Chapter 85 Implant-Related Complications and Failures










C H A P T E R 8 5
Implant-Related
Complications and
Failures
Stuart J. Froum, Perry R. Klokkevold, Sang Choon Cho, Scott H. Froum
CHAPTER OUTLINE
Definitions of Implant Survival and Success
Types and Prevalence of Implant Complications
Types of Dental Implants
Surgical Complications
Biologic Complications
Complications Related to Augmentation Procedures (e-
only)
Complications Related to Placement and Loading
Protocols (e-only)
Prosthetic or Mechanical Complications
Aesthetic and Phonetic Complications
Conclusions
4515

The successful use of osseointegrated dental implants has
dramatically changed dentistry and significantly improved dentists'
ability to provide tooth replacement options for patients.
3,115
Despite
implants' long-term predictability and success, implant-related
complications and failures happen in some cases.
4,29
Complications
can be surgical, biologic, mechanical, or aesthetic. Some
complications are relatively minor and easy to manage, but others
are more significant and challenging to resolve. The most serious
complications can result in failure of prostheses, loss of implants,
and severe loss of supporting bone.
Surgical complications are those problems or adverse outcomes
that result from surgery, including procedures used for implant site
development, implant placement, implant exposure, and tissue
augmentation. Implant complications commonly arise from
placement of an implant in a nonideal position. Malpositioned
implants, which usually result from poor preoperative treatment
planning or errors in surgical technique, can lead to an array of
implant problems ranging in severity from minor to major. Surgical
complications include compromised aesthetic and prosthetic
results, soft tissue and bone dehiscences, impingement on and
damage to anatomic structures, and implant failure. Unfortunately,
the problems that arise from implant malposition are often not
recognized until after osseointegration, when the prosthesis is being
fabricated.
Biologic complications involve the hard and soft tissues that
support the implant. Peri-implant tissue changes can be limited to
inflammation of surrounding soft tissues or be more significant,
such as progressive loss of supporting bone. The ultimate biologic
complication is implant loss or failure, which can produce soft and
hard tissue defects. Loss of implants can be caused by failure to
achieve osseointegration in the early stages before restoration or by
loss of osseointegration as a result of destruction of supporting
bone after the restoration is installed and functioning.
Prosthetic or mechanical complications and failures typically occur
in the form of material failure, such as abutment and prosthetic
screw loosening or fractures. The prosthesis can be rescued from
many mechanical problems if they are minor and recognized early.
However, some complications, such as implant fractures, are
4516

devastating and not salvageable.
Aesthetic complications arise when the patient's expectations are
not met. Satisfaction with the aesthetic outcome of the implant
prosthesis varies from patient to patient. The risk of aesthetic
complications is increased among patients with high aesthetic
expectations and suboptimal patient-related factors, such as a high
smile line, thin gingival tissues, or inadequate bone quantity and
quality.
This chapter reviews common implant-related complications. A
summary of the literature offers some insight into the prevalence of
implant-related complications. Implant failure and surgical
complications related to site development and variations in implant
placement protocols are discussed.
Definitions of Implant Survival and
Success
The criteria used to define and report implant success or failure can
vary substantially among publications. Selection of success criteria
can be based on the author's preference, study population, or some
other study objective. Because the level of success reported in an
article is based on the criteria used to define success, recognizing
the tremendous variation in the way investigators measure and
interpret success is crucial. Sometimes, outcomes are measured by
the presence or absence of implants at the time of the last
examination, which is a measure only of implant survival and
should not be confused with implant success. In contrast to this
simplified reporting, some investigators use detailed criteria to
measure implant success and failure, with variations of successful
outcomes separated and defined by additional criteria.
Implant survival is defined as an implant that remains in place at
the time of evaluation, regardless of any untoward signs,
symptoms, or history of problems. There is a difference between
implants that are functioning under an implant-retained restoration
and those that are not connected to a restoration and not providing
support or function. These implants are sometimes referred to as
sleepers, and they should not be considered successful merely
4517
because they remain osseointegrated. Sleeper implants instead
should be included in the discussion as surviving but counted as
failures because they did not fulfill the originally intended treatment
objective.
Implant success is defined by the presence of the implant and the
criteria evaluating its condition and function at the time of
examination. Various criteria for implant success and failure have
been published, but not all investigators agree with or use them. In
the classic definition, Albrektsson and colleagues
6
defined success
as an implant with no pain, no mobility, no radiolucent peri-
implant areas, and no more than 0.2 mm of bone loss annually after
the first year of loading. Roos-Jansaker and associates
157
added to
this by defining a successful implant as one that loses no more than
1 mm of bone during the first year of function.
Sometimes, the criteria are used as proposed, but in other cases,
they are used by investigators with modifications and additional
criteria. This makes it difficult to compare studies and draw
conclusions about any aspect of implant success or failure based on
one or a few studies.
Strictly defined, implant success is any implant-retained
restoration in which (1) the original treatment plan is performed as
intended without complications, (2) all implants that were placed
remain stable and functioning without problems, (3) the peri-
implant hard and soft tissues are healthy, and (4) the patient and
treating clinicians are pleased with the results. When these strict
criteria are used, the rate of implant success (i.e., absence of
complications) is only about 61% after 5 years for implant-
supported fixed partial dentures (FPDs) and 50% after 10 years for
combined tooth–implant FPDs.
113
An additional criterion of implant success that is not typically
reported but should be considered is the aesthetic success or patient
satisfaction with the outcome. Several methods have been proposed
to evaluate aesthetic results. A restorative index was proposed by
Jensen and coworkers
95
to appraise the aesthetics of the final
restoration. The index uses a scale of 1 to 10, with 1 being an
extremely poor result and 10 being a superlative aesthetic result.
Based on subjective and objective criteria, the index evaluates the
size and shape of the implant restoration compared with the
4518

equivalent contralateral tooth, how well it blends into the arch, and
the papillae, gingival form, color, and other factors considered
essential in determining an aesthetic result. The pink aesthetic score
is an index proposed by Furhauser and colleagues
72
that considers
seven soft tissue parameters, including evaluation of the color,
contour, and texture of the surrounding soft tissues (i.e., papilla and
facial mucosa). Each parameter is given a score of 0, 1, or 2, which
allows the best score of 14 to determine the highest level of
aesthetics.
Other indices were proposed for single-tooth implant restorations
in the aesthetic zone.
23,122
Proposed by Belser and colleagues,
23
one
index combines a modified pink aesthetic score with a white
aesthetic score that focuses on the visible part of the implant
restoration. Scoring includes five parameters: general tooth form,
hue, value, surface texture, and translucency. The maximum white
aesthetic score is 10. These indices are aimed at quantifying the
aesthetic result, which can provide an objective method of judging
implant aesthetic success.
Key Fact
Implant survival indicates that the implant has become
osseointegrated but does not consider associated problems. An
implant that is not restored can be included in survival percentages
while failing to fulfill its intended purpose. Implant success is
defined by criteria evaluating the condition and function of the
implant. Because different criteria have been used to define
implant success, it is difficult to make comparisons between
studies and often impossible to make conclusions about implant
success or failure based on only one or a few studies.
Types and Prevalence of Implant
Complications
The prevalence of implant-related complications has been reported
in several reviews. However, a systematic review of the incidence
of complications in studies of at least 5 years' duration revealed that
4519

biologic complications were considered in only 40% to 60% and
technical complications in only 60% to 80% of the studies. The
review found that the incidence of technical complications related
to implant components and suprastructures was higher for
overdentures than for fixed restorations.
24
In a systematic review of reports on the survival and
complication rates of implant-supported FPDs, Lang and
associates
113
found that the most common technical complication
was fracture of veneers (13.2% after 5 years), followed by loss of the
screw access hole restoration (8.2% after 5 years), abutment or
occlusal screw loosening (5.8% after 5 years), and abutment or
occlusal screw fracture (1.5% after 5 years and 2.5% after 10 years).
Fracture of implants occurred infrequently (0.4% after 5 years and
1.8% after 10 years).
A retrospective evaluation of 4937 implants by Eckert and
colleagues
54
found that implant fractures occurred more frequently
in partially edentulous restorations (1.5%) than in restorations of
completely edentulous arches (0.2%), and all observed implant
fractures occurred with commercially pure, 3.75-mm diameter
threaded implants.
In a literature review that included all types of implant-retained
prostheses, Goodacre and colleagues
77
found that the most common
technical complications were loosening of the overdenture retentive
mechanism (33%), resin veneer fractures with FPDs (22%),
overdentures needing to be relined (19%), and overdenture clip or
attachment fracture (16%). With the inclusion of edentulous
patients having overdentures, their review seemed to indicate a
significantly higher percentage of complications than Pjetursson's
systematic review
145
of patients with implant-supported FPDs.
Goodacre and associates
76
found it impossible to calculate an
overall prosthesis complication rate because most studies included
in their review did not report several of the complication categories.
The most common complication reported for single crowns was
abutment or prosthesis screw loosening. The rate of abutment
screw loosening varied dramatically from one study to another,
ranging from 2% to 45%.
77
The highest rate of abutment screw
loosening was associated with single crowns, followed by
overdentures. The rate of prosthesis screw loosening was similar,
4520

ranging from 1% to 38% in various studies. A higher frequency was
reported for single crowns in the posterior areas (i.e., premolar and
molar) than in the anterior region.
Implant fracture is an uncommon but significant complication.
Goodacre and colleagues
76
reported a 1.5% incidence in their
literature review. The incidence of implant fracture was higher in
FPDs supported by only two implants. Consistent with this finding,
Rangert and coworkers
149
reported that most implant fractures
occurred in single- and double-implant–supported restorations.
They also found that most of these fractures were in posterior
partially edentulous segments, in which the generated occlusal
forces can be greater than in anterior segments (Fig. 85.1).
FIG. 85.1 (A) Radiograph of a three-unit, posterior,
fixed partial denture supported by two standard-
diameter, screw-shaped threaded implants. Notice the
4521

long crown height, relatively short implant length, and
bone loss around the posterior implant. (B) Photograph
of the ultimate implant-supported restoration failure.
The anterior implant fractured between the second and
third threads, which resulted in loss of the restoration.
In a systematic review of prospective longitudinal studies (i.e.,
minimum of 5 years' duration) reporting biologic and technical
complications associated with implant therapy (i.e., all restoration
types included), Berglundh and collegues
24
found that the incidence
of technical complications was consistent with Pjetursson's
findings, with implant fracture occurring in less than 1% (0.08% to
0.74%) of cases. Consistent with the findings in Goodacre's review,
technical complications were higher for implants used in
overdenture therapy than implants supporting fixed prostheses.
In Lang and associates' systematic review
113
of survival and
complication rates for implant-supported FPDs, biologic
complications such as peri-implantitis and soft tissue lesions
occurred in 8.6% of patients after 5 years. In a later literature review
of the prevalence of peri-implant diseases, Zitzmann and
Berglundh
191
reported that although cross-sectional studies were
rare, data from the only two studies available showed that peri-
implant mucositis occurred in 80% of patients and 50% of implant
sites. Peri-implantitis was identified in 28% and 56% or more of
patients and in 12% and 43% of implant sites in the two studies that
followed patients with functional implants for at least 5 years.
A critical review of the literature by Esposito and associates
64
included 73 publications reporting early and late failures of
Brånemark implants; biologically related implant failures were
relatively low at 7.7%. Treatments involved all anatomic areas and
all types of prosthetic design. The study authors concluded that the
predictability of implant treatment was especially good for partially
edentulous patients compared with totally edentulous patients;
failures in the latter population were twice as high as those in the
other group. The incidence of implant failure was three times
higher for the edentulous maxilla than for the edentulous mandible,
whereas failure rates for the partially edentulous maxilla were
similar to those for the partially edentulous mandible.
Risk factors such as smoking, diabetes, and periodontal disease
4522

can contribute to implant failure and complications. Several studies
with numerous implants and years of follow-up have concluded
that smoking is a definite risk factor for implant survival.
13,50,51,56,134
A systematic review of the effect of risk factors on implant
outcomes concluded that smoking had an adverse effect on implant
survival and success; the effects were more pronounced in areas of
loose trabecular bone (i.e., posterior maxilla).
107
The review
suggested that type 2 diabetes could have an adverse effect on
implant survival rates but did not have enough studies to permit a
definitive conclusion.
107
The same review concluded that although
patients with a history of treated periodontitis did not show a
decrease in implant survival, they did experience more biologic
implant complications and lower success rates, especially with
longer-term follow-up.
107
Types of Dental Implants
Analysis of the data on the prevalence of implant complications
(i.e., failure, fracture, and peri-implantitis) in published systematic
reviews should consider the fact that many of these studies
reported on implants with earlier designs (i.e., machined surfaces
and external connections). Most current implant systems feature
surfaces with an altered microtopography (i.e., rough), and many
have internal connections. The prevalence and type of
complications associated with the newer implant designs may be
different.
Many modifications have been developed to try to improve the
long-term success rates of implants. More than 1300 types of dental
implants are available with different materials, shapes, sizes,
lengths, and surface characteristics or coatings. Although it has
been suggested that machined surfaces are more resistant to plaque
accumulation and peri-implantitis, there is limited evidence to
show that implants with relatively smooth surfaces (i.e., machined)
are less prone to bone loss from chronic infection than implants
with rough surfaces. To date, there is no evidence showing that any
particular type of dental implant has superior long-term success.
59
Different implant designs and surfaces must be studied in
prospective human trials over long periods. Until those data
4523

