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Nerve Damage Related to Implant Dentistry: Incidence, Diagnosis, and Management

  • Columbia University, College of Dentistry

Abstract and Figures

Proper patient selection and treatment planning with respect to dental implant placement can preclude nerve injuries. Nevertheless, procedures associated with implant insertion can inadvertently result in damage to branches of the trigeminal nerve. Nerve damage may be transient or permanent; this finding will depend on the cause and extent of the injury. Nerve wounding may result in anesthesia, paresthesia, or dysesthesia. The type of therapy to ameliorate the condition will be dictated by clinical and radiographic assessments. Treatment may include monitoring altered sensations to see if they subside, pharmacotherapy, implant removal, reverse-torquing an implant to decompress a nerve, combinations of the previous therapies, and/or referral to a microsurgeon for nerve repair. Patients manifesting altered sensations due to various injuries require different therapies. Transection of a nerve dictates immediate referral to a microsurgeon for evaluation. If a nerve is compressed by an implant or adjacent bone, the implant should be reverse-torqued away from the nerve or removed. When an implant is not close to a nerve, but the patient is symptomatic, the patient can be monitored and treated pharmacologically as long as symptoms improve or the implant can be removed. There are diverse opinions in the literature concerning how long an injured patient should be monitored before being referred to a microsurgeon.
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652 Volume 36, Number 9COMPENDIUM October 2015
amage to a branch of the trigeminal nerve (eg, inferi-
or alveolar, lingual, mental, and infraorbital nerves)
is a potential untoward consequence of performing
implant dentistry. Injury to a nerve can occur due to
direct trauma, inflammation, or infection.
Harm can
happen during the following procedures: anesthesia, flap elevation
or advancement, harvesting a bone graft, preparing an osteotomy,
and implant placement. Because repair of a damaged nerve is
problematic, wound avoidance is critically important. Therefore,
knowledge is necessary regarding oral nerve anatomy, histology,
familiarity with signs and symptoms of nerve damage, and testing
for the presence of a neuropathy. Upon diagnosis of nerve injury, a
decision must be made with respect to monitoring and document-
ing symptoms, pharmacologic therapy, implant removal, patient
referral for nerve repair, or combinations of the previous concepts.
This article addresses multiple issues associated with avoiding
injuries and managing patients who experience damage to the
trigeminal nerve due to dental implant-related procedures.
Trigeminal Nerve Anatomy and Histology
The trigeminal nerve is the fifth and largest cranial nerve.2 It has
three main branches: ophthalmic (V1), maxillary (V2), and man-
dibular (V3). The mandibular segment is the largest branch and
innervates the mandibular lip, chin, teeth, adjacent soft tissues,
mandible, and part of the external ear. The motor fibers of the man-
dibular branch are not subject to injury during implant procedures,
because they separate from V3 before they exit the foramen ovale.3
The basic unit of a nerve is a fiber.4 Myelinated nerve fibers pre-
dominate in V3. A single nerve axon and a Schwann cell are en-
cased in a connective tissue covering called endoneurium. Groups
of encased nerve fibers are referred to as a fascicle and they are
surrounded by perineurium. A group of fascicles is surrounded by
Abstract: Proper patient selection and treatment planning with respect to dental
implant placement can preclude nerve injuries. Nevertheless, procedures asso-
ciated with implant insertion can inadvertently result in damage to branches of
the trigeminal nerve. Nerve damage may be transient or permanent; this finding
will depend on the cause and extent of the injury. Nerve wounding may result
in anesthesia, paresthesia, or dysesthesia. The type of therapy to ameliorate the
condition will be dictated by clinical and radiographic assessments. Treatment
may include monitoring altered sensations to see if they subside, pharmaco-
therapy, implant removal, reverse-torquing an implant to decompress a nerve,
combinations of the previous therapies, and/or referral to a microsurgeon for nerve repair.
Patients manifesting altered sensations due to various injuries require dierent therapies. Transection of
a nerve dictates immediate referral to a microsurgeon for evaluation. If a nerve is compressed by an implant
or adjacent bone, the implant should be reverse-torqued away from the nerve or removed. When an implant is
not close to a nerve, but the patient is symptomatic, the patient can be monitored and treated pharmacologi-
cally as long as symptoms improve or the implant can be removed. There are diverse opinions in the literature
concerning how long an injured patient should be monitored before being referred to a microsurgeon.
Nerve Damage Related to Implant Dentistry:
Incidence, Diagnosis, and Management
Gary Greenstein, DDS, MS; Joseph R. Carpentieri, DDS; and John Cavallaro, DDS
continuing education 1
653 October 2015 COMPENDIUM
epineurium. Damage to any part of the nerve bundle can result in
neurosensory impairment.
The trigeminal nerve has 7,000 to 12,000 axons and the number
of fascicles varies in dierent regions of the mouth.5 The inferior
alveolar nerve (IAN) is polyfascicular (>10 fascicles), whereas the
lingual nerve (LN) has few fascicles.6 Because the IAN has more
fascicles than the LN, it has greater capacity to repair after injury
due to innervation from uninjured fascicles.3
Types of Nerve Damage
Injuries to the trigeminal nerve can include compression, stretching,
and partial or complete transection. Damage can result in neurosenso
ry alterations with respect to touch, pressure, temperature, and pain.7
Trigeminal nerve malfunctions can interfere with speaking, eating,
kissing, shaving, applying makeup, toothbrushing, and drinking.7 In
addition, these injuries can have psychological eects and aect social
interactions.8 Altered sensations (eg, pain) may be detected during
surgical manipulations or there may be a delayed onset of discomfort.
Terms used to describe injuries with respect to axonal damage
are listed:9
Neurapraxia: There is no loss of continuity of the nerve, but it has
been stretched or undergone blunt trauma. The altered sensa-
tions will subside and feeling returns in days to weeks.
