Orthodontic extraction of mandibular third molar to avoid nerve injury and promote periodontal healing.

Abstract

Impacted mandibular third molar extraction is a common procedure in oral surgery, not without risk of nerve injury and periodontal defects on the distal aspect of the adjacent second molar. The "orthodontic extraction" is proposed as a method to avoid mandibular nerve injury during the extraction of a deeply embedded third molar and to prevent or limit such periodontal problems.
A 28-year-old man presented a deeply impacted left mandibular third molar that required extraction. Radiographs revealed a very slight quantity of bone at the distal surface of the adjacent second molar. The third molar was extruded according to the "orthodontic extraction" technique. A 3-month retention phase elapsed to ensure adequate bone maturation and the tooth was finally extracted.
No neurological complications occurred. A minimal residual bone defect at the distal surface of the adjacent second molar was detected radiographically both post-operatively and at the 3-year follow-up.
Orthodontic extraction makes third molar removal easier and has no neurological risk. This procedure, followed by a 3-month retention phase, appears to be effective in preventing or limiting the development of periodontal problems on the distal aspect of the adjacent second molar.

Full text

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Case Report
Orthodontic extraction of
mandibular third molar to avoid
nerve injury and promote
periodontal healing
Alessandri Bonetti G, Incerti Parenti S, Checchi L. Orthodontic extraction of
mandibular third molar to avoid nerve injury and promote periodontal healing. J Clin
Periodontol 2008; 35: 719–723. doi: 10.1111/j.1600-051X.2008.01286.x.
Abstract
Aim: Impacted mandibular third molar extraction is a common procedure in oral
surgery, not without risk of nerve injury and periodontal defects on the distal aspect of
the adjacent second molar. The ‘‘orthodontic extraction’’ is proposed as a method to
avoid mandibular nerve injury during the extraction of a deeply embedded third molar
and to prevent or limit such periodontal problems.
Material and Methods: A 28-year-old man presented a deeply impacted left
mandibular third molar that required extraction. Radiographs revealed a very slight
quantity of bone at the distal surface of the adjacent second molar. The third molar was
extruded according to the ‘‘orthodontic extraction’’ technique. A 3-month retention
phase elapsed to ensure adequate bone maturation and the tooth was finally extracted.
Results: No neurological complications occurred. A minimal residual bone defect at
the distal surface of the adjacent second molar was detected radiographically both
post-operatively and at the 3-year follow-up.
Conclusions: Orthodontic extraction makes third molar removal easier and has no
neurological risk. This procedure, followed by a 3-month retention phase, appears to
be effective in preventing or limiting the development of periodontal problems on the
distal aspect of the adjacent second molar.
Key words: extraction; forced eruption; third
molar; tooth impaction
Accepted for publication 22 May 2008
Several complications may be related to
impacted mandibular third molarremoval
(Bruce et al. 1980, Peterson 1992,
Chiapasco et al. 1993). The major one
is temporary or permanent neurologic
damage to the inferior alveolar nerve,
promoted by a close anatomical relation-
ship between the roots of the third molars
and the mandibular canal (Kipp et al.
1980, Rud 1983). Furthermore, the
extraction may cause loss of bone, devel-
opment of periodontal pockets and expo-
sure of the cementum on the distal root
surface of the adjacent second molar
(Kugelberg et al. 1985, Kugelberg 1990,
Peng et al. 2001, Kan et al. 2002), all
of which may unfavourably affect the
long-term prognosis of the tooth. Surgical
interventions may be subsequently re-
quired to improve or to eliminate such
periodontal defects (Pecora et al. 1993,
Oxford et al. 1997, Karapataki et al.
2000a,b, Dodson 2004).
‘‘Orthodontic extraction’’ (Checchi
et al. 1996, Marchetti et al. 2004,
Alessandri Bonetti et al. 2007) is a com-
bined orthodontic–surgical approach for
extracting impacted mandibular third
molars that are in close contact with
the mandibular canal. This procedure
eliminates the risk of neurological com-
plications (Checchi et al. 1996, Hirsch
et al. 2003) and makes extraction easier.
