

• Advantages:High retention

• Disadvantages:Stresses generated in canal may lead to fractureNot conservative of coronal and radicular tooth structure

• Recommended Use:Only when maximum retention is essential

• Precaution:Care to avoid fracture during seating

TAPERED SMOOTH SIDED POSTS

• eg: kerr endo post

• Smooth sided tapered posts conform to the original

taper of the root canal preparation, thus conserving

tooth tissue and reducing the risk of post-

perforation apically, which is a potential problem

with parallel sided post preparation

• It has been suggested that tapered smooth-sided

posts have a ‘wedging’ effect under functional

loading and it is this, that leads to increased risk of

root fracture.

Recommended Use of Tapered Posts: Small circular canals and Very tapered canals

Precautions of Tapered Post: Not recommended for excessively flared canals

PARALLEL SMOOTH SIDED POSTSEg: Whaledent Para post, Boston post

• Parallel posts produce uniform

distribution of stress along the root

length and are reported to be less

likely to cause root fractures than

tapered posts

• They are cemented in to prepared

parallel channels.

• Parallel posts are proven to be more

retentive than tapered posts in case of

both metal and fiber posts

PARALLEL-TAPERED DESIGN

• The post is parallel throughout its length except for the most apical

portion, where it is tapered. This design permits preservation of the

dentin at the apex and at the same time achieves sufficient retention

because of parallel design

• Advantages:Minimal stress production within

rootEase of placement

• Disadvantages:Precious material post expensiveCorrosion of stainless-steelLess conservative of tooth structure

• Recommended Use:Small circular

canals

• Precaution:Care during

preparation

Retention : threaded> serrated> smooth

MATERIAL COMPATIBILITY

• Dissimilar alloys of the post and the core may create galvanic action, which

can lead to corrosion of the less noble alloy.

• These corrosion products cause a change in volume that has been postulated to

cause the root fracture.

• Of the various alloys used for posts, titanium alloys are the most corrosion

resistant. Alloys containing brass have lower strength and lower corrosion

resistance and, hence, are less desirable Noble metal alloys are corrosion

resistant, but their cost is higher.

• But with the availability of nonmetallic post materials, the corrosion factor is

eliminated.

BONDING CAPABILITY• The bonding of a post to the tooth structure should improve the prognosis of

the post-core restored tooth by increasing post retention and by reinforcing

the tooth structure.

• Studies have shown that resin luting agents have good adhesion to carbon

fiber posts and glass fiber posts..The adhesion to zirconia posts was found to

be unsatisfactory.

• It was also observed that to improve retention, the carbon fiber post did not

require any surface treatment as compared with the zirconia post.

• In spite of the creation of microretention on zirconia posts, the adhesion

between the post and resin luting agent was not uniform, thus indicating that

the nature of post material was responsible for the bonding of the post to the

tooth structure.

CORE RETENTION • Studies have reported that prefabricated metal posts with direct cores made of

glass ionomer, composite, or amalgam are less reliable than a one-piece cast post and core because of the interface between the post and the core.

• As the number of interfaces increase, the potential for failure also increases.• Thayer has expressed concern that post and core separation is more likely to

occur when composite is used as core material

RETRIEVABILITY•Ideally, the post system selected should be such that if the endodontic treatment fails or the post fractures, it is easy for the clinician to retrieve the post without substantial loss of tooth structure

•Carbon fiber posts have an advantage over metallic,ceramic,zirconia posts in that the removal is relatively easy, rapid, and predictable.

ESTEHTICS• In clinical situations in which the root has extensive damage or exhibits

immature development, the use of a custom cast post would compromise esthetics as the gray tint of the metal may show through the thin root wall. The overlying gingival tissue would also appear darker or grayish.

• With prefabricated metal posts, the core material can be composite, which may aid in masking the metallic color of the post depending on the thickness of the composite

• A ceramic crown with an opaque substructure may be necessary in situations where complete masking is difficult

• Another alternative to an esthetic post and core system is the use of opaque porcelain fused to the core portion of cast post and core in order to eliminate the grayish effect of cast metal.

• Also, the use of ceramic core material such as IPS Empress cosmo core (IvoclareVivadent, New York, NY) is advocated . The availability of different cement shades permits minor esthetic corrections under all-ceramic crown

CROWN MATERIAL• The metal ceramic crown will permit the clinician to use any post and

core material.• All ceramic crowns are translucent and allow metal to show through.• The influence of nonmetallic carbon fiber and zirconia post systems on

all-ceramic crowns depends on the substructure and thickness of crown.