Axonotmesis: The nerve is damaged, degeneration and regenera-
tion occur, but the axon is not severed and feeling returns within
2 to 4 months. Eventual recovery of sensation is often less than
normal, and it may be accompanied by dysesthesia.
• Neurotmesis: The nerve is severed and there is a poor prognosis
for resolution of all neurosensory alterations.
The International Association for the Study of Pain standardized
nomenclature concerning nerve injuries. In particular, they altered
the definition of paresthesia, which used to denote loss of feeling.10
Currently, the following definitions are employed:
Paresthesia: Altered sensation that is not unpleasant (eg, pins
and needles).
• Dysesthesia: Altered sensation that is unpleasant.
• Anesthesia: Loss of feeling or sensation.
Other terms used to describe changed responses include: allodyn-
ia—pain to a stimulus that does not normally hurt; causalgia—per-
sistent burning pain; hypoesthesia—decreased sensitivity to stimu-
lation; and hyperesthesia—increased sensitivity to stimulation.10
When nerves are stretched or compressed, the perineurium
protects the fascicles. However, elongation >30% can result in
structural failure of the nerve.
With respect to partial or com-
plete transection of a nerve, total transections usually cause an
anesthetic response with poor function. In contrast, partial nerve
injuries can have a varied response with respect to dysesthesia.11
Others mentioned that persistent postsurgical pain is a poor predic-
tor for spontaneous rejuvenation of a nerve injury.12,13
Subsequent to peripheral nerve injury, Wallerian degeneration
starts and continues over weeks to months.
Distally, past the place of
injury, the axons undergo necrosis. This degeneration is progressive
and becomes irreversible at zero to 18 months.14 Factors aecting
healing include the patient’s general health, age, and type of injury.
A defining moment for the damaged nerve is reached when a large
mass of endoneurial tubules has changed into scar tissue.15
Assessing Patients’ Injuries Concerning the
Trigeminal Nerve
The most commonly injured nerve during implant dentistry is the
Damage to this structure may manifest itself as anesthesia
or paresthesia or dysesthesia of the skin adjacent to the mental
foramen, the lower lip, buccal mucous membranes, and gingiva as
far posteriorly as the second molar.17 In contrast, patients with an
LN injury may report drooling, tongue biting, burning, loss of taste,
changes in speech, swallowing, alterations of taste perception, and
numbness of the lingual mucosa or tongue.15
During surgery or post-implantation, all signs or symptoms (eg,
pain, altered sensation, numbness) of a nerve injury should be docu-
mented. Areas of neurosensory deficit should be mapped (eg, altered
sensation areas ought to be measured in millimeters). This will facili-
tate monitoring recovery and help determine if micro-reconstructive
surgery may be needed.
Both subjective and objective sensory tests
can be employed to document and evaluate injuries. There are two
basic categories of tests: mechanoceptive (response to mechanical
pressure or distortion) and nociceptive (perception of pain) (Table 1).
Mechanoceptive tests include static light touch, two-point discrimi-
nation, and brush-stroke direction.
Pin-tactile discrimination and
thermal testing are nociceptive tests. The side opposite to the injury
should be stimulated to help confirm there has been an alteration
of sensation at the supposedly damaged location. If loss of taste
was reported, it can be assessed with salt or sugar on a cotton swab.
Incidence of Nerve Injuries
Subsequent to implant procedures, the occurrence of permanent
nerve damage that results in altered lip sensations ranges from
0% to 36% in dierent studies.20-22 However, citations of old litera-
ture can be misleading and not relevant to contemporary implant
dentistry. Historically, many damaged nerves may have been due
to vestibular incisions that were employed to facilitate implant
placement. Currently, midcrestal incisions are usually used and
computerized tomography helps avoid injuries. In this regard, re-
cent articles have noted injury rates lower than previously reported.
Dannan et al reported a transient trigeminal nerve damage rate after
dental implants of 2.95% (5/169 patients) and 1.7% of the patients
had permanent neuropathy.
Another recent university study in
an outpatient setting indicated an injury rate of 2.69% (42/1,559)
after oral surgical procedures and the permanent injury rate was
less (not reported for all types of surgery).
In the authors’ opinion,
even these reduced incidences of nerve damage are too high. It
should also be noted that transient altered lip sensations can be
due to edema for 1 to 2 weeks and are not considered nerve damage.
Lingual Nerve Damage During Surgical Procedures
The LN in the mandibular molar areas resides within the lingual
soft tissue. It may be coronal to the bone within the tissue and
lies close to the lingual cortical plate.
Therefore, caution must
654 Volume 36, Number 9COMPENDIUM October 2015
be exercised when performing surgical procedures in this region.
After third-molar removal, damage to the LN occurs 0.5% to 2.1%
of the time.26 However, it is unusual for the LN to be damaged dur-
ing periodontal or implant surgery.
As a general rule, implants
placed in the mandibular molar region should be performed as
follows: intrasulcular incisions, no vertical releasing incisions on
the lingual aspect, and a full-thickness mucoperiosteal flap on the
lingual aspect; avoid overstretching the flap and maintain safety
distance to the nerve when creating the osteotomy. It has been
documented that around 90% of LN injuries are transitory and
resolve 8 to 10 weeks postoperatively.28
Preoperative Planning: Preventing Nerve Injuries
To ensure correct implant placement with the least amount of
complications, preoperative planning is necessary. Avoiding nerve
injuries starts with proper patient selection, which is done in as-
sociation with good diagnostics. If it is believed that a computerized
tomography (CT) scan or surgical guide would be beneficial, then it
should be utilized. Individuals performing surgeries must confirm
the path of the mandibular nerve that may have been outlined on
a scan by a radiologist. When placing dental implants, a 2-mm
safety zone should be left apical to implants over the IAN to accom-
modate minor drilling errors and drill lengths should be adjusted
to take into account radiographic distortion.19,29 In addition, the
2-mm safety zone may help avoid pressure placed on the nerve
due to bone compression when the implant is placed close to the
mandibular or mental canals (Figure 1 and Figure 2). If necessary,
short implants can be used to remain in the safety zone.
cians should also be aware that drill markings to denote bur length
do not take into consideration the extra length of the tapered drill
tip, which can add anywhere from 0.4 mm to 1.5 mm to the actual
drill size.
