|Year : 2016 | Volume
| Issue : 2 | Page : 51-56
Implant failure: A dentist's nightmare
Madhura Avinash Kate, Sangeeta Palaskar, Prakhar Kapoor
Department of Oral Pathology and Microbiology, Sinhgad Dental College and Hospital, Pune, Maharashtra, India
|Date of Web Publication||15-Mar-2017|
Madhura Avinash Kate
150, Anand Avinash Niwas, S.T. Road, Dapodi, Pune - 411 012, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Dental implants are commonly used in clinical situations for replacement of natural teeth. Despite many advances in materials, techniques, and implant design, implant failure is a significant concern for the dentist and patient. Peri-implantitis and lack of osseointegration are considered to be the major factors leading to implant failure. Occlusal overloading, medical status of the patient, smoking, and implant characteristics are among the other causes for implant failure. The purpose of this concise review is to discuss the etiology of implant failures by highlighting the various classification put forth by different authors and formulating a new classification.
Keywords: Classification, fracture, implant failure, osseointegration, overloading, peri-implantitis, prosthesis, smoking
|How to cite this article:|
Kate MA, Palaskar S, Kapoor P. Implant failure: A dentist's nightmare. J Dent Implant 2016;6:51-6
| Introduction|| |
An implant is “a graft or insert set firmly or deeply into or onto alveolar process that may be prepared for its insertion.” Implants are used for single tooth replacements, partially edentulous arches and for completely edentulous arches. They are inert, alloplastic materials most commonly made of titanium or titanium alloy or vitalinium. Alternatively, ceramics such as hydroxyapatite, bioglass, or aluminum oxides can be used. Depending on their placement within the bone, they are classified into epiosteal, endosteal, and transosteal., The most common one is endosteal (screw shaped or cylindrical). An implant consists of an implant body which is placed within the bone, implant screw placed on the superior surface of the body to which is attached the healing cap. Abutments are placed over the implant body which provides retention to the prosthesis., Implants are placed into the bone either in 1 stage or 2 stage surgery. In spite of taking many precautions and surgical precision, implant failures do occur attributing to certain factors.
| Review of Literature|| |
The aim of this article is to study the various causes of implant failure by focusing on the various classifications given from time to time. Implant failure is caused by a number of factors which include peri-implantitis, absence of osseointegration, and implant fracture. It may also be caused due to surgical trauma, micromotion, and overloading. Over the years, differed classifications of Implant failures have been proposed by various authors [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6].
|Figure 1: Classification of Implant Failures as stated by Nallaswamy |
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|Figure 2: Classification of Implant Failures as stated by Rosenberg et al.|
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|Figure 3: Classification of Implant Failures as given by Esposito et al.|
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|Figure 4: Classification of implant failures as stated by Truhlar  and Tonetti and Schmid|
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|Figure 6: Classification of implant failures as given by El Askary et al.|
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Compiling the various classification systems given from time to time, we have put forward a new working classification which divides implant failures broadly into early and late failures. They are further classified based on etiology, personnel responsible, failure mode, and biological causes [Table 1].
| Discussion|| |
Improper selection of patient, poor oral hygiene due to bacterial plaque accumulation, improper prosthetic restoration, debris retention, and bone preparation without the use of coolants have been contributing factors in the breakdown of successfully placed implants.
Early failures occur soon after placement of implants in the bone which is between few weeks to months. They interfere with the healing process or cause altered healing.,,
Etiologically, improper implants such as short implants cause implant failure due to unfavorable crown root ratio., In a study carried out by Bahat on treatment planning and placement of implants in posterior maxilla in the year 1993, 732 placed implants in posterior maxilla of partially edentulous patients reported a failure rate of 9.5% for 7 mm implants as compared to 3.8% for all other lengths. Similarly, implants with a smaller diameter are less apt to withstand stresses leading to fracture of the implant components. Bahat and Handelsman compared the clinical outcomes of the placement of different combinations of implants at one site in the posterior areas and found the failure rate for all 5 mm implants was 2%–3%, and that for all double implants was 1%–2%. The superstructure tends to loosen in the mouth due to conical screw design. Implant properties such as surface roughness, impurities help to retain the implant in the bone, thus playing an important role in implant success. As implant characteristics are crucial in success of an implant, the type of bone which receives an implant is equally significant.