become available, clinicians should be aware that historical data
reporting success rates for earlier implant designs may not reflect
the outcomes for current implants. Moreover, new implant surfaces
and designs are commonly introduced with limited or no data
available on potential complications.
a
Surgical Complications
As with any surgical procedure, implant surgery has risks. Proper
precautions must be taken to prevent injuries, including (1) a
thorough review of the patient's medical history, (2) a
comprehensive clinical and radiographic examination, (3)
establishment of a comprehensive interdisciplinary treatment plan,
and (4) good surgical techniques.
Surgical complications include perilous bleeding, damage to
adjacent structures such as teeth, injury to nerves, and iatrogenic
jaw fracture. Postoperative complications include bleeding,
hematoma, and infection. They may be minor, transient, and easily
managed or more serious and require postoperative treatment.
Hemorrhage and Hematoma
Bleeding during surgery is expected and usually easily controlled.
However, if a sizable vessel is incised or otherwise injured during
surgery, the hemorrhage can be difficult to control. Smaller vessels
naturally constrict or retract to slow the hemorrhage. If bleeding
continues, it may be necessary to apply pressure or suture the
hemorrhaging vessel. Cauterizing the hemorrhaging vessel also
may be warranted. This can be especially difficult if there is a
vascular injury to an artery that is inaccessible, such as in the floor
of the mouth or posterior maxilla. Serious bleeding from an
inaccessible vessel can be life-threatening, not by exsanguination
but rather as a result of airway obstruction. This is most
problematic when the point of bleeding is inaccessible and internal
(i.e., in connective tissues and soft tissue spaces).
Postoperative bleeding is an equally important problem to
manage (Fig. 85.2). Patients should be given postoperative
instructions on normal expectations for bleeding and how to
4524

prevent and manage minor bleeding. Historically, standard practice
is that they should be advised, with their physician's approval, to
discontinue or reduce medications that increase bleeding tendency
3 to 10 days before surgery. However, recent evidence suggests that
this may not be necessary and may increase the risk of hematologic
or cardiovascular problems
96,97,134,159
(see Chapter 39).
FIG. 85.2 Clinical photograph of postoperative
bleeding around healing abutments after second-stage
implant exposure surgery.
Dental health care providers should consult with medical health
care providers regarding the best management for each patient.
Dental health care providers and patients should always include
the treating medical practitioner in management decisions if
postoperative bleeding is excessive or persistent.
Submucosal or subdermal hemorrhage into the connective tissues
and soft tissue spaces can result in hematoma formation.
Postoperative bruising is a typical example of minor submucosal or
subdermal bleeding into the connective tissues (Fig. 85.3). Bruising
and small hematomas typically resolve without special treatment or
consequence. However, larger hematomas or those that occur in
medically compromised individuals are susceptible to infection as a
result of the noncirculating blood that sits in the space. It is prudent
to prescribe antibiotics for patients who develop a noticeably large
hematoma. Referral to the appropriate medical physician may be
warranted for nonresolving hematomas.
88
4525

FIG. 85.3 Clinical photograph of postoperative
(extraoral) bruising indicative of subdermal bleeding
into connective tissue spaces. This is a normal
expectation that resolves in 7 to 14 days.
Although the incidence of a life-threatening hemorrhage from
implant surgery is extremely low, the seriousness of the problem
warrants the attention of everyone who participates in this type of
surgery. Potentially fatal complications have been reported for
implant surgical procedures in the mandible, especially the anterior
region.
b
Massive internal bleeding in the highly vascular region of
the floor of the mouth can result from instrumentation or implants
that perforate the lingual cortical plate and sever or injure the
arteries running along the lingual surface. Depending on the
severity and location of the injury, bleeding may become apparent
immediately or only after some delay. In either case, the
progressively increasing hematoma dissects and expands to
displace the tongue and soft tissues of the floor of the mouth,
ultimately leading to upper airway obstruction.
Emergency treatment includes airway management (primary
importance) and surgical intervention to isolate and stop the
bleeding. Clinicians must be aware of this risk and be prepared to
act quickly. It is important to recognize that bleeding, although
considered a complication at the time of surgery, can become a
serious complication in the hours and days after surgery.
47
Clinical Correlation
Although the incidence of a life-threatening hemorrhage from
4526

implant surgery is extremely low, it is a serious problem that can
occur. Implant surgical procedures in the anterior mandible have
been associated with potentially fatal complications. Massive
internal bleeding in the floor of the mouth from inadvertent injury
to lingual arteries can cause an expanding hematoma that displaces
the tongue and soft tissues, obstructing the upper airway.
Emergency treatment includes airway management and surgical
intervention to isolate and stop the bleeding. Clinicians must be
aware of this risk and be prepared to act quickly.
Neurosensory Disturbances
One of the more problematic surgical complications is an injury to
nerves. Neurosensory alterations caused by damage to a nerve can
be temporary or permanent. Neuropathy can be caused by a
drilling injury (i.e., cut, tear, or puncture of the nerve) or by implant
compression or damage to the nerve (Fig. 85.4; see Fig. 76.18). In
either case, the injury causes neuroma formation, and two patterns
of clinical neuropathy may follow. Hypoesthesia is a neuropathy
defined by impaired sensory function that is sometimes associated
with phantom pain. Hyperesthesia is a neuropathy defined by pain
with minimal or no sensory impairment.
79
Some neuropathies
resolve, whereas others persist. The type of neuropathy does not
indicate the potential for recovery.
4527

FIG. 85.4 (A) Cross-sectional computed tomography
(CT) image shows the implant impinging on the inferior
alveolar nerve canal. (B) Panoramic CT scan shows
the implant in the lower left first molar area impinging
on the inferior alveolar nerve canal. The nerve is
marked by tracing with software.
For several reasons, it is likely that neurosensory disturbances
occur more frequently after implant surgery than is reported in the
literature. First, many of the changes are transient in nature, and
most patients recover completely or at least recover to a level that is
below a threshold of annoyance or daily perception. Second, wide
variation exists in the postoperative evaluation of patients by
clinicians. Some clinicians do not assess or inquire about
postsurgical neurosensory disturbances, allowing this complication
to go unnoticed. Likewise, some patients expect altered sensation as
part of surgery and may never acknowledge or comment on its
presence, especially if the disturbance is minor. It is therefore likely
that minor neuropathies exist but go unrecognized and unreported.
4528
According to a systematic review of inferior alveolar nerve
injuries after implant placement, the importance of early diagnosis
and treatment is considered essential for preventing long-term,
permanent neurologic problems. If a diagnosis is established and
treatment is rendered within the first 36 hours, a high percentage of
successful outcomes can be achieved. An estimated 25% of patients
with iatrogenic paresthesia suffer permanent effects.
104
Several
researchers and clinicians proposed that early implant removal (i.e.,
within the first 24 to 36 hours after implant placement) may lead to
better healing with the return of sensation.
104,105
Neurosensory disturbances reported in the literature are most
prevalent and significant when they are more serious and occur
more frequently, such as those associated with lateral transposition
of the mandibular nerve.
93,101
This relatively uncommon procedure
is used to reposition the nerve and allow longer implants to be
placed in the atrophic posterior mandible. Lateral nerve
transposition procedures are associated with an almost 100%
incidence of neurosensory dysfunction immediately after surgery.
More than 50% (range, 30% to 80%) of these neurosensory changes
are permanent.
101
Several articles have been written on the
treatment of neurosensory disturbances.
7,128,151
Implant Malposition
Many of the complications that arise during implant surgery can be
attributed to the dental implant being placed in an undesired or
unintended position. Malpositioning of dental implants is usually
the result of poor treatment planning before surgery, lack of
surgical skill, or poor communication between the implant surgeon
and the restorative dentist. Optimal implant aesthetics and the
avoidance of positional complications can be achieved by placing
the implant in a prosthetically driven manner.
123,140
The implant
should be placed with reference to the three dimensions dictated by
the position of the final restoration and not by the availability of
bone.
Angulation is another important determinant of implant position
that affects outcome aesthetics. The ideal implant position entails an
accurate preparation, insertion, and placement into the alveolus in a
4529

proper three-dimensional geometry according to apicocoronal,
mesiodistal, and buccolingual parameters and implant angulation
relative to the final prosthetic restoration and gingival margins
108,160
(see Chapter 78).
Apicocoronally, the implant should be placed so the platform is
about 3 mm apical to the gingival margin of the anticipated
restoration.
28
The implant position varies slightly from one implant
system to another, depending on abutment design and space
requirements. If the implant platform is placed too far coronally,
there will not be sufficient room to develop a natural-looking
emergence profile, and the tooth may have a boxy, unaesthetic
appearance. If the platform is placed at or above the level of the
gingival margin, metal collar or implant exposure can occur,
yielding an unaesthetic result (Fig. 85.5). If the implant platform is
placed too far apically, a long transmucosal abutment will be
necessary to restore the implant. This can lead to a deep pocket and
difficult hygiene access for the patient and clinician.
FIG. 85.5 Clinical photograph of gingival recession
around a maxillary anterior implant (left central incisor)
resulting in exposure of the crown margin, the implant
collar, and several threads of the implant.
The implant should be placed at a distance of 1.5 to 2 mm from
an adjacent natural tooth and 2 to 3 mm from an adjacent implant
to maintain an adequate biologic dimension.
81
Similar to natural
teeth, violation of biologic width around an implant can lead to
4530

bone loss.
87
Implants that are placed too close to each other (Fig.
85.6) or to natural teeth can be difficult to restore. Impression
copings and impression-taking techniques must be modified.
Improperly spaced implants invariably lead to chronic
inflammation and peri-implantitis.
57,181
Conversely, an implant
placed at an excessive distance from an adjacent tooth or implant
may require prosthetic compensation in the form of mesial or distal
cantilevers, which can predispose the implant to biologic (i.e., bone
loss) and mechanical (i.e., screw loosening,
77
screw fracture,
179
and
implant fracture
149
) complications and difficulties with hygiene.
181
FIG. 85.6 Radiograph of two mandibular anterior
implants placed too close together (i.e., no proximal
space), resulting in implants that are impossible to
restore.
Ideally, an implant should be placed buccolingually so there is at
least 2 mm of bone circumferentially around it.
172
Implant exposure
through the lingual or buccal cortex can predispose an individual to
abscess and suppuration.
38
Implants that are placed too palatally or
lingually require prosthetic compensation in the form of a buccal
ridge lap, which may be difficult for the patient to clean and can
4531

lead to tissue inflammation.
22
To obtain ideal aesthetics, to avoid potential aesthetic
complications, and to correct bodily placement of the dental
implant, it must be correctly angulated on insertion. In most
anterior cases, it is desirable to have the long axis of the implant
directed so it is emerging toward the cingulum. In the posterior
region, the implant axis should be directed toward the central fossa
or the stamp cusp of the opposing tooth. Implants that are placed
with mild to moderate misangulations can often be corrected
prosthetically with implant abutments. Minor misangulations (i.e.,
15 to 20 degrees) can be corrected with prefabricated or customized
angled abutments; moderate misangulations (i.e., 20 to 35 degrees)
can usually be managed with customized UCLA-type abutments;
and extreme errors in implant angulations (>35 degrees) may make
an implant unrestorable and require it to be left submerged (i.e., a
sleeper) or be removed (Fig. 85.7).
FIG. 85.7 Clinical photograph of a maxillary anterior
implant (i.e., left central incisor) placed with an extreme
facial angulation, resulting in an implant that emerges
through the gingiva at a level that is more apical than
the adjacent natural tooth gingival margins. (A)
4532

