4. CONTENTS
• INTRODUCTION
• HISTORIC BACKGROUND
• CHARACTERISTICS OF ENDODONTICALLY TREATED
TEETH
• DIAGNOSIS AND TREATMENT PLANNING
• DEFINITION
• INDICATIONS FOR POST AND CORE
• PRINCIPLES OF POST AND CORE
5. • 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
6. 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.
7. • 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.
8. • 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
9. • 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.
10. • 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.
11. 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 .
12. • 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
14. 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
15. Prosthetic Considerations
1. 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
16. 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)
18. 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
19. 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
20. 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
21. pRINCIpLES FOR pOST
AND CORE
1) Preservation of tooth structure
a) Preparation of the canal
b) Preparation of the coronal
tissue
2) Retention
3) Resistance
22. 1) PRESERVATION OF TOOTHSTRUCTURE :
a) Preparation of the canal
o 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 .
23. 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
24. 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
25. 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
26. 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.
27. 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
28. 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.
29. 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.
30. 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.
31. • 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.
32. Consequences of Inadequate Ferrule
Catastrophic root fracture
Cement failure and post loosening
Post fracture
33. Methodology
1. Post selection
2. Removal of endodontic filling
3. Post space preparation
4. Preparation of coronal structure
5. Post fabrication
6. Core fabrication
7. Temporization
8. Try in and cementation
34. 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
35. 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
36. 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
37. 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.
38. POST WIDTH
• Post width must be controlled to
preserve radicular dentin
reduce the potential for perforations
permit 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 .
39. 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
40. 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
41. 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
42. 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.
43. 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
44. 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
45. 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
47. 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.
48. • 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.
49. 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
50. 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
51. 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
52. 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
J Dent, 1999. 27: p. 275-278.
Int J Prosthod, 2004. 17: p.
53. 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.
54. • 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.
55. 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.
56. 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
57. Metal v. Fiber Reinforced
Metal
Coronal impact is
transmitted to remaining
tooth
Fiber reinforced
Coronal impact is dispersed
through the post alleviating
force on remaining tooth
58. 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
59. 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
60. • 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
61. PRETAPPED POSTS
Eg: 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
62. • Advantages:
High retention
• Disadvantages:
Stresses generated in canal may lead to fracture
Not conservative of coronal and radicular tooth structure
• Recommended Use:
Only when maximum retention is essential
• Precaution:
Care to avoid fracture during seating
63. 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
64. PARALLEL SMOOTH SIDED POSTS
Eg: 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
65. 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
root
Ease of placement
• Disadvantages:
Precious material post expensive
Corrosion of stainless-steel
Less conservative of tooth structure
• Recommended Use:
Small circular
canals
• Precaution:
Care during
preparation
67. 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.
68. 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.
69. 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.
70. 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
71. 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.
72. 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
73. 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
76. 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
77. 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.
78. 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 .
79. CORE MATERIALS
IDEAL REQUISITES OF A CORE MATERIAL
o High compressive strength
o High tensile strength.
o High modulus of elasticity (rigidity).
o High fracture toughness
o Dimensional stability
o Ease of manipulation
o Short setting time for cement
o An ability to bond to both tooth and
dowel.
o Biocompatible
o Natural tooth color, when indicated.
o Low plastic deformation.
o Low cost
81. 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
82. Amalgamcore 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
83. 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
84. Glass ionomercore
Advantages:
• Anti cariogenic
• Chemically adhesive to the
tooth
• Small buildups/undercuts
Disadvantages:
• Low fracture resistance
• Low retention to
prefabricated posts
• Sensitive to moisture
85. 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.
86. 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.
87. 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
88. 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.
89. Failures iN POsT & COre
Root perforationRoot fractures
Apical lesion and cariesPost loosening
90. 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
91. 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.
92. 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
93. 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
94. 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
95. 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
Notas del editor
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.
This was obviously evident when divergent paths of insertion of the post space and remaining tooth structure existed, especially for
abutments of fixed partial dentures. One piece dowelcrown restorations also presented problems when the crown or FPD required removal and replacement. These difficulties led to development of a post and core restoration as a separate entity with an artificial crown cemented over a core and remaining tooth structure.
ANTERIOR TEETH HAVE TO WITHSTAND SHEARING OR LATERAL FORCES
MOLARS HAVE TO WITHSTAND VERTICAL FORCES
Threaded tapered exerts maximum stress
Thermal removal by a heated instrument such as a lateral compactor that can be inserted into the gutta-percha to the desired length to remove the gutta percha
Mechanical removal by a non-end cutting bur such as a Gates-Glidden or Peeso reamer is efficient and probably the most commonly used technique, but it is a technique that can result in the most damage to tooth tissue.
Chemical removal by solvents such as oil of eucalyptus, oil of turpentine and chloroform have been used to soften guttapercha for removal, with the latter two being the most efficient.
•Lightly lubricate canal and make sure plastic post extends to full depth of post space
Use the bead brush technique and add GC resin to canal space, then add “speedy post” inside the canal and seat completely
•Do NOT allow resin to set completely. Loosen and reset it several times while it is still rubbery
•Once resin has polymerized, remove the pattern
•Inspect for any undercuts in pattern and trim away
•Measure and verify pattern post is same as prepared post length
•Check that pattern goes in and out of canal without binding
•Additional resin is added for the core