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Submitted by:
Ali Khalaf Anber
Mahmood Abd Al-Sadah Majed
Ali Nasser Zuwayd
Supervised by:
Lecturer Dr. Hanan Ali Hameed
Assit.Prof. Dr. Malath Azeez
Dedication
To all those who are enlightened by the knowledge of the
mind of othors , to candles that burn to light up for others ,
to everyone who taught me a letter , dedicate this humble
research , asking god to find acceptance and success
July 2020 A.D. 1441 A.H.

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Abstract
The mainstream use of dental implants has allowed millions of patients to
benefit from the predictability of dental implant therapy and, in many instances,
dental implants have become the standard of care. Even though success rates in
implant dentistry are well above 90 percent, complications do occur. Most
complications are preventable with proper planning and execution. Others are
inherent to the risks of surgery and may require intervention. The purpose of
this review is to classify the possible complications that may occur and to
discuss their prevention and management and compare it with different material
(Zirconium , Titanium).
This review started with a PubMed and Google Scholar search from 1969 to
2019. The search was conducted using key words: zirconia , titanium, dental,
and implant. The full text of articles was obtained where possible. If it was not
possible to obtain a full text, the electronically available abstracts were
collected.
General information about our review we found that: titanium abutments
showed high resistance to screw loosening when compared to the zirconia
abutments, zirconia and titanium abutment surfaces exhibit more or less similar
clinical characteristics of peri-implant health and microbiological features,
titanium abutment system was significantly more fracture resistant than the
zirconia abutment, zirconia implants are better than titanium in the aesthetic
zone.
Key words: Implant complications, Implant failures, Implant, Zirconia, Titanium.

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Introduction
Prosthetic dentistry, during the past decade, has significantly improved and
developed to replacement missing parts of teeth, bone, gums, or facial
structures, restoring functions and esthetic according to advancements in the
science and patient’s demand and need. Conventional options in prosthodontics
for substituting missing teeth include the removable partial and complete
denture, partial and full coverage bridgework, and resin‑bonded bridgework [1].
An attractive alternative to conventional dentures and bridges became available
with the introduction of implants into dental industry [2,3].
For so many years, virtually all dental implants were derived from one material
called titanium. Since the 1960s, titanium has remained the industry standard
for dental implants. In fact, titanium implants have become one of the most
successful medical devices with a long-term medical success rate of 94-97%.
But with the advent of technology, more and more dental implants are now
made from different dental implant materials such as zirconium [4].
At present, titanium dental implant have side effect in discoloration when it
placed inside the bone. Therefore studies and research have turned to the use of
zirconium because it is more aesthetic. Zirconia implants show promise, their
long-term success is not proven. If, aesthetics or allergy sensitivity is what is
driving you towards Zirconia, a Zirconia abutment with a Titanium implant may
be the best solution [4].
The basis for dental implants is osseointegration, where osteoblasts grow and
directly integrate with surface of the implants surgically placed inside the
alveolar bone [3]. Osseointegrated dental implants are an effective alternative in
the rehabilitation of partial or total edentulous patients [5]. Several
complications may affect the success of bone integrated implants in specific
situations [6] which can be of a biological of biomechanical nature. According

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to El Askary et al [7] the signs of implant failure are: loosening or breaking of
the screws that hold the crowns and abutments in place, edema or bleeding of
soft tissue surrounding the implant, purulent exudate from the peri-implant
sulcus, pain (rare), prosthesis fracture, angular bone loss and chronic infections.
The most important factor in implant longevity, i.e. clinically successful implant
treatment is the formation of a direct interface between the implant and the
bone, without intervening soft tissue, a process called “osseointegration”.
Osseointegrated dental implants represent an advance in modern odontology
which has become a great option for the rehabilitation of missing single teeth in
partially or completely edentulous patients. Despite the very high success rates,
complications associated with implant treatment may occur [8]. Early loading
failure may affect 2% to 6% of implants, and as many as 15% of restorations
failure as a result of this problem [9,10]. Excess load on a final restoration after
successful implant integration can result in failure of the implant itself.
Therefore, it is important to clarify the risk factors for failure of implant
prostheses in order to further improve the good success rate.
The consequences of overload of dental implants can be divided into two
groups: biological and biomechanical complications [11]. Biological
complications can be divided into early failures and late failures [12]. In case of
early failures, osseointegration was insufficient: the implant is lost before the
first prosthetic loading. Late biological failures are characterized by
pathological bone loss after full osseointegration was obtained at an earlier
stage [13]. They are associated with overload. Some insight into bone
physiology is needed for a proper understanding of these mechanisms [14].
In case of biomechanical complications, one or more components of an implant
system failure are fracture of an implant itself, loosening or fracture of
connecting screws or abutment screws, loosening or excessive wear of