Surgical exposure of the malpositioned implant. (B)
Surgically removed implant. (C) Alveolar defect
resulting from surgical removal of the malpositioned
implant.
The ultimate complication of malpositioning is implant or
instrument invasion into vital structures. The most common
violation of neighboring anatomy is placement of the dental
implant into the adjacent tooth root. Surgical procedures used to
prepare osteotomy sites and place implants adjacent to teeth can
injure them by directly cutting into the tooth structure or by
damaging nearby supporting tissues and nerves. Instrumentation
(e.g., drills) directed at or near the adjacent tooth can injure the
periodontal ligament, tooth structure, and nerve of the tooth.
Depending on the extent of the injury, the tooth can require
endodontic therapy or extraction.
On insertion, dental implants follow the trajectory of the
osteotomy prepared by the drill. Care must be taken when
preparing the osteotomy to stay true to the planned path of
insertion. Radiographs taken periodically during implant surgery
with a guide pin in the osteotomy site can greatly reduce the
potential for damaging adjacent teeth (see Fig. 76.15). Radiographic
analysis before implant surgery should include detection of curved,
convergent, or dilacerated root structures of adjacent teeth that can
limit implant placement.
Particular care must be taken when placing implants in the
mandible so as to not encroach on the inferior alveolar canal or the
mental foramen (see Chapter 58 for a description of the anatomy).
Encroachment on the mandibular canal or mental foramen during
osteotomy or implant placement by direct contact or mechanical
compression of bone can injure nerves and blood vessels.
Paresthesia, hypoesthesia, hyperesthesia, dysesthesia, or anesthesia
of the lower lip, skin, mucosa, and teeth can result, as can arterial or
venous bleeding.
78
The reported incidence of sensory disturbances
after mandibular implant placement is 0% to 40%.
18,104
In the maxilla, care must be taken to avoid dental implant
perforation into the maxillary sinus or nasal cavity. Displacement of
the entire dental implant into the maxillary sinus cavity may
require a Caldwell-Luc procedure for retrieval. The online section
4533

on Sinus Bone Augmentation provides further information about
complications related to the maxillary sinus.
The risks of surgery always exist, but the complications can be
minimized by an understanding of the causes and with proper
diagnosis and treatment planning. Three-dimensional imaging (i.e.,
computed tomography [CT] and cone beam CT [CBCT]) provides
the surgeon with useful preoperative information for diagnosis and
treatment planning (see Chapter 76). Careful surgical exposure for
direct visualization and identification of the mental nerve are
indicated. The surgeon should establish a zone of safety and keep
instrumentation and implants a safe margin (≥2 mm) away from the
nerve.
78
Key Fact
Malpositioned implants can be avoided by proper planning, good
communication, and meticulous surgical skills. Radiographs taken
periodically during implant surgery with guide pins in the
osteotomy site can greatly reduce damage to adjacent teeth.
Radiographic analysis before implant surgery should include
detection of curved, convergent, or dilacerated root structures of
adjacent teeth that can limit implant placement.
Biologic Complications
Biologic complications involve pathology of the surrounding peri-
implant hard and soft tissues. Frequently, soft tissue problems are
an inflammatory response to bacterial accumulation around
implants. Bacteria can accumulate at the junction of an ill-fitting
implant–abutment or abutment–crown connection. Some of the
highly textured, macroscopically rough implant surfaces (e.g.,
titanium plasma–sprayed [TPS] or hydroxyapatite [HA] coating)
may also perpetuate the accumulation of bacteria on the implant
surface.
Inflammation and Proliferation
4534

Because inflammation of the peri-implant soft tissues is similar to
the inflammatory response in gingival and other periodontal
tissues, the clinical appearance also is similar. Inflamed peri-
implant tissues demonstrate the same erythema, edema, and
swelling around teeth. Occasionally, the reaction of peri-implant
soft tissues to bacterial accumulation is profound and unusual, with
dramatic inflammatory proliferation (Fig. 85.8). This type of lesion
is somewhat characteristic around implants and indicates a loose-
fitting implant-to-abutment connection or trapped excess cement
that remains buried within the soft tissue space (i.e., pocket).
FIG. 85.8 Inflammatory proliferation caused by a
loose-fitting connection between the abutment and the
implant. (Courtesy Dr. John Beumer, UCLA Maxillofacial Prosthetics, Los
Angeles, CA.)
The precipitating local factor ultimately becomes infected with
bacterial pathogens, leading to mucosal hypertrophy or
proliferation and possible abscess formation (Fig. 85.9). Correction
of the precipitating factors (e.g., loose connection, retained cement)
can effectively resolve the lesion. Another type of lesion resulting
from a loose abutment connection is a fistula (Fig. 85.10), and
correcting the etiologic factor can quickly resolve it.
4535

FIG. 85.9 (A) Clinical photograph of an abscess
caused by excess cement trapped within the soft
tissues. (B) Radiograph of an implant with a cemented
crown (same patient as in A). Notice the subgingival
depth of the crown–abutment (cement line) junction,
which is below the level of the adjacent interproximal
bone and therefore impossible to adequately access
with an explorer to remove the excess cement. (Courtesy
Dr. John Beumer, UCLA Maxillofacial Prosthetics, Los Angeles, CA.)
FIG. 85.10 Fistula caused by a loose implant–
abutment connection (i.e., maxillary left lateral incisor).
4536

Dehiscence and Recession
Dehiscence or recession of the peri-implant soft tissues occurs when
support for the tissues is lacking or has been lost. Recession is a
common finding after implant restoration and should be
anticipated, especially when soft tissues are thin and not well
supported (Fig. 85.11). Improper implant positioning also
predisposes peri-implant tissues to recession. Placement or
angulation of the implant too far buccally causes the buccal plate to
resorb, resulting in greater recession.
171
FIG. 85.11 (A) Clinical photograph of a single-tooth
implant crown (maxillary right central) with moderate
recession that occurred 1 year after the final
restoration. In this case, recession most likely occurred
because the labial bone around this wide-diameter
implant was very thin or nonexistent. (B) Radiograph of
a wide-diameter (6-mm) implant supporting a maxillary
central incisor crown (same patient as in A).
Another factor is the thickness of the buccal plate of bone. Spray
and colleagues
172
recommended a buccal bone thickness of 2 mm or
greater to support the buccal soft tissue. If it is insufficient,
preoperative or simultaneous site development using guided bone
4537

regeneration is indicated. Recession is a problem that is particularly
disconcerting in anterior aesthetic areas. Patients with a high smile
line or high aesthetic demands consider recession a failure (Fig.
85.12).
FIG. 85.12 Poor aesthetics resulting from gingival
recession and exposure of the crown margins, implant
collars, and threads of several maxillary and
mandibular implants supporting full-arch, fixed partial
dentures. Notice the thin labial tissues and erythema,
especially around the mandibular implant sites.
The anatomy and soft tissue support around implants are
different from those around teeth. Periodontal tissues have the
advantage of soft tissue support supplied by circumferential and
transseptal connective tissue fibers that insert into the cementum at
a level that is more coronal than the supporting bone. In the
absence of inflammation, these fibers support periodontal soft
tissues far above the level of crestal bone. As a result, gingival
margins and interdental papillae are supported and maintained
higher around teeth than around implants, even when the
periodontal tissues are very thin.
Peri-implant soft tissues, however, depend entirely on the
surrounding bone for support. Soft tissue thickness accounts for
some soft tissue height, but there are no supracrestal inserting
connective tissue fibers to aid the soft tissue support around an
implant. The soft tissue height around implants is typically limited
4538

