Coronectomy

[sushantpatel_doc]

Coronectomy is the removal of the crown of a
tooth, leaving the roots in situ.

When applied to a lower wisdom tooth or any lower un-
erupted posterior tooth, it is a measure adopted to avoid
damage to the Inferior Alveolar Nerve (IAN) (the nerve that
supplies feeling / sensation to the lip and chin) when the X-
ray has suggested an intimate relationship between the
roots of the lower wisdom tooth and the IAN and the tooth
still needed to be removed.

The expectation after removing the top of the tooth is that
the roots will remain in place and eventually cover with
bone.

Roots encased in bone can remain buried in the jaw for
years and rarely cause problems.

Coronectomy of lower molars is NOT carried out in the
following situations:

Wisdom tooth roots are not touching the IAN canal
Wisdom tooth with either active root tip or crown infection
Pre-existing numbness of the IAN
Pre-existing mobility of the tooth as any retained roots may act as a mobile foreign body and become a nidus for infection / migration.
Teeth that are horizontally impacted along the course of the IAN as sectioning the tooth crown could endanger the IAN.
Systemic condition predisposing to local infection such as diabetes, AIDS and concurrent chemotherapy.
Local factors predisposing to infection such as metabolic bone diseases (e.g. fibrous dysplasia),
history of radiotherapy to the lower jaw.

        

[sushantpatel_doc]

Coronectomy / Intentional Partial OdontectomySpecific
Warnings:

Antibiotics (pre- & post-op). These are recommended to
lower the chance of infection either in the socket or the
tooth pulp. These will be given at the clinicians’ discretion.

Primary Closure. The retained roots are covered over by
the gum to facilitate healing of the pulp, socket and to
lessen the chance of operation site infection.

Root Canal Treatment of retained roots is not necessary.

Osteo-cementum Growth.
The root margins are trimmed
several millimetres below the crest of the socket to
encourage bone & osteo-cementum formation over the
retained roots, sealing off the roots from the mouth.

Roots inadvertently removed at the time of attempted
coronectomy.
When it came to removing the crown, it was
found that the roots as well were mobile. This ranges from
3 – 9%. If the roots are mobile, we are obliged to remove
them and there is obviously the risk to the IAN (which this
procedure was trying to avoid).

Numbness of Chin, Lip ± Tongue.
The Inferior Alveolar &
Lingual Nerves may still be damaged during the procedure
resulting in numbness affecting the tongue +/- the chin and
lower lip. The numbness of the tongue seems to be quite
short-lived and has a low incidence. The numbness of the
chin ± lip tended to occur when on attempting the
coronectomy, the roots were found to be mobile and had
to be removed.

Root Migration.
Subsequent migration of the roots away
from the IAN occurred in 14 – 81% of cases.

Later Removal of Roots.
This can happen in up to a 2 –
6% of cases. If the roots irritate overlying tissues or the
adjacent tooth or otherwise become symptomatic, they
may need to be removed. Even though a 2nd surgery
would be needed, the possibility of nerve damage should
be negligible since the roots would have migrated away
from its original resting place next to the IAN. Since the
purpose of the coronectomy is to avoid this damage, this
goal would have been accomplished even though a 2nd
surgical procedure was necessary to remove the remaining
root.

        

[sushantpatel_doc]

General Surgical Warnings:

Pain. As it is a surgical procedure, there will be soreness
after the tooth removal. This can last for several days.
Painkillers such as ibuprofen, paracetamol, Solpadeine or
Nurofen Plus are very effective. Obviously, the painkiller
you use is dependent on your medical history & the ease of
the operation.

Swelling. There will be swelling afterwards. This can last
up to a week. Use of an icepack or a bag of frozen peas
pressed against the cheek adjacent to the tooth removed
will help to decrease the swelling. Avoidance in the first
few hours post-op, of alcohol, exercise or hot foods/drinks
will decrease the degree of swelling that will develop.

Bruising & Bleeding into Cheeks. Some people are prone
to bruise. Older people, people on aspirin or steroids will
also bruise that much more easily. The bruising can look
quite florid; this will eventually resolve but can take several
weeks (in the worst cases).

Swelling that does not resolve within a few days may be
due to bleeding into the cheek. The cheek swelling will feel
quite firm. Coupled with this, there may be limitation to
mouth opening and bruising. Both the swelling, bruising
and mouth opening will resolve with time.