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mesostructural components in overdentures and excessive wear or fracture of
suprastructural porcelain or acrylic teeth [15,16].
In addition to biomechanical complications the bacterial infection is considered
one of the rising complications after implant placement. The postoperative
infection rate was reported to be 4-10% for patients receiving dental implants in
spite of success rate of the dental implants was reported to be as high as 90-
95%[17,18] . The recurrent incidence of this infection is also a concern, which
is about 5-8% and is even more difficult to control and treated by antibiotics.
The implant materials placed within the oral cavity can interfere with the host
defense mechanism and it might influence the required clinical dose of
antibiotics to safeguard against infections[19,20]. Interestingly, no single
complication has been closely associated with dental implant failure. Based on
the above, the aim of the current review is to discuss specific complications
associated with dental implants. Management protocols and possible means of
avoiding certain complications are also briefly discussed.
Post dental implants complications
For the last years the usage of dental implants to replace missing teeth and
restoration of masticatory function has been accepted as a routine method in
clinical practice. Along with the high success rate, biological and biomechanical
complications are observed in some cases [21-23]. Long term studies have
demonstrated that loss of osseointegrated implant can be caused by secondary
infections (peri-implantitis) functional overload and implant fracture [24,25].
Screw loosening
It has been observed that screw loosening is a matter of concern for both
manufacturers and dental professionals. Loosening of abutment screw is one of
the most common mechanical complications breaking the integrity between the

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implant and abutment. The incidence varies between 4.3 and 10% and occurs in
a relatively short period after functional loading of implants[26,27]
Screw loosening leads to instability of the implant-abutment connection and the
formation of a micro-gap, which may provoke the fracture of implant
components [28]. The gap can cause the infiltration of microorganisms, which
is harmful for surrounding tissues [29]. Additionally, loosening or failure of
implant screws may result in component failure that may require more extensive
repair [30,31].
The reasons for such loosening may turn out to be inadequate tightening torque,
settling of implant components, inappropriate implant position, inadequate
occlusal scheme or crown anatomy, poorly fitting frameworks, presence of
microleakage at abutment-implant interface, improper screw design / material,
and heavy occlusal forces [32,33]. Abutment screw loosening may result in
mobility of prosthesis, which necessitates removing the prosthesis in order to
tighten abutment. The most usual complications of abutment screw loosening
include inflammation of gingival, failure of implant, and fracture of screws [34].
Sahin and Ayyildiz’s studies indicated that the loosening of abutment screw
can be brought about by the presence of microleakage between the implant and
abutment, permitting fluid penetration around the abutment screw. As a
consequence of this the permeability is increased which provokes the
occurrence of bacterial infection as well as peri-implantitis in some time [35].
The results of some researches showed that parafunctional activity, cantilevers
and the time of complications setting in have a statistically significant impact
with typical effect size in observed cases of abutment screw loosening [36].
Bruxism has a significant impact upon the incidence of biomechanical
complications, including screw loosening due to repeated static and dynamic
loading. Such loadings can be both along the axial axis in clenching the teeth

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and in less favorable lateral directions in grinding the teeth. The increased
loading leads to fatigue and subsequent loosening and fracture of abutment
screw [37-39]. The obtained results revealed also a strong connection between
the cantilever extensions and cases of screw loosening.
The patient may complain of soreness at the interface between soft tissue and
fixture, swelling or fistula formation, and difficulty chewing.
Prevention screw loosening
To minimize screw loosening, various solutions are recommended, such as
using diamond-like carbon coating over abutment screws, retightening screws
after initial tightening, and increasing the torque value [40,41].
Preloading of the screw joint is essential for the prevention of screw loosening
[42]. Many research found that the application of an adhesive material on the
abutment screws is recommended to prevent or decrease screw loosening [43].
Graves et al reported a decrease of the force on a screw of 20%, and 33% when
the diameter of an implant was increased from 3.75 mm to 5.0 mm, and 6.0 mm
respectively. They postulated that this might indeed reduce the amount of screw
loosening. So The diameter of the implant and the design of the implant (more
surface area is better) are key factors and are paramount for implant success.
The wider the diameter of the implant, the better the distribution of stresses will
be [44].
Implant fracture
Fracture of dental implants is a rare phenomenon. According to Balshi [45],
only 0.2% of 4045 placed implants presented with fracture during 5 years of
function. Data from a study carried out by Adell [46], in which 4636 implants
were employed, revealed an average total fracture rate of less than 5%, 6% in

