Endodontically treated teeth ppt - a detail

3. CONTENTS
 OBJECTIVES
 INTRODUCTION
 HISTORIC BACKGROUND
 DIAGNOSIS AND TREATMENT PLANNING DEFINITION
 INDICATIONS FOR POST AND CORE
 METHODOLOGY
 FAILURES IN POST AND CORE
 CONCLUSION
 REFERENCES

4. OBJECTIVES
 Maintained coronal and apical seal of the root canal
treatment
 Protect and preserve the remaining tooth structure.
 Provided a supportive and retention, foundation for
the placement of definitive restoration
 Restore the function and esthetics.

5. 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.
 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.

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

7. 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

8.  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.

9.  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. This
2-step technique improved marginal adaptation and
allowed for a variation in the path of insertion of the
crown.

10. Diagnosis and treatment planning

11. Periodontal
Considerations
• Extent of underlying
periodontal disease
• Adequate biologic
width
• In cases with extensive
coronal destruction
crown lengthening can
be considered
• Presence of enough
coronal tooth structure
to incorporate ferrule
into cast restoration
Endodontic
Considerations
 Good apical seal
 No sensitivity to
pressure
 No exudate
 No fistula
 No apical sensitivity
 No active inflammation
 Retreatment should
occur if there are signs
or symptoms indicating
failure

12. Prosthetic
Considerations
• Extent of coronal
destruction
• Tooth type (anterior
vs. posterior)
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

13. POST & CORE

14. 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)

15. POST

16. The Role of Posts in the Restoration
of Endodontically Treated Teeth
 The primary purpose for a post is to retain a core
that can be used to support the final restoration.
 Posts do not reinforce endodontically treated teeth,
and a post is not necessary when substantial tooth
structure is present after a tooth has been prepared.

17. INDICATIONS
Post placement is indicated if both of the following
clinical conditions exist:
a. The remaining coronal tooth structure is
inadequate for the retention of a restoration.
b. When there is sufficient root length to
accommodate the post while maintaining an
adequate apical seal

18. FACTORS TO CONSIDER
 Post length
 Post diameter
 Post design

19. POST LENGTH
 The post should more
than the incisocervical or
occlusocervical
dimension of the crown.
 The post should be
longer than the crown.
 The post should be 1 1/3
the length of the crown.
 The post should end
halfway between the
crestal bone and the root
apex.

20.  Post length is unique and individualized for each
case. The clinician should have a thorough
knowledge of root morphology before placing a post.
 The longer the post, the greater the retention. A
guideline of one half to three quarters of the root
length is often followed but may not be reasonable
for extremely long, short, narrow, or curved roots.
 Retention of endodontic dowels: effects of cement,
dowel length, diameter, and design.

21. Post diameter
 The diameter of the post is dictated by the root canal
anatomy.
 A minimal dentin thickness of 1 mm around the post
should be provided.

22.  The diameter of the post is dictated by the remaining
root substance and root canal space: (A) too narrow;
(B) optimum size post; (C) too large.

23. Post Design

24. Parallel
Tapered
A. Smooth sided posts
B. Serrated posts
C. Threaded posts
A. Smooth sided posts
B. Serrated posts
c. Threaded posts

26. 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.

27. 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.

28.  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.
 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

29. With Ferrule
Without Ferrule
Consequences of
Inadequate Ferrule
• Catastrophic root
fracture
• Cement failure and
post loosening
• Post fracture

30. TYPES OF POSTS…

31. According to nature
of fit
•Passive
•Active
According to surface
configuration
•Smooth
•Serrated
•Threaded
According to
construction
•Custom made
•Preformed
According to shape
•Parallel
•Tapered

32. Castom-cast posts
• Gold alloys
• Chrome-
cobalt alloys
• Nickel-
chromium
alloys

33. 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

34. PREFABRICATED POSTS
 METAL
(i) Stainless Steel (ii) Titanium
(iii) Brass
 NON METAL
a. Carbon-fiber
b. Fiber-reinforced
 Glass fiber
 Quartz fiber
 Woven Polyethylene fiber
c. Ceramic and zirconia
Metal posts
Carbon-fiber
posts

35. PREFABRICATED 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
Less expensive
 less no. of appointments rotational forces

36. Prefabricated non metal posts
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

37. 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.