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C H A P T E R 8 5Implant-RelatedComplications andFailuresStuart J. Froum, Perry R. Klokkevold, Sang Choon Cho, Scott H. FroumCHAPTER OUTLINEDefinitions of Implant Survival and SuccessTypes and Prevalence of Implant ComplicationsTypes of Dental ImplantsSurgical ComplicationsBiologic ComplicationsComplications Related to Augmentation Procedures (e-only)Complications Related to Placement and LoadingProtocols (e-only)Prosthetic or Mechanical ComplicationsAesthetic and Phonetic ComplicationsConclusions4515 The successful use of osseointegrated dental implants hasdramatically changed dentistry and significantly improved dentists'ability to provide tooth replacement options for patients.3,115 Despiteimplants' long-term predictability and success, implant-relatedcomplications and failures happen in some cases.4,29 Complicationscan be surgical, biologic, mechanical, or aesthetic. Somecomplications are relatively minor and easy to manage, but othersare more significant and challenging to resolve. The most seriouscomplications can result in failure of prostheses, loss of implants,and severe loss of supporting bone.Surgical complications are those problems or adverse outcomesthat result from surgery, including procedures used for implant sitedevelopment, implant placement, implant exposure, and tissueaugmentation. Implant complications commonly arise fromplacement of an implant in a nonideal position. Malpositionedimplants, which usually result from poor preoperative treatmentplanning or errors in surgical technique, can lead to an array ofimplant problems ranging in severity from minor to major. Surgicalcomplications include compromised aesthetic and prostheticresults, soft tissue and bone dehiscences, impingement on anddamage to anatomic structures, and implant failure. Unfortunately,the problems that arise from implant malposition are often notrecognized until after osseointegration, when the prosthesis is beingfabricated.Biologic complications involve the hard and soft tissues thatsupport the implant. Peri-implant tissue changes can be limited toinflammation of surrounding soft tissues or be more significant,such as progressive loss of supporting bone. The ultimate biologiccomplication is implant loss or failure, which can produce soft andhard tissue defects. Loss of implants can be caused by failure toachieve osseointegration in the early stages before restoration or byloss of osseointegration as a result of destruction of supportingbone after the restoration is installed and functioning.Prosthetic or mechanical complications and failures typically occurin the form of material failure, such as abutment and prostheticscrew loosening or fractures. The prosthesis can be rescued frommany mechanical problems if they are minor and recognized early.However, some complications, such as implant fractures, are4516 devastating and not salvageable.Aesthetic complications arise when the patient's expectations arenot met. Satisfaction with the aesthetic outcome of the implantprosthesis varies from patient to patient. The risk of aestheticcomplications is increased among patients with high aestheticexpectations and suboptimal patient-related factors, such as a highsmile line, thin gingival tissues, or inadequate bone quantity andquality.This chapter reviews common implant-related complications. Asummary of the literature offers some insight into the prevalence ofimplant-related complications. Implant failure and surgicalcomplications related to site development and variations in implantplacement protocols are discussed.Definitions of Implant Survival andSuccessThe criteria used to define and report implant success or failure canvary substantially among publications. Selection of success criteriacan be based on the author's preference, study population, or someother study objective. Because the level of success reported in anarticle is based on the criteria used to define success, recognizingthe tremendous variation in the way investigators measure andinterpret success is crucial. Sometimes, outcomes are measured bythe presence or absence of implants at the time of the lastexamination, which is a measure only of implant survival andshould not be confused with implant success. In contrast to thissimplified reporting, some investigators use detailed criteria tomeasure implant success and failure, with variations of successfuloutcomes separated and defined by additional criteria.Implant survival is defined as an implant that remains in place atthe time of evaluation, regardless of any untoward signs,symptoms, or history of problems. There is a difference betweenimplants that are functioning under an implant-retained restorationand those that are not connected to a restoration and not providingsupport or function. These implants are sometimes referred to assleepers, and they should not be considered successful merely4517 because they remain osseointegrated. Sleeper implants insteadshould be included in the discussion as surviving but counted asfailures because they did not fulfill the originally intended treatmentobjective.Implant success is defined by the presence of the implant and thecriteria evaluating its condition and function at the time ofexamination. Various criteria for implant success and failure havebeen published, but not all investigators agree with or use them. Inthe classic definition, Albrektsson and colleagues6 defined successas an implant with no pain, no mobility, no radiolucent peri-implant areas, and no more than 0.2 mm of bone loss annually afterthe first year of loading. Roos-Jansaker and associates157 added tothis by defining a successful implant as one that loses no more than1 mm of bone during the first year of function.Sometimes, the criteria are used as proposed, but in other cases,they are used by investigators with modifications and additionalcriteria. This makes it difficult to compare studies and drawconclusions about any aspect of implant success or failure based onone or a few studies.Strictly defined, implant success is any implant-retainedrestoration in which (1) the original treatment plan is performed asintended without complications, (2) all implants that were placedremain stable and functioning without problems, (3) the peri-implant hard and soft tissues are healthy, and (4) the patient andtreating clinicians are pleased with the results. When these strictcriteria are used, the rate of implant success (i.e., absence ofcomplications) is only about 61% after 5 years for implant-supported fixed partial dentures (FPDs) and 50% after 10 years forcombined tooth–implant FPDs.113An additional criterion of implant success that is not typicallyreported but should be considered is the aesthetic success or patientsatisfaction with the outcome. Several methods have been proposedto evaluate aesthetic results. A restorative index was proposed byJensen and coworkers95 to appraise the aesthetics of the finalrestoration. The index uses a scale of 1 to 10, with 1 being anextremely poor result and 10 being a superlative aesthetic result.Based on subjective and objective criteria, the index evaluates thesize and shape of the implant restoration compared with the4518 equivalent contralateral tooth, how well it blends into the arch, andthe papillae, gingival form, color, and other factors consideredessential in determining an aesthetic result. The pink aesthetic scoreis an index proposed by Furhauser and colleagues72 that considersseven soft tissue parameters, including evaluation of the color,contour, and texture of the surrounding soft tissues (i.e., papilla andfacial mucosa). Each parameter is given a score of 0, 1, or 2, whichallows the best score of 14 to determine the highest level ofaesthetics.Other indices were proposed for single-tooth implant restorationsin the aesthetic zone.23,122 Proposed by Belser and colleagues,23 oneindex combines a modified pink aesthetic score with a whiteaesthetic score that focuses on the visible part of the implantrestoration. Scoring includes five parameters: general tooth form,hue, value, surface texture, and translucency. The maximum whiteaesthetic score is 10. These indices are aimed at quantifying theaesthetic result, which can provide an objective method of judgingimplant aesthetic success. Key FactImplant survival indicates that the implant has becomeosseointegrated but does not consider associated problems. Animplant that is not restored can be included in survival percentageswhile failing to fulfill its intended purpose. Implant success isdefined by criteria evaluating the condition and function of theimplant. Because different criteria have been used to defineimplant success, it is difficult to make comparisons betweenstudies and often impossible to make conclusions about implantsuccess or failure based on only one or a few studies.Types and Prevalence of ImplantComplicationsThe prevalence of implant-related complications has been reportedin several reviews. However, a systematic review of the incidenceof complications in studies of at least 5 years' duration revealed that4519 biologic complications were considered in only 40% to 60% andtechnical complications in only 60% to 80% of the studies. Thereview found that the incidence of technical complications relatedto implant components and suprastructures was higher foroverdentures than for fixed restorations.24In a systematic review of reports on the survival andcomplication rates of implant-supported FPDs, Lang andassociates113 found that the most common technical complicationwas fracture of veneers (13.2% after 5 years), followed by loss of thescrew access hole restoration (8.2% after 5 years), abutment orocclusal screw loosening (5.8% after 5 years), and abutment orocclusal screw fracture (1.5% after 5 years and 2.5% after 10 years).Fracture of implants occurred infrequently (0.4% after 5 years and1.8% after 10 years).A retrospective evaluation of 4937 implants by Eckert andcolleagues54 found that implant fractures occurred more frequentlyin partially edentulous restorations (1.5%) than in restorations ofcompletely edentulous arches (0.2%), and all observed implantfractures occurred with commercially pure, 3.75-mm diameterthreaded implants.In a literature review that included all types of implant-retainedprostheses, Goodacre and colleagues77 found that the most commontechnical complications were loosening of the overdenture retentivemechanism (33%), resin veneer fractures with FPDs (22%),overdentures needing to be relined (19%), and overdenture clip orattachment fracture (16%). With the inclusion of edentulouspatients having overdentures, their review seemed to indicate asignificantly higher percentage of complications than Pjetursson'ssystematic review145 of patients with implant-supported FPDs.Goodacre and associates76 found it impossible to calculate anoverall prosthesis complication rate because most studies includedin their review did not report several of the complication categories.The most common complication reported for single crowns wasabutment or prosthesis screw loosening. The rate of abutmentscrew loosening varied dramatically from one study to another,ranging from 2% to 45%.77 The highest rate of abutment screwloosening was associated with single crowns, followed byoverdentures. The rate of prosthesis screw loosening was similar,4520 ranging from 1% to 38% in various studies. A higher frequency wasreported for single crowns in the posterior areas (i.e., premolar andmolar) than in the anterior region.Implant fracture is an uncommon but significant complication.Goodacre and colleagues76 reported a 1.5% incidence in theirliterature review. The incidence of implant fracture was higher inFPDs supported by only two implants. Consistent with this finding,Rangert and coworkers149 reported that most implant fracturesoccurred in single- and double-implant–supported restorations.They also found that most of these fractures were in posteriorpartially edentulous segments, in which the generated occlusalforces can be greater than in anterior segments (Fig. 85.1).FIG. 85.1 (A) Radiograph of a three-unit, posterior,fixed partial denture supported by two standard-diameter, screw-shaped threaded implants. Notice the4521 long crown height, relatively short implant length, andbone loss around the posterior implant. (B) Photographof the ultimate implant-supported restoration failure.The anterior implant fractured between the second andthird threads, which resulted in loss of the restoration.In a systematic review of prospective longitudinal studies (i.e.,minimum of 5 years' duration) reporting biologic and technicalcomplications associated with implant therapy (i.e., all restorationtypes included), Berglundh and collegues24 found that the incidenceof technical complications was consistent with Pjetursson'sfindings, with implant fracture occurring in less than 1% (0.08% to0.74%) of cases. Consistent with the findings in Goodacre's review,technical complications were higher for implants used inoverdenture therapy than implants supporting fixed prostheses.In Lang and associates' systematic review113 of survival andcomplication rates for implant-supported FPDs, biologiccomplications such as peri-implantitis and soft tissue lesionsoccurred in 8.6% of patients after 5 years. In a later literature reviewof the prevalence of peri-implant diseases, Zitzmann andBerglundh191 reported that although cross-sectional studies wererare, data from the only two studies available showed that peri-implant mucositis occurred in 80% of patients and 50% of implantsites. Peri-implantitis was identified in 28% and 56% or more ofpatients and in 12% and 43% of implant sites in the two studies thatfollowed patients with functional implants for at least 5 years.A critical review of the literature by Esposito and associates64included 73 publications reporting early and late failures ofBrånemark implants; biologically related implant failures wererelatively low at 7.7%. Treatments involved all anatomic areas andall types of prosthetic design. The study authors concluded that thepredictability of implant treatment was especially good for partiallyedentulous patients compared with totally edentulous patients;failures in the latter population were twice as high as those in theother group. The incidence of implant failure was three timeshigher for the edentulous maxilla than for the edentulous mandible,whereas failure rates for the partially edentulous maxilla weresimilar to those for the partially edentulous mandible.Risk factors such as smoking, diabetes, and periodontal disease4522 can contribute to implant failure and complications. Several studieswith numerous implants and years of follow-up have concludedthat smoking is a definite risk factor for implant survival.13,50,51,56,134A systematic review of the effect of risk factors on implantoutcomes concluded that smoking had an adverse effect on implantsurvival and success; the effects were more pronounced in areas ofloose trabecular bone (i.e., posterior maxilla).107 The reviewsuggested that type 2 diabetes could have an adverse effect onimplant survival rates but did not have enough studies to permit adefinitive conclusion.107 The same review concluded that althoughpatients with a history of treated periodontitis did not show adecrease in implant survival, they did experience more biologicimplant complications and lower success rates, especially withlonger-term follow-up.107Types of Dental ImplantsAnalysis of the data on the prevalence of implant complications(i.e., failure, fracture, and peri-implantitis) in published systematicreviews should consider the fact that many of these studiesreported on implants with earlier designs (i.e., machined surfacesand external connections). Most current implant systems featuresurfaces with an altered microtopography (i.e., rough), and manyhave internal connections. The prevalence and type ofcomplications associated with the newer implant designs may bedifferent.Many modifications have been developed to try to improve thelong-term success rates of implants. More than 1300 types of dentalimplants are available with different materials, shapes, sizes,lengths, and surface characteristics or coatings. Although it hasbeen suggested that machined surfaces are more resistant to plaqueaccumulation and peri-implantitis, there is limited evidence toshow that implants with relatively smooth surfaces (i.e., machined)are less prone to bone loss from chronic infection than implantswith rough surfaces. To date, there is no evidence showing that anyparticular type of dental implant has superior long-term success.59Different implant designs and surfaces must be studied inprospective human trials over long periods. Until those data4523 become available, clinicians should be aware that historical datareporting success