Post and core

1. Restoration of endodontically
treated teeth
Composite / amalgam
restoration
Crown – metal /
ceramic

2. A post and core is a dental restoration used to sufficiently build-up
tooth structure for future restoration i.e crown when there is not
enough tooth structure to properly retain the crown.

3. post is placed within the body of the root of a tooth
that has already treated with root canal treatment.
The core is the part of the restoration that shows out
in the mouth that help anchor a cap or crown

4. Principles of tooth preparation
Conservation of tooth structure
Retention form
Resistance form

5. Conservation of tooth structure
-canal preparation-
enlargement of canal
should exceed about 1-2
additional file sizes
beyond the largest size
used.
Coronal part preparation-
removal of undercuts and
ferrule (extension of axial
wall of the crown apical to
the missing tooth
structure)

6. Retention form
Post length
Post diameter
Surface texture
Luting agent

7. Post length
Greater post
length=greater
retention
2/3 length of root /
post length should
equal crown length
Maintain 3 – 5mm
apical seal

8. Post diameter
Shouldn't exceed 1/3
diameter of the root
A

minimum of 1 mm
of sound dentin
should be maintained
circumferentially

9. SURFACE TEXTURE
Serrated or
roughened post is
greater retentive than
smooth post
LUTING AGENT
Znpo4,Resin and GIC
are greater to other
cements

10. Resistance form
Post design influences
the stress distribution and
in turn resistance
-post length
-parallel posts
-threaded posts produce
stress conc.
-cement layer results in
better stress distribution
-sharp angles
-rotational resistance

11. Post and core systems
Custom post and core – mainly used in
flared canals,elliptical crossection
canals ,multiple canal teeth
Prefabricated – circular crossection
canals

12. Steps in tooth preparation
Removal of RC filling material
Enlargement of the canal
Preparation of coronal tooth structure

13. Prefabricated post and core
system

14. Eliminate weaker residual walls, clean
up the cavity, preserving all healthy
dentine

15. Prepare the root canal according to your usual
procedure (Gates,paesso reamers ]
the post is chosen according to the canal's diameter,
not to the root's.

16. Prepare the composite bonding cement, coat the post
Insert it immediately into the canal

17. Fit the core form boxing system
Fill up with the core composite while pressing and
polymerize

18. Custom cast post system
Direct technique
Indirect technique

19. Remove any weak,
thin, and/or
unsupported tooth
structure.
Direct technique

20. Using progressively
larger diameter Pesso
reamers remove the gutta
percha to the
predetermined initial
depth
 Repeat this process as
necessary leaving 4-5
mm of gutta percha as an
apical seal.

21. Add a keyway to
resist rotation of the
post/core. Place the
keyway in the bulkiest
part of the remaining
tooth structure.

22. Try-in the preformed
plastic post and be sure it
goes all the way down the
prepared canal without
binding (a totally passive
fit). Trim it as necessary.
Measure the post relative
to the depth of the canal
with a periodontal probe

23. Lubricate the canal
with Duralay lubricant
Using the "bead brush"
technique, fill the canal
completely with Duralay resin.
Use the bristles of a brush
(bent at a 45 degree angle for
easier access) to force acrylic
down the canal and express
any trapped air

24. Immediately, dip the
plastic post in acrylic
liquid (to soften post and
enhance bond of acrylic)
and seat it in the canal to
its full depth.
Move the post up and
down in the canal 1-2 mm
(only after the Duralay is
nearly set) to avoid
getting it "locked in."

25. Using hemostats,
carefully remove the
post pattern and
inspect it to be sure it
is fully formed (with
no voids).

26. Cut off the top of the
plastic post so that
your patient can close
completely

27. Using a large
diameter coarse
diamond (high speed
handpiece at "near
stall" speed with
water spray), shape
the pattern to ideal
preparation form (on
the tooth).

28. Using hemostats (held
mesiodistally), remove
the pattern from the
tooth. The pattern should
not be removed (except
one time to check that the
post portion is fully
formed) until it is
completed. There is the
risk of breakage each
additional time the
pattern is removed.

29. Indirect technique
of making custom post and core

30. Post and core


The tooth is prepared
prior to the pattern
fabrication. A heated
endodontic condensor is
used to safely remove the
gutta percha (this is best
accomplished at the
same time the endodontic
therapy is rendered).
Gates & Parapost drills
are used to shape the
canals to an appropriate
size and depth. The most
common sizes used are
Brown Yellow and Red
(see the table below).

31. 

The minimum length of
the post is equal to the
length of the clinical
crown. The
recommended length is
two-thirds the length of
the root in bone while
maintaining 5 mm of
gutta-percha at the apex.
Remember chances of a
perforation increase as
the length of the post
approaches the apex of
the tooth.

32. The prefabricated posts
are inserted into the
canals. In this case a
precious metal post is
being used in the lingual
canal because the canal
diameter is only
equivalent to a brown
sized Parapost (Gates #3
- see table). The
precious metal posts are
issued from the
Dispensing Window, and
require an additional fee.

33. 

An assistant holds the
Duralay powder, liquid,
and suction - while the
core portion is made in
resin. First lubricate the
remaining tooth structure
with a water soluble
lubricant (Surgilube) then
apply the resin. The
assistant may move the
suction near the resin,
evaporating monomer
from its surface, thus
preventing the resin from
slumping or running.

34. The completed resin
core is allowed to
polymerize - then it is
prepared to the shape
of an ideal crown
preparation

35. Using conventional
diamond instruments,
water and suction, the
resin core is prepared
in the same manner
as a conventional
preparation

36. The preparation is
completed to ideal
form and in this case
its path of insertion is
aligned with the
preparation of tooth
#11

37. The completed post &
core pattern is
submitted to the
Service Laboratory for
investing & casting in
gold alloy.

38. The casting is cleaned
and sandblasted with
alumina oxide in
preparation for try-in,
shaping, and
cementation. The canals
are dried and the casting
inserted using light
pressure. Small shiny
marks on the casting
surface help indicate
where adjustment should
be made.

39. The completed post is
cemented