In addition, over the IAN or mental nerve, it is ad-
vantageous to use drill stops to avoid over-drilling.19,31 It should be
underscored that the thickness or density of the bone surrounding
the IAN does not provide substantial resistance to drill penetration
and excess force should be avoided when drilling over the IAN.32
Finally, it should be noted that 50% of lawsuits related to nerve
injury after implant therapy are associated with a lack of informed
consent obtained prior to surgery; thus this document must be
signed by the patient.33 It also is a good idea to do a neurosensory
assessment before initiating procedures to rule out pre-existing
sensation impairments.16
Local Anesthesia: Potential to Cause Nerve Damage
Injury to the IAN or LN can occur during block injections due to
needle trauma, hematoma formation, or injected chemicals.
ever, it is unknown how the needle or injection ingredients cause
nerve damage. In one retrospective study, it was estimated that
the incidence of nerve injury was 1/26,762 to 1/160,571,6 whereas
Haas and Lennon34 projected it happened 1/785,000. Others, after
assessing the literature, indicated the incidence of short-term im-
paired LN and IAN damage after injections was 0.15% to 0.54%,26
whereas permanent damage due to injection of local analgesics is
very unusual, at 0.0001% to 0.01%.35
When performing a mandibular block injection, patients may feel
an electric shock around 3% to 7% of the time.36,37 Needle trauma
usually resolves spontaneously.37 However, when a clinician sees
a patient react (wince in pain) to an injection, the needle should
be withdrawn a little and repositioned. Furthermore, with respect
to nerve damage due to local anesthesia, there is no known treat-
ment or method of prevention,6 besides avoiding block injections.
It has been noted that 70% to 89% of the injuries that occur as a
result of block injections are to the LN.38,39 A possible explanation
for this is that the LN has few fascicles, whereas the IAN is polyfas-
cicular and has a greater potential for healing. From a geometric
perspective, which may influence the potential for damage or repair,
the tip of a 25-gauge needle is 0.45 mm, and the LN and IAN are
1.86 mm and 3 mm wide, respectively.40,41
After block injections, the greatest incidence of neuropathy
occurred among individuals who were injected with 4% articaine
Fig 1.
Fig 2.
Fig 1.AnimplantwasplacedatsiteNo.30.Immediatelyafterthe
apparentimplantpenetrationintotheinferioralveolarcanal.Fig 2.The
655 October 2015 COMPENDIUM
or prilocaine.
Studies assessing 4% prilocaine and 4% artic-
aine noted an increased number of neuropathies occurred when
compared to lidocaine, 7.3 and 3.6 times more, respectively.
Garisto et al reported 4 of 9 investigations that demonstrated 4%
prilocaine or articaine was associated with a higher incidence of
paresthesia than anesthetics with lower concentrations.
and others believe that regional blocks with these drugs should be
avoided to reduce the risk of creating a neuropathy.39,42 However,
Malamed indicated there was no supporting data besides anec-
dotal reports that articaine caused an increase in neurosensory
alteration when compared to lidocaine.44 Similarly, in 2013, after
an extensive literature review, Toma et al concluded that studies
suggesting articaine caused increased neurotoxicity were retro-
spective, biased in data recruitment, and provided a low level of evi-
They concluded that procedural trauma emerged as a valid
explanation for reported neurological issues. There is controversy
in the literature regarding this issue; therefore, clinicians need
to make decisions with respect to using higher concentrations of
anesthetics based on the data in the literature, their interpretation
of this information, and recommendations by drug manufacturers.
Osteotomy Preparation for Dental Implants
Osteotomies should be prepared using sharp drills with copious ir-
rigation. Conceptually, it is possible that too much generated heat
could result in postoperative nerve damage.
The size of the necrotic
areas induced by heat is directly proportional to the heat generated
during the surgery.47 Eriksson and Albrektsson suggested 47º for 1
minute could produce bone resorption.48 However, the few seconds
used to drill an osteotomy probably will not cause nerve damage.
When there is advanced resorption of the mandibular alveolar
ridge the position of the mental foramen may be at the alveolar
crest; therefore, a midcrestal incision in the edentate area is con-
traindicated. The incision should be made on the lingual aspect of
the ridge to avoid injuring the emerging mental nerve.19,39
If an implant is to be placed anterior to the mental foramen and
its length is greater than the distance from the alveolar ridge to
Fig 3.
Fig 3.ApatientpresentedwithintensepainintoothNo.31.Aperiapicalradiographdemonstratedacuteapicalperiodontitis.Itwasnotpossible
toidentifytheextentoftheperiapicallesionwithrespecttotheinferioralveolarcanal.Fig 4.ACTscanwasobtained.Thescandemonstrated
Fig 4.
the infundibulum of the mental foramen, it is important to verify
with a CT scan that there is no anterior loop to the mental nerve.39
Flap Advancement Procedures
Flap advancement will not usually predispose a patient to nerve
damage, but caution must be exercised especially in the mental
foraminal area.49 In this regard, the clinician should know precisely
where the mental nerve emerges from the mental canal to avoid
damaging the nerve when a flap is advanced in this region.
Extracting Teeth
Before extracting a mandibular molar or premolar in preparation
for an implant, assess the location of their roots in relation to the
IAN and mental nerve, because if a nerve is juxtaposed to the roots
of teeth, tooth removal has the potential to induce nerve damage.
