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652 Volume 36, Number 9COMPENDIUM October 2015
D
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.
1
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 dierent 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
•discussanddierentiate
betweensignsof
nervedamage
•explainwhentorefera
patienttoamicrosurgeon
iftherearealtered
neuralsensations
•describetechniques
thatwillhelptoavoid
nerveinjuries
LEARNING OBJECTIVES
continuing education 1
IMPLANT-RELATED NERVE DAMAGE
653
www.compendiumlive.com 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 dierent 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 eects and aect 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.
11
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.
14
Distally, past the place of
injury, the axons undergo necrosis. This degeneration is progressive
and becomes irreversible at zero to 18 months.14 Factors aecting
healing include the patient’s general health, age, and type of injury.
14
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
IAN.
3,16
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.
17
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.
18,19
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 dierent 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.
23
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).
24
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.
25
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.
27
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.
30
Clini
-
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.
19,31
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.
17
How-
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
CONTINUING EDUCATION 1 | IMPLANT-RELATEDNERVEDAMAGE
Fig 1.
Fig 2.
Fig 1.AnimplantwasplacedatsiteNo.30.Immediatelyafterthe
eectofthelocalanesthesiasubsidedthepatientcomplainedof
paresthesia(nopain)ofthemandibularrightlipandchin.Aperiapical
radiographtakenatthetimeofimplantplacementdemonstratedno
apparentimplantpenetrationintotheinferioralveolarcanal.Fig 2.The
implantrestorationwascompleted10yearsagoandthepatienthas
beenabletoaccommodatethealterednervesensation.Recently,the
patientpresentedatoneoftheauthors’ocesandaCBCTscanwas
ordered.ItdemonstratedthattheimplantatsiteNo.30iscloserto
theinferioralveolarcanalthanpreviouslyenvisionedandmaybecaus-
ingcompressiononthenerve.
655
www.compendiumlive.com October 2015 COMPENDIUM
or prilocaine.
39,42
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.
36,43
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.
39
They
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-
dence.
45
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.
46
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.ApatientpresentedwithintensepainintoothNo.31.Aperiapicalradiographdemonstratedacuteapicalperiodontitis.Itwasnotpossible
toidentifytheextentoftheperiapicallesionwithrespecttotheinferioralveolarcanal.Fig 4.ACTscanwasobtained.Thescandemonstrated
theproximityoftheapicallesiontothecanal.Withproperpreoperativeplanningandimaging,thetoothwassuccessfullyremovedandthe
granulomatoustissuecarefullydebridedwithoutinducinganyalterednervesensation.
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
(NSAIDs).
3,12,16,19,50-53
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.
12
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 dierent monitoring intervals: 2 months,19,55 3
months,
3,14
before 4 months,
18
and 3 to 6 months.
56
Ziccardi and
Zuniga stated that microsurgery should be done before 1 year, be-
cause after that the surgery’s ecacy 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.
12,51,54,60,61
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
dierent 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
CONTINUING EDUCATION 1 | IMPLANT-RELATEDNERVEDAMAGE
TAB L E 1
Tests to Determine if Neurosensory Damage Has Occurred
Light touch test
Pain test
Two-point discrimination test
Temperature test
Asoftbrushisappliedtothelipandthepatientisaskedinwhichdirectionthe
stimuluswasapplied.18
A27-gaugeneedlecanbeusedtodeterminewhetherthepatientperceivespain.18
Caliperscouldbeopenedprogressivelyat2-mmincrementsuntilthepatientis
abletodiscriminatethecaliperendsastwoseparatepointsofcontact.19
Iceoraheatedmirrorhandle(43°)canbeusedtodetermineifthepatientis
abletodiscriminatebetweenhotandcold.19
TAB L E 2
Suggested Pharmacotherapies for Trigeminal Nerve Injury Associated with Implant Placement
CONDITION
Alteredsensationduetoinjection
Tractionorcompressionofnervetrunk
ortraumaduringsurgery
Nerveinjury
Alteredsensation
Neuropathyfollowedbyimplantremoval
Chronicneuropathy
Post-traumaticneuropathy
THERAPY
Immediatedexamethasone4g/mlinjectionintosite,then3daysof
decreasingsteroiddoses.3
1mlto2mlofIVformdexamethasone(4mg/ml)topicallyappliedfor
1to2minutes,then6daysoraldexamethasone(4mg,2tabsAMfor3
days,then1tabAMfor3days).3
Taperingdoseofsteroidfor5to7days.19Note:Dexamethasone8mgto
12mghasgreateranti-inammatoryeectthanothercorticosteroids.50
800mgibuprofenthreetimesaday,for3weeks.19
Ibuprofen800mgthreetimesaday,amoxicillin500mgthreetimesa
day,for5to7days,andprednisolone50mgoncedailyfor5dayswith
stepdownof10mgperdayfor5days.51
Engageincounselingandpossiblytheapplicationof5%lidocainepatches.12
Low-doseantidepressants,antiepileptics.12,52,53
657
www.compendiumlive.com 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.
51
The implants were removed, and then two of the four patients’ neu-
ral issues quickly resolved.
12
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.
58
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.
54
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 dierent
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 aect 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.
62
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 dierent; 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.
63
Therefore, prevention of injuries is the best way to ensure patients
a speedy recovery after dental implant procedures.
Conclusion
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.
