There are few absolute contraindications to dental implant placement. Relative contraindications include cognitive decline, American Society of Anesthesiology patient status IV or higher categories, or medical conditions that may jeopardize the life or lifespan of the patient. Precautions for placing dental implants should be viewed with respect to the evidence-based exposures that can contribute to risk of failure, including but not limited to local, behavioral, and medical factors. Risk for dental implant failure increases in association with (1) past history of periodontal disease, (2) bruxism, (3) smoking, and (4) radiation therapy.
Key points
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There are few absolute contraindications to dental implant placement.
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Relative contraindications include cognitive decline, American Society of Anesthesiology Patient Status IV or higher categories, or medical conditions that may jeopardize the life or lifespan of the patient.
- •
Precautions for placing dental implants should be viewed with respect to the evidence-based exposures that can contribute to risk of failure, including but not limited to local, behavioral, and medical factors.
- •
Risk for dental implant failure increases in association with (1) past history of periodontal disease, (2) bruxism, (3) smoking, and (4) radiation therapy.
Introduction
Dental clinicians on a daily basis should be mindful of the indications, precautions, and contraindications of treatment in order to achieve the best patient outcomes. Indications for treatment generally are considered when a patient initially presents with a problem or complaint. After the indication, the precautions and contraindications should be considered as balancing components of the decision-making and informed consent process. Precautions and contraindications involve taking into account the relative seriousness of a particular treatment and when specific treatment would be inadvisable because of the harm or serious adverse outcome that may, or is likely to, occur. A precaution indicates that there is ability to prevent or mitigate the adverse event. In contrast, a contraindication is a more serious situation in which the likelihood and severity of the adverse event outweighs any potential benefit to the patient ( Fig. 1 ).
Contraindications are recognized as being either absolute or relative. An absolute contraindication indicates that the procedure could cause a life-threatening event or the risk of the procedure clearly outweighs any possible therapeutic benefit. A relative contraindication indicates that caution should be exercised and it is likely that the benefit of the procedure outweighs the risks involved.
Placing a dental implant is an elective procedure that requires consideration for the desires, oral anatomy, potential trauma, and healing capacity of the patient. Hence, indications, precautions, and contraindications are key components of the diagnostic work-up. During the planning phase, health conditions and medical comorbidities are to be respected, and caution should be used before engaging in a procedure or treatment to ensure that the benefits are likely to outweigh the risks.
Expert opinion suggests that there are few situations or medical conditions that create an absolute contraindication for placing a dental implant. Relative contraindications are those situations associated with patients who are categorized with a health condition that may increase the risk of an adverse event, implant failure, or postoperative problem. These patients include those categorized as American Society of Anesthesiology patient status IV or higher (eg, oropharyngeal malignancies, recent cerebrovascular accidents and myocardial infarction, uncontrolled or poorly controlled epilepsy, diabetes mellitus or psychiatric illness, risk of osteoradionecrosis, bleeding disorders, profound immunosuppression, drug and alcohol abuse, active cancer chemotherapy and receiving intravenous antiresorptive medication, or conditions that may jeopardize the life or lifespan of the patient). However, little evidence exists to date to support contraindications to placing a dental implant, but there are contrasting opinions that exist among practitioners. Readers are referred to other publications on this topic for additional perspectives.
In the context of decision making and dental implants, evidence suggests that 90% to 95% of dental implants are successfully maintained for 10 years and 51.97% to 75.8% survive at 16 to 20 years. The most common causes for failure of a dental implant include peri-implantitis, peri-mucositis, failure of osseous integration, placement error, anatomic anomalies, persistent pain, and breakage caused by force applied during function.
In as much as dental implants have a high rate of success and few contraindications for placement, this article focuses on conditions associated with increased risk of dental implant failure, generally defined as cases in which the implant is removed because of disease, pain, or mobility. In this article, our opinions focus on systematic reviews (SRs) of the literature because this is the highest level of evidence. Readers are referred to primary studies on proton pump inhibitors and selective serotonin reuptake inhibitors as well as case series regarding chronic pain and neuropathic pain following implant placement for additional information on this topic. Readers are cautioned that although SRs provide a high level of evidence for decision making, SRs are not without flaws and some are better than others. Detailing the limitations of SRs is beyond the scope of this article, and the authors do not attempt to analyze the quality of the SR. Readers should be aware that SRs can vary at many levels, including whether investigators of the primary studies or the SR used accurate and consistent definitions of disease or proper inclusion/exclusion criteria; measured publication bias, type, and frequency of treatment provided; or measured the outcome domains (ie, success, survival, failure). For this report, risks for dental implant failure have been categorized into local factors, behavioral factors, and medical factors.