Furthermore, caution should be exercised when debriding large
periapical radiolucencies, because these lesions may communicate
with a nerve canal (Figure 3 and Figure 4).
Pharmacologic Therapies for Neuropathies
Associated with Dental Implant Placement
There is no consensus with respect to use of pharmaceuticals
after a nerve injury. However, some authors suggest the use
of corticosteroids and nonsteroidal anti-inflammatory drugs
Pharmaceuticals may be appropriate when
signs or symptoms of neurosensory alterations occur and the clini-
cian is certain that the nerve was not transected.
Table 2 lists several situations where drug application may be ben-
eficial. In conjunction with pharmaceutical intervention, Renton
and Yilmaz recommend that patients with chronic neuropathy en-
gage in psychological counseling with respect to pain management.
The goals of these therapies are to decrease discomfort and to help
patients manage their pain. Contrastingly, Bagheri and Meyer stated
that it is unlikely that corticosteroids would be of benefit after injury
of the IAN, because it is contained within the inferior alveolar canal
and drug penetration would be minimal.54 Pertinently, no clinical
656 Volume 36, Number 9COMPENDIUM October 2015
trials were found that investigated the use of corticosteroids or
NSAIDs after nerve injury caused by dental implants.
When to Refer a Patient to a Microsurgeon
At present, there are no uniform guidelines concerning when a
patient with an injured trigeminal nerve should be referred to a
microsurgeon. If altered sensations occur post-implantation, some
authors suggest immediate referral.33 Others recommend seeking
consultation after dierent monitoring intervals: 2 months,19,55 3
before 4 months,
and 3 to 6 months.
Ziccardi and
Zuniga stated that microsurgery should be done before 1 year, be-
cause after that the surgery’s ecacy is diminished.57
Subsequent to nerve injury, the clinician needs to determine if
immediate referral is necessary or a pharmacologic approach is
warranted or if implant removal or reverse-torquing it a little would
best serve a patient. There are diverse opinions in the literature per-
taining to when and under what conditions referral to a microsur-
geon is needed.58,59 It is generally agreed that if a clinician believes
that a nerve has been transected as a result of an implant procedure,
immediate referral is warranted.
On the other hand, if a
patient manifests neurologic symptoms post-implantation, but the
clinician is sure that the drill never entered the mandibular canal,
it is possible that postoperative altered sensation is caused by trac-
tion of a nerve or an inflammatory process. Then a pharmacologic
approach may be warranted.3 A clinician can be almost sure that
the drill did not enter the mandibular or mental canal if after each
drill, the floor of the osteotomy was checked with an implant probe
or if a radiograph clearly depicts the osteotomy terminated several
millimeters from the nerve canal. The previous remark is qualified,
because there is the remote possibility that some unusual branch
of the IAN was present and damaged. From another perspective,
a CBCT scan can be ordered to attain an enhanced view of the im-
plant’s relationship to vital structures if a 2-dimensional radiograph
was initially used to assess the situation (Figure 1 and Figure 2).
With respect to discomfort after implant placement, if it can be
confirmed that the implant is not near the nerve canal, there are
dierent recommendations. Bagheri and Meyer suggest waiting 3
to 4 months to see if altered sensations improve before referring
a patient to a microsurgeon.14 They also advise that if an implant
is close to the nerve, it could be reversed a little to decrease bone
Tests to Determine if Neurosensory Damage Has Occurred
Light touch test
Pain test
Two-point discrimination test
Temperature test
Suggested Pharmacotherapies for Trigeminal Nerve Injury Associated with Implant Placement
657 October 2015 COMPENDIUM
compression. Contrastingly, after surgical placement, if a patient
has neurosensory discomfort, despite no apparent transection of
the nerve, it was recommended to remove the implant within 36
hours and prescribe a steroid.33,51 Pertinently, Khawaja and Renton
discussed four cases where patients became symptomatic after
implant placement without apparently encroaching upon the IAN.
The implants were removed, and then two of the four patients’ neu-
ral issues quickly resolved.
With respect to the four cases, implants
were removed after 18 and 36 hours vs 3 and 4 days.
With regard to the controversy as to whether surgical interven-
tion is needed prior to 3 months if there is no observed transection
of the nerve—there is no definitive answer.58 Renton, Dawood, and
colleagues suggest that clinicians should not wait too long, because
after 3 months they believe neural changes occur that diminish posi-
tive responses to microsurgical repair.59 Contrastingly, Ziccardi and
Steinberg in their review article suggest that when there are altered
sensations, but unobserved damage to the nerve, the patient should
be monitored for 1 month, and as long as symptoms are improving,
monitoring should be continued.58 However, if there is no improve-
ment, or pain worsens, consider microsurgery. It was concluded
that patients treated 6 to 8 months after injury do as well as patients
treated earlier.
They pondered that earlier intervention may be bet-
ter, but at present the data does not support this conclusion. It was
also mentioned that minor altered sensations are best left untreated,
because surgery is not totally predictable to achieve a desired result.
Others mentioned the “12 week rule,” which refers to the timeline
in which surgeons often wait before making decisions about micro-
surgery for the patient who manifests intolerable continual loss of
sensory function.
This monitoring period would be curtailed for a
patient who has pain. In summary, the patient’s radiographic and
clinical findings, symptoms, and concern about neural scarring
dictate when a patient should be referred for microsurgical con-
sultation. Pertinently, there are medico-legal considerations with
respect to a timely referral. Therefore, when in doubt pertaining
to the etiology of altered neurosensory issues, early transfer to a
nerve specialist is prudent.
