Endodontically treated / prosthodontic courses

Restoration of
Endodontically
Treated Teeth
Post andand Core System
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Characteristics of endodontically treated teethCharacteristics of endodontically treated teeth
1. Tooth structure loss by:
i. Caries, trauma, erosion, abrasion, attrition.
ii. Previous restorations and recurrent caries under restorations.
iii. Endodontic treatment; due to removal of coronal and intraradicular
Dentine during access and root canal preparation.
2. Micro cracks in remaining tooth structure produced by endodontic
procedures.
3. Weakened collagen intermolecular cross-links of Dentine  lower shear
strength.
4. Dehydration; non-vital teeth have less moisture content than vital teeth.
5. Esthetics; biochemically altered Dentine modifies light refraction through the
tooth and modifies its appearance.
 The combined result of these changes are: increased fracture
susceptibility and decreased translucency.

Treatment planning for non-vital teethTreatment planning for non-vital teeth
1. Pretreatment Evaluation:
i. Quality of the endodontic
treatment
ii. Periodontal condition
iii. Restorative evaluation
i.i. Strategic importanceStrategic importance
ii.ii. Anatomic position of theAnatomic position of the
toothtooth
iii.iii. The amount of remainingThe amount of remaining
coronal tooth structurecoronal tooth structure
iv.iv. The functional load on theThe functional load on the
toothtooth
iv. esthetic evaluation
2. Treatment plan:
i. Post
ii. Core
iii. Definitive restoration

Treatment planning for non-vital teethTreatment planning for non-vital teeth
1. Pretreatment Evaluation:
i. Quality of the endodontic treatment:
• The endodontic treatment should be properly done.
• Retreatment should be considered if tooth exhibits any clinical
signs of inflammation, a periapical pathology exists, or
inappropriate endodontic filling material was used ( silver
pointes).
i. Periodontal condition:
• This is important for long-term success of teeth.
• Weak teeth should be extracted.
• A mutilated tooth in which the restorative treatment would violate
the junctional epithelium or the attachment level (e.g. extensive
caries, perforations, external root resorption) should be
considered for crown- lengthening surgery or orthodontic
extrusion.

iii. Restorative evaluation:
a.a. Strategic importance:Strategic importance:
• does the final restoration depends on this tooth ? Are the
adjacent teeth reliable? What about an implant ?
b.b. Anatomic position of the tooth:Anatomic position of the tooth:
• Anterior teeth:
• They receive mainly angular forces  reinforcement
effect of posts is doubtful.
• If the tooth is intact except for the endodontic access
opening  etched resin in the access is sufficient.
• A post and core is only indicated when the tooth is
weakened by the presence of large or multiple coronal
restorations or they require form or/and color changes
that cannot be affected by bleaching, resin bonding or
laminate veneers.
• Mandibular incisors and maxillary lateral incisors 
usually require a post.
• Maxillary central incisors and canines  crown
preparation, the remaining tooth structure, is
accomplished before deciding a post should be placed.

• Posterior teeth:
• They receive mainly vertical forces.
• When there is sufficient tooth structure to retain a core and
crown  posts are not needed.
• Teeth which don’t have occlusal interdigitation or have an
bucco-occlusal form that preclude interdigitation ( e.g.
Mandibular 1st
premolars with small poorly developed lingual
cusps) , with sufficient coronal tooth structure,  restoration
of the access should be acceptable.
• Teeth which have interdigitation with opposing teeth  full
coverage crowns or onlays should be used as occlusal forces
push the cusps apart.
• Maxillary premolars are subjected to angular and vertical
forces  if the clinical crown length > its cervical width a post
may be indicated.

c.c. The amount of remaining coronal tooth structure:The amount of remaining coronal tooth structure:
• More than half  conservative treatment with coronal
restorations without posts.
• minimal  post, core, and definitive restoration.
d.d. The functional load on the tooth:The functional load on the tooth:
• The post, core, and crown system is indicated, when more
extensive protective and retentive features are required in
the restoration:
1) Bruxism and heavy occlusion.
2) Abutment teeth for long-span fixed bridges.
3) Abutment teeth for free end removable partial denture.

iv. esthetic evaluation:
• Esthetic zone (Anterior teeth, premolars, and
often 1st
molar) requires:
1) Careful selection of restorative materials.
2) Careful handling of the tissues.
3) Timely endodontic intervention to prevent
darkening of the root as it looses vitality.