Local
Periodontal disease
Periodontal disease is a global disease that is a diagnostic consideration for patients seeking a dental implant. Both a history and the presence of periodontal disease are well-recognized risk factors for periimplant disease and implant failure. The increased risk may be caused by compromised bone level; reduced bone quality; immune dysregulation; or concurrent exposures, such as poor oral hygiene, tobacco use, or persistent periodontal pathogens. At present, there are 10 SRs on periodontal disease and dental implants. Both aggressive and chronic periodontitis have been evaluated in SRs.
There are 2 SRs on the topic of aggressive periodontitis and dental implants ( Table 1 ). In the Al-Zahrani SR, 9 primary studies involving 72 patients who had a history of aggressive periodontitis were evaluated. These patients, in general, received periodontal treatment for several years before implants were placed. There were 4 case reports and 5 longitudinal studies. Patients ranging from 17 to 82 years of age received more than 260 dental implants and were followed for 2 to 36 months. More than 90% of the dental implant survived 24 to 36 months; however, patients with a history of aggressive periodontitis showed greater periimplant crestal bone breakdown than patients without a history of periodontal disease. Hazard ratios were not calculated, and the primary studies were not evaluated for level of evidence or publication bias.
| Condition | Number of SRs | Number of Primary Studies | Number of Patients | Number of Implants | Number of Cases | Number of Controls | Duration of Primary Studies | Odds Ratio of Dental Implant Failure |
|---|---|---|---|---|---|---|---|---|
| Periodontal disease (aggressive and chronic) | 10 | 35 | 975 | 14,332 a | 10,481 a | 385 a | 1.2–10 y | NR |
| Smoking | 4 | 110 | 24,618 | 104,350 a | 19,836 a | 60,464 a | 8 mo to 20 y | 2.92 (95% CI, 1.76–4.83) ( P <.001) |
| Bruxism | 3 | 24 | 2297 | 7043 a | 1356 a | 3924 a | 1 mo to 15 y | 4.72, (95% CI, 2.66–8.36) |
| Diabetes mellitus | 8 | 41 | 9519 | 37,782 a | 9606 a | 16,137 a | 4 mo- 17 y | 0.62, (95% CI, 0.0225–1.705; P = .354) |
| Osteoporosis | 2 | 18 | 9066 | 30,381 a | 790 a | 4609 a | 1–22 y | Risk for periimplantitis 1.89, (95% CI, 1.31–2.46; P <.01) |
| Bisphosphonate | 5 | 19 | 1988 | 5927 a | 2039 a | 3888 a | 1 mo to 11 y | 1.43, P = .156 |
| Radiation | 5 | 58 | 2622 | 10,570 a | 5647 a | 3854 a | 1 mo to 23 y | RR 2.63 (95% CI, 1.93–3.58; P <.001) |
a Not all studies reported the number of implants, cases, or controls.
The Monje and colleagues SR included 6 prospective human studies. Five of the studies were from the Mengal and colleagues author group and 4 studies had been previously evaluated by Al-Zahrani. The 2014 SR provides a more rigorous study design than the Al-Zahrani SR, with the inclusion of meta-analysis and assessments for heterogeneity, quality, and publication bias. Here the survival rates for 264 dental implants in 60 patients with aggressive periodontitis were 83.3% to 100%, with a follow-up period ranging from 12 to 120 months. A meta-analysis yielded an overall failure rate risk ratio (RR) of 4.00 (95% confidence interval [CI], 1.79–8.93; P <.001) in patients who had a history of aggressive periodontitis compared with healthy controls. Risk was also increased in patients who had aggressive periodontitis compared with chronic periodontitis (RR, 3.97; 95% CI, 1.68–9.37).