Surgical Repair of a Damaged Trigeminal Nerve
There are specific reasons for undergoing nerve repair and dierent
factors impact the success of these procedures. Ziccardi and Zuniga
listed several indications for microsurgery: altered sensations that
persist for more than 3 months and interfere with daily functions,
observed nerve transection, no improvement of hypoesthesia, or
development of pain caused by nerve entrapment.57 When nerve
repair procedures are performed, numerous factors can aect the
results: time between injury and repair, the type and extent of injury,
the vascularity of the injury site, skill of the surgeon, harvesting and
preparation of the graft, the tension (if any) across the repair, and
the age and general health of the patient.60
Microsurgical repair of injured branches of the trigeminal
nerve (IAN and LN) can be accomplished.
However, the suc-
cessful repair rate and amount of sensory restoration are variable
(Table 3).60,62-66 Furthermore, it should be noted that most of the
cited studies had limited populations and the final assessment
methods were dierent; therefore it is not possible to directly
compare the success rates of these studies.
It appears that 50% to 60% of the time there is a perceived neu-
rological improvement by patients after microsurgery. However,
Ziccardi and Zuniga caution that patients with moderate to severe
nerve damage need to be informed that they will not usually expe-
rience complete sensory recovery.57 Pertinently, others lamented
that the success of microsurgical procedures has been overstated
and that signs of anesthesia, dysesthesia, and spontaneous pain
are negative predictors for repair even with surgical interven-
tions.51 Overall, it can be concluded that microsurgery can help
some individuals; however, it cannot predictably resolve all issues.
Therefore, prevention of injuries is the best way to ensure patients
a speedy recovery after dental implant procedures.
There are situations when a decision must be made as to whether
to retain an implant that is osseointegrated, but its insertion has
caused a tolerable paresthesia (no pain). There are two sides to this
dilemma. Implant removal may not improve the patient’s altered
sensation; therefore, the implant can be restored. On the other hand,
a patient must be informed that there is a remote possibility that
a traumatic neuroma could form if an implant rests on a damaged
nerve. A neuroma results from exaggerated neural healing and
hyperplasia and may need to be surgically removed. To take into
account both points of view, a treatment plan needs to be made
after discussion with a patient and this conversation should be
documented in the chart.
Response to Microsurgical Repair of Branches of the Trigeminal Nerve
Bagheri et al60
Susarla et al62
Lam et al64
Strauss et al65
658 Volume 36, Number 9COMPENDIUM October 2015
The authors had no disclosures to report.
Gary Greenstein, DDS, MS
Joseph R. Carpentieri, DDS
John Cavallaro, DDS
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27. ChanHL,LeongDJ,FuJH,etal.Thesignicanceofthelingualnerve
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659 October 2015 COMPENDIUM
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660 Volume 36, Number 9COMPENDIUM October 2015
Nerve Damage Related to Implant Dentistry: Incidence, Diagnosis, and Management
Gary Greenstein, DDS, MS; Joseph R. Carpentieri, DDS; and John Cavallaro, DDS
1. If the clinician believes a nerve has been transected as a
result of an implant procedure, it is generally agreed that what
is warranted?
A. pharmaceuticaltherapy
B. referraltoamicrosurgeon
C. monitoringtheareafor3months
D. placingtheimplantshortofthenervecanal
2. Which is the largest branch of the trigeminal nerve?
A. maxillarynerve
B. inferioralveolarnerve
C. lingualnerve
D. mandibularnerve
3. A fascicle is composed of what structures?
A. agroupofnervebers
B. groupsofepineuria
C. agroupofperineuria
D. groupsofendoneuria
4. What distinguishes neurotmesis from other conditions?
A. thenerveisnotsevered
B. thenerveissevered
C. thenerveregenerates
D. thenerveinvaginates
5. What is the current definition of paresthesia?
A. lossoffeeling
B. alteredsensationthatisunpleasant
C. alteredsensationthatisnotunpleasant
D. continuouspain
6. Elongation of a nerve by more than what percentage can
result in its structural failure?
A. 10%
B. 20%
C. 30%
D. 40%
7. If a patient has altered sensation after an implant placement,
when might he or she not be referred to a microsurgeon?
A. ifsymptomsaregettingbetter
B. ifsymptomsaregettingworse
C. ifpainisincreasing
D. ifpainiscontinuous
8. Methods to avoid causing mandibular nerve damage include
which techniques?
A. usingdrillstops
B. leavinga2-mmsafetyzoneoverthenerve
C. accountingfortheextralengthofthetapereddrilltip,
 whichcanaddtotheactualdrillsize
 D. Alloftheabove
9. What percentage of the time does it appear that there is a perceived
neurological improvement by patients after microsurgery?
A. 20%to30%
B. 30%to40%
C. 50%to60%
D. 60%to70%
10. To avoid nerve damage when the mental foramen is at the
alveolar crest, an incision should be:
A. midcrestal.
B. onthelingualaspectofthemandibularalveolarridge.
C. onthebuccalaspectofthemandibularalveolarridge.
D. vestibular.
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... Sensory changes after dental implant surgery can be caused by pressure on the IAN due to bone compression 14 when the implant fixture is placed within 2 mm of the IAN canal or to hematoma formation due to dental implant surgery. Such nerve damage belongs to the neurapraxia type of Seddon and Sunderland's classification of nerve damage, and complete recovery of sensation can be expected. ...
... Several studies have mentioned that a safe distance of at least 2 mm should be maintained between the implant fixture or drilling location and the IAN canal during dental implant surgery in the mandible. They demonstrated that pressure on the IAN canal due to bone compression could occur at an implant fixture placed adjacent to the IAN canal 14,18,22 . The results showed a relatively higher possibility of sensory change even without direct invasion of the IAN canal in Group II. ...