rates for earlier implant designs may not reflectthe outcomes for current implants. Moreover, new implant surfacesand designs are commonly introduced with limited or no dataavailable on potential complications.aSurgical ComplicationsAs with any surgical procedure, implant surgery has risks. Properprecautions must be taken to prevent injuries, including (1) athorough review of the patient's medical history, (2) acomprehensive clinical and radiographic examination, (3)establishment of a comprehensive interdisciplinary treatment plan,and (4) good surgical techniques.Surgical complications include perilous bleeding, damage toadjacent structures such as teeth, injury to nerves, and iatrogenicjaw fracture. Postoperative complications include bleeding,hematoma, and infection. They may be minor, transient, and easilymanaged or more serious and require postoperative treatment.Hemorrhage and HematomaBleeding during surgery is expected and usually easily controlled.However, if a sizable vessel is incised or otherwise injured duringsurgery, the hemorrhage can be difficult to control. Smaller vesselsnaturally constrict or retract to slow the hemorrhage. If bleedingcontinues, it may be necessary to apply pressure or suture thehemorrhaging vessel. Cauterizing the hemorrhaging vessel alsomay be warranted. This can be especially difficult if there is avascular injury to an artery that is inaccessible, such as in the floorof the mouth or posterior maxilla. Serious bleeding from aninaccessible vessel can be life-threatening, not by exsanguinationbut rather as a result of airway obstruction. This is mostproblematic when the point of bleeding is inaccessible and internal(i.e., in connective tissues and soft tissue spaces).Postoperative bleeding is an equally important problem tomanage (Fig. 85.2). Patients should be given postoperativeinstructions on normal expectations for bleeding and how to4524 prevent and manage minor bleeding. Historically, standard practiceis that they should be advised, with their physician's approval, todiscontinue or reduce medications that increase bleeding tendency3 to 10 days before surgery. However, recent evidence suggests thatthis may not be necessary and may increase the risk of hematologicor cardiovascular problems96,97,134,159 (see Chapter 39).FIG. 85.2 Clinical photograph of postoperativebleeding around healing abutments after second-stageimplant exposure surgery.Dental health care providers should consult with medical healthcare providers regarding the best management for each patient.Dental health care providers and patients should always includethe treating medical practitioner in management decisions ifpostoperative bleeding is excessive or persistent.Submucosal or subdermal hemorrhage into the connective tissuesand soft tissue spaces can result in hematoma formation.Postoperative bruising is a typical example of minor submucosal orsubdermal bleeding into the connective tissues (Fig. 85.3). Bruisingand small hematomas typically resolve without special treatment orconsequence. However, larger hematomas or those that occur inmedically compromised individuals are susceptible to infection as aresult of the noncirculating blood that sits in the space. It is prudentto prescribe antibiotics for patients who develop a noticeably largehematoma. Referral to the appropriate medical physician may bewarranted for nonresolving hematomas.884525 FIG. 85.3 Clinical photograph of postoperative(extraoral) bruising indicative of subdermal bleedinginto connective tissue spaces. This is a normalexpectation that resolves in 7 to 14 days.Although the incidence of a life-threatening hemorrhage fromimplant surgery is extremely low, the seriousness of the problemwarrants the attention of everyone who participates in this type ofsurgery. Potentially fatal complications have been reported forimplant surgical procedures in the mandible, especially the anteriorregion.b Massive internal bleeding in the highly vascular region ofthe floor of the mouth can result from instrumentation or implantsthat perforate the lingual cortical plate and sever or injure thearteries running along the lingual surface. Depending on theseverity and location of the injury, bleeding may become apparentimmediately or only after some delay. In either case, theprogressively increasing hematoma dissects and expands todisplace the tongue and soft tissues of the floor of the mouth,ultimately leading to upper airway obstruction.Emergency treatment includes airway management (primaryimportance) and surgical intervention to isolate and stop thebleeding. Clinicians must be aware of this risk and be prepared toact quickly. It is important to recognize that bleeding, althoughconsidered a complication at the time of surgery, can become aserious complication in the hours and days after surgery.47 Clinical CorrelationAlthough the incidence of a life-threatening hemorrhage from4526 implant surgery is extremely low, it is a serious problem that canoccur. Implant surgical procedures in the anterior mandible havebeen associated with potentially fatal complications. Massiveinternal bleeding in the floor of the mouth from inadvertent injuryto lingual arteries can cause an expanding hematoma that displacesthe tongue and soft tissues, obstructing the upper airway.Emergency treatment includes airway management and surgicalintervention to isolate and stop the bleeding. Clinicians must beaware of this risk and be prepared to act quickly.Neurosensory DisturbancesOne of the more problematic surgical complications is an injury tonerves. Neurosensory alterations caused by damage to a nerve canbe temporary or permanent. Neuropathy can be caused by adrilling injury (i.e., cut, tear, or puncture of the nerve) or by implantcompression or damage to the nerve (Fig. 85.4; see Fig. 76.18). Ineither case, the injury causes neuroma formation, and two patternsof clinical neuropathy may follow. Hypoesthesia is a neuropathydefined by impaired sensory function that is sometimes associatedwith phantom pain. Hyperesthesia is a neuropathy defined by painwith minimal or no sensory impairment.79 Some neuropathiesresolve, whereas others persist. The type of neuropathy does notindicate the potential for recovery.4527 FIG. 85.4 (A) Cross-sectional computed tomography(CT) image shows the implant impinging on the inferioralveolar nerve canal. (B) Panoramic CT scan showsthe implant in the lower left first molar area impingingon the inferior alveolar nerve canal. The nerve ismarked by tracing with software.For several reasons, it is likely that neurosensory disturbancesoccur more frequently after implant surgery than is reported in theliterature. First, many of the changes are transient in nature, andmost patients recover completely or at least recover to a level that isbelow a threshold of annoyance or daily perception. Second, widevariation exists in the postoperative evaluation of patients byclinicians. Some clinicians do not assess or inquire aboutpostsurgical neurosensory disturbances, allowing this complicationto go unnoticed. Likewise, some patients expect altered sensation aspart of surgery and may never acknowledge or comment on itspresence, especially if the disturbance is minor. It is therefore likelythat minor neuropathies exist but go unrecognized and unreported.4528 According to a systematic review of inferior alveolar nerveinjuries after implant placement, the importance of early diagnosisand treatment is considered essential for preventing long-term,permanent neurologic problems. If a diagnosis is established andtreatment is rendered within the first 36 hours, a high percentage ofsuccessful outcomes can be achieved. An estimated 25% of patientswith iatrogenic paresthesia suffer permanent effects.104 Severalresearchers and clinicians proposed that early implant removal (i.e.,within the first 24 to 36 hours after implant placement) may lead tobetter healing with the return of sensation.104,105Neurosensory disturbances reported in the literature are mostprevalent and significant when they are more serious and occurmore frequently, such as those associated with lateral transpositionof the mandibular nerve.93,101 This relatively uncommon procedureis used to reposition the nerve and allow longer implants to beplaced in the atrophic posterior mandible. Lateral nervetransposition procedures are associated with an almost 100%incidence of neurosensory dysfunction immediately after surgery.More than 50% (range, 30% to 80%) of these neurosensory changesare permanent.101 Several articles have been written on thetreatment of neurosensory disturbances.7,128,151Implant MalpositionMany of the complications that arise during implant surgery can beattributed to the dental implant being placed in an undesired orunintended position. Malpositioning of dental implants is usuallythe result of poor treatment planning before surgery, lack ofsurgical skill, or poor communication between the implant surgeonand the restorative dentist. Optimal implant aesthetics and theavoidance of positional complications can be achieved by placingthe implant in a prosthetically driven manner.123,140 The implantshould be placed with reference to the three dimensions dictated bythe position of the final restoration and not by the availability ofbone.Angulation is another important determinant of implant positionthat affects outcome aesthetics. The ideal implant position entails anaccurate preparation, insertion, and placement into the alveolus in a4529 proper three-dimensional geometry according to apicocoronal,mesiodistal, and buccolingual parameters and implant angulationrelative to the final prosthetic restoration and gingival margins108,160(see Chapter 78).Apicocoronally, the implant should be placed so the platform isabout 3 mm apical to the gingival margin of the anticipatedrestoration.28 The implant position varies slightly from one implantsystem to another, depending on abutment design and spacerequirements. If the implant platform is placed too far coronally,there will not be sufficient room to develop a natural-lookingemergence profile, and the tooth may have a boxy, unaestheticappearance. If the platform is placed at or above the level of thegingival margin, metal collar or implant exposure can occur,yielding an unaesthetic result (Fig. 85.5). If the implant platform isplaced too far apically, a long transmucosal abutment will benecessary to restore the implant. This can lead to a deep pocket anddifficult hygiene access for the patient and clinician.FIG. 85.5 Clinical photograph of gingival recessionaround a maxillary anterior implant (left central incisor)resulting in exposure of the crown margin, the implantcollar, and several threads of the implant.The implant should be placed at a distance of 1.5 to 2 mm froman adjacent natural tooth and 2 to 3 mm from an adjacent implantto maintain an adequate biologic dimension.81 Similar to naturalteeth, violation of biologic width around an implant can lead to4530 bone loss.87 Implants that are placed too close to each other (Fig.85.6) or to natural teeth can be difficult to restore. Impressioncopings and impression-taking techniques must be modified.Improperly spaced implants invariably lead to chronicinflammation and peri-implantitis.57,181 Conversely, an implantplaced at an excessive distance from an adjacent tooth or implantmay require prosthetic compensation in the form of mesial or distalcantilevers, which can predispose the implant to biologic (i.e., boneloss) and mechanical (i.e., screw loosening,77 screw fracture,179 andimplant fracture149) complications and difficulties with hygiene.181FIG. 85.6 Radiograph of two mandibular anteriorimplants placed too close together (i.e., no proximalspace), resulting in implants that are impossible torestore.Ideally, an implant should be placed buccolingually so there is atleast 2 mm of bone circumferentially around it.172 Implant exposurethrough the lingual or buccal cortex can predispose an individual toabscess and suppuration.38 Implants that are placed too palatally orlingually require prosthetic compensation in the form of a buccalridge lap, which may be difficult for the patient to clean and can4531 lead to tissue inflammation.22To obtain ideal aesthetics, to avoid potential aestheticcomplications, and to correct bodily placement of the dentalimplant, it must be correctly angulated on insertion. In mostanterior cases, it is desirable to have the long axis of the implantdirected so it is emerging toward the cingulum. In the posteriorregion, the implant axis should be directed toward the central fossaor the stamp cusp of the opposing tooth. Implants that are placedwith mild to moderate misangulations can often be correctedprosthetically with implant abutments. Minor misangulations (i.e.,15 to 20 degrees) can be corrected with prefabricated or customizedangled abutments; moderate misangulations (i.e., 20 to 35 degrees)can usually be managed with customized UCLA-type abutments;and extreme errors in implant angulations (>35 degrees) may makean implant unrestorable and require it to be left submerged (i.e., asleeper) or be removed (Fig. 85.7).FIG. 85.7 Clinical photograph of a maxillary anteriorimplant (i.e., left central incisor) placed with an extremefacial angulation, resulting in an implant that emergesthrough the gingiva at a level that is more apical thanthe adjacent natural tooth gingival margins. (A)4532 Surgical exposure of the malpositioned implant. (B)Surgically removed implant. (C) Alveolar defectresulting from surgical removal of the malpositionedimplant.The ultimate complication of malpositioning is implant orinstrument invasion into vital structures. The most commonviolation of neighboring anatomy is placement of the dentalimplant into the adjacent tooth root. Surgical procedures used toprepare osteotomy sites and place implants adjacent to teeth caninjure them by directly cutting into the tooth structure or bydamaging nearby supporting tissues and nerves. Instrumentation(e.g., drills) directed at or near the adjacent tooth can injure theperiodontal ligament, tooth structure, and nerve of the tooth.Depending on the extent of the injury, the tooth can requireendodontic therapy or extraction.On insertion, dental implants follow the trajectory of theosteotomy prepared by the drill. Care must be taken whenpreparing the osteotomy to stay true to the planned path ofinsertion. Radiographs taken periodically during implant surgerywith a guide pin in the osteotomy site can greatly reduce thepotential for damaging adjacent teeth (see Fig. 76.15). Radiographicanalysis before implant surgery should include detection of curved,convergent, or dilacerated root structures of adjacent teeth that canlimit implant placement.Particular care must be taken when placing implants in themandible so as to not encroach on the inferior alveolar canal or themental foramen (see Chapter 58 for a description of the anatomy).Encroachment on the mandibular canal or mental foramen duringosteotomy or implant placement by direct contact or mechanicalcompression of bone can injure nerves and blood vessels.Paresthesia, hypoesthesia, hyperesthesia, dysesthesia, or anesthesiaof the lower lip, skin, mucosa, and teeth can result, as can arterial orvenous bleeding.78 The reported incidence of sensory disturbancesafter mandibular implant placement is 0% to 40%.18,104In the maxilla, care must be taken to avoid dental implantperforation into the maxillary sinus or nasal cavity. Displacement ofthe entire dental implant into the maxillary sinus cavity mayrequire a Caldwell-Luc procedure for retrieval. The online section4533 on Sinus Bone Augmentation provides further information aboutcomplications related to the maxillary sinus.The risks of surgery always exist, but the complications can beminimized by an understanding of the causes and with properdiagnosis and treatment planning. Three-dimensional imaging (i.e.,computed tomography [CT] and cone beam CT [CBCT]) providesthe surgeon with useful preoperative information for diagnosis andtreatment planning (see Chapter 76). Careful surgical exposure fordirect visualization and identification of the mental nerve areindicated. The surgeon should establish a zone of safety and keepinstrumentation and implants a safe margin (≥2 mm) away from thenerve.78 Key FactMalpositioned implants can be avoided by proper planning, goodcommunication, and meticulous surgical skills. Radiographs takenperiodically during implant surgery with guide pins in theosteotomy site can greatly reduce damage to adjacent teeth.Radiographic analysis before implant surgery should includedetection of curved, convergent, or dilacerated root structures ofadjacent teeth that can limit implant placement.Biologic ComplicationsBiologic complications involve pathology of the surrounding peri-implant hard and soft tissues. Frequently, soft