|Year : 2015 | Volume
| Issue : 1 | Page : 53-59
Implant failures: A broader perspective
Smriti Kapur Dewan, Aman Arora, Monika Sehgal, Anika Khullar
Department of Prosthodontics, D.A.V. (C) Dental College, Yamuna Nagar, Haryana, India
|Date of Web Publication||2-Apr-2015|
Smriti Kapur Dewan
Department of Prosthodontics, D.A.V. (C) Dental College, Yamuna Nagar - 135 001, Haryana
Source of Support: None, Conflict of Interest: None
| Abstract|| |
An implant-supported restoration offers a predictable treatment for tooth replacement. Reported success rates for dental implants are high. Nevertheless, failures that mandate immediate implant removal do occur. The consequences of implant removal jeopardize the clinician's efforts to accomplish satisfactory function and esthetics. For the patient, this usually involves further cost and additional procedures. The main objective of this paper is to describe different failures in dental implants and treatment modalities to deal with implant failure. The main topics for discussion include identifying the failing implant, management of implant failures and higher stress on the implant maintainance methods. This article describes the many failures and complications that can occur when using implants to support restorations. Most of these failures can be prevented with proper patient selection and treatment planning
Keywords: Implant failures, osseointegration, prosthodontic management
|How to cite this article:|
Dewan SK, Arora A, Sehgal M, Khullar A. Implant failures: A broader perspective. J Dent Implant 2015;5:53-9
| Introduction|| |
The goal of modern dentistry is to restore the patient to normal contour, function, comfort, esthetics, speech and health regardless of the atrophy, disease or injury to the stomatognathic system. As a result of continued research in treatment planning, implant designs, materials and techniques, predictable success is now a reality for many challenging clinical situations.  Implants have become the treatment of choice in both completely, and partially edentulous patients, if not most, situations when missing teeth require replacement. In many situations, the implant-supported restoration has emerged as the treatment of choice for replacement of a single missing tooth. Few studies, however, systematically address the frequency or nature of the risk factors responsible for failure and complications in the use of dental implants. 
Complications do arise in implant dentistry. These are more often due to aging, changing health conditions, long-term wear and tear, poor home care and inadequate professional maintenance. Knowledge regarding the types of complications that can occur with dental procedures is an important aspect of treatment planning, dentist patient communication, and post treatment care. Hence, a better understanding of the factors associated with implant failure provide data for the planning of future studies, facilitate clinical decision-making and may enhance implant success.
Criteria for Implant Success: Given by Schnitman and Shulman 1979: 
- The individual implant is immobile when tested clinically
- No radiographic evidence of peri-implant radiolucency
- Bone loss no >0.2 mm annually
- Gingival inflammation amenable to treatment
- Absence of symptoms of infection and pain
- Absence of damage to adjacent teeth
- Absence of parasthesia, anesthesia or violation of the mandibular canal or maxillary sinus
- Should provide functional survival for 5 years in 90% of the cases and for 10 years in 85%.
| Evaluation of failed implants|| |
The most common diagnostic criteria employed for the evaluation of established implant failures (failed implants) are as follows:
Clinical signs of early infection
During the healing period complications such as swelling, fistulas, suppuration, early/late dehiscences, and osteomyelitis can occasionally be present and may indicate implant failure. The most rational and common explanation for this is an infection.
Pain or sensitivity
Pain or discomfort is often associated with mobility and could be one of the first signs, which indicate an implant failure.
Clinical discernible mobility
Mobility is always a clear sign of failure. Several different types of mobility have been recognized.
- Rotational mobility
- Lateral or horizontal mobility
- Axial or vertical mobility
Occasionally, clinically discernible mobility can be present without distinct radiographic bone changes. Therefore, mobility is the cardinal sign of implant failure.
Clinical researches in osseointegration indicate that when mobility occurs the implants become tender on percussion on pressure. Thus, mobility is a definitive sign of certain failure. For this reason, the absence of mobility is an important criterion for implant success.
Radiographic signs of failure
Standardized periapical radiographs should be made at regular follow up intervals to detect peri-fixtural radiolucency and/or progressive marginal bone loss or "saucerization" [Figure 1].
Based on the measurements on these radiographs, the baseline value for future marginal bone changes can be established.
The radiographic examination remains one of the primary tools for detection of failed implants in clinical routine, even though it is not as accurate as the mobility test.
Dull sound on percussion
It has been suggested that a subdued sound upon percussion is indicative of soft tissue encapsulation, whereas a clear crystallization sound indicates successful osseointegration.
