Restoration of endodontically treated teeth 1 /certified fixed orthodontic courses by Indian dental academy

RESTORATION OF
ENDODONTICALLY
TREATED TEETH

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

www.indiandentalacademy.co
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Contents:
• INTRODUCTION
• DEFINITION
• HISTORY
• PRETREATMENT EVALUATION
• EFFECT OF ENDODONTICS ON
TOOTH
• TREATMENT PLANNING
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• NEED FOR POST
• FACTORS AFFECTING POST
SELECTION
• CLASSIFICATIONS
• PRINCIPLES OF POST SELECTION

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INTRODUCTION
The overwhelming success of
endodontic therapy has allowed for
retention of more number of teeth
than ever in the history of dentistry.
Following endodontic treatment the
restorative dentist is faced with
deciding how to restore treated teeth
for use as individual units or
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as abutments for fixed or removable
restorations. The technique &
guideline of how & when to restore
endodontic treated teeth have
evolved from clinical tradition.
Although any number of post designs
or no post at all may be used in a
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clinical situation, success can only be
achieved when the technique of
choice best meets the need of
individual clinical diagnosis.

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DEFINITIONS:

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• Dowel : a post, usually made of
metal that is fitted into a prepared
root canal of a natural tooth. When
combined with an artificial crown or
core, it provides retention and
resistance for the restoration
(GPT-8)

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Core : the center or base of a
structure
Post-core crown: a restoration in
which the crown and cast post is one
unit

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Ferrule (GPT-8):
l: a metal band or ring used to fit the
root or crown of a tooth
2: any short tube for making a tight
joint

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• Apex (GPT-8): in dentistry, the
anatomic end of a tooth root.
• Biologic width: the combined
width of connective tissue and
epithelial attachment superior to
the crestal bone
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HISTORY:

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• In 1747, Pierre Fauchard described
the process by which roots of
maxillary anterior teeth were used
for the restoration of single teeth
and the replacement of multiple
teeth.

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• Posts were fabricated of gold or
silver and held in the root canal
space with a heat-softened adhesive
called “mastic” (prepared by gum,
turpentine and white coral powder).

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• In Fauchard’s days, replacement
crowns were made from bone, ivory,
animal teeth, and sound natural
tooth crowns. Gradually, the use of
these natural substances declined,
and were replaced by porcelain.

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• A pivot (what is today termed a
post) was used to retain the artificial
porcelain crown into a root canal,
and the crown-post combination was
termed a “pivot crown.”
• In the early 1800s Dubois de
Clemant described Porcelain pivot
crowns.
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• Early pivot crowns used seasoned
wood (white hickory) pivots. The
pivot was adapted to the inside of an
all-ceramic crown and also into the
root canal space. Moisture would
swell the wood and retain the pivot
in place.

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• Subsequently, pivot crowns were
fabricated using wood/metal
combinations, and then more durable
all-metal pivots were used.

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• Richmond crown:
• By C.M Richmond, a US dentist in
1879.
• It was an artificial crown consisting
of a metal base that has a post for
insertion & a porcelain facing
reinforces the metal backing

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• Metal pivot retention was achieved
by various means such as threads,
pins, surface roughening, and split
designs that provided mechanical
spring retention.

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PRETREATMEN
T EVALUATION:

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• THIS INCLUDES –
• ENDODONTIC EVALUATION
• PERIODONTAL EVALUATION
• ESTHETIC EVALUATION

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ENDODONTIC EVALUATION
• In addition to the identification of
non-vital teeth and the endodontic
evaluation of the vital teeth, the
prerestorative evaluation should
include an inspection of the quality
of the existing endodontic treatment.

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• New restorations particularly
complex ones ones, should not be
placed on abutments with
questionable endodontic prognosis.

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• endodontic retreatment may be
indicated for teeth that exhibit
radiographic periapical disease .
• Restorations that need a dowel need
a dowel space which is made by
removing GP .

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• Canals obturated with a silver cone
should be identified & endodontically
retreated.

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PERIODONTAL EVALUATION
• Maintainence of periodontal health is
critical to the long term success of
the endodontically treated & restored
teeth.
• In addition to the conventional
periodontal examination ,the effect
of the planned restoration on the
attachment apparatus must be
considered.
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• Extensive caries, tooth #,previous
restoration,perforations,external
resorption can destroy the tooth at
the level of the periodontal
attachment .
• Attempts to place the restorative
margins on sound tooth structure
beyond these defects further invades
biologic width.
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the biological attachment zone.

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• A mutilated tooth in which
restorative treatment would
compromise the junctional
epithelium or connective tissue levels
should be scheduled for periodontal
crown lengthening surgery or
orthodontic extrusion.