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the maxilla, and 3% in the mandible after 15 years of follow-up. Eckert [47]
reported that among 4937 implants, the fracture rate was just 0.6% with no
statistically significant difference noted between the arches. Causes of implant
fracture may be divided into 3 categories:(1) defects in the design of the
material, (2) non passive fit of the prosthetic structure, and (3) biomechanical or
physiologic overload [47]. Possible causes of fracture include failure in the
production and design of dental implants, bruxism or large occlusal forces,
superstructure design, implant localization, implant diameter, metal fatigue, and
bone resorption around the implant [48]. In addition, the galvanic activity of
metals used in prosthetic restorations can cited as a cause [49]. Defects in the
production and design of dental implants are very unlikely reasons for fracture.
Microscopic analysis of fractured fixtures revealed no porosity or any other
defects in the titanium structure, a finding that eliminated failure in the
manufacturing process as causative [47,50]. Load factors are related to the
magnitude and direction of occlusal forces. Ninety percent of dental implant
fractures are located in the molar and premolar regions of the mouth, where
chewing forces and lateral movements associated with cusp inclination generate
undesirable forces [51]. Biomechanical and physiologic overload seems to be
the most common cause of dental implant fracture; overload may be caused
primarily by two factors: Parafunctional habits and prosthesis design [47].
Parafunctional habits such as bruxism or clenching may increase overload on
the implant prosthesis system through the magnitude, duration, frequency, and
direction of forces applied. According to Rangert [52], around 56% of patients
with fractured dental implants presented with bruxism and marked occlusal
forces. Parafunctional habits have been identified as the major causative factor
associated with fixture fractures [47]. In any clinical situation, the presence of
an extension or cantilever considerably increases the load on implants [53].
Shackleton and Slabbert [54] studied the existence of a relationship between
survival time span of implant-supported prostheses and the length of their

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posterior cantilever extensions. They concluded that short cantilevers provide
longer survival rates and recommended the use of mandibular extensions for a
maximum of 15 mm. According to Rangert et al [51], good mandibular bone
quality allows the use of cantilevers that measure 15-20 mm in length, whereas
porous maxillary bone should not support cantilevers longer than 10 mm. It has
been suggested that posterior cantilevers should be avoided or minimized,
especially in partially edentulous patients. Implants with small diameters tend to
fracture more easily than those with large diameters, especially when placed in
the posterior region [48]. According to Krogh [55] among the causes of implant
fracture are standard implants used in the molar region. In an implant of 3.75
mm diameter just 0.4 mm corresponds with the thickness of the titanium wall.
Therefore, implants that are 5 and 6 mm in thickness are 3 and 6 times more
resistant, respectively, than standard implants [56]. As well as the type of
material can be one of influencing factors so the studies showed, zirconia
implants exhibited high rates of fractures in preclinical animal studies using
canine mandibles. In two different studies, Thoma et al [57,58] reported a
higher incidence of zirconia implant fractures before and after loading in
comparison with titanium implants. The localization position of dental implants
also has a direct influence on the biomechanical distribution of forces. If the
implant axis is placed at a certain distance from the center of the prosthetic
crown, forces created by this distance from the occlusal contact point to the
implant axle may cause screw loosening or component fracture.
Management of implant fracture
Balshi [45] suggested three methods for treating fractures of dental implants: (1)
removal of the fractured implant (replace the implant and manufacture a new
prosthesis), (2) alteration of the existing prosthesis and maintenance of the
osseointegrated fractured part, and (3) alteration of the fractured implant and
remanufacturing of the prosthetic portion. Treatment of fractured implants