Dense compact bone and porous compact bone found in the anterior mandible are more favorable as they hold the implant firmly in the socket. In contrast to this, porous and trabecular bone found in the posterior maxilla decrease the stability of the implant in the bone., Jaffin and Berman (1991), in their 5-year analysis, reported that as many as 35% of all implant failures occurred in porous trabecular bone due to its thin cortex. Placing the implant in immature bone grafted sites increases the chances of failures.
Surgical accuracy is an important criterion for a successful implant. This depends on axial placement of implant, spacing between adjacent implants and its initial stabilization in the bone. Buccally placed implants jeopardize the buccal cortical plate. Similarly, lingually placed implant interferes with tongue movements hampering speech. Less space between two implants causes injury to interdental bone leading to bone loss. On the other hand, if the spacing is more than required, additional cantilevers are placed which increase the stress on supporting implants, leading to fracture of implants, thereby its failure. Atilla Sertgoz et al. in 1996 reported that maximum stresses were concentrated at the most distal bone/implant interface, located on the loaded side of terminal implant, increasing cantilever length resulted in increased stress value at bone-implant interface. Over preparation of the bone site due to excessive in and out motion decreases the density of bone. Use of dense bone drills in low-density bone decreases the bone quality. Excess heating of bone causes bone necrosis  (47° for more than 1 min). Salonen et al. (1993) found that 5.8% of implants were lost due to failures of osseointegration caused by excessive heating of bone. Irrigation helps to reduce the chances of bone necrosis.
Maintaining sterile conditions during the surgical procedure is of utmost importance. Saliva, perioral skin, unsterile instruments, contaminated gloves, operating room air, or air expired by the patient, all interfere in the surgical procedure leading to contamination of the implant site, causing infection in the implant site.
Prosthetic rehabilitation and occlusal adjustments should be taken into consideration for a successful implant. Fumihiko Watanabe et al. in 2002 reported that an implant was placed in an incorrect inclination in spite of cooperation between the surgeon and prosthodontist. This failure suggested the necessity of clearly presenting the prosthodontic aspect of treatment to each member of the team before surgical treatment is rendered. Distribution of forces enhances the success of implant. Increased force on one implant leads to prosthetic component breakage., Hence, excessive load on single implant should be avoided. Misfit of the implant leads to constant tension in the components which leads to screw loosening or fracture., Robert L. Simon in 2003 concluded that the implant failure rate was 4.6% with complications of abutments screw loosening (7%). Poor implant design and excessive loading of implant (especially cantilever abutments) increase the failure chances. Greater the cantilever distance, greater the chances of failure.,
As certain factors are responsible for causing early failures, there are a different set of factors which cause delayed failures. These failures arise from pathologic processes in previously osseointegrated implants. These are mostly associated with medical status of the patient. They are categorized as host factors.
Patients with diabetes experience delayed wound healing which impairs osseointegration process.,, Uncontrolled diabetes leads to implant failure. Fiorellini et al. (2000) demonstrated a lower success rate of only 85% in patients with diabetes, while Olson et al. (2000) found that the duration of diabetes had an effect on implant success: more failures occurred in patients who had diabetes for longer periods. In osteoporotic and arthritic conditions, density of bone is adversely affected. This leads to porous bone. Such bone is unsuitable for implant success., John C. Keller et al. in 2004 have reported that osteoporosis-like bone conditions affect the osseointegration characteristic of implant. Overweight is a metabolic syndrome which leads to increase in peri-implant inflammations which in turn affect implant prognosis. A study carried out on implants, and relative risk factors stated that increasing age was also a major risk factor. Compared to patients younger than 40, patients in the range of 60–70 years had a higher risk of implant failure.