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ESTHETIC EVALUATION:
• Potential esthetic complications must
be investigated before the initiation
of endodontic therapy.
• Thin gingiva may transmit a shadow
of dark root through the tissue.
• The colour & translucency of most
uncrowned teeth is adversely
affected by opaque substances.
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• Endodontic & restorative materials in
these aesthetically critical cases
must be selected to provide best
possible service.

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Effects of
endodontics on
tooth

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*Pathways of the Pulp,Stephen Cohen,6th edn,Mosby

• The tooth structure that remains
after endodontic treatment has been
undermined & weakened by all of
the previous episodes of- caries,
fracture, tooth preparation &
restoration.
• Endodontic manipulation further
removes important intracoronal &
intraradicular dentin.
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• Finally endodontic treatment changes
the actual composition of the
remaining tooth.
• The combined result of these
changes is the increased #
susceptibility & decreased
translucency in non-vital teeth.

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• Endodontic procedures have been
shown to reduce tooth stiffness by
only 5%, whereas an MOD
preparation reduces stiffness by
60%.*

*

J Endodont 16,512,1989
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• Endodontic access into the pulp
chamber destroys the structural
integrity provided by the coronal
dentin of the pulpal roof & allows
greater flexing of tooth under
function.*

* JPD 67;458;1992
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Altered physical characteristics• Changes in the collagen cross-linking
& dehydration of dentin results in
14% reduction in strength &
toughness.

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TREATMENT
PLANNING:

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• Tooth structure loss can range from
very minimal access preparation to
very extensive damage.
• Before restoration existing
endodontic tooth needs to be
assessed for• Good apical seal
• No sensitivity
• No exudate
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• No fistula
• No apical sensitivity
• No active inflammation

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• Restorative treatment decision
depends on the:
• Amount of remaining tooth structure
• Functional demand
• Need for the tooth as abutment for
large restorations.

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• If coronal structures are largely
intact & loading is favorable as on
anterior teeth that are farther
removed from the fulcrum line a
simple filling can be placed in the
access cavity.

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• If a substantial amount of tooth
structure is missing, a cast post &
core is indicated.
• Molars are often restored with
amalgam or a combination of 1 or
more cemented posts & amalgam or
composite resin.

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• Prefabricated metal, cabon fibre,
ceramic & glass fibre posts are
available.
• They are used in conjunction with a
plastic material such as- composite
resin,amalgam or glass ionomer.

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Considerations for anterior
teeth:
• Endodontically anterior tooth do not
always need complete coverage by
placing a crown

• Unless tooth has a large proximal
composite restoration & unsupported
tooth structure.
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• Cementing a post in an
endodontically treated teeth is a
fairly clinical practice despite paucity
of data to support it.
• A study determined that there was
no significant reinforcement .*

* JPD 62,166,1989
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• When the tooth is loaded, stresses
are greatest at the facial & lingual
surfaces of the root & an internal
post, being only minimally stressed
does not prevent #.

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Disadvantage of routine use of
cemented post in intact anterior teeth:

• Requires additional operative
procedure
• Removes additional tooth structure
for post space preparation.

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• May be difficult to restore the teeth
later when crown is needed, because
this post may fail to provide
adequate retention for the core
material.
• Post can complicate or prevent
further endodontic re treatment if it
becomes necessary.
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Discoloration:
• In the absence of significant tooth str
loss
treated by bleaching.
• In the presence of tooth str loss
complete crown.
• If tooth is abutment for RPD or FPD
complete crown mandatory.
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Considerations for posterior
teeth:
• Endo treated posterior teeth are
subject to greater occlusal loading
than anterior teeth because of their
close proximity to the transverse
horizontal axis.

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• This combined with their
morphological characteristics [having
cusps that can be wedged
apart]makes them more susceptible.
• Endodonticaly treated posterior teeth
should receive cuspal to prevent
biting forces from causing #.

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• Complete coverage is recommended
on teeth with high risk of #
•

Maxillary Premolar

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• Possible exceptions are
• Mandibular premolars & 1st molars.

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• When significant tooth structure loss
has occurred, a cast post & core or
an amalgam foundation restoration is
needed.

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NEED FOR POSTS:*

• THE MANIPULATION OF the pulp
chamber leads to the greatest
weakness of a treated teeth.

*Endodontoc therapy,Franklin Weine,6th edn,Mosby
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Access into the pulp
chamber-

• There is a need for stronger interior
as well exterior support.
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Canal enlargement-

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• So the motivation for placing a post
should not be for reinforcement.
Studies of posts used to reinforce
teeth offer mixed results.

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• These studies lend credence to the
contention that the strength of the
remaining dentin around the post
provide strength & resistance to #
rather than the post itself.