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represents a clinical challenge. First, the fractured fragment must be
atraumatically removed with minimum bone removal. A new fixture is placed
and the time to osseointegration must pass; only after that, the prosthetic phase
begins [49]. It is suggested that, for removal of the intraosseous portion of a
dental implant, a trephine bur should be used and if possible, another implant
with a larger diameter should be installed immediately [49][55].
Prevention of implant fracture
A titanium alloy implant should ideally be used to reduce the possibility of
implant body fracture. Parafunctional habits should be addressed with occlusal
guards, narrow occlusal tables, no lateral contacts, and an ideal occlusal
scheme.
Peri-implantitis
Peri-implant disease is defined as the inflammatory pathological change that
takes place in the soft and hard tissues surrounding an osseointegrated
implant[59]. When an implant is successfully osseointegrated, the peri‐implant
disease that occurs is the consequence of disparity between the host defense and
increasing bacterial load[60]. It usually takes about 5 years for the peri‐implant
disease to progress and exhibit clinical signs and symptoms [61-63]. The
incidence of peri‐implantitis and implant loss could be greater if the studies with
longer follow‐up periods are evaluated[64]. In a healthy environment around the
implant, the tissues play a pivotal role in preventing the spread of agents that
can be pathognomonic, and if the biological barrier is breached, it could lead to
bacterial contamination around the bone resulting in hasty destruction of the
tissues surrounding the implant[65]. The peri‐ implant disease is also related to
unequal occlusal load distribution, which may lead to loosening of the
superstructure, infection of the surrounding area, eventually culminating into

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the inflammatory process [66]. Predisposing systemic conditions include
uncontrolled diabetes mellitus, osteoporosis, smoking, long‐standing treatment
with steroids, uncontrolled periodontitis, radiation therapy, and
chemotherapeutics [60,67,68]. So far, the zirconia as an abutment material has
offered superior esthetic and gingival healing advantages over titanium .
Nevertheless, the biofilm formation on titanium and zirconium oxide surfaces is
still a discussion point . Due to the lack of long-term studies, the zirconia has no
proven advantage or disadvantage over titanium implants regarding peri-implant
infection risk but probing depths around Ti abutments were slightly deeper than
around ZrO2 abutments. The peri‐implant disease treatment strategies have
been explored and employed to prevent failure of the implant treatment[64].
They include nonsurgical mechanical debridement, local antimicrobial delivery
in periodontitis and peri‐implantitis, and surgical debridement with bone
grafting. Implant removal is warranted if there is more than 60% of bone loss
following peri‐implantitis, and there is an evidence of mobility[69].
Antibiotics for peri-implantitis
The use of prophylactic antibiotics during implant placement remains
controversial. A Cochrane review found insufficient evidence advocating or
dissuading their use[70]. An update of the review, however, determined there
was some evidence that 2 g of amoxicillin given orally 1 h preoperatively
significantly reduced early failures of dental implants[71]. The review
concluded by recommending the routine use of one dose of 2 g of prophylactic
amoxicillin immediately prior to placing dental implants. However, it also
stated that further research was required to confirm the findings . At present,
there is no reliable evidence for the most successful method of treating peri-
implantitis [72]. Despite a variety of therapeutic options infected implants are
difficult to treat and usually require removal[73]. Some clinicians advise

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systemic antibiotics for the treatment of failing implants and a variety of drug
regimens are described[74]. Oral agents such as doxycycline, clindamycin, co-
amoxiclav, penicillin V, amoxicillin and a combination of amoxicillin and
metronidazole have been recommended. Nevertheless, no double blind,
randomised, placebo-controlled trial has been undertaken. Others strategies
aimed at reducing bacterial adhesion and biofilm formation on implant
abutment surfaces are of pertinent clinical interest and can be used for the
maintenance of soft tissue health or possibly in the treatment of peri-implantitis.
Studies have shown that antimicrobial (e.g. vancomycin or chitosan)
derivatization of a Ti alloy surface renders it less susceptible for bacterial
colonization in vitro [75]. Implant coatings that deliver antibiotics have been
described as well, predominantly in the field of orthopaedics [76]. It was shown
that the physical properties of the Ti surface can be adapted, for example by
applying a coating of Ti-nitride through vapour deposition. This reduces plaque
adhesion compared with uncoated Ti surfaces both in vitro and in vivo [77,78]
and still facilitates cellular adhesion of human fibroblasts in vitro [79]. In
addition, it has been observed that silver and zinc oxide-modified surfaces
possess antibacterial properties as well so this can use to prevent the
infection[80].
Discoloration
Titanium is the gold standard material used to produce dental implants over
more than 30 years [81], showing a high success rate in different clinical
scenarios [82,83].
Nevertheless, titanium implants may present some esthetic issues: the gray color
of titanium implant may be visible in the presence of thin peri-implant tissue,
leading to esthetic concern, especially in the anterior area [84]. This aspect can
get dramatically worse in case of peri-implant mucosa recedes over time. The

