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Rationale of post endodontic restoration /certified fixed orthodontic courses by Indian dental academy
1. RATIONALE OF POST
ENDODONTIC
RESTORATION
INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
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2. Contents
Introduction
Historical perspective
Causes of tooth fracture
Treatment planning
Post systems
Evidence based practice
Principles of tooth preparation
Core
Corono-radicular restoration
Restoration of resected root
Over dentures
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Conclusion
4. Historical perspective
More than 200 years
1747, Pierre Fauchard: Posts
made of gold or silver and held
in the root canal space with a
heat-softened adhesive called
“mastic.”
“Pivot crown.” Dubois de
Chemant – 1800, used seasoned
wood
Prothero reported removing two
central incisor crowns with
wooden pivots that had been
successfully used for 18 years.
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5. Historical perspective
Metal pivot retention similar to Richman’s
Crown
Dental Physiology and Surgery, written by Sir John
Tomes in 1849. Tomes’s post length and
diameter conform closely to today’s principles
in fabricating posts
minimal efforts to clean, shape, and obturate
Wooden post associated with swelling &pain.
But allowed escape of “morbid humors.”
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6. Causes of tooth fracture
Altered physical properties of the tooth
Weakening due o the loss of tooth
structure
Prestressed laminates – Tidmarsh 1974
Loss of proprioception
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8. Active Passive
Threaded, engage dentin Retained by luting agent
More retentive, more stress Retention & stress less
Thick but short roots Long slender roots
Parallel Tapered
More retentive Less retentive
Less stress Wedging forces
Less removal, slender & delicate
More dentin removal
roots
Success rate high
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10. Metallic Posts
Rigid except titanium posts
Round hence lack rotational
resistance
Metallic posts tend to corrode,
except Ti posts
Ti posts – not strong & easily
fracture; retrieval difficult
Flexi-post
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11. Cast Post & Cores
Used for many years
Unpopular – 2 appointments, laboratory fee,
temporization
Advantageous in certain clinical situations:
multiple teeth requiring posts
mal-aligned tooth
slender roots like mandibular incisors
Requires proper temporization to prevent inter
appointment contamination
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12. Ceramic & Zirconia Posts
Metal posts & all ceramic crowns
White or translucent – esthetic posts
Lack rigidity hence require larger post diameter
Zirconia posts cannot be etched
Retrieval is difficult
Ceramic posts can be ground but procedure is
dangerous
Zirconium posts are impossible to grind
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13. Fiber Posts
Carbon posts were first of its kind; mod of
elasticity similar to dentin
When bonded with resin cement, distribute
stresses evenly
Retrieval easy – boring through the uniaxial fibers
Dark – esthetic incompatibility
Newer fiber posts – quartz fiber, glass fiber,
silicon fiber
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14. Treatment Planning
Good apical seal
No sensitivity to pressure
No exudates
No sinus
No apical sensitivity
No active inflammation
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15. Considerations For Anterior Teeth
do not always require complete
coverage
fracture toughness for teeth with
and without endodontic treatment-
SAME (lab)
strengthen the teeth replacing part
of the root canal filling with a
metal post
when the tooth is loaded, the
lingual side is under tension and
the buccal side under compression
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16. Considerations For Anterior Teeth
When there is considerable loss of crown structure or
when the tooth is to serve as an abutment for FPD or
RPD, complete crown becomes mandatory.
Retention and support then must be derived from
within the root canal because the coronal dentine
remaining after tooth preparation will be thin and
fragile.
Use of powerful organic solvents
ZOE sealers and composite resins
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17. Considerations For Posterior Teeth
Closer to the transverse horizontal axis & cuspal
morphology
Exceptions to cuspal coverage are mandibular
premolars and first molars - intact marginal
ridges, conservative access preparations, less
load.
Complete coverage is required on teeth with a
high risk of fracture. This is especially true in
maxillary premolars.
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18. Minimal loss of tooth structure
GP should be cleared off the access cavity with
hot instruments or GG drills.