Stitches. The coronectomy site will often be closed with
stitches. These dissolve and will ‘fall out’ within 10 – 14
days.

Limited Mouth Opening. Often the chewing muscles and
the jaw joints are sore after the procedure so that mouth
opening can be limited for the next few days. If you are
unlucky enough to develop an infection afterwards in the
socket, this can make the limited mouth opening worse and
last for longer (up to a week or so).

Post-op Infection. You may develop an infection in the
socket after the operation. This tends to occur 2 – 4 days
later and is characterised by a deep-seated throbbing pain,
bad breath and an unpleasant taste in the mouth. This
infection is more likely to occur if you are a smoker, are on
the contraceptive pill, on drugs such as steroids and if bone
has to be removed to facilitate tooth extraction.

If antibiotics are given, they are likely to react with alcohol
and / or the Contraceptive Pill (that is, the ‘Pill’ will not be
providing protection).

Surrounding Teeth. The surrounding teeth may be sore
after the extraction; they may even be slightly wobbly but
the teeth should settle down with time. It is possible that
the fillings or crowns of the surrounding teeth may come
out, fracture or become loose. If this is the case, you will
need to go back to your dentist to have these sorted out.
Every effort will be made to make sure this doesn’t
happen. In very rare instances, the surrounding teeth may
actually come out as well as the intended tooth.

Failure of Anaesthesia. In rare cases, the tooth can be
difficult to ‘numb up’. This can be due to a number of
reasons. The more common ones include inflammation ±
infection associated with the tooth, anatomical differences
& apprehension. If the tooth fails to ‘numb up’ then its
removal will be rescheduled with antibiotic cover or
perhaps done under sedation or even a GA.

        

[Anonymous]

Purpose: Damage to the inferior alveolar nerve when extracting lower third molars is often caused by
the intimate relationship between the nerve and the roots of the teeth. The technique of coronectomy,
or intentional root retention, may minimize this problem.
Patients and Methods: Forty-one patients underwent coronectomy on 50 lower third molars with
follow-up of at least 6 months. The technique of coronectomy deliberately protected the lingual nerve
as part of the surgical procedure. All roots were left at least 3 mm below the buccal and lingual plates
of bone. All patients were radiographed preoperatively, immediately postoperatively, and after 6 months.
Results: There were no cases of inferior alveolar nerve–involved damage in this study of 41 patients
who underwent 50 coronectomies. There was 1 case of transient lingual nerve involvement, probably
from the use of the lingual retractor. One patient required subsequent removal of the roots of both lower
third molars because of failure to heal, and 1 patient required subsequent removal of a root because of
subsequent migration to the surface. Root migration was noted in approximately 30% of patients over a
6 month period.
Conclusion: Coronectomy appears to be a viable technique in those cases where removal of the whole
tooth might put the inferior alveolar nerve at considerable risk of damage. The technique appears to be
associated with a low incidence of complications, but subsequent migration of the roots may be an issue
in the long term.

        

[Anonymous]

SPECIFIC TECHNIQUE
The intention of coronectomy or deliberate root retention
is that the part of the root intimately related to
the inferior alveolar nerve is undisturbed. However,
enough of the root must be removed below the crest of
the lingual and buccal plates of bone to enable bone to
form over the retained roots as part of the normal healing
process. It was also felt to be important not to
mobilize the roots because they might damage the nerve
and then become mobile foreign bodies, and for this
reason complete transection of the crown and roots of
the tooth was felt to be necessary.
The technique used is as follows:
1. All patients were placed on appropriate preoperative
prophylactic antibiotics.
2. A conventional buccal flap with releasing incision
was raised, elevated, and retained with a
Minnesota retractor.
3. A lingual flap was raised and the lingual tissues
retracted and an appropriate lingual retractor,
such as a Walter’s lingual retractor,12 was
placed to protect the lingual nerve.
4. Using a 701-type fissure bur, the crown of the
tooth was transected at an angle of approximately
45° (Fig 1). The crown was totally
transected so that it could be removed with
tissue forceps alone and did not need to be
fractured off the roots. This minimizes the
possibility of mobilizing the roots. However,
the lingual retractor is essential during this
technique because the lingual plate of bone
can be inadvertently perforated (Fig 2), and
otherwise the lingual nerve would be at risk.
Following removal of the crown of the tooth,
the fissure bur is used to reduce the remaining
root fragments so that the remaining roots are
at least 3 mm below the crest of the lingual and
buccal plates in all places (this involves removing
the shaded portion in Fig 3).
An alternative technique is to use a round bur
from a superior aspect and remove the crown
and superior part of the roots by drilling it
away. In this case, only minimal lingual retraction
may be required.
5. There is no attempt at root canal treatment or
any other therapy to the exposed vital pulp of
the tooth.
6. Following a periosteal release, a watertight primary
closure of the socket is performed with 1
or more vertical mattress sutures.