Eight SRs were published between 2008 and 2016 that considered periodontal disease and implant survival. The most comprehensive data sets were found in the 2014 and 2016 SRs. Here, 22 and 24 primary studies were evaluated, respectively, and 16 primary studies appeared in both data sets. In 12 prospective studies, the investigators evaluated 2825 implants placed in 843 patients with treated periodontitis. In the 9 retrospective studies, 8102 implants were evaluated in 2086 patients. In total, more than 10,000 implants placed in persons who had periodontal disease were compared with 3851 implants placed in 1606 healthy patients over a period of 1.2 to 10 years. Evidence from these SRs indicate that there is increased risk of marginal bone loss, periimplantitis, and implant failure (odds ratios [ORs] ranging from 1.7 [CI, 1.23–2.79]; 95% CI, 1.12–8.15) with chronic periodontitis. Survival rates of implants in patients without periodontitis ranged from 91.7% to 100% compared with 71% to 100% for patients with treated periodontitis. The severity of periodontal disease also contributed to lower implant survival, but duration of disease generally was not assessed in the SRs. Periodic periodontal maintenance program is documented to be associated with improved implant survival. The rationale of increased risk is not well established; however, the literature suggests that adjacent periodontally involved teeth may contribute to the cause through the transfer of periodontal pathogens from adjacent disease sites to the implant site.
Although large-scale case-control clinical trials are lacking, the findings from these SRs suggest that dental implants can be used in patients treated for aggressive and chronic periodontitis. However, clinicians need to consider several factors, including the length of time between active periodontal therapy and when an implant should be placed, whether questionable teeth should be extracted before implant placement, and the maintenance program that will be provided regularly to periodontally compromised teeth that are adjacent to the implant. Caveats to consider in the interpretation of these data include that periodontal disease is often associated with confounders (ie, tobacco smoking) and comorbidities (eg, diabetes) and that these factors are not always well controlled for in the SRs published to date. Also, the SRs reviewed generally showed variability in the definitions in periodontitis and implant failure, loading and follow-up period, details regarding the type and frequency of periodontal treatment provided, and outcome criteria, each of which contribute to difficulty in accurate interpretation of the findings.
Behavioral Factors
Smoking
Smoking is a well-recognized risk factor for periodontal diseases that contributes to an anaerobic environment, growth of periodontal pathogens, and detachment of the periodontal ligament. Together, these factors can lead to implant failure. It is estimated that 37.8 million (15.5%) adults smoke cigarettes every day, and about 15 of every 100 adults aged 18 years or older in the United States smoke cigarettes. Smoking is considerably higher among American Indians/Alaska Natives (31.8%) and persons of color, and lowest among Asians (9.0%). Smoking is directly correlated with educational status. Although smoking rates decreased from 42.4% in 1965 to 15.7% in 2016, the Healthy People 2020 national objective of 12% has not yet been reached.
There are 4 SRs on smoking and implant failure. These SRs evaluated 113 primary studies and more than 28,000 dental implants over a 20-year period. Evidence from these SRs indicates increased risk of implant failure among smokers. The data support that the risk of implant failure, postoperative infections, and marginal bone loss for smokers is at least twice that for nonsmokers. One SR reported 1259 (6.35%) failures of 19,836 dental implants placed in smokers and 1923 failures (3.18%) of 60,464 dental implants placed in nonsmokers. Evidence from this SR indicates that smokers experienced higher rates of implant failure (RR, 2.23; 95% CI, 1.96–2.53). The success rate of dental implants dropped considerably when patients smoked more than 10 cigarettes per day. Overall, the risk of dental implant failure seems to be at least twice as high in smokers as in nonsmokers.
Bruxism
Bruxism, a condition in which the patient clenches and grinds the teeth, is a recognized risk factor for implant fracture and failure as a result of abnormal physical force. It is important for clinicians who are planning dental implants to consider that patients who brux often report morning stiffness or tightness in masticatory muscles, and show wear of the dentition. Assessment of these clinical features is critical for the long-term success of dental implants. There are 2 SRs and 1 meta-analysis on bruxism and dental implants that evaluated 38 primary studies over a 15-year period. The meta-analysis evaluated 760 implants in patients who showed bruxism and 2989 control (nonbruxism) patients. This analysis reported 49 (6.45%) implant failures that occurred in the patients who showed bruxism compared with 109 (3.65%) implant failures in nonbruxism patients. The findings support about a 2-fold higher risk for those who are bruxers versus nonbruxers.