All traces of sealer must be removed to prevent
discoloration of the crown
Effective use of alcohol
Posterior teeth can be restored with amalgam or
composite resin
The core must extend 2-3 mm into the canal
entrances.
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19. Moderate loss of tooth structure
Anterior teeth - minimal loss of tooth structure.
Treatment options may be simple core restoration or
post and core
Posterior teeth, loss of one or both marginal ridges
additional to tooth lost in access preparation. Amalgam
or composite cores emanating 2-3 mm from canals,
post and core with compulsory cuspal coverage. Extra
coronal restoration must extend 1-2 mm onto sound
tooth structure
Interim restoration for cuspal coverage – bonded
amalgam or composite resin.
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20. Extensive loss of tooth structure
Little or no coronal tooth structure is remaining
Crown lengthening, forced eruption followed by
cast post & diaphragm with a ferrule. Or pre-
fabricated posts with crown. Metal collar must
extend 2-3mm onto sound tooth structure
Immature tooth, relined with dentine bonding
composites followed by fiber posts.
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21. Evidence Based Practice
The conscientious, explicit and
judicious use of current BEST
EVIDENCE in making decisions
about the care of individual patients
Sackett DL, et al BMJ 1996;312:71-2
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22. SHOULD CROWNS BE PLACED ON
ENDODONTICALLY TREATED
TEETH?
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23. • 1,273 teeth endodontically treated 1 to 25 years.
Coronal coverage crowns did not significantly improve
the success of endodontically treated anterior teeth
• Structurally weakened or they require significant
form/color changes that cannot be effected by
bleaching, resin bonding, or porcelain laminate veneers
• A significant increase in the clinical success was noted
when cuspal coverage crowns were placed on maxillary
and mandibular molars and premolars. Scurria et al.
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24. • Multiple clinical studies of fixed partial dentures, many
with long spans and cantilevers, have determined that
endodontically treated abutments failed more often
than abutment teeth with vital pulps owing to tooth
fracture
• It has been shown that endodontic procedures reduce
tooth stiffness by 5%, attributed primarily to the access
opening. Also, with aging, greater amounts of
peritubular dentin are formed, which decreases the
amount of organic materials that may contain moisture.
• Dentin from endodontically treated teeth has been
shown to exhibit significantly lower shear strength and
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toughness than vital dentin. (Tidmarsh )
25. • Rivera et al. stated that the effort required to
fracture dentin may be less when teeth are
endodontically treated because of potentially
weaker collagen intermolecular cross-links.
Conclusions:
• Restorations that encompass the cusps of
endodontically treated posterior teeth have been
found to increase the clinical longevity of these
teeth.
• Limited use in anterior teeth
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26. WITH PULPLESS TEETH, DO POSTS
IMPROVE LONG-TERM CLINICAL
PROGNOSIS OR ENHANCE
STRENGTH?
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27. Laboratory Data
Lovdahl and Nicholls - endodontically treated maxillary
central incisors were stronger when the natural crown
was intact, except for the access opening, than when
they were restored with cast posts and cores or pin-
retained amalgams
Lu found that posts placed in intact endodontically
treated central incisors did not lead to an increase in the
force required to fracture the tooth or in the position
and angulation of the fracture line
Trope et al. determined that preparing a post space
weakened endodontically treated teeth compared with
ones in which only an access opening was made but no
post space.
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28. Laboratory Data
A potential situation in which a post and core could
strengthen a tooth was identified by Hunter et al. using
photoelastic stress analysis. They also determined that
minimal root canal enlargement for a post does not
substantially weaken a tooth, but when excessive root
canal enlargement has occurred, a post strengthens the
tooth.
When loaded vertically along the long axis, a post
reduced maximal dentin stress by as much as 20%.
However, only a small (3 to 8%) decrease in dentin
stress was found when a tooth with a post was
subjected to masticatory and traumatic loadings at 45
degrees to the incisal edge.