A long-term case report of an impacted
mandibular third molar extraction is
presented, and the results at the 3-year
follow-up are evaluated. The ‘‘ortho-
dontic extraction’’ technique appears
to protect the second molar from perio-
dontal breakdown following the surgical
extraction of the third molar.
Case Report
A healthy 28-year-old man was referred
by his general practitioner to the
Giulio Alessandri Bonetti1, Serena
Incerti Parenti1and Luigi Checchi2
1Department of Orthodontics;
of Periodontology, University of Bologna,
Bologna, Italy
2Department
Conflict of interest and source of
funding statement
The authors declare that they have no
conflict of interests.
No funding was available for this research.
J Clin Periodontol 2008; 35: 719–723 doi: 10.1111/j.1600-051X.2008.01286.x
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Department
Implantology, University of Bologna,
Bologna, Italy, for evaluation and treat-
ment of his deeply impacted left man-
dibularthird molar.
complained of pain and swelling related
to that tooth. The panoramic radiograph
(Fig. 1) showed the presence of a fully
mesio-angulated impacted left mandib-
ular third molar (tooth #38), with the
mesial cusp lying lateral and close to the
apical third of the distal root of
the second molar (tooth #37). Because
the third molar was deeply impacted, a
computed tomography (CT) was per-
formed to assess the precise topographic
localization of the impacted tooth.
Despite thehigher
required as compared with routine
radiographical examination (panoramic
or periapical radiograph), CT scan still
represents the most appropriate diagnos-
tic tool to provide accurate topographic
diagnosis in the case of deeply impacted
mandibular third molars, thus assess-
ing the exact anatomical relationships
between the roots of the third molars
and the mandibular canal. A close
ofPeriodontologyand
Thepatient
radiation dose
anatomical relationship between the
molar roots and the mandibular canal
was confirmed (Fig. 2). Furthermore,
evaluation of the periapical radiograph
revealed a well-defined radiolucency
surrounding the crown of the impacted
tooth and involving the distal root of the
neighbouring second molar (Fig. 3a).
Because of this anatomical situation, a
small amount of alveolar bone was
present at the distal surface of the sec-
ond molar, thus jeopardizing the long-
term periodontal status of this tooth
(Peng et al. 2001). A probing pocket
depth (PPD) of 11mm at the lingual
location and of 7mm at the buccal
location of the distal root surface of
the second molar was observed. Crestal
bone loss at the distal surface of the
second molar was also measured on the
periapical radiograph, with the distance
from the cementoenamel junction (CEJ)
to the bottom of the defect being 14mm.
The CT scan also confirmed the severity
of the bone defect. It was therefore
decided to use the ‘‘orthodontic extrac-
tion’’ technique to solve the case.
Before surgery, the orthodontist applied
a lower lingual arch from the first molar
to the first molar and adapted a passive,
sectional stainless-steel wire to engage
the brackets on the buccal surface of the
mandibular left molars and pre-molars
to provide a stable anchorage for the
extrusive movement. Subsequently, the
crown of the impacted tooth was surgi-
cally exposed under local anaesthesia
and an orthodontic wire was bonded
directly onto it. At the time of surgical
exposure of the third molar crown, root
surface debridement was performed at
the distal aspect of the adjacent second
molar. After 1 week of healing, the
orthodontic appliance was activated.
A cantilever was applied to the first
molar and tied on the occlusal surface
of the impacted tooth, thus stimulating
tooth eruption. A periodontal re-evalua-
tion and professional oral hygiene on the
distal root surface of the second molar
was routinely performed every month to
ensure complete plaque removal. After
5 months of orthodontic extrusion, the
radiograph showed that the third molar
roots were further from the mandibular
canal (Fig. 3b). The cantilever was
passivated. The
extracted after a 3-month retention
phase (Fig. 3c). No neurological com-
plications occurred during the extrac-
tion. Healing was uneventful and post-
operativeclinical
examinationsafter
revealed good clinical results with a
minimal residual bone defect at the
distal surface of the second molar. At
the 3-year re-evaluation, PPD was 3mm
at the disto-lingual location and 2mm at
the disto-buccal location, and a great
amount of crestal bone apposition (cres-
tal bone loss: 2mm) was observed on
the distal surface of the second molar
(Fig. 3d).
