Crowns significantly improve the success of endodontically treated posterior teeth. Posts are primarily used to retain cores and do not strengthen teeth. The appropriate post length is to extend to the radiographic apex with 5mm of gutta percha retained. Post diameter should not exceed 1/3 of the root diameter and range from 0.6-1.2mm. A ferrule of at least 2mm is recommended to prevent root fracture.

1. Restoration of endodontically
treated teeth :
Answers to important questions
Charles J. Goodacre, DDS, MSD
Professor of Restorative Dentistry
Loma Linda University School of Dentistry
This program of instruction is protected by copyright ©. No portion of this
program of instruction may be reproduced, recorded or transferred by any
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2. Do endodontically treated teeth
need crowns?

3. • Greater force required to activate
proprioception (can bite harder before
protective mechanism activated). One study
showed 57% higher biting force required to
activate pressoreceptors
• Some physical properties are not affected
and others are altered such as flexibility
(decreased)
• Greater cuspal deflection after RCT
Summary of Changes After RCT

4. Mandibular Molar Cuspal Deflection
• Up to 1 µm with intact teeth
• MO cavity preparation causes < 2µm of
movement
• MOD cavity preparation produces 3 to 5 µm
• Endodontic access preparations produces 7 – 8
µm in the MO group and 12 – 17 µm of
movement in the MOD group (a 2 – 3 fold
increase)
Panitvisai, J Endod 1995;21:57-61

5. Clinical Fractures
• 1639 RCT posterior teeth were restored with
amalgam – no cusp coverage
• Maxillary premolars with MOD amalgams had
the highest fracture rate
– 28% fractured within 3 years,
– 57% fractured after 10 years, and
– 73% fractured after 20 years
Hansen, Endod Dent Traumatol 1990;6:49-55

6. Survival of RCT Teeth & The
Presence Of Crowns
• RCT teeth without crowns lost at 6 times the rate of
those with crowns (did not compare anterior vs.
posterior teeth).
• 2nd molars had appreciably poorer 10 year survival
than all other teeth.
• Teeth with 2 proximal contacts had significantly longer
survival than teeth with 1 or no proximal contacts.
Aquilino, 2002

7. Survival of RCT Teeth & The
Presence Of Crowns
• 116 RCT teeth that were extracted.
• RCT teeth without crowns were lost after an
average time of 50 months.
• RCT teeth with crowns were lost after an
average time of 87 months.
Vire, 1991

8. Failure of Molars with No Crowns
• 220 molars observed for time periods between 6
mo & 10.2 yrs
• 101 teeth failed (46%) after 5 years (caries, crack
in tooth or filling, loss of filling, root fracture)
• 14 of 101 teeth were unrestorable
• 1, 2, 5 yr survival rates (96%, 88%, 36%)
• Teeth with maximum tooth structure (like Class I
filling) – 5 yr survival of 78%
Nagasiri, J Prosthet Dent 2005;93:164-170

9. Composite Resin & RCT Molars
• Completely intact except for conservative
access opening
• Can be successfully restored with composite
resin and no crown
Nagasari, J Prosthet Dent 2005

10. Crowns
significantly
improved the
success of
endodontically
treated posterior
teeth but did not
improve the
success of
anterior teeth
Sorensen, 1985

11. True or False Question
• Crowns should be placed on all root canal
treated teeth
• False
• Which teeth require crowns most of the time?
• Posterior teeth

12. Do posts improve the longevity of
endodontically treated teeth or
enhance strength?

13. Intact Anterior Crowns Provide Better
Fracture Resistance Than Posts &
Cores
• Maxillary incisors, without posts, resisted higher
failure loads than the other groups with posts and
crowns
Pontius, J Endod 2002;28:710-715
• Mandibular incisors with intact natural crowns
exhibited greater resistance to transverse loads
than teeth with posts and cores
Gluskin, J Endod 1995;21:33-37

14. Effect of Posts – Their Purpose
• In laboratory tests on extracted teeth, posts
either weakened the teeth or had a neutral
effect.
• There is no clinical data to show posts
strengthen a tooth.
• Therefore, there is no strengthening effect and
the only function of a post is retention of a core.

15. Restorative Material Core
vs
Post and Core
• Preference for restorative material core (without a
post) whenever it can be properly retained. This
concept works best for molars but can work on
premolars and anterior teeth where sufficient
material bulk can be present.
• Core retention can be obtained using undercuts,
slots, grooves, boxes, pulp chamber, pins, bonding.

16. PULP CHAMBER RETENTION
Amalgam cores

17. Composite resin cores

18. With All Core Materials, There
Needs to be Adequate Bulk To
Resist Transverse Fracture.
When The Bulk Is Not There,
Then A Post Is Needed

19. True or False Question
• Posts strengthen teeth.
• False, except perhaps thin coronal tooth
structure. They weaken roots.
• The main purpose of a post is to retain a core.
• True

20. • Post loosening (5%)
• Root fracture (3%)
• Caries (2%)
• Periodontal Health (2%)
• Root perforation (1%)
• Bent / fractured posts (1%)
What are the most common
complications associated with posts
and cores?

21. • As with all clinical procedures, we
should focus upon preventing or
minimizing complications
associated with posts and cores.

22. Retention & Root Fracture
• Threaded posts are the most retentive but
clinical study data indicates they reduce tooth
survival by about 10%
• Parallel posts are more retentive than tapered
posts. Parallel posts have a slightly lower tooth
fracture incidence than tapered posts

23. Parallel vs Tapered Posts
• It appears that prefabricated parallel – walled
posts have some advantages
• However, some teeth are not well suited for
parallel posts

25. Post Form Summary
• It is generally recommended that
posts not be threaded. However,
threaded posts may be useful in the
presence of short roots that possess
adequate root thickness, where
retention is the primary concern and
cemented posts will not be sufficiently
retentive

26. Post Form Summary
• Parallel – walled cemented posts are
generally preferred over tapered cemented
posts. However, custom cast, tapered
posts are recommended for teeth with
tapered roots and roots with substantial
concavities such as mandibular incisors,
maxillary first premolars and certain molar
roots where preparation of round post
spaces will result in excessive tooth
reduction.