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29. Clinical Data
Sorenson and Martinoff clinically evaluated
endodontically treated teeth with and without posts and
cores. Posts and cores significantly decreased the
clinical success rate of teeth with single crowns and
improved the clinical success of RPD abutment teeth
but had little influence on the clinical success of FPD
abutments
A 1994 survey (1,066 practitioners and educators)
10% of the dentist respondents felt that each
endodontically treated tooth should receive a post. 62%
of dentists > 50yrs believed that a post reinforces the
tooth, whereas only 41% of the dentists under age 41
believed in that concept.
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30. Conclusions
Both laboratory and clinical data fail to provide
definitive support for the concept that posts
strengthen endodontically treated teeth.
Therefore, the purpose of a post is to provide
retention for a core.
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31. WHAT IS THE CLINICAL
FAILURE RATE OF POSTS AND
CORES?
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32. A 9% overall average for absolute failure was calculated
by averaging the absolute failure percentages from eight
studies (an average study length of 6 years). Range 7 –
14 %
Kaplan-Meier survival statistics ranged from a high of
99% after 10 years or more of follow-up to a 78%
survival rate after a mean time of 5.2 years. The percent
failure per year has also been calculated and ranged
from 1.56%/year to 4.3%/year.
Conclusions
Posts and cores had an average absolute rate of failure
of 9% (7 to 14% range) when the data from eight
studies were combined (average study length of 6
years).
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33. WHAT ARE THE MOST COMMON
TYPES OF POST AND CORE
FAILURES?
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34. Turner reported on 100 failures of post-retained
crowns and indicated that post loosening was the most
common type of failure. 59%
42 - apical abscesses
19 - carious lesions
10 - root fractures
6 - post fractures
Lewis and Smith presented data regarding 67 post and
core failures after 4 years.
47 (70%) - posts loosening
8 - root fractures
7 - caries
4 -bent or fractured posts
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35. Sorenson & Martinoff evaluated 420 post &
cores and recorded 36 failures
8 - restorable tooth fractures
12 -non-restorable tooth fractures
13 - loss of retention
3 - root perforations
Torbjörner et al. reported on the frequency of 3
technical failures (loss of retention, root fracture,
and post fracture)
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36. Conclusions
Loss of retention and tooth fracture are the two
most common causes of post and core failure.
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37. WHICH POST DESIGN PRODUCES
THE GREATEST RETENTION?
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38. Laboratory Data
Threaded posts provide the greatest retention, >by
cemented > parallel-sided posts. Tapered cemented
posts are the least retentive.
Cemented, parallel-sided posts with serrations are more
retentive than cemented, smooth-sided parallel posts.
Clinical Data
Torbjörner et al – 7%
Sorenson and Martinoff - 4%
Bergman et al. and Mentink et al - 6%
Weine et al. They found no clinical failures from loss of
retention with cast tapered posts.
Hatzikyriakos et al. - tapered threaded posts, parallel
cemented posts, and tapered cemented posts.
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39. Conclusions
Tapered posts are the least retentive and
threaded posts the most retentive in laboratory
studies. Most of the clinical data support the
laboratory findings.
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40. IS THERE A RELATIONSHIP
BETWEEN POST FORM AND THE
POTENTIAL FOR ROOT FRACTURE?
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41. Laboratory Data
Henry - threaded posts
Standlee et al - tapered, threaded posts
Deutsch et al - tapered, threaded posts increased root
fracture by 20 times that of the parallel threaded posts
Thorsteinsson et al- determined that split-threaded
posts did not reduce stress concentration during
loading
Henry - parallel- sided posts distribute stress more
evenly to the root
parallel posts concentrate stress apically and tapered
posts concentrate stress at the post-core junction.
Assif et al. - tapered posts -equal stress distribution
between the CEJ and the apex compared with parallel
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posts (apical pressure).
42. Sorenson and Engelman determined that
tapered posts > fractures than parallel-sided
posts, but the load required to create fracture
was significantly higher with tapered posts
In analyzing the stress distribution of posts,
tapered posts generate the least cementation
stress: thin root walls, are nearly perforated, or have
perforation repairs.
