Factors associated with early and late failure of dental implants

Abstract

Osseointegration is a good indication of the clinical success of titanium implants referring to the direct anchorage of such implants to the surrounding host bone. Despite the high success rate of endosseous dental implants, they do fail. A lack of primary stability, surgical trauma, and infection seem to be the most important causes of early implant failure. Early signs of infection may be an indication of a much more critical result than if the same complications occur later, because of disturbance of the primary bone healing process. Occlu-sal overload and periimplantitis seem to be the most important factors associ-ated with late failure. Suboptimal implant design and improper prosthetic constructions are among those risk factors responsible for implant complica-tions and failure. This concise review highlights the main causes associated with early and late implant failure, as thorough knowledge of this unavoidable clini-cal fact is essential in the field of oral implantology.

Full text

REVIEW ARTICLE
Oral Rehabilitation
Factors associated with early and late failure of dental
implants
Salah Sakka
1,2
, Kusai Baroudi
3,4
& Mohammad Zakaria Nassani
5,6
1 Department of Oral and Maxillofacial Surgery, Al-Farabi Dental College, Riyadh, Saudi Arabia
2 Department of Oral Surgery, Faculty of Dentistry, University of Al-Baath, Homs, Syria
3 Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, Al-Farabi Dental College, Riyadh, Saudi Arabia
4 Department of Pediatric Dentistry, Faculty of Dentistry, University of Al-Baath, Homs, Syria
5 Department of Prosthetic Dental Sciences, Al-Farabi Dental College, Riyadh, Saudi Arabia
6 Department of Removable Prosthodontics, Faculty of Dentistry, University of Aleppo, Aleppo, Syria
Keywords
dental implants, early failure, late failure,
osseointegration.
Correspondence
Salah Sakka, Al-Farabi Dental College,
PO Box 85184,
11691 Riyadh, Saudi Arabia.
Tel: (+966)-55-96 6-1906
Email: salah.sakka@hotmail.com
Received 21 February 2012; accepted 27 May
2012.
doi: 10.1111/j.2041-1626.2012.00162.x
Abstract
Osseointegration is a good indication of the clinical success of titanium
implants referring to the direct anchorage of such implants to the surrounding
host bone. Despite the high success rate of endosseous dental implants, they do
fail. A lack of primary stability, surgical trauma, and infection seem to be the
most important causes of early implant failure. Early signs of infection may be
an indication of a much more critical result than if the same complications
occur later, because of disturbance of the primary bone healing process. Occlu-
sal overload and periimplantitis seem to be the most important factors associ-
ated with late failure. Suboptimal implant design and improper prosthetic
constructions are among those risk factors responsible for implant complica-
tions and failure. This concise review highlights the main causes associated with
early and late implant failure, as thorough knowledge of this unavoidable clini-
cal fact is essential in the field of oral implantology.
Introduction
The concept “osseointegration” as a direct anchorage of the
implant fixture to surrounding host bone is apparently the
most important feature to affirm the reported long-term
clinical success of dental implants. However, in spite of the
high success rate, implant failure has been reported.
1,2
Clinical examination as a prime indicator for a success-
ful osseointegration is very much essential. The concept
of osseointegration stresses both histomorphometric as
well as clinical definitions. The understanding of both of
these aspects is still growing and impacts significantly on
the ongoing clinical determinants of the success of dental
implant.
3
Implant failure is a static outcome situation that
requires removal of a failed implant. It may be referred to
as the position status of the implant that when using
some quantitative measurements falls below an acceptable
level. This definition includes clinical situations, ranging
from all symptomatic mobile implants to implants that
show more than 0.2 mm of crestal bone loss after the first
year of loading.
4
Referring to Esposito et al.
5
implant failure can be
divided into:
(a) biological failures, which can be further divided
according to chronological criteria into “early fail-
ures” (failure to achieve osseointegration that might
indicate an interference with the initial bone healing
process) and “late failures” (failure to preserve the
achieved osseointegration);
(b) mechanical failures, which include fracture of
implants and related suprastructures;
(c) iatrogenic failures, where osseointegration is achieved
but due to wrong alignment of the implant it is
excluded from being used as part of the anchorage
unit – removal of implants due to violation of the
neighboring anatomical structures such as the inferior
alveolar nerve is also included in this class of failure;
6
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Journal of Investigative and Clinical Dentistry (2012), 3, 258–261