Once the clinician has verified that the abutment is properly attached to the implant, the test is conducted by tapping the abutment with a loosely held metallic instrument.
| Classification of Implant Failures|| |
Implant failures can be classified according to timing of failure, inappropriate diagnosis and treatment planning,  etiology, , failure mode, origin of infection, condition of failure (Clinical and radiographic status), supporting tissue type and according to the osseointegration concepts.
According to Jividen and Misch
- A surgical failure describes the failure or failed attempt to place the implant at the time of surgery. This usually results from a bone fracture during the osteotomy formed by compression or expansion, failure to obtain rigid fixation or fenestration of a lateral wall during the preparation of an osteotomy. 
- An osseous healing failure describes failure occurring from the time of implant placement to the early development of the bone implant interface and usually results in mobile implants
- An early loading failure describes the failure of an implant during the 1 st year the implant serves as a prosthetic abutment and includes the period of the function in a transitional prosthesis. When immediate loading is performed, the osseous healing and early loading period overlap, and failures during the 1 st year generally are classified under this heading
- Late implant failure describes failures after the prosthesis has been loaded for > 5 years and fewer than 10 years
- Long-term implant failure occurs after 10 years in function binding, rather than removal, of the endotoxin from the implant surfaces.
According to etiology
a. Medical status
- Osteoporosis and other bone diseases
- Uncontrolled diabetes
- Parafunctional habits
c. Oral status
- Poor home care
- Juvenile and rapidly progressive
d. Irradiation therapy.
- Impaired healing and infection due to improper flap design
- Overheating the bone and exerting too much pressure
- Contamination of implant body before insertion
- Placement of the implant in immature bone grafted site
- Placement of the implant in infected site
- Severe angulation
- Minimum space between implants
- Lack of initial stabilization.
Implant selection factor
- Implant design and biomechanics
- Character of the forces applied - magnitude, duration, type, direction, magnification
- Surface area
- Implant constrains on surface area optimization
- Implant macrogeometry and design characteristics.
- Excessive cantilever
- Improper fit of the abutment
- Bending moments
- Connecting implants to natural teeth
- Improper occlusal scheme.
| Warning Signs of Implant Failure|| |
There are several warning signs, which indicate implant failure. These are loss of osseointegration, pain, long-standing infection and soft tissue sloughing during the healing period of first stage surgery, mobility of implant body, connecting screw loosening, connecting screw fracture, gingival bleeding and enlargement, recession, purulent exudates from large pockets, fracture of prosthetic components. , In most cases, connecting screw loosening is the major warning sign for the early stage of failure.  It indicates increased load on the implant components or increased torque as in single tooth replacements. This could also be caused by excessive micro movement with a subsequent increase in stresses. Then, angular bone loss sets in. If this process is long standing, it will lead to definite failure. Mobility, with or without purulent exudates, is the final evidence of failure.
| Prosthodontic Considerations|| |
Various prosthodontic factors should be kept in mind during the diagnosis and treatment planning of implant placement.
Forces on implants
Implants and implant components tolerate vertical forces well but not lateral bending forces.  Bending results through the fulcrum line that passes through the distal most abutments.
Tripod effect allows for cantilevering the greater the tripod, the more resistance to bending. This support capacity is not as prominent in the short span prosthesis often seen in the partially dentulous patient because of the more typical in line placement of the implants, leading to increased bending.
Geometric load factors
Geometric load factors that can compromise the support and result in increased bending over load include:
- Fewer than 3 implants
- Implants connected to teeth
- Implants in a line
- Cantilever extension
- Occlusal planes beyond the implant support
- Excessive crown: Implant ratio.
Overloading of an implant may lead to marginal bone resorption. A bone loss pattern around the implants is described as "Cupping."  It is a reaction to percolation of inflammatory infiltrate from repeated micro-opening of initial fatigue cracks.
Crown: Implant ratio
Lateral forces on a restoration with large crown: Implant ratio are much better tolerated in a full arch restoration and are not tolerated well or at all in a partially edentulous patient with the same ratios.
Lateral forces on an implant restoration introduce bending movements. Therefore, it is important to establish centric contact over the implants but not lateral contacts. If it is possible to use the natural teeth for lateral guidance, then a minimum of three implants must be present for resisting the bending forces. In order to centralize the centric contacts as directly over the implants as possible to minimize bending in a posterior mandibular implant restoration, one can design a lingualized occlusion in which the maxillary lingual cusps contact the mandibular central fossa with no mandibular buccal cusps contacts. Whatever, design is necessary to minimize bending is the design of choice.