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43. Clinical Data
threaded posts - mean fracture rate of 7%
(5 studies)
parallel-sided cemented posts - 1% (4 studies)
tapered posts - 3% ( 7 studies)
Creugers et al. - 91% tooth survival rate for cemented
cast posts and cores & 81% survival rate for threaded
posts with resin cores
In comparing fracture rates - parallel and tapered
posts
Hatzikyriakos et al, Ross & 2 other studies – no
difference in fracture rates bet parallel & tapered posts
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44. Conclusions
Threaded posts ↑ root fracture – lab & clinical
Stress analysis & fracture rates - Tapered and
parallel cemented posts
Further research to study designs of posts
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45. WHAT IS THE PROPER LENGTH
FOR A POST?
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46. Various recommendations……
equal the incisocervical or occlusocervical dimension of
the crown
longer than the crown
one and one-third the crown length
half the root length
two-thirds the root length
four-fifths the root length
terminated halfway between the crestal bone and root
apex
as long as possible without disturbing the apical seal.
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47. Radiographic study of 217 posts - only 5% of the posts
were 2/3 to ¾ the root length
Sorensen and Martinoff - clinical success was markedly
improved when the post was equal to or greater than
the crown length
Ideal root length – 2/3rds post length, but hampered
apical seal in short roots.
Abou-Rass et al. 150 molar teeth. They determined
that molar posts should not be extended more than 7
mm apical to the root canal orifice ( risk of root
perforation)
diminished bone support, ↑ stresses are concentrated in
the dentin near the post apex. To ↓ stress in the dentin
& in the post, the post should extend > 4 mm apical
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to the bone
48. Conclusions
Reasonable clinical guidelines for length include
the following:
(1) three-quarters - long-rooted teeth
(2) When average root length - retain 5 mm of
apical gutta-percha
(3) Whenever possible, posts should extend at
least 4 mm apical to the bone crest to
decrease dentin stress
(4) Molar posts should not be extended more than
7 mm into the root canal apical to the base of
the pulp chamber
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49. HOW MUCH GUTTA-PERCHA
SHOULD BE RETAINED TO
PRESERVE THE APICAL SEAL?
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50. Apical seal….
4 mm of GP - only 1 of 89 specimens showed
leakage
Mattison et al. 3, 5, and 7 mm
Nixon et al. 3, 4, 5, 6, and 7 mm
Kvist et al. radiographic examination of 424
posts. Teeth with 3mm seal leaked the most
Conclusions
Greater leakage - 2 to 3 mm
4 to 5 mm should be retained apically to ensure
an adequate seal.
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51. DOES POST DIAMETER AFFECT
RETENTION AND THE
POTENTIAL FOR TOOTH
FRACTURE?
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52. Krupp et al - retention - post diameter was a
secondary factor
Mattison - stress - increased diameter
Deutsch et al - six fold increase in the potential
for root fracture with every millimeter the
tooth’s diameter was decreased.
Conclusions
Laboratory studies on retention - mixed results,
definitive relationship between root fracture and
large-diameter posts.
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54. WHAT IS THE RELATIONSHIP
BETWEEN POST DIAMETER AND
THE POTENTIAL FOR ROOT
PERFORATIONS?
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55. Lloyd and Palik – 3 distinct philosophies of post
space prep.
the conservationists
the proportionists
the preservationists
Tilk et al 1,500 roots based on the proportionist
0.6 to 0.7 mm – small teeth
Large-diameter roots - 1.0 mm
Remaining teeth - 0.8 to 0.9 mm.
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56. Shillingburg et al- 700 root dimensions - minimize
the risk of perforation
mandibular incisors- 0.7 mm
maxillary central incisors or other large roots, 1.7
mm (max)
post tip diameter, at least 1.5 mm less than root
diameter at that point
post diameter at the middle of the root length,
2.0 mm less than the root diameter.