tissue problems arean inflammatory response to bacterial accumulation aroundimplants. Bacteria can accumulate at the junction of an ill-fittingimplant–abutment or abutment–crown connection. Some of thehighly textured, macroscopically rough implant surfaces (e.g.,titanium plasma–sprayed [TPS] or hydroxyapatite [HA] coating)may also perpetuate the accumulation of bacteria on the implantsurface.Inflammation and Proliferation4534 Because inflammation of the peri-implant soft tissues is similar tothe inflammatory response in gingival and other periodontaltissues, the clinical appearance also is similar. Inflamed peri-implant tissues demonstrate the same erythema, edema, andswelling around teeth. Occasionally, the reaction of peri-implantsoft tissues to bacterial accumulation is profound and unusual, withdramatic inflammatory proliferation (Fig. 85.8). This type of lesionis somewhat characteristic around implants and indicates a loose-fitting implant-to-abutment connection or trapped excess cementthat remains buried within the soft tissue space (i.e., pocket).FIG. 85.8 Inflammatory proliferation caused by aloose-fitting connection between the abutment and theimplant. (Courtesy Dr. John Beumer, UCLA Maxillofacial Prosthetics, LosAngeles, CA.)The precipitating local factor ultimately becomes infected withbacterial pathogens, leading to mucosal hypertrophy orproliferation and possible abscess formation (Fig. 85.9). Correctionof the precipitating factors (e.g., loose connection, retained cement)can effectively resolve the lesion. Another type of lesion resultingfrom a loose abutment connection is a fistula (Fig. 85.10), andcorrecting the etiologic factor can quickly resolve it.4535 FIG. 85.9 (A) Clinical photograph of an abscesscaused by excess cement trapped within the softtissues. (B) Radiograph of an implant with a cementedcrown (same patient as in A). Notice the subgingivaldepth of the crown–abutment (cement line) junction,which is below the level of the adjacent interproximalbone and therefore impossible to adequately accesswith an explorer to remove the excess cement. (CourtesyDr. John Beumer, UCLA Maxillofacial Prosthetics, Los Angeles, CA.)FIG. 85.10 Fistula caused by a loose implant–abutment connection (i.e., maxillary left lateral incisor).4536 Dehiscence and RecessionDehiscence or recession of the peri-implant soft tissues occurs whensupport for the tissues is lacking or has been lost. Recession is acommon finding after implant restoration and should beanticipated, especially when soft tissues are thin and not wellsupported (Fig. 85.11). Improper implant positioning alsopredisposes peri-implant tissues to recession. Placement orangulation of the implant too far buccally causes the buccal plate toresorb, resulting in greater recession.171FIG. 85.11 (A) Clinical photograph of a single-toothimplant crown (maxillary right central) with moderaterecession that occurred 1 year after the finalrestoration. In this case, recession most likely occurredbecause the labial bone around this wide-diameterimplant was very thin or nonexistent. (B) Radiograph ofa wide-diameter (6-mm) implant supporting a maxillarycentral incisor crown (same patient as in A).Another factor is the thickness of the buccal plate of bone. Sprayand colleagues172 recommended a buccal bone thickness of 2 mm orgreater to support the buccal soft tissue. If it is insufficient,preoperative or simultaneous site development using guided bone4537 regeneration is indicated. Recession is a problem that is particularlydisconcerting in anterior aesthetic areas. Patients with a high smileline or high aesthetic demands consider recession a failure (Fig.85.12).FIG. 85.12 Poor aesthetics resulting from gingivalrecession and exposure of the crown margins, implantcollars, and threads of several maxillary andmandibular implants supporting full-arch, fixed partialdentures. Notice the thin labial tissues and erythema,especially around the mandibular implant sites.The anatomy and soft tissue support around implants aredifferent from those around teeth. Periodontal tissues have theadvantage of soft tissue support supplied by circumferential andtransseptal connective tissue fibers that insert into the cementum ata level that is more coronal than the supporting bone. In theabsence of inflammation, these fibers support periodontal softtissues far above the level of crestal bone. As a result, gingivalmargins and interdental papillae are supported and maintainedhigher around teeth than around implants, even when theperiodontal tissues are very thin.Peri-implant soft tissues, however, depend entirely on thesurrounding bone for support. Soft tissue thickness accounts forsome soft tissue height, but there are no supracrestal insertingconnective tissue fibers to aid the soft tissue support around animplant. The soft tissue height around implants is typically limited4538 to about 3 or 4 mm, and bone loss around implants often leads torecession. Flash BackThe peri-implant soft tissue seal is weaker than the periodontal softtissue seal. The soft tissue seal around implants depends on tissuethickness and a long junctional epithelial attachment withhemidesmosomes. It is inferior to the periodontal attachmentaround natural teeth because it lacks the inserting connective tissuefibers (i.e., Sharpey fibers) of the periodontium. Periodontalpapillae and gingival margins are also supported at a highersupracrestal level compared with peri-implant soft tissues.Periodontal soft tissues are supported by circumferential andtransseptal connective tissue fibers that insert into the cementum ata level that is more coronal than the supporting bone.Peri-Implantitis and Bone LossPeri-implantitis is an inflammatory process that affects the tissuesaround an osseointegrated implant and results in the loss ofsupporting bone.129 The reported prevalence of peri-implantitisvaries from less than 7% to 37% of implants.106 The variation can beattributed to differences in studied populations, length of follow-uptime, implant variables, and the criteria used to define peri-implantitis.109,158 Two systematic reviews concluded that peri-implantitis affected 10% of implants and 20% of patients during the5 to 10 years after placement.11,131A classification for early, moderate, and advanced peri-implantitis based on the degree of bone loss was proposed toimprove communication when describing prevalence andtreatment.71 Soft tissue measurements using manual or automatedprobes have been suggested to diagnose a compromised implantsite.71a Although some reports state that probing is contraindicated,careful monitoring of probing depth over time seems useful indetecting changes of the peri-implant tissue.44,148,174,175 Standardizedradiographic techniques, with or without computerized analysis,have been useful in evaluating peri-implant bone levels.4,25,29,99,1484539 Periodic evaluation of tissue appearance, probing depth changes,and radiographic assessment are the best means of detectingchanges in bone support.Clinicians should monitor the surrounding tissues for signs ofperi-implant disease by observing changes in probing depth andradiographic evidence of bone destruction, suppuration, calculusbuildup, swelling, color changes, and bleeding.130,136 Peri-implantitiscan be perpetuated by bacterial infection that has contaminated arough (e.g., TPS- or HA-coated) implant surface and by excessivebiomechanical forces.188,189 The classic trough-type defect is typicallyassociated with peri-implantitis (Fig. 85.13). In cases with severelyreduced bone support extending into the apical half of the implant(Fig. 85.14) or in cases demonstrating mobility, implant removalshould be considered.6,135FIG. 85.13 Moderately advanced bone loss around animplant with the typical circumferential trough type ofbony defect. (From Garg AK: Implant dentistry: a practical approach, ed 2,Mosby, St. Louis, 2010.)4540 FIG. 85.14 Severe horizontal and vertical bone lossaround several mandibular implants.The number and distribution of implants and the occlusalrelationships influence the biomechanical forces applied toimplants.147,153 A review by Lindhe and Meyle from the ConsensusReport of the Sixth European Workshop on Periodontologyconcluded that risk indicators for peri-implantitis included (1) poororal hygiene, (2) a history of periodontitis, (3) diabetes, (4) cigarettesmoking, (5) alcohol consumption, and (6) implant surface.117 Riskfactors 1 to 4 have been recognized and reported in the literature.107The report suggests that although data for risk factors 5 and 6 arelimited, they appear to be relevant to peri-implantitis.117 One studyfound little evidence to support smoking as a risk factor for peri-implantitis.167 Another proposed risk factor involves individualgenetic polymorphisms.33,112 More research is needed to study therelation of this risk factor to the development of peri-implantitis.Other risk factors, including excess and retained cement, havebeen implicated in peri-implantitis. One article said that excessdental cement was associated with signs of peri-implant disease in81% of cases evaluated using a dental endoscope.187 The radiopacityof some commonly used cements affects their detectability.183 Thisemphasizes the importance of proper cementation, use of screw-retained rather than cemented restorations when possible, andcareful clinical examination after final crown cementation onimplants.Other proposed peri-implantitis predisposing factors include the4541 presence of aggressive bacteria, excessive mechanical stress, andcorrosion. Each was documented as a factor that could actsynergistically with biofilm or existing peri-implantitis to worsenthe condition.133Nine systematic reviewsc concluded that no predicable method oftreatment for peri-implantitis could be recommended. However, aclinical study of 170 consecutively treated implants with peri-implantitis using a regenerative protocol reported a more than 98%success rate.70Implant Loss or FailureImplant loss or failure is considered relative to the time ofplacement or restoration. Early implant failures occur beforeimplant restoration. Late implant failures occur after the implanthas been restored. When an implant fails before restoration, itprobably did not achieve osseointegration, or the integration wasweak or jeopardized by infection, movement, or impaired woundhealing (Fig. 85.15). Late implant failures occur after prosthesisinstallation for a variety of reasons, including infection and implantoverload (Fig. 85.16). In a review of the literature to evaluatebiologic causes for implant failure, Esposito and colleagues63 foundthat infections, impaired healing, and overload were the mostimportant contributing factors. Two systematic reviews of theliterature concluded that a single dose of preoperative antibiotictherapy could decrease the failure rate of dental implants.60,1684542 FIG. 85.15 (A) Radiograph of an early failed implantcaused by lack of osseointegration. In addition to thecrestal bone loss, notice the radiolucency along thesides of the implant. (B) Photograph of the failed(nonintegrated) implant (shown in A) that was easilyremoved along with surrounding connective tissue.4543 FIG. 85.16 A four-unit fixed partial denture in theposterior maxilla was supported by only two implants.(A) Clinical photograph of implant abutments in theposterior maxilla. (B) Radiograph taken 30 months4544 after restoration. Notice the bone loss around the distalimplant. (C) Failed distal implant attached to a failedprosthesis. The biologic failure of one (posterior)implant resulted in a long-span cantilever extensionfrom the other (anterior) implant that ultimately led toits mechanical failure (i.e., abutment screw fracture).(Courtesy Dr. John Beumer, UCLA Maxillofacial Prosthetics, Los Angeles, CA.)A review of the reasons for failure of oral implants concludedthat several situations increased the failure rate: a low insertiontorque on immediately placed or early loaded implants,inexperienced surgeons, implants inserted in the maxilla andposterior regions of the jaws, implants placed in heavy smokers,implant insertion in poor-quality (i.e., type III and IV) bone, lack ofinitial stability, and prosthetic rehabilitation with implant-supported overdentures.39The risk of implant failure varies among patients, but patterns ofloss tend to cluster. A second attempt at dental implant placementshould be approached cautiously if placing the implant in the samesite as the one that previously failed. It is often challenging toachieve adequate diameter, length, and stability of replacementimplants due to the residual defect created by removal of the failedimplant. In 2007, Grossmann and Levin reported an overall survivalrate of 71% for dental implants that were placed in sites ofpreviously failed single implants. In that study, all of the originalimplants failed during the early healing phase (mean of 2.3 to 3.2months after placement).80 In a 2008 study, Machtei andcolleagues119 reported an overall survival rate of 83.5% for thesecond attempt at dental implants. They concluded that replacingfailed implants resulted in a lower survival rate compared with thatfor implants placed in pristine sites. This could not be associatedwith conventional implant- or patient-related factors. Theysuggested that a site-specific negative effect might be associatedwith this phenomenon.119In 2011, Machtei and coworkers reported a lower survival rate(60%) for third reimplanted sites.118 This outcome represents afurther diminished prognosis compared with implants in originalsites or after a second attempt.43 Replacement of a failed implantposes a challenge in achieving osseointegration in a healed bone4545 site and can reduce the implant survival rate.118Complications Related toAugmentation ProceduresA common problem encountered in implant dentistry is insufficientbone quantity to allow implant placement according to standardprocedures. Deficiencies in alveolar bone result fromdevelopmental defects, periodontal disease, tooth loss, ortrauma.9,32,164 For most cases with alveolar ridge resorption, boneregeneration procedures are required to correct the defects beforeor simultaneously with implant placement.The success of bone augmentation procedures has been assessedby experienced clinicians in several workshops.5,38,66,83,84 Onesystematic review of the literature (2003 Workshop onContemporary Science in Clinical Periodontics) found that survivalrates of dental implants in augmented bone achieved a high level ofpredictability and showed that these rates were similar to those forimplants placed in natural bone.66 However, another systematicreview of the literature (2008 Consensus Report of the SixthEuropean Workshop on Periodontology) concluded that boneaugmentation procedures could fail and that implants placed inthese areas did not enjoy the high long-term survival rates of dentalimplants placed in pristine sites.182 Research is needed to answerquestions concerning (1) the long-term performance of dentalimplants placed in augmented bone, (2) the clinical performance ofdental implants placed in augmented or pristine sites, and (3) theclinical benefits of bone augmentation with respect to alternativetreatments.The procedures most often used to regenerate bone includeautogenous bone harvesting and grafting, guided boneregeneration, and sinus bone augmentation (see Chapters 79 and80). The following is a brief review of the most commoncomplications related to these three augmentation procedures.Autogenous Bone Harvesting and Grafting4546 Histologically and biologically, autogenous bone has beenconsidered the gold standard for osseous reconstruction. Boneblock grafts of autogenous bone from extraoral and intraoralsources are predictable sources for reconstruction of defective oratrophic alveolar ridges.127 Complications can occur at the donor orrecipient sites.The most common extraoral donor sites include the ilium andtibia. Complications related to extraoral donor sites are beyond thescope of this chapter. The most common intraoral donor sitesinclude the mandibular symphysis, mandibular ramus, andmaxillary tuberosity. Although each donor area has specificassociated complications, the most common complications ofintraoral autogenous harvesting and grafting concern donor tissuefrom the mandibular symphysis.The ramus donor site is associated with a much lower incidenceof complications compared with the symphysis area.82,126 Potentialcomplications associated with surgical harvesting of bone from theramus include damage to the inferior alveolar nerve and trismusafter surgery. Damage to the buccal nerve, although rare, has beenreported. Surgical harvesting of bone from the mandibularsymphysis region is associated with a higher incidence of alteredneurosensory disturbances to the mandibular anterior teeth andsoft tissues of the chin