By strategically extracting the compromised adjacent tooth, one eliminates the potential for more dental treatment in the near future but one also improves the support design of the implant restoration by placing more implants and improving on the tripod effect.
Tooth implant connection
The tooth, with its periodontal ligament, exhibits certain mobility whereas the implant is rigidly anchored to bone. Thus, the tooth moves slightly before it counteracts the applied forces, whereas the implant is loaded immediately.
The best solution is to design the restoration to be fully implant supported and to place an adequate number of implants in the proper positions. Any tooth next to an edentulous site that needs help should be extracted and additional implants be placed.
| Management of Implant Failures|| |
Management requirements vary widely amongst patients depending on the condition or type of failure. Balshi summarized the various fundamental complications that arise with osseointegration treatment and suggested methods to prevent and resolve these complications.  He divided the complications into 6 categories.
Identification of potential esthetic problem areas prior to fixture installation frequently permits alternative planning and avoids more complex treatment or retreatment at a later date. Using guide stents, the most frequently encountered esthetic complication of facially angulated screw access holes is often avoided. The use of diagnostic imaging, including pantographs, lateral cephalometric films, as well as computerized tomography scans, help determine ideal reception sites for the titanium fixtures.
Lip line effects
Maxillary high and mandibular low lip lines may present an esthetic compromise created by either advanced horizontal and vertical bone loss necessitating a space between the tissue integrated prosthesis and the mucosal tissue or abutment fracture, framework, and other metallic component visibility. Use of either extended fixed acrylic or porcelain gingival facades provide improved esthetics but often make oral hygiene more difficult for the fixed tissue integrated prosthesis.
Phonetic complications may occur if the spatial position of the prosthetic teeth are different from the natural dentition or if patients experience long term accommodation to a prosthesis with poor tooth position. Phonetic difficulties may also be experienced by patients when the space between the prosthesis and the residual ridge is excessive. Using shorter abutment connections or adding material to the prosthesis to close the space often improves the phonetic difficulty. 
Reduction of anterior tongue space or impingement on the lingual muscle attachments has been experienced by patients with lingually inclined fixtures. Alteration of the emergence alignment of these fixtures helps to reduce the impingement.
Lip, cheek and tongue biting
Functional complications are minimal yet should be noted, as their occurrence is annoying for the patient. Lip, cheek and tongue biting are the most common functional complications with patients who have experienced long-term edentulism without the benefit of prosthetic replacement. Increased buccal overjet for correcting cheek or lip biting may be necessary. Widening of the posterior arch form decreases biting the lateral border of the tongue.
Temporomandibular joint dysfunction
Functional disabilities, such as temporomandibular joint dysfunction, often benefit greatly from restoration of occlusal vertical dimension and posterior dental support provided by affixed tissue integrated prosthesis.  However, with long standing severe joint dysfunction, dental replacement itself may be inadequate in providing total comfort. The solution to this complication may be additional occlusal appliance therapy or joint surgery.
Parafunctional habits such as bruxing and clenching are not contraindication for implant therapy, but they do influence the treatment planning. These may produce added muscle exertion or even spasm. Relaxation techniques, physical therapy, and time are often the most appropriate and conservative treatment for this condition.
When severe atrophy prohibits fixture placement, augmentation of the ridge through a variety of autogenous bone grafting procedures may be used. In general, 6 months to 1-year may be necessary for adequate bone healing and maturation following graft placement.
Inferior alveolar neurovascular bundle
Anatomic structures may also compromise the potential for a successful implant placement. The posterior mandible in particular presents a significant challenge when severe atrophy leaves little if any bone superior to the inferior alveolar canal.  The solution to limited space for posterior mandible fixture placement includes detailed initial treatment planning and careful surgery to unroof the canal and move the neurovascular bundle inferiorly prior to fixture installation.
Fixtures placed near the inferior alveolar canal may traumatize the area sufficiently to create a transient or long-lasting parasthesia. The use of computed tomography scans with reformatted images, such as those provided by the Dentascan software may be helpful in identifying the position of the mandibular canal or other anatomic landmarks restricting fixture placement.
Periodontally compromised teeth
The biologic problems associated with the periodontally compromised teeth include potential periodontal infection, swelling and pain associated with the hopeless teeth. Antibiotic therapy and even surgical drainage may be required to maintain a hopeless tooth in function as an abutment until osseointegration of the fixture occurs.
