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Pulp exposures and Pulp
capping
Upon occasion, while filling a tooth, a dentist will expose the
bleeding nerve of the tooth. Since the patient is already
numb, this does not cause any immediate pain, however it always puts
the nerve at risk for eventual death. In order to prevent, or
at least delay the death of the dental pulp which would necessitate
a root canal or eventual extraction, the dentist may attempt a
simple procedure to stop the bleeding and cover up the nerve with a
sedative base. This procedure is called a pulp cap.
The success of this procedure depends on several factors. If
the pulp cap is unsuccessful, the patient will develop a toothache
sometime between the time the anesthesia wears off and several weeks
after the patient leaves the office.
There are two types of pulp caps:
- A direct pulp cap is done whenever the nerve is
directly exposed revealing a relatively small bleeding wound.
There are two types of pulpal exposures:
- A mechanical exposure is generally a small
bleeding point caused after all decay is removed from the
tooth. It happens when the dentist is attempting to
refine the shape of the cavity preparation in order to
retain the filling. They often occur in younger
patients where the nerve is fairly large, and the tooth
structure around it is less bulky. They also happen
when the nerve of the tooth forms very close to the occlusal
(top) surface of a tooth. If the tooth was
asymptomatic (painless) prior to receiving the filling, and
the exposure was very small, the prognosis for a pulp cap
under these circumstances is fairly good.
- A Carious pulp exposure often happens when the
decay is close to the nerve, and the nerve is exposed while
the dentist is attempting to remove it. These
exposures are often larger, and the nerve is generally
already somewhat inflamed due to the proximity of the decay.
The prognosis for a pulp cap on this type of exposure is
generally poor.
- An indirect pulp cap is often done in order to
prevent exposing the nerve. In this procedure, the dentist
intentionally leaves some decay directly over the nerve to
prevent any bleeding at all. If the tooth was asymptomatic
prior to the procedure, the prognosis for pulpal survival is
fairly good, although the tooth will probably need a root canal
a number of years later. The decay left over the nerve
becomes inactive since the base used over it causes it to harden
up over time, and also because the composite or amalgam filling
should "waterproof" the cavity sealing off any nutrients that
could allow the bacteria in the decay to live.
How a pulp cap is done:
- The bleeding from the exposure is stopped. If
the pulp is not inflamed to begin with, this can be done
applying pressure to the bleeding point with a dry cotton pellet
for about three minutes. If this does not work, the
bleeding can generally be stopped with a brief jolt from an
electrosurge unit. If the bleeding does not stop, then any
attempt at pulp capping will fail.
- The exposure is then covered with one of three possible bases:
- Calcium hydroxide paste (generally combined with
other components so it sets hard) is placed over the
exposure. Calcium hydroxide is the traditional
material used for this purpose. Calcium hydroxide has
been shown to cause the living pulp under the exposure to
build secondary dentin between the base and the
underlying nerve tissue.
- MTA (mineral trioxide aggregate) is actually just
a form of Portland cement which can be used instead of
calcium hydroxide. Prior to applying the MTA, the
cavity preparation is disinfected with sodium hypochlorite
(bleach). MTA has been shown to be more
effective than calcium hydroxide at stimulating secondary
dentin formation, and sets harder making a better seal to
prevent bacterial penetration into the nerve space.
MTA has also been shown to stimulate bone growth in
instances in which a dentist mistakenly perforates the tooth
during a root canal procedure.
- Resin Modified Glass Ionomer (RMGI)--This
material is actually a base used under composite filings.
Even though it is an off-label use for this material, it has
steadily replaced calcium hydroxide preparations as a pulp
capping agent. It appears to be more effective than
calcium hydroxide in preventing post operative pain as well
as long term outcomes.
Apexification
Before there is a tooth, there is a nerve. The nerve is the
organ that actually forms the tooth. In general, the tooth
begins forming from the top of the crown and proceeds down toward
the apex (tip) of the root. If a tooth is badly injured before
the tooth is fully formed, the dentist may attempt a procedure known
as apexification. If the nerve is still alive, but a part must
be amputated due to the injury, the dentist may be able to coax the
rest of the root to form by stopping the bleeding, and placing MTA
(mineral trioxide aggregate) over the stump. In many cases,
the remainder of the nerve will recover and allow the root to form
naturally. In most cases, it will be necessary to do a regular
root canal after root formation to prevent early sclerosis and
discoloration of the tooth.