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57. mesial roots of mandibular molars & buccal roots of
maxillary molars
For the principal roots not more than 7 mm into the
root canal
Instrument size - No. 2 Peeso instrument safe. but
perforations are more likely when the larger No. 3 and
4 Peeso instruments were used.
Raiden et al. 0.7 mm or less for maxillary I pre-molars
with single canals (mesial and distal developmental root
depressions). Dual canals, as large as 1.1 mm because
the canals are located buccally and lingually into thicker
areas of the roots.
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58. CAN GUTTA-PERCHA BE REMOVED
IMMEDIATELY AFTER ENDODONTIC
TREATMENT AND A POST SPACE
PREPARED?
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59. Bourgeois and Lemon- immediate & 1 week later
when 4 mm of GP were retained
Madison & Zakariasen; Zmener – imme & 48 hrs
Harrington - immediate GP removal - warm and
rotary instruments.
Karapanou et al- immediate and delayed removal
of two sealers (ZOE & resin sealer)
Portell et al - removal after 2 weeks > leakage
than immediate removal when only 3 mm of
gutta-percha were retained apically.
Fan et al. found more leakage from delayed
removal of gutta-percha.
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60. Conclusion
Adequately condensed gutta-percha can be
safely removed immediately after endodontic
treatment.
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61. WHAT INSTRUMENTS REMOVE
GUTTA-PERCHA WITHOUT
DISTURBING THE APICAL
SEAL?
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62. Suchina & Ludington and Mattison et al. found
no difference between hot instrument removal
and removal with GG burs
Camp & Todd found no difference between
Peeso reamers, GG burs, and hot instruments
Haddix et al. a heated plugger < a GPX
instrument or GG drills
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63. Conclusion
Both rotary instruments and hot hand
instruments can safely be used to remove
adequately condensed gutta-percha when 5 mm
are retained apically.
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64. CAN A PORTION OF A SILVER
POINT BE REMOVED AND STILL
MAINTAIN THE APICAL SEAL?
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65. In one study, all of the specimens leaked when 1
mm of a 5mm long silver point was removed
using a round bur.
Neagley found that removal of the filling
material coronal to the silver point with a Peeso
reamer caused no leakage. However, when all of
the filling material and 1 mm of the silver point
were removed, complete dye penetration
occurred in 8 of 9 specimens.
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66. DOES THE USE OF A CERVICAL
FERRULE THAT ENGAGES TOOTH
STRUCTURE HELP PREVENT TOOTH
FRACTURE?
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67. Studies to investigate…
1. Core Vs crown ferrule
2. Manner of engaging the tooth ( beveled Vs parallel)
3. Amount of tooth engaged
Assif et al. found no difference in the tooth fracture
patterns with different types of posts when they were
covered by a crown that grasped 2 mm of tooth
structure
Isidor et al. compared no ferrule with 1.25 and 2.55
mm crown ferrules. Ferrule length was more
important than post length in increasing a tooth’s
resistance to fracture under cyclic loading.
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68. Libman & Nicholas- improved resistance to
fatigue failure with crown ferrule extending
1.5mm apical to core margin
Loney et al – higher mean stress in core ferrule
than crown ferrule
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69. Conclusions
Crown ferrule > core ferrule
Length of ferrule more important than length
of post
More effective when the crown encompasses
relatively parallel prepared tooth structure than
when it engages beveled/sloping tooth
surfaces.
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70. Principles of Tooth Preparation
Conservation of tooth structure
Preparation of the canal
Minimal preparation
Teeth with posts thicker than 1.8mm fractured more
easily than those with thinner posts(1.3mm)
Strength of the root = R4 – r4
one or two additional files than the largest size
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71. Principles of Tooth Preparation
Preparation of coronal tissue
Amount of remaining tooth
structure is the most important
predictor of clinical success
Cast post-core will require
reduction to accommodate a
complete crown and to remove
undercuts from the chamber
and internal walls
Extension of the axial wall of
the crown apical to the missing
tooth structure is known as the
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ferrule
72. Principles of Tooth Preparation
ferrule may not be possible in short clinical
crowns
surgical crown lengthening procedure or
orthodontic extrusion
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74. Principles of Tooth Preparation
Retention Form
Anterior Teeth
Preparation geometry
Round canal configuration can be prepared
with minimal taper to accommodate
prefabricated post
Elliptical canals – minimal taper(6-8 degrees)
Threaded posts improve retention
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75. Principles of Tooth Preparation
Post length
Longer the post better the retention & stress
distribution
minimum length of root filling -3 to 7mm
Root morphology also influences the length
Post length
• In teeth with loss of periodontal support the post
should extend apical to the alveolar bone.