area. The incidence of mental nerveparesthesia after symphysis grafts is as high as 43%.146 Manyparesthesias are temporary.Fracture of the mandible has been reported after bone graftharvesting from the symphysis.42 Many complications can beavoided by proper surgical technique, good planning, and anexperienced operator.Recipient site complications include wound dehiscence, flapnecrosis, graft exposure, graft contamination, infection, andproblems with bone graft incorporation and resorption. Proper flapreflection, intimate fixation of the graft, and flap coverage withouttension can avoid many postoperative complications. Bone graftmaterial, including barrier membranes, should be immobilized (i.e.,fixated). Provisional restorations should be adjusted to preventpressure over grafted areas. Block grafts and other augmentationprocedures require experience in handling hard and soft tissues and4547 a clinician who is prepared to recognize and treat complicationswhen they arise.53,150Guided Bone RegenerationGuided bone regeneration (GBR) is a procedure that uses a barriermembrane to isolate an area for bone growth. The technique hasbeen well documented for horizontal and limited vertical ridgeaugmentation27,44,100 (see Chapter 79). The most commoncomplication associated with GBR is premature exposure of thebarrier membrane and necrosis of the overlying flap (eFig. 85.1).Exposure rates of expanded polytetrafluoroethylene (ePTFE)membranes during various GBR procedures range from 41% whenthe technique was first introduced in the early 1990s for horizontalridge augmentation27 to 12.5% after surgical techniques improvedand clinicians became more familiar with handling the material.169EFIG. 85.1 Clinical view of flap necrosis over areatreated with a guided bone regeneration procedure.After it is exposed to the oral environment, the membranebecomes colonized with bacteria in 3 to 4 weeks, and the potentialfor bone regeneration under the membrane is limited to an area thatis at least 2 to 3 mm from the contaminated surface.20,170 Topicalapplication of chlorhexidine to the exposed membrane has beenadvocated as a method of reducing the amount of bacteria, but it4548 does not solve the problem, and removal of the exposed membraneis necessary.Other complications associated with GBR procedures include softtissue or bone graft infection, failure to regenerate adequate bonevolume, and mucogingival problems, including loss of keratinizedtissue and decrease in the vestibule.27 Most of these complicationsare related to insufficient soft tissue healing after tooth extraction,inadequate flap design, movement of the membrane or graft causedby transmucosal loading and improper provisionalization, flapsuturing under tension, poor surgical technique, contamination ofthe membrane or surgical site, compromise of the vascular supply,and flap advancement for graft coverage that reduces thekeratinized tissue and vestibular depth. To prevent complicationsassociated with GBR procedures, proper surgical technique shouldbe employed.69,92,111,124Sinus Bone AugmentationLateral Window Sinus LiftThe lateral window sinus lift and bone augmentation procedure hasbeen well documented and evaluated in three systematicreviews.5,48,185 Although survival rates of implants placed in sinus-grafted areas have been high (95%), there are intraoperative andpostoperative complications associated with this procedure.The most common intraoperative complications include bleedingand perforation of the schneiderian membrane. Bleeding usuallyoccurs when the vascular supply to the lateral wall of the sinus issevered or damaged.55 In most cases, if the patient does not have anunderlying bleeding problem and is not taking anticoagulants, thebleeding is usually minor and relatively easy to control with localmeasures. Perforation of the schneiderian membrane has anincidence that varies from 11%190 to 56%,103 with most cliniciansreporting an incidence of 20% to 30%.Minor membrane perforations can be treated by reflection of themembrane that folds on itself, whereas medium or large membraneperforations require the use of an absorbable membrane placedover the perforation to patch the opening (eFig. 85.2). Very largemembrane tears may be too big to repair intraoperatively and4549 require aborting the procedure. Careful surgical technique and theuse of newer instruments (e.g., piezoelectric surgery) havesignificantly reduced this complication186 (see Chapter 83).EFIG. 85.2 (A) Large perforation of the schneiderianmembrane during a sinus elevation procedure. (B)Attempt to close or reduce the size of the perforationwith resorbable sutures. (C) Use of resorbable barriermembranes to cover the perforation.The most common, although still infrequent, postoperativecomplication associated with sinus bone augmentation isinfection.17,103,127 The incidence of infection varies from 2% to 5.6%.Careful surgical techniques, adherence to sterility, and judicioususe of antibiotics can minimize the risk of postoperative infections.Some infections resolve with antibiotic treatment alone, whereasothers require surgical debridement of the infected area.Consultation with or referral to a specialist may be indicated forpersistent infections.The Sinus Consensus Conference of 1996 was revisited in 2016and reaffirmed the validity of the sinus graft. It concluded thatnoninductive materials with slow resorption might be superior in4550 forming and maintaining bone compared with inductive materials.The consensus also questioned the need for biologic enhancementwith growth factors and morphogenic proteins.94Crestal (Osteotome) Sinus LiftAnother method of sinus elevation and bone augmentationinvolves the use of osteotomes. This technique is indicated whenthere is enough native bone to stabilize the implant and a minimalneed for sinus floor elevation. Bone is added through the crestalosteotomy by means of osteotomes and a mallet, the floor of thesinus is fractured, and the schneiderian membrane is lifted by thebone graft (see Chapter 80).This method is thought to be a relatively less invasive techniqueof great utility in certain patients. However, it has been associatedwith the complication of benign paroxysmal positional vertigo(BPPV),143 which is a consequence of working the implant bed withosteotomes. During the osteotomy preparation and sinus floorelevation using the osteotome technique, the trauma induced bypercussion with the surgical hammer, along with hyperextension ofthe neck during the operation, can displace otoliths in the inner earand induce BPPV. It has been reported that 1.25% of the patientstreated suffered vertigo when trying to sit up immediately aftersurgery and were diagnosed with BPPV. Because implant treatmentis increasingly being carried out on older patients and because ofthe widespread use of bone expansion technique with osteotomes,the incidence of BPPV can be expected to increase.144 In suspectedcases of BPPV, the patient should be informed about the conditionand then referred to an otoneurologic specialist to determine whichsemicircular canal is affected and to carry out the appropriateotolithic reinstatement maneuver.To prevent this complication, care should be taken when usingthe osteotome technique. The application of manual force instead ofhammer percussion and the use of a surgical fraise in combinationwith osteotomes can minimize the trauma to the craniofacial area,especially in older patients. Many alternative methods for a crestalapproach to sinus elevation and bone augmentation have beendeveloped, including inflatable balloon techniques, selective drillsystems, and piezoelectric surgical instruments that cut bone while4551 leaving the schneiderian membrane intact (see Chapters 80 and 83).These newer methods should be considered to avoid BPPV. Theeffectiveness of the procedure can be affected by the level ofexperience in implant dentistry.68Complications Related to Placementand Loading ProtocolsThe traditional implant placement protocol required a healededentulous ridge into which implants were placed and allowed tointegrate for 3 to 6 months without occlusal loading. In contrast tothe early standards, some current protocols advocate dramaticallydifferent approaches, including (1) implant placement immediatelyafter tooth extraction, (2) implant loading immediately afterplacement, and (3) flapless implant placement surgery. Each ofthese approaches has distinct advantages but also have specificrisks of complications.Immediate Implant PlacementImmediate implant placement is a protocol that places an implantin an extraction socket immediately after tooth removal and socketdebridement. This procedure, which was originally described bySchulte and associates165 and Lazzara,114 has survival rates similar tothose of implants placed into healed ridges,36,120 with long-termsurvival rates of approximately 94%.184 The advantages of thisprotocol include fewer surgical procedures, decreased morbidity,decreased time of treatment, decreased cost, and decreased softtissue healing time by avoiding flap reflection and advancement.166However, as with any surgical protocol, complications are possible,and specific complications are associated with immediate implantplacement, including implant failure, poor implant position, boneloss, recession of the peri-implant marginal soft tissues, andcompromised aesthetic outcomes.After tooth extraction, there may be a compromised socket as aresult of the predisposing pathology (i.e., periodontal, endodontic,or root fracture) of the hopeless tooth. Proper implant position may4552 be difficult to establish when the socket walls are missing ordeficient. For example, the implant osteotomy for extractedmaxillary anterior teeth should be made on the lingual incline of thelingual wall of the socket. The burs often slip buccally, causing theosteotomy to be made too far buccally or at an undesiredangulation. Careful use of a surgical stent, round bur, sharp initialbur, or side-cutting bur can avoid slipping and improve theaccuracy of implant site preparation. Although success rates ofimmediately placed implants are excellent, failure to attain primarystability in native bone apical or lateral to the socket can increasefailure rates. Inability to debride or incomplete debridement of aninfected or compromised socket (e.g., tooth with an apicoectomy)can increase the risk of failure.116Buccal plate resorption and gingival margin recession afterimplant placement can expose the implant surface after integrationof the implant (see Figs. 85.5 and 85.11). This can compromise theaesthetic results or necessitate hard and soft tissue augmentationprocedures to improve the aesthetic outcome.103 A published caseseries documented this problem for immediate implant placementin extraction sites without flap elevation.65 The risk of complicationscan be decreased with proper case selection, proper procedures,and experience in using this protocol. Until clinicians have theknowledge and experience to use an immediate implant placementprotocol, they should avoid using it in the aesthetic zone.Immediate Loading After Implant PlacementBränemark established the concept and predictability ofosseointegrated dental implants based on a requirement for anunloaded healing period of 3 to 6 months.26 The original protocolpurported that premature loading would cause micromotion of thedental implant, leading to fibrous encapsulation and implantfailure. However, several studies in the literature showed thatimmediately loaded dental implants can have success rates similarto those of conventionally loaded dental implants.d Whetherrestoring a single tooth or a complete dentition, there are manyadvantages to early or immediate loading, although theseadvantages may come with increased risks of complications. The4553 most significant complications are failure to achieve primarystability and implant failure.Studies have shown that using longer and wider implants canproduce increased success rates when immediately loading thedental implant.162,163 When placing multiple implants in anedentulous area, the implants should be placed in a fashion thatmaximizes the anterior-to-posterior spread, leading to a greaterdistribution of forces over a wider area and a reduction incantilever forces. Implants placed around the arch can lead to cross-arch stabilization, which can decrease the individual force andmotion experienced by any individual implant.156,177 For the fullyedentulous case, a minimum of four to six implants of adequate sizeand good stability that are properly spaced throughout the ridge isrecommended to improve success with immediate loading.46Mandibular cases may require fewer implants than maxillary casesbecause of greater bone density, especially in the interforaminalregion. If the opposing arch is restored with a removable prosthesis,fewer implants may be needed to immediately support arestoration because of a decreased opposing occlusal force.Other factors associated with increased failure rates ofimmediately loaded implants are implant surface and implantdesign. Lower success rates with immediately loaded implants havebeen reported with smooth (i.e., turned or machined) surfaceimplants, especially in cases of single-tooth, immediately loadedrestorations.90,154,161 The macrodesign features of an implant (e.g.,threaded vs. cylindrical) can affect initial stability and success ratesin immediately loaded cases.35,102 Some newer macrothread designscan overcome the transient loss of stability in the early postinsertionhealing phase.121 Two studies concluded that bruxism, clenching,and sites in the posterior maxilla can reduce the likelihood ofimplant success under an immediate loading protocol.21,74Complications of immediately loaded implants can arise from apoorly constructed or inserted restoration despite all things goingwell with surgical placement. Extreme care must be taken toachieve a passive fit of the restoration and to eliminate nonworkingor balancing contacts on the restoration. In full-arch cases that areimmediately loaded, the restoration must be designed to withstandthe direct occlusal force. This can be accomplished by a rigid4554 connection and by splinting the implants together in cross-archfashion. Loosening or unseating of the provisional restorationusually indicates mismanagement of occlusal forces and can be anearly predictor of failure.Immediately loading dental implants is a technique that offersmany advantages but can also increase the incidence ofcomplications and failure. This technique should be performed onlyby an experienced operator who is prepared and informed.Controlling micromotion after loading is paramount to success.Meticulous case selection, which incorporates stabilizing the cross-arch, controlling occlusal overload, minimizing cantilevers, andincreasing the anterior-posterior distribution of implant placement,can significantly increase the success rate of loading dental implantsimmediately after placement.Implant Placement Using a FlaplessApproachIn flapless implant surgery, the dental implant is placed withoutelevation of the epithelium, connective tissue, and periosteumcovering the alveolar bone. It is performed by drilling through thesoft tissue with twist drills or by first removing a small circularsection of the soft tissue (eFig. 85.3A), preparing the osteotomy, andplacing the implant (see eFig. 85.3B) without reflecting a full-thickness flap.14555 EFIG. 85.3 (A) Removal of a small circular section oftissue before osteotomy. (B) Dental implant in place.Flapless surgery has been successful and has many advantagesbecause it is minimally invasive.30,31 The benefits of flapless surgeryinclude a decrease in associated surgical morbidity, includingpostoperative pain, ecchymosis, and swelling, and a reduction insurgical time and intraoperative bleeding.143 Studies show thatwhen a full-thickness mucoperiosteal flap is raised, there is loss ofbone volume,75 whereas a flapless approach results in less boneresorption.The lack of operator visualization of the alveolus when preparingosteotomies and placing implants can increase the potential forcomplications. The most common problems associated with flaplesssurgery are loss of keratinized tissue when excising the crestal circleof soft tissue and improper positioning of the dental implant in thebone resulting from a lack of direct vision. Improper positioningcan result in a dehiscence or fenestration defect (eFig. 85.4) ordamage to adjacent vital structures.4556 EFIG. 85.4 (A) Preoperative clinical view of a singlemissing tooth, #5. There appears to be a good alveolarridge shape with adequate keratinized gingiva. (B)Radiograph shows good bone height and mesial-distalspace available for a single tooth implant. (C) Occlusalview of the circular punch incision used to access boneand prepare the implant osteotomy. (D) Full-flapreflection (after noticing a suspicious protrusion in thelabial vestibule) revealed an implant protruding fromthe alveolar bone on the buccal surface.An anatomically correct, computer-generated surgical guidefabricated from a three-dimensional CT or CBCT scan isrecommended when performing flapless surgery to reducepotential implant malposition complications. Several systems(Nobelguide, Materialize SurgiGuide) can generate a precisesurgical guide with metal sleeves of the exact dimensions that candirect the implant into the proper position (eFig. 85.5). These guidestypically are used in fully edentulous arches and have fixationscrews that keep them in place. When using a flapless approach,before initiating the osteotomy, the operator should sound the softtissue with a periodontal probe to ascertain the tissue thickness and4557 account for this dimension when determining the final position ofthe implant platform in the apical–coronal dimension (eFig. 85.6).4558 EFIG. 85.5 (A) Clinical view of a computer-generatedsurgical guide shows metal drill sleeves in the positionof the planned implants. (B) Clinical buccal view of theimplant mounts emerging from gingival tissue showsaccurate placement of four implants in the posteriormaxilla using the computer-generated surgical guide.