• When crown thickness is reduced, the color of foundation restoration shows through a nonopaque thin crown.

2) REMOVAL OF ROOT FILLING MATERIAL .

Chemical removal by solvents such

as oil of eucalyptus, oil of turpentine

and chloroform

Mechanical removal by a non-end

cutting bur such as a Gates-Glidden

or Peeso reamer

Thermal removal by a

heated instrument such as

a lateral compactor

3) PREPARATION OF THE CORONAL TOOTH STRUCTURE

• After the post space has been prepared, the coronal tooth structure is reduced for the extracoronal restoration.

• Ignore any missing tooth structure (from previous restorative procedures, caries, fracture or endodontic access) and prepare the remaining tooth as though it were undamaged.

• Remove all internal and external undercuts that will prevent withdrawal of the pattern.

• Remove any unsupported tooth structure, but preserve as much of the crown as possible.

• Be sure that part of the remaining coronal tissue is prepared perpendicular to the post because this will create a positive stop to prevent over seating and splitting of the tooth.

• Complete the preparation by eliminating sharp angles and establishing a smooth finish line.

4) POST FABRICATIONPRE-FABRICATED POSTS .

a) Direct pattern

CUSTOM-CAST POSTS

b)Indirect Procedure

• An orthodontic ‘J’ shaped wire is selected & coated with an adhesive

• Canal is lubricated.

• Seat the wire and syringe in more impression material to cover coronal preparation and insert the impression tray

• Remove the impression and Pour the cast and fabricate the post and core on the cast

• Fill canal with elastomeric impression material using a lentulospiral

5) CORE FABRICATION

• It can be shaped in resin or wax and added to the post pattern before the assembly

is cast in metal.

• This prevents possible failure at the post-core interface.

• The core can also be cast onto most prefabricated post systems.

• A third alternative is to make the core from a plastic restorative material such as

amalgam, glass ionomer or composite resin.

Direct procedure for single-

rooted teeth

• Add a additional wax to form a

core

• Shape the core with carvers

• Remove the pattern, invest

immediately.

• If acrylic resin used – after

polymerization shaping done

with carbide burs.

Direct pattern for multi-rooted teeth

• The core is cast directly onto the post of one canal.

• Into The other canals - prefabricated posts are passed through holes in the core

• One post (to which core is cast onto) is roughened and rest lare eft smooth & lubricated

• Fit prefabricated posts into the prepared canals

• Build up the core

• Grip the smooth lubricated posts with force and remove them.

• Remove the pattern, invest and cast, the core with the roughened post .

CORE MATERIALS

IDEAL REQUISITES OF A CORE MATERIALo High compressive strength

o High tensile strength.

o High modulus of elasticity (rigidity).

o High fracture toughness

o Dimensional stability

o Ease of manipulationo Short setting time for cemento An ability to bond to both tooth and

dowel.

o Biocompatible

o Natural tooth color, when indicated.

o Low plastic deformation.

o Low cost

CORE MATERIALS Cast core • Metal• Ceramic

Plastic core • Amalgam• Composite• Glass ionomer• Resin modified glass

ionomer

Cast core: Metal

Advantages

• High strength

• Avoids dislodgement

Disadvantages

• More root fracture

• Casting inaccuracies

• Time consuming

• Expensive

type III / IV Gold alloys, base metal alloys, silver palladium alloys

Amalgam core Advantages:

• High compressive strength

• High modulus of elasticity

• Easy manipulation and placement

• Stable to thermal and functional stresses

Disadvantages:

• Unesthetic

• mercury toxicity

• Tendency to discolor adjacent gingiva

• Tendency to corrode

• Low early strength –preparations cannot be done immediately

Composite resin core

Advantages:• High compressive strength

• Easy to manipulate

• Esthetic

• Bondable

• Adequate strength

• Command set- preparation can be done immediately Disadvantages:

• Microleakage due to

• polymerization shrinkage

• Dimensionally unstable

• Tendency to deform plastically and thus cannot be used in high stress areas

• Isolation

Glass ionomer core

Advantages:

• Anti cariogenic

• Chemically adhesive to the tooth

• Small buildups/undercutsDisadvantages:

• Low fracture resistance

• Low retention to prefabricated posts

• Sensitive to moisture

Resin modified glass ionomer core

Advantages:• Properties lie in between composites and

GIC• Anticariogenic• More adhesive than GIC• Decreased moisture sensitivity• Decreased microleakage

Disadvantages:

• Tendency to expand in presence of moisture- can lead to fracture of ceramic crowns.