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availability of a “white” implant may be crucial in those clinical cases in which
esthetic result is mandatory.
Furthermore, titanium particles due to wear and corrosion products may be
released in tissues close to implants, and they were found in regional lymph
nodes [85]. In some cases, this may lead to host reaction or sensitization [86].
Some cases of allergic reaction to titanium are documented, even if rare [87,88].
So, using some nonmetallic material as an alternative to the titanium implant
may be useful and, in some cases, critical. Last but not least, always more
patients request completely metal-free prosthetic reconstructions.
Ceramic implants were introduced to overwhelm some esthetic and biological
problems that can arise from titanium. Today a new type of implant made out of
Zirconia has recently been introduced into dental implantology as an alternative
to titanium implants. Zirconia possesses many advantages over titanium in its
biologic, esthetic, mechanical, and optical properties, as well as its inherent
biocompatibility and low plaque affinity. This zirconia-based material has been
shown to have improved flexural strength and fracture resistance over early
versions of ceramic implants.[84]
Zirconia implants have a definite aesthetic advantage over titanium implants
(Healthy , Pink beautiful tissue around implant , No gum show through, like
natural tooth , Resembles real tooth esthetics).
Zirconia is advocated to have high biocompatibility and to have no adverse
effect on the surrounding tissues [89]. Many studies evaluated tissue response
to zirconia, concluding that zirconia has the ability to interact with peri-implant
soft tissues [90]. The low bacterial colonization typical of the zirconia surface
maybe plays a role in this high biocompatibility [91]. In a randomized-
controlled trial (RCT), both titanium and zirconia one-piece implants supporting
overdentures were evaluated [92]. Even if the crestal bone level changed

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greatly, no difference in clinical parameters (probing depth, bleeding index,
plaque index, etc.) was found around the two types of implants after 12 months
of function.
Unfortunately, long-term follow-ups are missing, so no solid clinical evidence is
currently available to recommend routine use of zirconia implants or to replace
titanium implants, which is still found to be the gold standard for dental
implantology. So, even if zirconia implants are a good option from theoretical
and experimental point of view, the clinical long-term response is not yet
available. Almost all the authors agree to be cautious for proposing zirconia
implants as substitutes of titanium implants for replacing teeth. Long-term,
well-designed perspective clinical studies are needed to address the missing
aspects of this undoubtful promising alternative.
Conclusions
Our research concluded that titanium abutments showed high resistance to
screw loosening when compared to the zirconia .
Abutment screws that were tightened by the adhesive material showed a
significant increase in removal torque value. Thus, the microleakage in
abutment implant interface can be reduced not only by filling the gap exist in
that interface, but also by improving the retention of screw retained abutments.
Long screws have more threads that engage the implant and abutment. These
features may help distribute the applied loads to the implants and surrounding
bone more efficiently, making long screws more resistant to fracture.
Also found that zirconia and titanium abutment surfaces exhibit more or less
similar clinical characteristics of peri-implant health and microbiological
features during the first 3 months could not be convincingly rejected for most

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parameters with the exception of the pocket probing depth somewhat shallower
probing depths were observed around zirconia abutments after 3 months.
But about the fracture titanium and zirconia abutments were tested in a stepped
fatigue loading protocol. Within the limitations of this in vitro study, the
titanium abutment system was significantly more fracture resistant than the
zirconia abutment system.
Researches do not support any obvious advantage of titanium or zirconia
abutments over each other. However, there is a significant tendency in zirconia
abutments evoking better color response of peri-implant mucosa and superior
esthetic outcome.
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