Medical Factors
Bleeding disorders
Hemorrhage is a potential complication during or after dental implant placement. A surgical procedure can lead to hemorrhage in patients who have a congenital (hemophilia A – factor VIII deficiency; hemophilia B – factor IX deficiency) or acquired bleeding disorder; however, medical consultation with the patient’s physician and precise treatment planning before the surgical procedure can minimize adverse outcomes. Most patients taking antiplatelets (low-dose aspirin) or oral anticoagulants (coumadin, Warfarin) should not have their medication discontinued before implant placement. However, elective surgery should not be performed if hemostasis is not possible. Patients with International Normalized Ratio (INR; prothrombin ratio = patient prothrombin/control prothrombin) value of higher than 3.5 should be referred to their physicians for improved control and, once controlled, considered for treatment in a setting that will provide for good hemostasis. The INR value should be current (ie, taken between 24 and 72 hours before surgery). Direct oral anticoagulant (DOAC) drugs are newer agents prescribed for persons with deep vein thrombosis, pulmonary embolism, atrial fibrillation, myocardial infarction, and heart valve prosthesis. Although there is some controversy regarding whether DOACs should be temporarily discontinued during the surgical placement of a dental implant, accumulating data indicate that DOACs should not be discontinued for this procedure.
Abnormalities in platelet count and function can also contribute to abnormal bleeding during or after implant surgery. Low platelet levels are associated with leukemia, radiotherapy, idiopathic thrombocytopenia purpura, and myeloablation. The reference value for platelet count is between 150,000 and 400,000 cells/mm 3 . Abnormal postsurgical hemorrhage may be noticed in mild thrombocytopenia (50,000–100,000 cells/mm 3 ). In case of severe thrombocytopenia, platelet values less than 50,000 cells/mm 3 can complicate implant placement or lead to postoperative hemorrhage. In patients with very low platelet values (<20,000 cells/mm 3 ), hemorrhage of mucous membranes often occurs, and these patients require transfusion before invasive dental procedures such as placement of a dental implant.
At present, there are no SRs on the topic of dental implants and failure or contraindications in patients who have bleeding disorders. However, precautions are advised and should be taken with these patients before and during the procedure to prevent bleeding-related adverse events that may occur.
Diabetes mellitus
Diabetes is a well-recognized risk factor for poor wound healing after surgical procedures caused by abnormal glucose blood levels and altered immune response, both of which may contribute to implant failure. Diabetes can also hinder the process of osteointegration. A patient is diagnosed with diabetes if the fasting blood glucose is 126 mg/dL or higher, or the hemoglobin A1c is 6.5% or greater. In the United States, more than 29 million people have diabetes mellitus and 25% of affected persons are unaware of their condition. Approximately 86 million are prediabetic, and 90% of these persons do not know it. Hispanic and Latino people, African Americans, American Indians, Pacific Islanders, and Asian Americans are at higher risk for diabetes than white people.
There are 8 SRs on diabetes that have analyzed 14 to 22 primary studies. These SRs evaluated the failure rate of more than 3000 dental implants placed in more than 2000 (type I or type II) diabetic patients. In the Moraschini and colleagues SR, 14 primary studies published between 2000 and 2015 were evaluated. Most involved prospective studies. Overall, this SR analyzed 802 diabetics and 1532 nondiabetic patients between the ages of 15 and 89 years, with a follow-up period of 3 months to 17 years. The investigators did not consider the glycemic control levels, and reported that survival rates of diabetics were similar to those of healthy controls (95.1 vs 97%, 97.2 vs 95%, 92 vs 93.2%, and 97 vs 98.8%) in 4 primary studies that had a follow-up of more than 1 year; however, 2 studies showed a shorter survival period, which yielded an RR of 4.8 and 2.75 for implant failure in diabetic patients. Because of the predominance of favorable outcomes, Moraschini and colleagues reported there was no difference in the rate of implant failure in diabetic patients versus nondiabetic patients. Similar findings are reported by Naujokat and colleagues, who evaluated 22 primary studies in which survival was measured within the first 6 years of placement; however, dental implant failure was observed to be increased in diabetic patients when the observation period was 20 years.