Full-text available
Objectives: This retrospective study aimed to analyze data on nerve damage in patients who complained of sensory changes after dental implant surgery, the clinical results according to proximity of the implant fixture to the inferior alveolar nerve (IAN) canal, and the factors affecting recovery of sensation. Materials and methods: The electronic medical records of 64 patients who had experienced sensory change after implant surgery were reviewed. Patients were classified by sex, age, implant installation sites, recovery rate and the distance between the implant fixture and IAN canal on computed tomography (CT). The distance was classified into Group I (D>2 mm), Group II (2 mm≥D>0 mm), and Group III (D≤0 mm). Results: The 64 patients were included and the mean age was 57.3±7.3 years. Among the 36 patients who visited our clinic more than two times, 21 patients (58.3%) reported improvement in sensation, 13 patients (36.1%) had no change in sensation, and 2 patients (5.6%) reported worsening sensation. In Group II, symptom improvement was achieved in all patients regardless of the removal of the implant fixture. In Group III, 8 patients (40.0%) had reported symptom improvement with removal of the implant fixture, and 2 patients (33.3%) of recovered patients showed improvement without removal. Removal of the implant fixture in Group III did not result in any significant difference in recovery (P=0.337), although there was a higher possibility of improvement in sensation in removal cases. Conclusion: Clinicians first should consider removing the fixture when it directly invades the IAN canal. However, in cases of sensory change after dental implant surgery where the drill or implant fixture did not invade the IAN canal, other indirect factors such as flap elevation and damage due to anesthesia should be considered as causes of sensory change. Removal of the implant should be considered with caution in these situations.
... Nerve damage in the oral and Ivyspring International Publisher maxillofacial area interferes with daily life, which adversely affects the patient's psychosocial state and causes his or her quality of life to deteriorate [5]. There have been reports of permanent neurological damage from 0 to 36% causing lip paresthesia after implant placement [6][7][8], but recent studies have reported that 2.95% of patients have transient neurological damage and 1.7% have permanent neurological damage [9,10]. ...
Full-text available
Background: This experimental research aimed to determine whether No-ozone Cold Plasma (NCP) has regenerative effect on crushed injured sensory nerves in a rat model (Wistar A) and to evaluate whether NCP can be used as an alternative treatment method for sensory nerve injury in the oral-maxillofacial region. Methods: A total of 10 Wistar A rats were used for this experiment. They were divided into three groups according to whether the mental nerve of the left mandible was injured and NCP was applied or not: group 1 (n=3) (non-mental nerve damage, non-MD) - the left mental nerve was exposed and non-damaged; group 2 (n=3) (mental nerve damage, MD) - the left mental nerve was exposed and damaged, NCP was not applied; and group 3 (n=4) (mental nerve damage and NCP, MD-NCP) - the left mental nerve was exposed and damaged, NCP was applied with regular intervals (three times a week). Results: For the behavior analysis, von Frey test was used. Furthermore, the nerve tissues were examined with hematoxylin and eosin (H&E) staining, and the extent of neurorecovery was evaluated with the immunofluorescence staining of certain markers. The behavioral analysis showed that the function recovery sensory nerve was faster in group 3 (MD-NCP). In the histomorphologic and immunofluorescence analyses, the expression of the factors involved in neurorecovery was much higher in group 3 than in group 2 (MD). Conclusions: The expeditious recovery of sensory nerve function as well as the higher expression of the factors indicating nerve function recovery in the NCP-treated group suggest that NCP has a positive effect on regeneration after sensory nerve crushing injury. Therefore, in the case of sensory impairment of the oral-maxillofacial region, no-ozone cold plasma can be applied for therapeutic effect.
... Patients sustaining LA, orthognathic, oncology and trauma-related nerve injuries will mainly be managed therapeutically [101][102][103][104]. ...
Full-text available
The trigeminal nerve constitutes the largest sensory cortex representation in the brain compared to any other sensory nerve. This is likely due to the fact that the trigeminal nerve underpins our very existence, as it protects, sensorially, our senses including the organs that provide sight, smell, taste, hearing, speech and meninges protecting our brain. Neurophysiologically, our affective and limbic systems in our brains are alerted before we even set foot in the dental surgery and the patient’s brain is anticipating and aligned for pain experience. Thus, when trigeminal nerve injuries occur, which in the main are preventable, the majority of patients experience mixed symptoms including ongoing and elicited neuropathic pain, numbness and altered sensation. These neuropathic features cause significant impact on the patients’ ability to function, for example, cold allodynia prevents the patient enjoying cold foods and drinks and undertaking outdoor activities or elicited pain on touch frequently interferes with sleep. The resultant chronic symptoms and functional impedance often result in significant psychological morbidity. There is no magic bullet to resolve these sensory nerve injuries, and our specialty is beholden to prevent nerve injuries where possible. The patient must have the appropriate consent, and their expectation is managed with understanding the potential benefits and risks for their chosen interventions. Prevention and management of nerve injuries related to local anaesthesia, implants and third molar surgery are outlined in this chapter. There is insufficient capacity to go in-depth for each area, but the author has provided up to date evidence base where it exists and some strategies to minimize and manage optimally these unfortunate complications.
... Damage to the Inferior Alveolar Nerve (IAN) is a potential major complication in mandibular dental implant surgeries. Physical harm can occur during anesthesia, flap elevation or advancement, bone graft harvest, osteotomy preparation or implant placement [4][5][6][7]. The prevalence of nerve damage that results in altered lip sensations ranges from 0% to 40% in old literature [8][9][10]. ...
Full-text available
Dental implant surgeries are widely used in dentistry due to their numerous advantages. Many articles have focused on local accidents and complications of this treatment. One of the major complications is the injury of the inferior alveolar nerve, which could potentially be damaged permanently. In order to protect clinicians and patients, some authors recommend leaving a safety zone around this nerve. The aim of this article is to review guidelines proposed to avoid this complication, and discuss critical clinical situations when this recommendation could be reappraised.