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Primary function of post• To aid in retaining a core to restore
lost tooth structure & not provide
strength or resistance to #.

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Factors affecting
Post selection:
*Pathways of the Pulp,Stephen Cohen,6th edn,Mosby
*Endodontoc therapy,Franklin Weine,6th edn,Mosby

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Non-threatening role of post
• Occlusal forces are transmitted
through the core to the dowel &
ultimately along the length of root.
• The remaining dentin & dowel
together must have adequate rigidity
to withstand functional load.

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• Dowels should be retained by
cementation to the dentin walls of
the root; active engagement of
dowel space by screw threads is
contraindicated.

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• 40% of self-threaded dowels failed
by angular # & vertical root #;
whereas 98% of cemented parallel
posts were successful.*

*

JPD 52;28;1984.
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Dowel design:
• The non threatening & retentive
capacity of the dowel depends on the
appropriate combination of
mechanical design features- Dowel length
- Taper
- Diameter
- Surface configuration
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• The basic post design may be
tapered or parallel sided.

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3 types of threaded posts:*

Dentin spreading
screw

Tapped screw

Self-threading screw


* Felton et al JPD 1991;65:179
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• Parallel sided posts are more
retentive .As the angle of
convergence exceeds 3.5 degree,
surface area of post & resistance to
displacement decreases.
<

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• Parallel-sided dowels are 2 to 4 times
as retentive as tapered ones.*
• Tapered dowel is generally reserved
for the significantly tapered canal
system.

* JPD 1978;40;645
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Dowel classification:
• Preformed dowel system
• Custom cast dowel system
• Preformed dowel system include
various sizes of ready made metallic
dowels.

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• Matching instrumentation-

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• Custom cast dowel system- utilize a
casting procedure to fabricate a 1piece metal dowel & core.

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• By using instrumentation that is
paired with castable plastic patterns
the dowel space is shaped.

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CLASSIFICATIONS:

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Contemporary Fixed
Prosthodontics,Rosenstiel,3rd edn
• Prefabricated post
• Tapered smooth sided posts
• Tapered serrated posts
• Tapered Threaded posts
• Parallel smooth sided
• Parallel serrated posts
• Parallel Threaded posts
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• Custom made post
• Direct technique
• Indirect technique

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Endodontoc therapy,Franklin
Weine,6th edn,Mosby

• A. Tapered smooth sided
• B Parallel, serrated and vented
• C. Parallel threaded posts
• D. Parallel threaded split shank.

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BDJ 2005;198: 533
1 . Active Posts
• A. Pre tapped posts
• B. Self threading
2.Passive Posts
• A. Custom made or prefabricated
• B. Parallel smooth or serrated
• C. Tapered smooth or serrated
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Dowel length:
• Dowel retention is proportional to
dowel length.
• Increase in dowel length from 5 to
8mm increases retention by47%.*
• The dowel should be long enough
without jeopardizing the root
integrity.
* JPD 1979;41;163

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• The standard parameters for dowel
length- 2/3rd length of canal

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• Coronal length of the tooth

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• Approx.. Half the bone supported
length of the root.

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• The final length of the root is
limited by 2 variables1. Root morphology
2. Need for sufficient apical seal

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• Root morphology• At least 1mm of dentin around post
in all direction to resist perforation.*

* DCNA 1976;20;299
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• Short post
• Long post

in tapered root
in parallel-sided root

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• Root curvature:
• Greater the curve
shorter the
dowel.
• Deep concavities:*
- Maxillary 1st molar-94% MB roots
- Mand 1st molar- all M & 99% D roots

*JPD 1992;67;458
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JPD 1991;65:179
• Most of the root # resulting from
dowel insertion occurred on mesial &
distal root surfaces as a result of the
presence of flutes [external
depressions] .

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At CEJ

2mm

Max 1st premolar

4mm

6mm

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• Need for apical seal• Retaining the last 3-5m of filling
material at the apex is sufficient for
endodontic seal

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Dowel diameter:
• The dowel must be of sufficient dia
to resist fonctional forces.
• A large dia gives
little or no
improvement in the dowel-to-root
retention
reduces resistance
to # .

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• Preservation of dentin should take
precedence over larger dia dowel

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JPD 1991,65:179
• The amount of remaining dentin &
existing root morphology may be a
determining factor for endo treated
teeth to resist fracture.

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Surface configuration:
•
1.
2.
3.
4.

Can be:
Smooth
Serrated
Threaded
Sand blasted & silica coated

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• Serrated surface provide mechanical
undercut for cement & increase
retention over that of smooth
surface.