TAB L E 3
Response to Microsurgical Repair of Branches of the Trigeminal Nerve
STUDY
Bagheri et al60
Susarla et al62
Pogrel63
Lam et al64
Strauss et al65
Gregg66
PATIENT RESPONSES*†
81.7%surgicalmendingoftheIAN
63.1%ratedtheirsatisfactionasgoodtoexcellentfortrigeminalnerverepair
59.4%showedsomeimprovementofcasesconcerningtheIANandLN
55%ratedtheiroverallsatisfactionasgoodtoexcellentforIANandLNrepair
54.9%ofthepatientswhohadsurgicalrepairoftheIANhadasignicantimprovement
50%overallreductioninpainseverity
*Patientresponseslistedasreportedinarticles.
† Listedindecreasingorderofsuccess.
658 Volume 36, Number 9COMPENDIUM October 2015
DISCLOSURE
The authors had no disclosures to report.
ABOUT THE AUTHORS
Gary Greenstein, DDS, MS
ClinicalProfessor,CollegeofDentalMedicine,ColumbiaUniversity;PrivatePractice,
SurgicalImplantologyandPeriodontics,Freehold,NewJersey
Joseph R. Carpentieri, DDS
ClinicalAssistantProfessor,CollegeofDentalMedicine,ColumbiaUniversity;
PrivatePractice,SurgicalImplantologyandProsthodontics,WhitePlains,NewYork
John Cavallaro, DDS
ClinicalProfessor,CollegeofDentalMedicine,ColumbiaUniversity;PrivatePractice,
SurgicalImplantologyandProsthodontics,Brooklyn,NewYork
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CHICAGO2016
the AMERICAN PROSTHODONTIC SOCIETY
FEBRUARY 25–26, 2016 • SWISSÔTEL • CHICAGO, ILLINOIS
Changing Patient
Care in the
New Millennium
88th ANNUAL MEETING OF THE
AMERICAN PROSTHODONTIC SOCIETY
Learn more and register at prostho.org
FEATURING WORLD-RENOWNED SPEAKERS
Dr. David Bartlett
Dr. Carlo Ercoli
Dr. Marc Geissberger
Dr. Charles Goodacre
Dr. Joseph Kan
Dr. Robert Kelley
Dr. Baldwin Marchack
Dr. Carlo Marinello
Dr. Regina Mericske-Stern
Dr. Steve Parel
Dr. Kirk Pasquinelli
Dr. Harold Preiskel
Dr. Robert Schneider
Dr. Arun Sharma
Dr. Chandur Wadhwani
Dr. Terry Walton
Dr. Matthew Kattadiyil
88th Annual Meeting
Program Chair
Dr. Steven Sadowsky
2015 APS President
CHICAGO2016
the AMERICAN PROSTHODONTIC SOCIETY
FEBRUARY 25–26, 2016 • SWISSÔTEL • CHICAGO, ILLINOIS
Changing Patient
Care in the
New Millennium
88th ANNUAL MEETING OF THE
AMERICAN PROSTHODONTIC SOCIETY
Learn more and register at prostho.org
FEATURING WORLD-RENOWNED SPEAKERS
Dr. David Bartlett
Dr. Carlo Ercoli
Dr. Marc Geissberger
Dr. Charles Goodacre
Dr. Joseph Kan
Dr. Robert Kelley
Dr. Baldwin Marchack
Dr. Carlo Marinello
Dr. Regina Mericske-Stern
Dr. Steve Parel
Dr. Kirk Pasquinelli
Dr. Harold Preiskel
Dr. Robert Schneider
Dr. Arun Sharma
Dr. Chandur Wadhwani
Dr. Terry Walton
Dr. Matthew Kattadiyil
88th Annual Meeting
Program Chair
Dr. Steven Sadowsky
2015 APS President
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. pharmaceuticaltherapy
B. referraltoamicrosurgeon
C. monitoringtheareafor3months
D. placingtheimplantshortofthenervecanal
2. Which is the largest branch of the trigeminal nerve?
A. maxillarynerve
B. inferioralveolarnerve
C. lingualnerve
D. mandibularnerve
3. A fascicle is composed of what structures?
A. agroupofnervebers
B. groupsofepineuria
C. agroupofperineuria
D. groupsofendoneuria
4. What distinguishes neurotmesis from other conditions?
A. thenerveisnotsevered
B. thenerveissevered
C. thenerveregenerates
D. thenerveinvaginates
5. What is the current definition of paresthesia?
A. lossoffeeling
B. alteredsensationthatisunpleasant
C. alteredsensationthatisnotunpleasant
D. continuouspain
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. ifsymptomsaregettingbetter
B. ifsymptomsaregettingworse
C. ifpainisincreasing
D. ifpainiscontinuous
8. Methods to avoid causing mandibular nerve damage include
which techniques?
A. usingdrillstops
B. leavinga2-mmsafetyzoneoverthenerve
C. accountingfortheextralengthofthetapereddrilltip,
whichcanaddtotheactualdrillsize
D. Alloftheabove
9. What percentage of the time does it appear that there is a perceived
neurological improvement by patients after microsurgery?
A. 20%to30%
B. 30%to40%
C. 50%to60%
D. 60%to70%
10. To avoid nerve damage when the mental foramen is at the
alveolar crest, an incision should be:
A. midcrestal.
B. onthelingualaspectofthemandibularalveolarridge.
C. onthebuccalaspectofthemandibularalveolarridge.
D. vestibular.
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