38. GLASS FIBER- REINFORCED
POSTS

39. 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.
Ceramic posts

40. Zirconia posts
1994, Sandhaus and Pasche
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

41. 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

42. Self-threading post

43. 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
counterthreads. 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
fracture. Not conservative of coronal and radicular tooth
structure
 Recommended Use: Only when maximum retention is essential
 Precaution: Care to avoid fracture during seating

44. TAPERED SMOOTH SIDED POSTS
eg: kerr endo post
 Recommended Use of
Tapered Posts: Small
circular canals and Very
tapered canals
 Precautions of Tapered
Post: Not recommended
for excessively flared
canals

45. PARALLEL SMOOTH SIDED POSTS
 Eg: Whaledent Para
post, Boston post
 Parallel posts are
proven to be more
retentive than tapered
posts in case of both
metal and fiber posts

46. CORE

47. IDEAL REQUISITES OF A CORE MATERIAL
 High compressive strength
 High tensile strength.
 High modulus of elasticity (rigidity).
 High fracture toughness
 Dimensional stability
 Ease of manipulation
 Short setting time for cement
 An ability to bond to both tooth and dowel.
 Biocompatible
 Natural tooth color, when indicated.
 Low plastic deformation.
 Low cost

48. CORE MATERIALS
Cast core
• Metal
• Ceramic
Plastic core
• Amalgam
• Composite
• Glass ionomer
• Resin modified
glass
ionomer

49. Cast core: Metal
Type III / IV Gold alloys, base metal alloys, silver palladium
alloys
Advantages
• High strength
• Avoids dislodgement
Disadvantages
• More root fracture
• Casting inaccuracies
• Time consuming
• Expensive

50. 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

51. 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

52. Glass ionomer core
Advantages:
 Anti cariogenic
 Chemically adhesive to the tooth
 Small buildups/undercuts
Disadvantages:
 Low fracture resistance
 Low retention to prefabricated posts
 Sensitive to moisture

53. 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 moisturecan lead to
fracture of ceramic crowns.

54. METHODOLOGY

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

56. 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

57. 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

58. REMOVAL OF ROOT FILLING
MATERIAL
 Thermal removal by a
heated instrument
such as a lateral
compactor
 Mechanical removal
by a non-end cutting
bur such as a Gates-
Glidden or Peeso
reamer
 Chemical removal by
solvents such as oil of
eucalyptus, oil of
turpentine and
chloroform

59. PREPARATION OF THE CORONAL
TOOTH STRUCTURE
 After the post space has been prepared, the coronal
tooth structure is reduced for the extracoronal restoration.
 Remove all internal and external undercuts.
 Remove any unsupported tooth structure, but preserve
as much of the crown as possible.
 The remaining coronal tissue is prepared perpendicular
to the post to create a positive stop to prevent over
seating and splitting of the tooth.

60. Post fabrication

61. CUSTOM-CAST POSTS [Direct pattern]

62. Core fabrication

63. Direct procedure for
singlerooted
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

64. TEMPORIZATION/PROVISIONAL
RESTORATION
To prevent drifting of opposing or adjacent teeth, an
endodontically treated tooth requires a proper
provisional restoration immediately following
completion of endodontics.

65. CEMENTATION
 Zinc phosphate
 Polycarboxylate
 Glass ionomer
 Resin-modified glass ionomer
 Composite resins
Retention provided by luting cements:
zinc phosphate < Polycarboxylate < GIC< adhesive
resin cements

66. Failures in POST & CORE
 Post loosening
 Root fractures
 Apical lesion and caries
 Root perforation
Root perforation Apical lesion
Post loosening, Root fracture

67. 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.

68. REFERENCES
•Rosenstiel – Contemporary fixed prosthdontics
•Shillingburg – Fundamentals of fixed prosthodontics
•Trabert & Cooney - The endodontically treated tooth