The required length of the post must be weighed
against the occlusal loading. If loading is minimal;
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long posts will become unnecessary.
76. Principles of Tooth Preparation
Post length
In any case post length less than that of crown
height is least retentive and also increases the
chances of root fracture( Fuss et al). The latter
occurs because stress is distributed over a small
surface area.
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77. Principles of Tooth Preparation
Surface texture
Dramatic effect on retention and stress distribution
Retention decreases as one progresses from
threaded to serrated to smooth surface
configurations
Radicular stress is greatest with threaded posts to
smooth-tapered post followed by parallel-serrated
posts
Of the threaded designs, the tapered screw creates
greatest wedging effect and highest stress
concentration.
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78. Principles of Tooth Preparation
Surface texture
Threaded posts with countersink also generate very
high stresses when the countersink is fully engaged.
These stresses can be reduced by counter-rotation of
the post by half a turn. Placing a split in the shank of
tapered threaded posts create stresses comparable to
parallel-sided serrated posts
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79. Principles of Tooth Preparation
Luting agent
Adhesive resin luting agents have improved the
performance of post and core restorations
Resin cements are affected by eugenol containing
sealers. This should be removed by irrigation with
ethanol or etching with 37% ortho phosphoric acid
or alcohol
Zinc phosphate and glass ionomer have similar
retentive properties. Polycarboxylate and composite
resins have slightly less.
RMGIC – hydrophilic resins
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80. Principles of Tooth Preparation
Posterior teeth:
Long posts are not indicated in posterior teeth
which often have curved roots and elliptical or
ribbon shaped root canals. For these teeth retention
is better provided by two or more relatively short
posts in divergent canals.
If more than 3-4 mm of coronal tooth structure
remains, use of post is unnecessary. Core build-ups
in molars with one or more missing cusps will
benefit from cemented posts and amalgam
condensed around it.
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81. Principles of Tooth Preparation
Resistance form: laterally directed forces
The greatest stress concentrations are found at the
shoulder, particularly at the inter-proximal region
and the apex. Dentin should be conserved in these
areas whenever possible.
stresses are reduced as post length increases
Parallel sided posts distribute stresses more evenly
than tapered posts, which tend to have a wedging
effect. However, parallel post concentrate stresses at
the apex
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82. Principles of Tooth Preparation
Resistance form:
Sharp angles should be avoided
Increased stress can be generated during post
insertion, especially with smooth- parallel
sided posts that have no vent.
Threaded posts produce stresses during
insertion and loading but distribute stresses
evenly if backed off.
The cement layer tends to distribute stresses
more evenly.
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83. Principles of Tooth Preparation
Rotational resistance
circular cross-section
In areas where coronal dentin has
been completely lost, a small
groove is placed in the canal can
serve as an anti-rotational element.
The groove is place in the bulkiest,
usually on the lingual aspect.
Alternatively, rotation can be
prevented by placing a pin in the
root surface.
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84. Principles of Tooth Preparation
Hydrostatic Forces
Post cementation – retention, stress distribution,
sealing irregularities
During cementation – development of hydrostatic
pressure
This pressure causes problems with seating & also
causes root fracture
Provision of cement vent
Viscosity of cement – Zn PO4 cement
Auto-polymerizing resin cement may polymerize
prematurely – Dual cure cements
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85. CORE
It consists of the restorative material placed in
the coronal area of the tooth that replaces
carious, fractured or otherwise missing tooth
structure.