thirdmolar was
andradiographic
extractionthe
Discussion
Mandibular third molar removal is a
common procedure in oral and maxillo-
facial surgery(Bruce etal. 1980,Peterson
1992). Great emphasis is given to the
risk of lingual and inferior alveolar
nerve injury (Chiapasco et al. 1993),
which can be caused by trauma suffered
during and after the surgical removal of
the third molar. The rate of neurological
complications increases when a true
anatomical relationship between the
roots of the third molar and the mandib-
ular canal exists (Kipp et al. 1980, Rud
1983). The long-term effect on the
Fig.1. Initial panoramic radiograph. Note the deep impaction of tooth #38.
Fig.2. Computed tomographic scan. Note the close relationship of the mandibular third
molar to the inferior alveolar nerve.
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periodontal status of the neighbouring
tooth following third molar extraction
should also be taken into account. How-
ever, there is still no general consensus
within the literature regarding such
complications. Some studies report an
infrabony periodontal defect on the dis-
tal surface of the adjacent second molar
as a possible adverse effect after third
molar removal (Kugelberg et al. 1985,
Kugelberg 1990, Peng et al. 2001, Kan
et al. 2002). Other studies (Krausz et al.
2005, Richardson & Dodson 2005) have
demonstrated that
dontally involved or bony-impacted
third molars may result in improved or
unchanged alveolar bone height at the
distal surface of the adjacent second
molar. This is more likely in the case
of young (425 years) and plaque-free
people (Kugelberg 1990). However,
older patients with high plaque scores
and deep pockets have an increased risk
of developing deep infrabony defects
following third molar surgery, a risk
that increases with age (Kugelberg
et al. 1985, Kugelberg 1990). It has
alsobeenreported
impacted third molar surgery, the pre-
sence and the severity of an infrabony
periodontal defect distal to the adjacent
second molar is related to the residual
amount of periodontal ligament on this
tooth and to the extent of involvement
before surgery (Karapataki et al. 2000a).
extracting perio-
that, following
The presence of pre-operative bone
defects is a risk factor for persistent
post-operative infrabony
(Kugelberg et al. 1991, Kan et al. 2002).
The use of guided-tissue regeneration
(GTR) therapy has been proposed to
enhance periodontal healing after third
molar removal (Pecora et al. 1993,
Karapataki et al. 2000b). But in other
studies, GTR therapy (Oxford et al.
1997, Karapataki et al. 2000a, Dodson
2004) as well as the use of bone-grafting
materials (Dodson 2004), on the con-
trary, do not appear to offer predictable
benefits when compared with no inter-
vention. Higher costs and risk of post-
operative inflammatory complications
associated with further surgery should
also be taken into account.
The ‘‘orthodontic extrusion’’ of a
single tooth has also been used as a
means of eliminating or reducing bone
defects without compromising the perio-
dontal attachment apparatus of the
neighbouring teeth, or in other words,
as an old method to positively modify
osseous contours (Ingber 1974, 1976). It
is well known that an eruptive tooth
movement produces tensional forces on
the periodontal fibers, thus resulting in
new bone apposition along the tooth
eruption path (Reitan 1967). There is
greater bone apposition in impacted
teeth that are in a vertical position than
there is in those that are in a horizontal
defects
position (Alessandri Bonetti et al. 2007)
because of the greater shift of the CEJ.
After active tooth movement, a retention
phase seems to be necessary in order to
allow a proper maturation of the newly
formed bone. Various studies indicated
3 weeks (Van Venrooy & Raymond
1985), 8 weeks (Ingber 1974, 1976,
Berglundh et al. 1991) and 2 months
(Felippe et al. 2003) as the ideal reten-
tion period. Alveolar distraction osteo-
genesis and bone tissue formation in the
tooth extraction site can be seen as a
similar biological model. Histological
and histomorphometrical
show that distracted bone 70 days after
the end of distraction consisted of
mature well-organized lamellar bone
(Marchetti et al. 2007). Following tooth
extraction, it takes several weeks until
thenewly formed
bone’’) in the extraction socket is remo-
delled into lamellar and marrow bone.