        

[Anonymous]

The issue of inferior alveolar nerve involvement
during the removal of lower third molars is a clinical
and medicolegal problem. Any technique that can
reduce the possibility of this involvement is worthy of
exploration. The technique of coronectomy, or deliberate
root retention, has been studied intermittently
in the past, but has no strong body of support.
It does seem appropriate that if this technique is to
be performed, the following rules appear sensible:
1. Teeth with active infection around them, particularly
infection involving the root portion,
should be excluded from this technique.
2. Teeth that are mobile should be excluded from
this technique because it might be felt that the
roots may act as a mobile foreign body and
become a nidus for infection or migration.
3. Teeth that are horizontally impacted along the
course of the inferior alveolar nerve may be
unsuitable for this technique because sectioning
of the tooth itself could endanger the nerve
. The technique is therefore better
utilized for vertical, mesioangular, or distoangular
impactions where the sectioning itself does
not endanger the nerve.. Completed coronectomy on lower right third molar. Note
retained roots are 3 mm below the crest of bone and exposed pulp is
untreated..
4. There does not appear to be any need to treat
the exposed pulp of the tooth and root treatment
appears to be contraindicated.13-16 Animal
studies have shown that vital roots remain vital
with minimal degenerative changes. Osteocementum
usually extends to cover the roots.
5. The technique of leaving the retained root fragment
at least 3 mm inferior to the crest of bone
seems appropriate and does appear to encourage
bone formation over the retained root fragment.
This distance of 2 to 3 mm has been
validated in animal studies.13-15
6. Late migration of the root fragment does appear
to occur in some cases, but is unpredictable.
However, in all cases the root fragments move
into a safer position with regard to the nerve,
and it can be envisaged that should removal
ever become necessary the nerve would not
then be at high risk. The authors are aware of
anecdotal reports from colleagues of retained
root fragments migrating right up to the surface
of the mucosa and appearing through the mucosa
and requiring removal. This happened
only once in the present study, but at least the
root fragments are mobile and easy to remove
without complication and without risk to the
nerve. It is possible that roots will migrate more
if they are mobilized in any way during the
initial surgical procedure.
One difficulty with regard to a study such as this is the
decision as to which patients are at risk and whom to
perform this technique on. In the end it is a personal
decision between the surgeon and the patient. Previous
studies evaluating the risk of inferior alveolar nerve damage
with third molar extraction have relied on either
periapical or panorex radiographs.1-3 Rood and Shehab3
suggested that diversion of the inferior alveolar canal,
darkening of the root interruption of the white line of
the canal, narrowing of the canal, and deflection of the
root were indicators of possible nerve injury. In their
prospective study of 125 teeth with signs suggesting an
increased risk of nerve involvement, 14% developed
nerve injury. Similarly, Blaeser et al,2 in their study,
showed that when increased risk factors are shown on
a panorex radiograph, the incidence of nerve involvement
may rise from a background risk of 1% to between
1.7 and 12%. The advent of low dose cone beam computed
tomography technology, which is now becoming
readily available in a dental outpatient setting,
should provide a much more accurate prediction of the
likelihood of nerve injury, and in cases where the pan-CORONECTOMY
radiograph suggests an increased risk of nerve
involvement, the use of cone beam computed tomography
technology may be indicated to assess the exact
relationship in 3 dimensions. When it is seen that there
is truly an intimate anatomic relationship between the
nerve and the tooth in 3 dimensions, coronectomy may
be a useful option.
There are currently no standards regarding the timing
and frequency of follow-up of patients having coronectomy.
At the present time, we are taking radiographs
immediately postoperatively and 6 months postoperatively.
Later radiographs are taken if the patient becomes
symptomatic. We would not advocate seeing the patient
after 6 months unless he or she becomes symptomatic,
though for research purposes patients may need to be
followed and radiographed for longer periods.

        

[sushantpatel_doc]

images..

        

[sushantpatel_doc]

more images..

        

[Author]

Posts