Patients previously treated for malignancies associated with the facial skeleton; especially in the area of anticipated fixture installation, should be observed for 12 months following the last radiation treatment prior to fixture placement. Use of hyperbaric oxygen may also be considered following radiation therapy in conjunction with fixture placement.
Prosthetic screw fractures
Mechanical complications are primarily related to failure of prosthodontic materials to resist forces and stresses of oral function.
When fractures are related to the prosthetic materials, such as the casting, the solution is to use an additional thickness of the metal casting or the change of the prosthetic design. When fractures occur in the screw joint component system, there is a strong indication of either a discrepancy in the occlusal scheme or more likely, a discrepancy in the accuracy of fit of the framework.
Bent or fractured abutment screw
Fracture of the abutment screw at the level of the fixture head or neck requires modification for removal of the remaining screw.
Swallowed and aspirated hardware
Ergonomic complications focus on the ability of the clinician to easily manipulate the surgical and prosthetic component. For the most part, accidental ingestion of hardware generally passes safely through the alimentary canal. Aspiration of tiny components into the lungs presents a more complex problem. To prevent accidental swallowing or aspiration of components and instruments, the surgeon and prosthodontist must be exceptionally careful in manipulation of the components as well as the position of the patients head during these procedures.
| Maintenance|| |
Proper hygiene is critical since poor oral hygiene has been related to marginal bone loss. Plaque control should begin immediately after the second stage surgery, and the patient should understand the importance and necessity of this aspect of treatment. 
Each patient may not need every gadget, but rather the devices are selected to meet the particular patient's needs. The practitioner should help evaluate and select devices which best suit the individual's need.
Debridement is accomplished with implant-safe instruments. Plastic, graphite and gold-tipped instruments can be used to remove deposits without damaging the implant surface.
An ultrasonic tip may be used only with a plastic covering that prevents gouging and disturbance of the titanium surface. Polishing the visible surface of the implant can be accomplished with rubber cups and nonabrasive polishing paste or tin oxide. ,
For optimum home care at the gingival/implant junction, use of an interdental brush or a rotator unitufted brush (Rota-Dent; Pro Dentec) is advised. Unitufted brush is particularly effective in posterior segments and from lingual aspects where access is difficult, and the superstructure hides the implant post from normal oral hygiene procedures[Figure 2],[Figure 3].
|Figure 3: Interdental brush for maintenance of implant-based fixed prosthesis|
Click here to view
Dental floss can be used to deliver chlorhexidine to the implant on a daily basis. Floss should be inserted at the buccal surface of the implant, threaded around the lingual aspect and crossed back to the buccal to completely surround the abutment. Gauze strips, yarn or thicker dental floss or dental tape can assist with plaque control in wide embrasures.
In the 1 st year following restoration of the implant, the client should be evaluated every 3 months. Maintenance visits include peri-implant evaluations, prosthetic evaluations, deposit removal, home-care reinforcement and modifications and radiographs when indicated.
Treatment of the failure depends on the type of failure and the cause of it. If the causative factor can be eliminated at the ailing implant or failing implant stage then the condition can be reversed. Early detection is the key factor. However, in most cases careful planning is the only solution.
| Conclusion|| |
Since, the introduction of the concept of osseointegration, the success of dental implants has increased dramatically because of better understanding of bone response and the improvement in bone loading concept. Improper patient selection, accumulation of bacterial plaque because of poor oral hygiene, traumatic occlusion, debris retention resulting from improper prosthetic restoration, and bone preparation without the use of internally cooled, high torque, slow speed hand pieces have been the factors contributing to the breakdown of otherwise successful implants.
Implant prosthodontics can be straightforward when fixture position and angulation are ideal. Component and framework breakage, inadequate tissue support, poor fixture position and angulation and fixture loss complicate prosthetic treatment and may compromise the final prosthetic result.
Failure of the implant has a multifactorial dimension. Often many factors come together to cause the ultimate failure of the implant. One needs to identify the cause not just to treat the present condition but also as a learning experience for future treatments. Proper data collection, patient feedback, and accurate diagnostic tool will help point out the reason for failure. An early intervention is always possible if regular check-ups are undertaken. 
As someone well said, it is not how much success we obtain, but how best we tackle complex situations and failures, which determine the skill of a clinician. No, doubt, failures are stepping stones to success but not until their etiologies are established, and their occurrence is prevented.
After all, as correctly said by Henry Ford,
"Failure is the opportunity to begin again,
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[Figure 1], [Figure 2], [Figure 3]