... Peripheral nerve injuries during intraoral surgeries are challenging adverse events for both the patient and the surgeon. 1 The inferior alveolar nerve (IAN) is the most commonly injured nerve during mandibular third molar surgery 2 and dental implant procedure in the posterior mandible 3 as the incidence of this complication has been estimated to occur up to 20% and 40% respectively. 2,4 The primary risk factors include the difficulty of the procedure, initial surgeons' experience, and the close proximity of the mandibular third molar or implant fixture to the IAN. 2 In cases of such nerve injuries, patients may experience different neurosensory alterations including hypoesthesia, hyperesthesia, paresthesia, and anesthesia. ...
Full-text available
Introduction: Inferior alveolar nerve (IAN) injury is a serious complication during intraoral surgeries. We aimed to evaluate the outcome of photobiomodulation (PBM) therapy in patients with IAN injury associated with third molar or implant procedures. Methods: Eight patients with an alteration of sensory function of the IAN after third molar or implant surgeries were enrolled in this case series study. The patients received 10 sessions of PBM therapy (810 nm diode laser, 200 mW, 10 J/cm2 per point, three times a week). Pinprick (PP) and visual analogue scale (VAS) neurosensory tests were recorded at each treatment session and 14 days after the last treatment. The association between explanatory variables and the outcome of interest was analyzed using generalized estimating equations. Results: The median percentage change of outcomes from the first to the last visit was as follows: VAS score: +125.00% (range: 50.00 to 166.67); PP score: +350% (range: 150 to 800). The duration of paresthesia was inversely correlated with changes in VAS and PP scores. No significant association was found between patients' gender or age and changes in VAS and PP scores. Conclusion: Considering the limitations of this study, PBM with the parameters used in this study presented positive effects on neurosensory recovery in patients suffering from IAN injury associated with routine intraoral procedures. Patients with shorter duration of paresthesia tended to respond more favorably to PBM therapy.
Tensionless adaptation of nerve ends is a challenging task in the repair of damaged inferior alveolar nerve (IAN). A new technique is introduced with posterior ostectomy of a mandibular distal segment after sagittal splitting for nerve bundle traction to tensionless anastomosis of nerve ends. We were able to create tensionless anastomosis of an IAN defect without autogenous or alloplastic graft using this method. This method is suitable for neurorrhaphy after neuroma removal in cases of IAN damage during dental procedures.
Full-text available
The nervous system is the part of a human body that coordinates its behavior and transmits signals between different body areas. The orofacial region receives a rich network of sensory and motor nerves mainly facial (VII) and trigeminal (V) nerves which provides facial expressions and helps in functions like mastication, swallowing and respiration. There are close functional and anatomical relationships between these two nerves in both their sensory and motor distributions. Neurological lesion or trauma to these nerves affect the normal expressions and and hence thorough knowledge of these nerves and lesions affecting these nerves is must along with the management before fabricating prosthesis for the patient. Hence, this article briefly reviews the anatomy and disorders of these cranial nerves and problems encountered while fabricating prosthesis for patients affected by disorders of these nerves and its prosthodontic managements
Full-text available
In overdenture treatment, the teeth are encompassed as part of the residual ridge. The retention of teeth provides a psychological benefit, and also helps in the preservation of alveolar bone, proprioception, increases stability and retention, and maintains the vertical dimension of occlusion. This case report describes prosthodontic rehabilitation of mandibular partially edentulous arch with tooth-supported overdenture using ball attachment.
Full-text available
In overdenture treatment, the teeth are encompassed as part of the residual ridge. The retention of teeth provides a psychological benefit, and also helps in the preservation of alveolar bone, proprioception, increases stability and retention, and maintains the vertical dimension of occlusion. This case report describes prosthodontic rehabilitation of mandibular partially edentulous arch with tooth-supported overdenture using ball attachment.
Full-text available
In general, trigeminal nerve injury is known as a potential risk of many surgical procedures in the oral cavity. Recent literature demonstrated that the risk of nerve injury is correlated with the experience of the surgeon. Therefore, the purpose of this study was to evaluate retrospectively the incidence of trigeminal nerve injuries in a teaching university setting. From January 2000 to December 2009, a total of 1,559 patients underwent one intervention in the postcanine region of the mandible. Interventions included extractions, osteotomies, periradicular surgery, and implant surgery. In 2010, all 1,559 patient charts were screened. A record was made if trigeminal nerve injury was documented within the first month following surgery. These patients were re-evaluated. Documentation in the charts revealed that sensorial disturbance following surgery was seen in 42 patients (2.69 %). Among them, nine patients were clinically re-evaluated by the authors and 12 were interviewed by phone and observed by their dentist without any problems. Persistence of sensory disturbance was found in 5 of the 21 patients (0.32 %), and four of these five lesions were in the lingual nerve (0.25 %). Related to the type of surgery, most sensory disturbances were seen following periradicular surgery. Within the limitations of this study, it may be stated that oral surgery in an outpatient setting of a teaching university hospital resulted in very low rates of trigeminal nerve injuries. It may be concluded that adequately surveyed trainees can perform mandibular surgery without an increased risk of trigeminal sensorial disturbance.
Full-text available
The purpose of present article was to review aetiological factors, mechanism, clinical symptoms, and diagnostic methods as well as to create treatment guidelines for the management of inferior alveolar nerve injury during dental implant placement. Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were inferior alveolar nerve injury, inferior alveolar nerve injuries, inferior alveolar nerve injury implant, inferior alveolar nerve damage, inferior alveolar nerve paresthesia and inferior alveolar nerve repair. The search was restricted to English language articles, published from 1972 to November 2010. Additionally, a manual search in the major anatomy, dental implant, periodontal and oral surgery journals and books were performed. The publications there selected by including clinical, human anatomy and physiology studies. In total 136 literature sources were obtained and reviewed. Aetiological factors of inferior alveolar nerve injury, risk factors, mechanism, clinical sensory nerve examination methods, clinical symptoms and treatment were discussed. Guidelines were created to illustrate the methods used to prevent and manage inferior alveolar nerve injury before or after dental implant placement. The damage of inferior alveolar nerve during the dental implant placement can be a serious complication. Clinician should recognise and exclude aetiological factors leading to nerve injury. Proper presurgery planning, timely diagnosis and treatment are the key to avoid nerve sensory disturbances management.