6) TEMPORIZATION/PROVISIONAL RESTORATION

o To prevent drifting of opposing or adjacent teeth, an endodontically

treated tooth requires a proper provisional restoration immediately

following completion of endodontics.

o If a cast post-and-core is made, an additional provisional restoration is

needed while the post and core is being fabricated. This can be

retained by fitting a wire (e.g. a paper clip or orthodontic wire) into the

prepared canal.

o The restoration is then conveniently fabricated with autopolymerizing

resin by the direct technique.

7) CEMENTATION

Five main groups of dental materials are used to cement posts

o zinc phosphate

o polycarboxylate,

o glass ionomers

o resin-modified glass ionomers

o composite resins

Retention provided by luting cements: zinc phosphate < polycarboxylate< GIC< adhesive resin cements

LUTING METHOD

o Place the luting agent on the post and

also in the canal with a lentulospiral, a

paper point, and an endodontic explorer.

o After the luting agent is placed in the

canal, the post is coated with the luting

agent and inserted.

Failures IN POST & CORE

Root perforationRoot fractures

Apical lesion and cariesPost loosening

POST Removal techniques 1) Masserann technique• Masserann developed and designed an instrument for extracting posts or

rigid instruments that are broken deeply within the roots with minimum

damage.

• The method involves gripping the object through a tube or trephine which

acts as a tube-vice.

• This method is relatively harmless to the tooth and periodontium.

• The advantages of this technique are its simplicity, little generation of heat

and elimination of excessive forces

2) Eggler post remover• The Eggler device can be easily applied

to anterior teeth and to most first

premolar teeth, but its size prevents it

from being used in most second

premolars and virtually all molar teeth 3) Ultrasonic scalers• For posts that extend into the pulp

chamber, vibrations from the

ultrasonic scaler are able to break the

cement bond between the canal and

the post by touching the post with the

ultrasonic tip.

Gonon post removal technique:

• Free the head of the post from the

coronal tooth structure

• The high strength trephine is used to

bore and gauge the protruding post to

the exact size of a corresponding

mandrel which is specially

manufactured to thread the post

• The extracting pliers are fixed on the

mandrel and jaws of the pliers are

expanded by tightening the knurled

knob

Conclusion • Use of post-and core restorations has changed markedly

in the past several decades.

• The evolution from wooden to metal to the most recent

fibre ones or from the custom cast to the pre fabricated

ones, they have been very promising in restoring

endodontically treated tooth

• It is possible to achieve high levels of clinical success

through the application of sound biomechanical principles,

maximum preservation of healthy tooth structure and use

of restorative materials with mechanical properties similar

to dental structure

References •Rosenstiel – Contemporary fixed prosthdontics 4th ed.

•Shillingburg – Fundamentals of fixed prosthodontics 3rd ed.

•Trabert & Cooney - The endodontically treated tooth – DCNA Oct

1984

•Cohen – Pathways of the pulp 8th & 9th ed.

•INTERNATIONAL DENTAL JOURNAL OF STUDENT’S

RESEARCH| Feb 2013-May 2013| Volume 1| Issue 4

•Robbins JW. Guidelines for the restoration of endodontically treated

teeth. J Am Dent Assoc 120:558–566, 1990.

•Schwartz: Post Placement and Restoration of Endodontically

Treated Teeth: A Literature Review JOE Vol. 30, no. 5, May 2004

References •Fernandes AS, Shetty S, Coutinho I. Factors determining post

selection: literature review. J Prosthet Dent 2003;90:556-562.

•Tait CME, Ricketts DNJ, Higgins AJ. Post and core systems,

refinements to tooth preparation and cementation. British

Dental Journal 2005;198:533-541.

•Cheung W A review of the management of endodontically

treated teeth Post, core and the final restoration JADA, Vol.

136 www.ada.org/goto/jada May 2005

•Christensen: Post & cores: state of the art, JADA 1998

•Quintessence International 2008