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• Greatest retention from-increased
legth,llel sides,serrated surface*
• Ability to resist forces-increased
length, llel sides, mod dia.*

* JPD 1984;51;780m

Principles of
tooth
preparation*Contemporary Fixed
Prosthodontics,Rosenstiel,3rd edn
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1. Conservation of tooth structure
2. Preparation of coronal tooth
structure
3. Retention form
4. Resistance form

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Conservation of tooth
structure:
• Preparation of the canal• Caution advised- Great care in removing only minimal
tooth str from the canal
- Avoid excessive enlargement
- Thickness of remaining dentin –
prime variable in # resistance of
root.
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• Reasons- Perforate or weaken the tooth
- Root may split during cementation or
function.

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Photo elastic study*
• Internal stresses are reduced with
thinner posts.
• Therefore the strength of the
prepared root comes from its
periphery & not interior.

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• Most roots are narrower MD than FL
& often have proximal concavities

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• Along the length of the post space,
enlargement seldom needs to exceed
what would have been accomplished
with 1 or 2 additional size files
beyond the largest size used for
endo treatment.

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*Endodontoc therapy,Franklin m
Weine,6th edn,Mosby

Preparation of the coronal
tissues:
• Endo treated teeth often have lost
much coronal tooth structure as a
result of caries, previous restn,endo
preparation.

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• If a cast core is used further tooth
structure is needed to accommodate
a complete crown & to remove
undercuts

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• This may leave very little dentin.
Every effort must be made to
conserve as much coronal tooth
structure as possible.
• Extension of the axial walls of the
crown apical to missing tooth
structure- to save tooth structure.
[FERRULE EFFECT]
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FERRULE• Def*- a ferrule is defined as a metal
ring or cap placed around the end of
a cane or a tool.

* Endodontic Therapy-Franklin Weine
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• GPT-8 defl: a metal band or ring used to fit the
root or crown of a tooth
2: any short tube for making a tight
joint

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• When the post is in position, and
receiving lateral forces, the ferrule
ensures the dentine is under
compression (which it is good).
• If there is no ferrule, the dentine
would be under tension (which is
poor), and would fracture.

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Purpose of ferrule ( JPD 1990)
improve the structural integrity of pulpless
tooth by counteracting
• 1. the functional lever forces
• 2. the wedging effect of tapered dowels
• 3. the lateral forces exerted during
insertion of dowel
Thus prevents root fracture.
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Core ferrule-*
• ferrule is a part of cast metal core.

*endodontics,5th edn,John.Ingle,B.C.Decker
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• Ferrule formed as a part of core are
less effective than ferrule as a part of
crown
• Ferrule effect at both the levels did
not increase fracture resistance as
compared to ferrule only at crown
level.

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• Libman et al (IJP 1995;8:155) found
that 0.5-1 mm crown ferrule are
ineffective , whereas 1.5-2mm crown
ferrule is effective.
• Isidor et al (IJP 1999;12:78)
increasing crown ferrule length
increases fracture resistance (1.25 &
1.55 mm)
• Concluded : ferrule length was
more important than post length in
increasing tooth’s fracture
resistance.
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• the tooth’s resistance to fracture was
increased when a substantive
amount of tooth structure was
engaged
• 2 mm in the core ferrule
• 1 to 2 mm in the crown ferrule

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*Endodontics,5th edn,John.Ingle,B.C.Decker

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Extensively damaged teeth*
• Ferrule effect can be accommodated
by- Surgical crown lengthening
- Orthodontic extrusion.

*Contemporary Fixed Prosthodontics,Rosenstiel,3 rd edn
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^

Orthodontic
extrusion

Surgical CL

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RETENTION FORM:
• Is affected by- Preparation geometry
- Post length
- Post dia
- Surface texture
- Luting agent

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Preparation Geometry• For circular canals• Instrumentation- twist drills &
reamers
• Preparation – parallel canal with
minimum taper
• Indicated- prefabricated parallel post

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• For elliptical canals• Preparation-with tapered walls[6-8
degree]
• Indicated- for tapered prefabricated
or custom cast post.

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Retention study*
• Parallel post are more retentive than
tapered post & that threaded posts
are most retentive.
• However these studies are relevant
only when post fits the canal space.

* JPD 1977,38,515
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• Parallel posts- only effective in most
apical portion of the post space

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• Parallel post not effective in tapered
canals

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• Post length• As post length increases so does
retention.

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• Post diameter• Increase in post diameter weakens
the tooth

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• Surface texture• Serrated or roughened post>smooth
post
• Controlled grooving of the post &
canal considerably increases the
retention.

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Thank you
For more details please visit
www.indiandentalacademy.com

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Restoration of endodontically treated teeth 1 /certified fixed orthodontic courses by Indian dental academy

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