In cases in which the nerve is necrotic (dead) the dentist may
perform a regular root canal procedure down to the open end of the
root, create a 2 mm thick plug of MTA at the end of the root, wait
for it to set, and finally fill the remainder of the root with
cement and gutta percha.
The Apicoectomy and
retrofil
| In general, whenever a root
canal procedure seems to have failed, the dentist's first reaction is to
try to redo the root canal in standard fashion. In other words, he
or she will try to remove the old root filling materials (usually gutta
percha and endodontic cement) and re-instrument the tooth before
replacing them. This is not always possible to do since it can be
quite difficult to remove the original root filling. It is often
impossible to do if a
post
has been placed in the canal to stabilize the subsequent filling
for placement of a crown. In cases like this, if the failure can
be demonstrated (generally using x-rays) to be associated with one root,
it is possible to do a surgical procedure to remove the offending root
tip along with any abscess associated with it. This is called an
Apicoectomy procedure.
An apicoectomy is done by cutting a soft tissue flap
just above the tip of the root canal treated tooth, puncturing through
the bone and amputating the root tip. This generally removes any
offending dead (or living) tissue and often cures the problem. In
some instances, the dentist will prepare a tiny cavity preparation at
the tip of the root and seal off the rest of the canal with a tiny
amalgam filling. If this is not possible, it is still often
possible to melt some gutta percha at the tip of the root to seal it
off. This is called a retrofill (retro="from behind").
Apicoectomies and retrofills are generally thought of as a last resort
in an ongoing effort to save an otherwise hopeless endodontically
treated tooth. They are especially useful in treating a failed root
canal in a tooth with a
post
and core.
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Internal/External Resorption
The three images above show a fairly rare, but interesting phenomenon called
internal resorption. (Click on any of the images to see them enlarged.)
The x-ray image to the left shows a tooth with a large filling that is close to
the nerve. The yellow arrow points to the area of concern. Upon
occasion, when a live nerve becomes irritated (in this case due to the close
proximity of the filling), it may become "sick" and forget its usual function of
remaining inert and keeping the tooth hydrated. When this happens, it may
start to eat away at the very tooth that it is supposed to be protecting.
The image in the center was taken a little over a year after the first x-ray,
and shows a dark (radiolucent) area in the distal (back) root next to the
furcation (where the two roots join together). This radiolucency
represents a hole in the tooth structure at that point. The nerve simply
ate away the tooth from the inside out. This hole is an example of
internal resorption. The image on the right shows the extracted tooth in
which the defect caused by the resorption is clearly visible.
The reason that this defect is labeled internal/external resorption is that a
second phenomenon can cause the same defect. This involves cells in the
periodontal ligament which forget their usual function of supporting the root of
the tooth. If this happens, these external cells may eat the same hole in
the tooth, this time from the outside in. Once the nerve is exposed, as it
was in this image, it is impossible to tell from which direction the resorption
started.
If the internal resorption is noted before it perforates through to the
outside of the boundaries of the tooth, a root canal procedure will stop the
process and save the tooth.
All back teeth with root canals should be protected with a
crown.
WARNING: Once the pulp of the tooth has died or has been
removed, the tooth no longer has its hydrating mechanism and becomes somewhat
brittle and more prone to fracture. It is important that all back teeth (molars
and premolars) that have been endodonticly treated be protected with crowns to
prevent fracture and to restore their appearance. (This is somewhat less
necessary with front teeth because they have a smaller biting table and, as a
result, are less prone to fracture in function.)
| Crowns are a procedure done in addition to the root
canal and increases the ultimate expense of keeping the tooth. However
it is well worth doing since it protects the investment of the root
canal and is a good part of an overall treatment plan. These teeth
have root canals, and have been prepared to receive crowns. |
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| These are the crowns as they are received from the
lab where they are fabricated. They are sitting on the plaster
model of the crown preparations you see above. |
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| Crowns are generally made of porcelain and not only
look like teeth, but tend not to stain and can be built to correct the
bad appearance of crooked, discolored and malformed teeth. Front teeth
are frequently crowned even without root canals just to correct the
patient's smile. This is what the prepared teeth look like
immediately after crowns are inserted. |
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Can teeth with root canals, fillings, crowns or gum disease cause other
systemic diseases such as fibromyalgia, scleroderma, multiple sclerosis,
lupus, Chronic fatigue or various autoimmune diseases?
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