Full-text available
Background: Reported incidences of altered sensation after placement of mandibular implants range from 0% to almost 44%. Purpose: The aim of this retrospective study is to determine the incidence of altered sensation of the inferior alveolar nerve in a sample of patients undergoing mandibular dental implant placement in the posterior area. Materials and methods: According to specific inclusion criteria, records of patients who underwent mandibular dental implant placement in the posterior areas, in the period 2002-2008, at the Department of Oral Surgery, Faculty of Dental Medicine, University of Witten/Herdecke, were reviewed, followed by a radiographic analysis to obtain specific information concerning the distance between the implant apical tip and the upper wall of the mandibular canal. A self-administered questionnaire was sent to the patients who had a radiographic (implant apical tip–upper wall of mandibular canal) distance of less or equal to 2 mm. Results: Of the responding patients, only five reported altered sensation following implant surgery, with long-term changes occurring in 3 of them. Prevalence of altered sensation of the inferior alveolar nerve after dental implant placement in the posterior mandible reported in this study was 2.95%. Conclusion: There is a need for prospective studies to further evaluate any possible cases of altered sensation after mandibular implant surgery which could be noted.
Purpose: The aim of this study was to undertake a systematic review with meta-analysis on randomized controlled trials (RCTs) to compare the rates of survival, success, and complications of short implants to those of longer implants in the posterior regions. Materials and methods: Electronic literature searches were conducted through the MEDLINE (PubMed) and EMBASE databases to locate all relevant articles published between January 1, 1990, and April 30, 2013. Eligible studies were selected based on inclusion criteria, and quality assessments were conducted. After data extraction, meta-analyses were performed. Results: In total, 539 dental implants (265 short implants [length 5 to 8 mm] and 274 control implants [length > 8 mm]) from four RCTs were included. The fixed prostheses of multiple short and control implants were all splinted. The mean follow-up period was 2.1 years. The 1-year and 5-year cumulative survival rates (CSR) were 98.7% (95% confidence interval [CI], 97.8% to 99.5%) and 93.6% (95% CI, 89.8% to 97.5%), respectively, for the short implant group and 98.0% (95% CI, 96.9% to 99.1%) and 90.3% (95% CI, 85.2% to 95.4%), respectively, for the control implant group. The CSRs of the two groups did not demonstrate a statistically significant difference. There were also no statistically significant differences in success rates, failure rates, or complications between the two groups. Conclusion: Placement of short dental implants could be a predictable alternative to longer implants to reduce surgical complications and patient morbidity in situations where vertical augmentation procedures are needed. However, only four studies with potential risk of bias were selected in this meta-analysis. Within the limitations of this meta-analysis, these results should be confirmed with robust methodology and RCTs with longer follow-up duration.
Background: Nerve injury is a known and accepted risk of many oral surgical and dental procedures. Such injuries may occur despite the practitioner's providing the best of care. Taking proactive measures during evaluation and surgery may reduce the incidence of nerve injury. Results: Injuries to the peripheral branches of the trigeminal nerve can cause unfavorable effects on orofacial sensation and related functions such as eating, drinking, washing, speaking, shaving and kissing. Conclusions: When nerve injuries secondary to dental or oral surgery procedures fail to resolve promptly and the resulting dysesthesia is unacceptable to the patient, timely treatment gives the patient the best chance of a favorable outcome. Treatment may involve surgical exploration and repair of the injured nerve. Practical implications: Recognition of and prompt referral for nerve injuries give the patient the best chance of achieving improvement or recovery of sensory function in the distribution of the injured nerve.
/st> A growing number of dental implants are being placed each year in the United States. This upward trend is associated with an increased incidence of comorbidities. In this regard, use of a drill stop has the potential to decrease unintended consequences of overdrilling the depth of an osteotomy. /st> The authors did not find any studies in the dental literature in which researchers assessed the safety and effectiveness of using drill stops on twist drills. Nevertheless, the advantages of utilizing drill stops and the undesired results due to excessive drilling can be reasonably deduced. /st> The authors describe the following clinically relevant issues pertaining to overdrilling of osteotomies for dental implants: the anatomical effect of excessive drilling in different sections of the oral cavity, reasons for excessive drilling, methods to avoid overlengthening of implant sites and benefits of using drill stops on twist drills. /st> Use of drill stops enhances safety, accuracy and efficiency when creating an osteotomy. Drill stops also reduce the clinicians and patients stress during operative procedures. Practical implications Drills stops can be beneficial when utilized in situations in which there is reduced visibility, making it difficult to read the lines on a twist drill. They also are helpful when there is a dearth of bone over the mandibular or mental nerves, and precisely lengthened osteotomies are needed to avoid nerve injuries.
The objective of this study is to review surgical anatomy of the trigeminal nerve. We also demonstrate some pictures involving the trigeminal nerve and its surrounding connective and neurovascular structures. Ten adult cadaveric heads were studied, using a magnification ranging from 3× to 40×, after perfusion of the arteries and veins with colored latex. The trigeminal nerve is the largest and most complex of the cranial nerves. It serves as a major conduit of sensory input from the face and provides motor innervation to the muscles of mastication. Because of its size and complexity, it is essential to have thorough knowledge of the nerve before diagnoses and treatment of the pathologic processes in the orofacial, temporomandibular, infratemporal, and pterygopalatine areas. The trigeminal nerve is encountered with imaging or surgery of the skull base surgery. Thus, a comprehensive knowledge of the anatomy of the trigeminal nerve is crucial for performing the surgical procedures without significant complication. Clin. Anat., 2013. © 2013 Wiley Periodicals, Inc.