Retained by the post
Desirable properties of a core include:
High compressive strength
Dimensional stability
Ease of manipulation
Short setting time
An ability to bond to both tooth and dowel
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86. Cast core:
integral part of the restoration and does not
depend on mechanical means of retention.
Noble metals are non-corrosive. Ceramic cores
can also be fused to zirconia posts in the
laboratory.
Disadvantages:
Cast dowels and cores have shown to have a
higher incidence of root fracture.
laboratory technique sensitive
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87. Amalgam core:
High compressive strength and modulus of
elasticity.
Stable to thermal and functional stress and
therefore transmits minimal stress to the residual
tooth and to the crown and cement margins.
Amalgam cores are highly retentive when used
as a corono-radicular core. It requires more
force to dislodge than a cast-post metal core.
The disadvantage is the potential for corrosion
and subsequent discoloration of the gingival.
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88. Composite resin core:
Ease of manipulation, very rapid set and strong
compressive strength
Composite microleakage and retention to
tooth structure are dependant on dentin
bonding. Hence coronal build up with
composite resins requires 2mm of sound tooth
structure at the margins
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89. Glass ionomer core:
Glass ionomer and glass ionomer silver are adhesive
materials for small build ups or to fill undercuts. The
major benefit is its property of anticariogenecity.
Adhesive failure can result from contamination of the
tooth structure by saliva, blood, cutting debris or
protein. It is not indicated as a core for an abutment
tooth.
It is indicated in posterior tooth when:
a bulk of core material is possible
significant crown dentin remains
additional retention is available with pins and dentin
preparations
caries control is indicated
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90. Resin-modified glass ionomer core:
It exhibits moderate strength and water
solubility between GIC and composite resins.
Its bond is close to that of composite resins
and significantly reduces microleakage.
The property of fluoride release is equal to that
of GIC. It is indicated in moderate core build
ups.
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91. Corono-radicular Restoration
In this restoration, the core extends 2-4mm into the
coronal portions of the canal.
Retained by the divergence of the canal, the undercuts
in the pulp chamber and adhesion with dentin-
bonding agents
This type of restoration is indicated for posterior
teeth with large pulp chambers and multiple canals for
retention
It requires a minimum of 50% of tooth structure to
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92. CORONAL COVERAGE
It serves the function of isolating the endodontic filling
and dentin from microleakage. They also distribute the
stresses and protect the tooth against fracture. This can
be achieved with cast metal crowns and high strength
ceramic onlays.
The crown and crown preparation must achieve the
following requirements:
A minimum of 2mm dentin axial wall height
Parallel axial walls
The metal must encircle the tooth
Finish line must be on solid tooth structure
It must not invade the attachment apparatus
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93. Canal Rehabilitation
Done in immature and
hollowed-out roots
Makes use of dentin
bonding composites to
reinforce the canal
Key for success is the
remaining tooth
structure and length of
ferrule.
Endodontic Obturator
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94. Restoration of tooth with
Resected Root
Mandibular mesial root resection
Mandibular distal root resection
Maxillary distobuccal or mesiobuccal root
resection
Hemisection
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95. Over Dentures
As long as the root remains, the
bone remains
Support, stability and retention
The abutment selected must
have ↓ mobility, ↓ sulcus depth
& band of attached gingiva
Canines and premolars are ideal
abutment candidates
Diagonal cross-arch arrangement
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96. Crown Cementation
Functional forces cause strain against the crown margins,
resulting in bond failure. This results in microleakage and
secondary caries.
RMGIC has shown to expand hygroscopically causing cracking
or fracture of low strength all ceramic crowns.
Crowns cemented with light cured resin cement are more
resistant to fracture than when compared with RMGIC, GIC or
zinc phosphate cement. However removal of excess resin cement
after setting will be difficult.
Dual cure cement can be used. This allows the removal of excess
cement, while the internal cement sets chemically.
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97. ….. Success can only be achieved when the technique
choice best meets the needs of the individual clinical
diagnosis – specifically, the needs of the individual
diseased tooth and the clinical use for which it is
indicated.
- Weine
Now say Why!
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