The portion occupied by bone marrow is
75% from 60 to 90 days and increases to
85% at 180 days (Cardaropoli et al.
2003). In the present case report, a
3-month retention phase elapsed before
tooth extraction, which was thought to
be clinically sufficient to ensure ade-
quate bone maturation. Root scaling at
the distal aspect of the second molar
adjacent to the tooth to be extracted was
performed at the time of third molar
crown exposure in an attempt to remove
any plaque deposits or toxins that may
interfere with periodontal tissues heal-
ing. Specific attention was given to the
oral hygiene of the site throughout the
duration of therapy. The ‘‘orthodontic
extraction’’ makes surgery easier and
safer (Checchi et al. 1996, Marchetti
et al. 2004, Alessandri Bonetti et al.
2007). At the end of the orthodontic
extrusion, the tooth to be removed is
furtherfrom the
and has a certain degree of mobility
(Checchi et al. 1996), thus reducing
the need for surgical instrumentation.
Consequently, a greater quantity of
bone is saved at the distal surface of
the adjacent second molar (Checchi
et al. 1996). In this clinical case, there
would have been a high risk of residual
infrabony defects at the distal surface of
the adjacent second molar if surgical
extraction had been chosen. The ‘‘ortho-
dontic extraction’’ prevented such a
problem, giving an excellent long-term
result from a periodontal point of view.
This technique is not without some
drawbacks (Alessandri Bonetti et al.
2007). It involves two (albeit minor)
analyses
bone(‘‘woven
mandibularcanal
Fig.3. Periapical intraoral radiographs. (a) Before treatment, (b) at the end of the orthodontic
treatment (before tooth extraction), (c) after third molar extraction and (d) 3-year follow-up.
Mandibular third molar extraction
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surgical operations (exposure of the
third molar crown and extraction of the
tooth); it is more time-consuming than
simple extraction due to numerous
appointments and for that reason may
be more expensive. Patients’ coopera-
tion is necessary throughout the duration
of therapy in oral hygiene maintenance
and to tolerate some discomfort due to
impingement of the orthodontic appli-
ance on the mucosa of the cheek and the
gingiva. Limitations of this technique
are (a) the presence of tooth ankylosis,
which makes it difficult for the tooth to
be moved orthodontically and (b) the
radiological evidence of third molar
roots fused at the apex and the mandib-
ular canal passing between. In this case,
the orthodontic extrusion would create a
neurological damage to the inferior
alveolar nerve.
Conclusion
‘‘Orthodontic extraction’’ makes sur-
gery easier and safer for the patient.
The risk of neurological complications
is greatly reduced as the roots of the
impacted molar are pulled away from
the mandibular canal due to the ortho-
dontic extrusive movement and a great
amount of bone is created distal to the
second molar. Notwithstanding the lim-
itations of a single case report, it appears
that the orthodontic extraction followed
by a 3-month retention phase, which is
also indicated for those mandibular third
molars that present a high risk of post-
operative residual periodontal defects at
the distal aspect of the second molar.
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Mandibular second
Address:
Dott. Giulio Alessandri Bonetti
Department of Orthodontics
University of Bologna
Via San Vitale 59
40125 Bologna
Italy
E-mail: alessandribonetti@libero.it
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Clinical Relevance
Scientific rationale for the study: The
risk of nerve injury and periodontal
breakdown of neighbouring mandib-
ular second molars following extrac-
tion of deeply impacted third molars
is not uncommon.
Principal findings: By ‘‘orthodontic
extraction’’ of a deeply impacted
mandibular third molar (in close
relationship with the mandibular
canal),noneurological
occurred and minimal residual bone
defect at the distal surface of the
adjacent second molar was observed
damage
both postoperatively and at 3-year
follow up.
Practical implications: ‘‘Orthodon-
tic extraction’’ should be considered
as alternative method to extract man-
dibular third molars at high risk of
postoperative neurological damage
and residual periodontal defect.
Mandibular third molar extraction
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