27. What is the optimal post length?

28. Short Posts Increase Stress
• Standlee, 1972
• Davy, 1981
• Peters, 1983
• Hunter, 1989
• Standlee, 1992

29. Length & Fracture Resistance
• Increasing length
increases fracture
resistance
Trabert, 1978
• Posts should have maximal length and
therefore extend to the gutta percha.
• How much gutta percha is need for a good
apical seal?

30. Amount Of Gutta Percha
• 32 of 88 specimens leaked at 2 mm
Camp, 1983
• Significantly more post-treatment periapical
radiolucencies - < 3 mm
Kvist, 1989
• Most 3 mm specimens leaked
Portell, 1982
• Little leakage at 4 mm
Zmener, 1980; Camp, 1983
• No leakage at 4 mm
Neagley, 1969; Madison, 1984; Raiden, 1994
Due to radiographic angle variations, 5 mm of
radiographic gutta percha should be retained.

31. The 5 mm Rule Works For
All Teeth Except Molars
• Based on perforation
data from preparing
extracted teeth, the post
length should not
exceed a length of 7
millimeters in the
primary canals
Abou-Rass, 1982

32. True or False Question
• Post length is determined by retaining the
amount of apical gutta percha required to
maintain an apical seal
• True
• What is the appropriate amount of radiographic
gutta percha that should be retained?
• 5 millimeters

33. Completion Question
• Molar posts should not extend more
than ____ millimeters apical to the canal
orifice at the base of the pulp chamber
• 7 mm

34. What is the most
appropriate post diameter?

35. Diameter & Root Fracture
• Large posts increase stress.
Mattison, 1982
Hunter, 1989
• With large diameter posts
(1.5 mm or more), root fracture
increased sixfold for every mm
of decreased root diameter.
Deutsch, 1985
• Posts should not exceed
1/3rd the root diameter.

36. Avoiding Excess Diameter
• Controlling post diameter is best
accomplished by selecting instruments of the
proper size.
• Appropriate instrument size range is 0.6 to
1.2 millimeters in diameter.

37. Peeso
Instruments
• 1 – 0.5 mm
• 2 – 0.7 mm
• 3 – 0.9 mm
• 4 – 1.1 mm
• 5 – 1.3 mm*
• 6 – 1.5 mm*
* Do Not Use

38. Gates-Glidden
Instruments
• 1 – 0.4 mm*
• 2 – 0.6 mm
• 3 – 0.8 mm
• 4 – 1.0 mm
• 5 – 1.2 mm
• 6 – 1.4 mm*
* Do Not Use

39. Round Burs
• 2 – 0.8 to 1.0 mm
• 4 – 1.2 to 1.4 mm*
• 6 – 1.8 to 2.2 mm*
• Considerable diameter
variation occurs
between manufacturers
* Do Not Use

40. Para-Post Instruments
• 3 – Brown 0.9 mm
• 4 – Yellow 1.0 mm
• 5 – Red 1.25 mm
• 6 – Black 1.5 mm*
• 7 – Green 1.75 mm*
4 5 6 7
* Do Not Use

41. Completion Question
• The diameter of posts should not
exceed ____ of the root diameter
• One-third
• The diameter of posts should range
between ___ and ___ millimeters,
depending on the tooth
• 0.6-1.2 millimeters

42. Does the use of a cervical
ferrule (circumferential band of
metal that encompasses tooth
structure) help prevent tooth
fracture?

43. Crown Ferrule
Core Ferrule

44. • Data indicates ferrules formed as part of the
core are less effective than ferrules created
by the crown engaging tooth structure.
• Ferrule dimensions greater than 1 mm are
needed to provide the tooth with adequate
resistance to fracture. Therefore, 2.0 mm is
proposed as an appropriate dimension to
optimize resistance to fracture.
Effectiveness of Ferrules

45. Ferrule Uniformity
• 2 mm uniform crown ferrule was compared with 2
mm non-uniform (only 0.5 mm on the proximal
surfaces).
• The uniform ferrule produced significantly greater
fracture resistance than non-uniform ferrule but the
non-uniform was better than none.
• A post and core does not strengthen a tooth but it
also does not weaken a tooth when there is a 2
mm ferrule.
Tan, 2005

46. True & False and
Completion Questions
• Core ferrules are preferred over crown ferrules.
• False
• Ferrules should ideally encompass ___ millimeters of
apical tooth structure.
• Two
• Ferrules that encompass 2 mm on all 4 axial surfaces
are the best and when present the negative affect of
a post is counteracted.
• True

47. • Direct
• Indirect
• Prefabricated
• Custom cast
P & C Fabrication techniques

48. Direct Prefabricated Post &
Restorative Material Core
• One appointment
• Less expensive
• Judged to be easier by
many clinicians

49. Direct Pattern for Cast Post
& Core
• Resin or wax pattern
• With resin, be careful
not to lock pattern into
the tooth

54. • Five sizes:
• Five matching color
coded drills:
Brown 0.09 mm
Yellow 1.0 mm
Red 1.25 mm
Black 1.50 mm
Green 1.75 mm
ParaPost System

55. Stainless Steel Parapost &
Composite Resin Core

56. Charles J. Goodacre, DDS, MSD
Professor of Restorative Dentistry
Loma Linda University School of Dentistry
Thank You For Your
Kind Attention

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