Tissue abuse and parafunctional habits
Tissue abuse habits, parafunctional habits, and psychological disorders have a detrimental effect on implant success. Smoking is associated with significantly higher levels of bone loss. It reduces the density of bone which interferes with osseointegration, leading to increase the failure rate., A longitudinal study by Lambert et al. (2000) found more failures in patients who smoked, and Bain and Moy (1993) observed that a significantly greater percentage of failures implant occurred in smokers (11.3%) than in nonsmokers (4.8%). Based on the studies carried out by Dror Twito and Paul Sade between the years 1999 and 2008 in Israel, it has been proved that 4.2% of implants, i.e., 321 out of 7680 implants failed due to smoking which included passive smoking as well. Parafunctional habits such as bruxism increase the occlusal stress on implants. It leads to fracture of implants causing failures. Glauser et al., evaluated 41 patients who received 127 immediately loaded implants. Their results showed that implants in patients with a parafunctional habit (bruxers) were lost more frequently than those placed in patients with no parafunction (41% vs. 12%). Cognitive difficulty, mental retardation, and lack of support interfere with surgical procedures. Implant success is adversely affected due to psychological disorders.
Radiotherapy is provided to patients suffering from maxillary and mandibular tumors. It causes osteoradionecrosis of bone which decreases the volume of bone, thus interfering with osseointegration., Reported success rate is only about 70%, long-term studies are limited, but Jacobsson et al. (1988) showed increasing implant loss over time due to radiation.
Personnel responsible (early failures)
Placement of an implant is a surgical procedure carried out cumulatively by a periodontist, prosthodontist, and an oral surgeon. Extraction of natural tooth, assessment of bone quality and quantity, periodontal health as well as systemic condition of the patient are all assessed by periodontist and an oral surgeon. Prosthodontist takes care of the implant design, prosthesis, and occlusal scheme. Any discrepancy in any of these steps decreases the success of implant. Inaccurate design of the implant increases the occlusal loading on the implants resulting in implant failure. Russell A. Wick in 1994 reported that thoughtful design selection is crucial for the perpetual success of any dental implant restoration. Hence, laboratory technician also plays a significant role.
Personnel responsible (late failures)
After successfully placing the implant, it is the patient's duty to take care of its maintenance in the oral cavity. Inadequate postoperative care, carelessness in maintaining oral hygiene leads to infection in the implant site causing peri-implantitis. More bone resorption was noted around fixtures in edentulous patients with poor oral hygiene than in participants with good hygiene (Lindquist et al. 1988). This proves that in addition to surgical precision, personnel involved in its procedure and maintenance are responsible for the fate of implant.
The mode in which failure is caused is different in early and delayed failures. In early failures, it is due to lack of osseointegration, whereas in late failures, it is due to functional and psychological attributes of the patient. Osseointegration is direct communication between implant surface and bone.,,, Lack of osseointegration causes loosening of implant in the bone which decreases the success rate of implant. Failure rates are high due to fibrous union of tissues instead of osseointegration. Mobility of implants due to lack of osseointegration results in implant failure., Infection of implant site, poor bone quality, and improper design of the implant interfere in osseointegration process. Unacceptable esthetics, psychological problems such as emotional instability, emotional disturbances, dementia, and lack of support affect implant success. Failure of implants is also caused by infections in the oral cavity. These mostly include peri-implantitis in early stages that is during or immediately after implant placement. In late stages, retrograde infection is the primary causative agent. These infections are broadly grouped into biological causes. Peri-implantitis is an inflammatory process which affects the tissues around an osseointegrated implant.,,, It results in loss of supporting bone along with bleeding, suppuration, increased probing depth, and mobility. Bacterial infection is the prime reason for peri-implantitis.,,, Bacterial flora at failing implant site consists of Gram-negative anaerobic bacteria including Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus.,, Studies by Mombelli et al. (1987) and Rosenberg et al. (1991) showed the presence of periodontal microorganisms around failing implants. Retrograde peri-implantitis is also known as apical peri-implantitis or periapical implant lesion, occurring in the later stage of implant placement., It develops shortly after implant insertion while coronal portion of implant achieves a normal implant bone interface. However, very few failures have been reported due to retrograde infection.,
| Conclusion|| |
Failure of implant is a multifactorial occurrence. A combination of causes leads to ultimate failure of implant. Every dentist needs to identify the cause to treat the present condition. Proper data collection, patient feedback, and accurate diagnostic tools will help point out the reason for failure. An early intervention is always possible if regular checkups are undertaken. The treatment strategy for complications and failing implants is influenced by the identification of the possible etiologic factors. When a diagnosis is established and possible etiologic factors identified, the causative agent should be eliminated and treatment attempted as soon as possible.
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Conflicts of interest
There are no conflicts of interest.
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