2. Treatment plan: (post and core)
• The purpose of a post is to provide retention for a core; as both
laboratory and clinical data fail to provide definitive support for the
concept that posts strengthen endodontically treated teeth.
• If the walls of the root are thin owing to removal of internal root caries
or over-instrumentation during post preparation then a post may
strengthen the tooth.
• Reinforcement of a tooth by a post means: moving the point of
fracture from the gingival margin of the crown some distance up the
root towards the root apex.
• The following characteristics should be determined prior to beginning
the clinical procedures :
1) Post length
2) Post diameter
3) Type of post and core that will be used (prefabricated post and
restorative material core or anatomically customized cast post and core)
4) Root selection in multi-rooted teeth
5) Core material and definitive restoration.

1) Post Length:
• It is of more importance for retention than diameter.
• 4 - 5 mm of gutta-percha should be retained apically to ensure a good
seal.
• posts should be extended to that length, or equivalent to the crown
length, in all teeth except molars.
• With molars, posts should not be extended more than 7 mm from the
orifice of root canal in the base of the pulp chamber. Extension
beyond this length can lead to root perforation or only very thin areas
of remaining tooth structure.
• Posts should extend 4 mm apical to the bone crest to decrease stress
in dentine and in the posts.

2) Post Diameter:
• It is important to resist distortion or permanent bending under
functional forces.
• Ideally, after completion of endodontic treatment, the canal shouldn’t
be further enlarged. Rather, the post should be modified to fit the
canal.
• Do not exceed one-third the root diameter.
• Optimal post diameter measurements have been determined to be:
1) Mandibular incisors  0.6 – 0.7 mm
2) Maxillary central incisors, canines, and the palatal root of the
maxillary 1st
molar  1.0 – 1.2 mm & may even reach 1.7 mm.
3) The rest of teeth  0.8 mm.
• Mesial roots of mandibular molars and the buccal roots of maxillary
molars shouldn’t be used for posts.
• Mandibular premolars with oval or ribbon shaped canals shouldn’t be
prepared further for a post  the gap is filled with luting cement which
add elasticity to it.
• Roots with remaining dentine thickness less than 1mm are indicated
For custom made posts.
• The amount of remaining intraradicular dentine after endodontic
treatment:
• Canines, maxillary incisors, and the palatal root of maxillary 1st
molar = > 1mm.
• All other teeth = < 1mm.

 N.B
 Craze Lines:
Craze lines in dentin are areas of weakness where
further crack propagation may result in root fracture
and tooth loss.
The patient should be informed of their presence. If
possible, avoid post placement in favor of a restorative
material core.
If a post is required, it should passively fit the canal,
and the definitive restoration should entirely
encompass the cracked area, whenever possible, by
forming a ferrule.

3) Type of post:
A. Acc. to type of material:
• Metallic.
• Non-metallic:
1. Carbon fiber posts: composed of unidirectional carbon
fibers in an epoxy matrix. Esthetic version contains
quartz. It is smooth, rigid, highly radiopaque, and can be
removed.
2. Ceramic posts: composed of zirconium dioxide. It is hard
and can withstand high flexural stresses.
3. Fiber-reinforced posts: composed of woven polyethylene
fiber ribbon that is coated with a dentine bonding agent
and packed into the canal, when it is light cured. It is
esthetic, smooth, less stiff, reduce incidence of root
fracture, and less radiopaque.
• Excessive retention of zirconia (ceramic) posts may preclude
conventional endodontic retreatment if cannot be removed
atraumatically.
• Carbon fiber and Fiber-reinforced posts may not need to be as
long as traditional posts. A 1:1 ratio between the post and the
crown is sufficient.

• In laboratory tests metallic posts are more fracture resistant than carbon
fiber posts.
• Most metal, carbon fiber, and ceramic posts chemically bond to resin
cement.
• Stainless steel posts are more retentive to composite cores than carbon
fiber posts.
• Carbon fiber and Fiber-reinforced posts have a lower modulus of elasticity
than metal posts and are considered to have elasticity similar to dentine,
this provide more force dissipation, reducing the risk of root fracture.
• Stainless steel contains nickel which may cause allergy. Non-metallic posts
are highly biocompatible.
• Prefabricated Stainless steel posts may show corrosion. Custom-cast and
non-metallic posts don’t show corrosion.