(d) inadequate adaptation, which includes the patient’s
aesthetical dissatisfaction and psychological problems.
General factors contributing to early implant
failures
Poor bone quality and quantity
A high success rate for the preservation of the alveolar
bone around oral implants is predicated on good bone
quality.
7
Implantation into bone types 1, 2 and 3 results in
good clinical outcomes, whereas type 4 is associated with a
lower success rate.
8
The Hounsfield Units determined by
the software programs in the computed tomography (CT)
machines refers to the density of structures within the
image. Such density is quantitative and can be used to dif-
ferentiate various tissues in the examined site and charac-
terize bone quality.
9,10
Moreover, the local bone density
has an existing influence on primary stability, which is an
important determinant for implant success.
11
Studies also stress the importance of bone volume
when planning for oral implants where at least 10 mm
and 6 mm in height and 5 mm and 6 mm in width for
the maxilla and the mandible, respectively, are required
for successful implantation.
12
Bone healing and general health condition
Bone healing requires a great biological effort for the skel-
etal tissues in which the regenerative process restores the
original structure and function. Stages of osseointegration
can be compared with the similar process of fracture heal-
ing, in which fragments become united without the inter-
ference of fibrous tissue. A basic difference exists,
however; osseointegration unites bone to an implant sur-
face. The patient’s medical condition, including AIDS,
uncontrolled diabetes mellitus, osteoporosis, corticoster-
oids and bisphosphonates therapy, collagen disorders, and
other conditions, influences the initial healing process of
bone.
13,14
Smoking
Tobacco smoking may harmfully affect wound healing,
and thus endangers the success of bone grafting and den-
tal implantation. A higher degree of complications, or
implant failure rates, was found in smokers with and
without bone grafts.
15
Clinical signs of infection
Infection if left untreated might result in implant failure.
It is the most common reason for complications that
might occur during the primary healing period. The com-
plications of swelling, fistulas, suppuration, and early/late
mucosal dehiscence can occur and may point to implant
failure. Early signs may be an indication of a much more
critical result than if the same complications occur later,
because of the disturbance of the primary bone healing
process that results in the integration of the implant.
16
Post-insertion pain
Pain should not be associated with dental implants once
primary healing is achieved. Here, absence of pain under
vertical or horizontal forces is a primary subjective crite-
rion. When present, it is more often a pressure on the
soft tissue from the unfitted prosthetic components.
Absence of pain or discomfort or any negative subjective
sensation remains one of the implant success criteria. Fur-
thermore, success also requires the absence of any recur-
rent peri-implant mucositis and/or peri-implantitis
accompanied by swelling, redness and pain of the peri-
implant mucosa. Pain does not occur unless the implant
is either mobile or surrounded by inflamed tissue, or is
stable but impinges on a nerve.
6,17
Pain during function
is a subjective principle that refers to the status of
implant failure.
Lack of primary stability
Adequate provision of implant primary stability is imper-
ative to attain successful osseointegration. The local bone
density has a significant influence on such stability, which
is an important determinant for implant success.
11
Such
local density is quantitative and can be used to differenti-
ate various tissues in the examined site and characterize
bone quality.
9
Table 1. General causes of early and late implant failure
Causes of early failure Causes of late failure
Poor bone quality: type 4 bone
posterior upper jaws
Excessive loading
Poor bone quantity: severe alveolar
bone resorption
Peri-implantitis
Patient medical condition: AIDS,
uncontrolled diabetes mellitus, osteoporosis,
corticosteroids, bisphosphonates
therapy, etc
Inadequate prosthetic
construction
Smoking
Infection
Post-insertion pain
Lack of primary stability
Inadequate surgery and prosthodontics
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Inadequate surgical and prosthetic techniques
The quantity and quality of the bone available are highly
associated with the type of surgical technique and the
type of implant, and both of these factors play an impor-
tant role in the success of oral implant surgery.
1
On the
other hand, suboptimal implant design,
18
improper pros-
thetic designs, and related laboratory work are among
those risk factors responsible for implant complications
and failure
19
(Table 1).
General factors contributing to late implant
failures
Excessive loading
Failures associated with overload comprise those cases in
which the functional load applied to the implants exceeds
the capability of the bone to withstand it. Failures that
occur between abutment connection and delivery of the
prosthesis are most likely caused by unfavorable loads.
20
Peri-implantitis
Peri-implantitis is an inflammatory process that affects
both the hard and soft tissues around a functional
implant that results in gradual bone loss, which may lead
in the end to loss of osseointegration.
21
Bacterial infection
is known to play an initial role in the etiology of the dis-
ease. The recognition of this inflammatory reaction in
which there is a loss of the bony support of the implant
is based on the clinical signs of infection such as hyper-
plastic soft tissues, suppuration, color changes of the mar-
ginal peri-implant tissues and gradual bone loss.
22
Inadequate prosthetic construction
Improper fit of the prosthetic components may lead to
fracture and loose screws (Table 1).
19
Conclusion
Under unfavorable local and/or systemic conditions, one
of the causes for osseointegration to develop a progressive
marginal bone loss is the weakness of the implant-to-bone
connection. Here, the contact surfaces comprise dissimilar
tissues: titanuim and the jaw bone. Under normal envi-
ronment, this metal-to-bone contact is stable, well estab-
lished, and resists bone resorption. Under an unfavorable
chronic environment, often of a bacterial or traumatic
nature in addition to the weakening in the systemic
health, the tissue interface can become distressed. Despite
the high success rate, implants do fail. Lack of primary
stability, surgical trauma, and peri-operative contamina-
tion seem to be the most important causes of early
implant failure. At a late stage, occlusal overload and
peri-implantitis seem to be the most important factors
associated with late failure.
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