(C) Photograph of three surgical guides with increasingsleeve diameter that are used in the sequence ofimplant site preparation. (D) Radiographic view of fourimplants placed in the planned position using thecomputer-generated surgical guide.EFIG. 85.6 Use of a periodontal probe to sound thebone and measure the soft tissue thickness over thebone in the proposed implant site.4559 A common complication is placement of implants apical to thecrestal bone because it is difficult, even with a punch, to visualizethe alveolar bony crest in relation to the platform of the implant. Ifthis occurs, it is difficult to fully seat the abutment. The relationshipbetween implant and abutment connection must be verified byperiapical radiographs. If bone prevents abutment seating, theimplant must be backed out until it is at the crest, or the bone mustbe removed with a profile drill. If a fenestration occurs whenplacing the dental implant, full-flap reflection is required, and aGBR procedure should be performed to augment the bone andcover the fenestration.Although flapless implant surgery has many beneficial features,it is a technique-sensitive procedure that requires surgicalexperience, an accurate surgical guide, and knowledge of theanatomy surrounding the planned implant site.Prosthetic or MechanicalComplicationsProsthetic or mechanical complications occur when the strength ofmaterials is no longer able to resist the forces that are being applied.As materials fatigue, they begin to stretch and bend. Ultimately,depending on the applied forces, they will fracture. Materialfailures lead to prosthetic complications such as loose, broken, andfailed restorations.Screw Loosening and FractureScrew loosening has occurred frequently in screw-retained FPDs.Screw-retained single crowns attached to externally hexed implants(i.e., those with narrow- or standard-diameter restorative interfaceconnection surfaces) are particularly prone to this type ofmechanical complication. Screw loosening has been reported for 6%to 49% of cases at the first annual checkup.91,132 Screw loosening wasa more prevalent problem with earlier designs. For example,abutment screws were previously made with titanium, which didnot offer the clamping forces of current materials. Newer abutment4560 designs and improved abutment screws enable an increasedclamping force to be achieved without excessive torque, which hashelped to reduce the rate of screw loosening.Abutment or prosthesis screw loosening is often corrected byretightening the screws, but if screws continue to be stretched overtime, they become fatigued and eventually fracture. This problem isevident in the patient with a loose single crown. In the patient witha prosthesis retained by multiple implants, the ability to detect aloose screw is greatly diminished, and the problem may gounnoticed until additional screws stretch, fatigue, and fracture. Ineither case, the biomechanical support (and resistance) for therestoration must be evaluated and, if possible, changed to preventrecurrence of the problem.Implant FractureThe ultimate mechanical failure is implant fracture because itresults in loss of the implant and possibly of the prosthesis (Fig.85.17). Removal of a fractured implant creates a large osseousdefect. Factors such as fatigue of implant materials (Fig. 85.18) andweakness in prosthetic design or dimension are the usual causes ofimplant fractures.4,16 Balshi16 listed three categories of causes thatmay explain implant fractures: (1) design and material, (2)nonpassive fit of the prosthetic framework, and (3) physiologic orbiomechanical overload. Patients with bruxism seem to be at higherrisk for these events and therefore need to be screened, informed,and treated accordingly.15,16 These patients should be fitted withocclusal guards in conjunction with placement of the finalprostheses.4561 FIG. 85.17 (A) Radiograph of a fractured standard-diameter implant used to support a molar-sized singlecrown in the posterior mandible. (B) Crown andcoronal portion of the implant (same as shown in A)that fractured between the third and fourth threads.FIG. 85.18 The implant fractured at the internalconnection collar. Fracture was caused by rotationalforces applied to the implant at the time of placementinto dense bone and was likely the result of combinedmaterial weakness and density of the prepared site.Fracture of Restorative MaterialsFracture or failure of materials used for implant-retainedrestorations can be a significant problem. This is particularly truefor veneers (i.e., acrylic, composite, or ceramic) that are attached to4562 superstructures (Fig. 85.19).FIG. 85.19 Fractured porcelain from incisal edges ofan implant-supported fixed partial denture.Aesthetic and Phonetic ComplicationsAesthetic ComplicationsThe challenge of modern implant dentistry is achieving an aestheticand functional implant restoration. Harmonious tooth shape andsize and ideal soft tissue contours are key factors for successfulaesthetic outcomes.108Aesthetic complications arise when patient expectations are notmet. Patients' degree of satisfaction with the aesthetic outcome ofimplant prostheses varies. The risk of aesthetic complications isincreased for patients with high aesthetic expectations andsuboptimal patient-related factors such as a high smile line, thinperiodontal soft tissues, or inadequate bone quantity and quality. Inaddition to the appearance of the final restoration, factors such as apatient's perception and desires determine the acceptance of theresults. Aesthetic complications can result from poor implantposition, deficiencies in the existing anatomy of edentulous sitesthat were reconstructed with implants, and prosthetic-relatedfactors such as color mismatch.14Important prerequisites for achieving optimal gingival tissuecontour are sufficient peri-implant bone to support the soft tissues4563 and a sufficient zone of keratinized tissue. Soft and hard tissuedefects can be treated by a variety of augmentation procedures.Implant placement in the aesthetic zone requires precise three-dimensional tissue reconstruction and ideal implant placement.81,160This reconstructive procedure enables the restorative dentist todevelop a natural emergence profile of the implant crown. If theamount of available bone does not allow for ideal implantplacement and the implant is positioned too far apically or buccallyor in the proximal space, an unaesthetic emergence profile canresult (Fig. 85.20).4564 FIG. 85.20 Poor implant position makes it impossibleto correct the problem with an aesthetic, natural-appearing restoration. (A) Anterior view with theremovable partial dentures inserted. (B) Anterior viewwithout the removable partial dentures. Notice the highlevel of implant cover screw/head exposure (maxillaryright lateral incisor) that is significantly apical to the4565 level of the adjacent natural tooth (cuspid) gingivalmargin. (C) Occlusal view of the same patient. Noticethe labial projection of the same implant (maxillary rightlateral incisor) and the palatal position of the implant inthe premolar area. Any attempt to restore the anteriorimplants would not be aesthetically acceptable.If crown contours and dimensions are not ideal or gingivalharmony around the implant restoration is unaesthetic, the patientmay consider the implants or restorations to be failures because theoutcome does not represent a natural appearance (Fig. 85.21).Gingiva-colored materials used to replace lost gingival anatomyoffer an alternative to surgical augmentation in patients undergoingimplant therapy (Fig. 85.22). These restorations provide numerousadvantages over conventional restorations, including improved lipsupport, masking of interproximal spaces, and restoration ofgingival symmetry in selected cases.85FIG. 85.21 High gingival margin on single-tooth implantcrown in the maxillary lateral incisor position, showingthe discrepancy between gingival margin levels of theimplant and the adjacent natural teeth.4566 FIG. 85.22 Pink porcelain was used on an implant-supported fixed restoration to mask the high gingivalmargin and long implant crowns resulting from anuncorrected alveolar ridge defect.If the patient is truly dissatisfied with the aesthetic result andthere is a problem with the position of the implants that can becorrected (i.e., the patient's expectations are reasonable), theimplants can be removed. The case can be reevaluated and possiblyretreated. However, the clinician should consider prostheticsolutions before implant removal. Using angulated abutments,superstructures, or gingiva-colored materials, or submerging theimplant with a conventional fixed partial denture may result in anacceptable aesthetic result, avoiding multiple operations to rebuildhard and soft tissues if an integrated implant is removed.Careful patient evaluation and treatment planning with a solidunderstanding of and appreciation for the predictability andlimitations of implant procedures can minimize aestheticcomplications. Patients with a high smile line, high aestheticdemands, thin periodontium, or lack of hard and soft tissue supportin the anterior aesthetic region should be treated only afterextensive interdisciplinary treatment planning by experiencedclinicians. Key FactAesthetic complications arise when a patient's expectations are notmet. Satisfaction with the aesthetic outcome varies tremendously4567 among patients, and the increased risk of aesthetic complicationscorrelates with high aesthetic expectations and less than optimalpatient-related factors, such as a high smile line, thin periodontalsoft tissues, or inadequate bone quantity and quality. Risk factorsshould be carefully evaluated and discussed with the patientbefore initiating therapy, and the ability to meet the patient'sexpectations should be carefully considered.Phonetic ProblemsImplant prostheses that are fabricated with unusual palatalcontours (i.e., restricted or narrow palatal space) or that have spacesunder and around the superstructure can create phonetic problemsfor the patient. This is particularly problematic when full-arch,implant-supported, fixed restorations are fabricated for patientswho have a severely atrophied maxilla. Horizontal bone loss in thepremaxilla often causes palatal positioning of the dental implants,resulting in the prosthesis covering the incisive papilla region.Because some sounds are formed when the tip of the tongue lightlytouches the palate at the incisive papilla region, covering this areacan interfere with proper enunciation. Titanium-framed fullrestorations allow a thinner bulk of material in this region and canminimize phonetic complications.These complications are exacerbated when using an immediatefixed provisional restoration. Phonetic problems can be common infull-denture cases. However, with dentures, the clinician can figureout many of the speech issues in wax before the final restoration,making it easier to focus on the specific problem area. Ideal toothsetup and multiple adjustments are needed to minimize phoneticproblems. These patients are probably best served with an implant-assisted maxillary overdenture because the design facilitatesreplacement of missing alveolar structure and avoids creatingspaces that allow air to escape during speech.ConclusionsAlthough implants offer a highly predictable treatment option forthe replacement of single and multiple missing teeth, surgical,4568 biologic, mechanical, prosthetic, and aesthetic complications canoccur. Careful diagnosis and treatment planning with the use ofdiagnostic imaging, surgical guides, meticulous techniques, andadherence to proven principles can prevent many of the problemsdiscussed in this chapter.A thorough understanding of anatomy, biology, and woundhealing can reduce the incidence of complications. There is nosubstitute for good training, knowledge, and clinical experience.The clinician who places or restores implants must be wellprepared to diagnose, prevent, and manage complications. Case Scenario 85.1Patient:53-year-old maleChief Complaint:“I want implants to replace my teeth.”Background Information:The patient lost most of his posterior teeth more than 10 years agodue to periodontal disease. He has an upper partial denture butdoes not wear it. He has diabetes that is controlled with diet andoral medication (metformin) and hypertension controlled withmedication (lisinopril). He has smoked 1 to 1.5 packs of cigarettesper day for the past 30 years.Current Findings:The examination reveals generalized probing pocket depths of 2 to4 mm with localized depths of 5 to 6 mm. There is generalized mildto moderate plaque (i.e., biofilm), minimal gingival recession, andslight marginal gingival erythema. He is missing all maxillarymolars and the mandibular third molars. Radiographicexamination reveals pneumatized sinuses and loose trabecularbone in the posterior maxilla.CASE-BASED QUESTION SOLUTION AND EXPLANATION1. Is this patient a candidate forimplant replacement of hisAnswer: BExplanation: This patient has several risk factors that may4569 maxillary posterior dentition?A. Yes, he is an idealcandidate.B. Yes, but there areconcerns.C. Maybe, maybe not.D. No, absolutely not.reduce the likelihood of implant survival and implantsuccess. Smoking may be the most significant factor,especially for implants in the posterior maxilla.2. Which of the followingoptions is a surgicalcomplication of the lateralwindow sinus boneaugmentation procedure?A. Hemorrhage frominferior alveolar vesselsB. Neuropathic injury tothe inferior alveolarnerveC. Hemorrhage from theposterior superioralveolar vesselsD. Neuropathic injury tothe incisive nerveAnswer: CExplanation: Several arteries supply the maxillary sinus,including the posterior-superior alveolar artery, whichcan be encountered during the lateral window approachto sinus elevation and bone augmentation procedure. Case Scenario 85.2Patient:64-year-old white maleChief Complaint:“My implant feels loose, and it hurts to brush the area.”Background Information:The patient reports having implant #4 placed and restored with asingle crown 5 years ago.Current Findings:Examination reveals that implant #4 is mobile (i.e., class 1). Theimplant moves with the crown. The buccal soft tissue consistsprimarily of unattached mucosa. The apical end of the implant isdirected toward the palate. The implant crown is screw retained,with the screw access from the buccal cusp. The natural dentitionshows evidence of bruxism (i.e., severe wear facets).CASE-BASED QUESTION SOLUTION AND EXPLANATION1. The palatal position of theimplant contributed toAnswer: DExplanation: If any implant is mobile regardless of the4570 nonaxial occlusal loads, mostlikely causing what result?A. Fracture of the veneerB. Loosening of theprosthesisC. Screw looseningD. Loss ofosseointegrationcause, it has lost osseointegration, is no longer connectedto the bone, and should be removed.2. What prosthetic parametersare thought to reduceocclusal load on the implant?A. Narrow occlusal tableB. Increased buccalcantileverC. Maximized workingcontactsD. Maximized centriccontactsAnswer: AExplanation: A narrow occlusal table is favorable. A largecantilever would lead to unfavorable distribution ofocclusal forces. It is preferable to have no balancing andminimal working and centric contacts.3. What type of tissuesurrounding the implant candecrease the risk of peri-mucositis or peri-implantitis?A. A minimum of 2 mmof keratinized gingivaB. A minimum 1 mm ofkeratinized gingivaC. An entire border ofdetached mucosaD. 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