B. Acc. to retention:
• Active: include many designs (e.g. threaded, split threaded).
they produce high stresses which increase the potential for
vertical fracture. They should be unscrewed one fourth of a
turn after installation. Split threaded posts even produces
higher stresses. Active posts are indicated in short canals.
• Passive: it is cemented to the root canal using zinc
phosphate, glass ionomer, or a resin cement. Resin modified
glass ionomer is not indicated as hygroscopic expansion may
cause root fracture. Low expansion formulations of resin
modified glass ionomer can be used.
C. Acc. to fabrication:
• Pre-fabricated post:
• tapered smooth, se , or threaded.
• parallel smooth, se , or threaded
• Custom-cast post:
• indicated in:
i. Non-rounded root canals.
ii. Extremely divergent sidewalls of root canals.

• Tapered smooth posts are the least retentive. And may cause
wedging effect on the tooth.
• Tapered threaded posts are more retentive than parallel
threaded.
• Parallel posts distribute stresses less evenly and cause apical
stress concentration.
• Tapered posts cause post-core junction stress concentration and
equal stress distribution between the cementoenamel junction
and the apex. So , it should be considered for teeth that have thin
apex.
• Tapered posts require no further canal preparation after
endodontic treatment as it can be modified to fit into the canal.
So, it can be used in thin fragile roots.
• Venting and surface roughness are important features which
should be added to custom-cast posts.

4) Root selection in multi-rooted teeth
 posts are best placed in (the primary roots) in palatal roots of
maxillary molars distal roots of mandibular molars, they are the.
The buccal roots of maxillary molars and the mesial root of
mandibular molars should be avoided if at all possible. If these
roots must be used in addition to the primary roots, then the post
length should be short (3 to 4 mm) and a small-diameter
instrument should be used (no larger than a No. 2 Peeso
instrument, which is 1.0 mm in diameter).
 Use cast interlocking post:
It is two pieces, characterized by depressions parallel to the
sidewalls of other canal. The distal post is put first then the other
will interlock with it finally.

Technical procedure for prefabricated postsTechnical procedure for prefabricated posts

Pattern construction of custom-cast post
I. Direct method
• Material:
A. Wax.
B. Self cure A.R.
C. Plastic ready-made burn out post.
• Steps:
1. Lubrication of root canal (die lubricant).
2. If direct wax pattern:
1) Select a metallic sprue former:
- Fits loosely inside R.C.
- Length > than that of core.
- Serrated using diamond stone or disc (to ensure good retention
bet. wax & sprue).
2) Softening of blue casting wax and insertion into the R.C.
3) Heating of sprue.
4) Wait till hardening of wax.
5) Add for any deficiencies until it’s removed with slight resistance
“snugly fit”.
6) Core can be made of wax, followed by investing and casting.www.indiandentalacademy.com

3. If direct A.R. pattern:
1) Select a plastic dowel:
- Fits loosely inside R.C
- Long.
- Serrated (notched).
2) Mixing of A.R. and insertion into the R.C. before the dough stage.
3) Before complete curing, moisten the dowel with monomer and
insert into R.C.
4) Also before complete curing, move the plastic dowel inward and
outwards to prevent interlocking in any undercuts or roughness.
5) Add any modifications until it’s removed with slight resistance
“snugly fit”.
6) Investing and casting.
4. Plastic ready made burnout post:
1) Plastic posts supplied with its special drills (same size & shape).
2) Prepare root canal.
3) Build up core with wax or acrylic resin.
4) Investing and casting.

II. Indirect method:
Steps:
1. Impression:
- By light body elastomer applied by a syringe, starting from apex.
- Insert an st.steel wire to: 1- support imp. Material.
2- prevent imp. tearing during
removal.
- Use a (Cu band) or (tray) to complete impression procedures.
- Remove the impression and evaluate it, then pour a stone cast.

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Endodontically treated / prosthodontic courses

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