Glycemic control has also been evaluated. Shi and colleagues evaluated the failure rate of 286 dental implants placed in 252 well-controlled diabetics and 301 dental implants placed in poorly controlled patients reported in 7 primary studies. Findings from this meta-analysis showed no difference in the dental implant failure rate among well-controlled versus poorly controlled diabetics (RR, 0.620; 95% CI, 0.0225–1.705; P = .354). In contrast, an SR by Monje and colleagues published in 2017 that evaluated 12 primary studies with 2892 implants placed in 1955 subjects with a follow-up period of up to 11 years concluded that the risk of periimplantitis in patients with diabetes mellitus or hyperglycemia is 1.21 to 2.46 times higher than in nondiabetics or persons with normoglycemia.
Bone diseases
The presence of bone disease may be a risk factor for implant disease and failure. The literature to date provides little guidance on dental implant success rates in patients with osteogenesis imperfecta, ankylosing spondylitis, and polyarthritis, although SRs are present for osteoporosis. Osteoporosis is a medical condition characterized by low bone mass associated with imbalances in bone metabolism causing the bone to become brittle and fragile because of a decrease in bone volume and quantity. Osteoporosis mainly affects older women (>50 years old). Worldwide, more than 200 million women have osteoporosis and it affects approximately 75 million people in the United States, Japan, and Europe according to the International Osteoporosis Foundation. An estimated 14 million people by 2020 will have osteoporosis in the United States.
There are 2 SRs on osteoporosis and dental implants. These systematic reviews included 18 studies from 2001 to 2017, and examined more than 20,000 dental implants over a period of 1 to 22 years. Evidence from these SRs indicates that there is no difference in dental implant survival in patients with or without osteoporosis. In these studies, the survival rate is reported to be 96% in the osteoporosis group. Nevertheless, increased periimplant bone loss was observed in patients with osteoporosis.
Antiresorptive medications
Antiresorptive medications are prescribed for several diseases (eg, osteoporosis, Paget disease, hypercalcemia of malignancy, bone metastasis of prostate, lung and breast cancer) that affect bone quality and metabolism. Antiresorptive medications are available as bisphosphonates, receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors, and antiangiogenic agents ( Box 1 ). Antiresorptives are given either orally or intravenously. These agents show various potencies. Bisphosphonates have a high affinity for hydroxyapatite crystals and are used to increase bone strength and reduce the risk for fractures. Bisphosphonates are generally prescribed for osteoporosis as an oral medication or a single annual injection of zoledronic acid. In contrast, the more potent antiresorptive medications (eg, zoledronic acid) are often used intravenously in cancer therapy to limit bone metastases.
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Bisphosphonates
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Non–nitrogen-containing bisphosphonates:
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Etidronate (Didronel)
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Clodronate (Bonefos, Loron)
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Tiludronate (Skelid)
-
-
Nitrogen-containing bisphosphonates:
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Pamidronate (APD, Aredia)
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Neridronate (Nerixia)
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Olpadronate
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Aledronate (Fosamax)
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Ibandronate (Boniva)
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Risedronate (Actonel)
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Zoledronate (Zometa, Aclasta)
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RANKL inhibitors
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Denosumab (Prolia, Xgeva)
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Angiogenesis inhibitors
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Axitinib (Inlyta)
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Bevacizumab (Avastin)
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Cabozantinib (Cometriq)
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Everolimus (Afinitor, Zortress)
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Lenalidomide (Revlimid)
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Pazopanib (Votrient)
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Ramucirumab (Cyramza)
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Regorafenib (Stivarga)
The relationship between dental implant survival and bisphosphonate use has been documented in 5 SRs that evaluated more than 4500 dental implants. The most comprehensive data sets are found in 2 recent publications. Here 14 and 15 primary studies were evaluated. Ten primary studies appeared in both data sets. Data from the de-Freitas and colleagues SR included 8 retrospective studies, 1 prospective study, and 6 case series. In total, 1330 implants were placed in 528 bisphosphonate users and 2418 implants were placed in 811 healthy patients. The follow-up period was up to 11 years. During this time, 113 dental implants failed in bisphosphonate users (8.5%) and 39 in healthy patients (1.6%). Osteonecrosis was reported to occur in 78 patients (53 in mandible and 23 in maxilla) who used bisphosphonates, with the highest prevalence in those who had combined use of oral and intravenous bisphosphonates.
In 2 SRs, implant survival rates in individuals with a history of bisphosphonate use ranged from 95% to 100% versus 99% in healthy individuals with a follow-up period of 4 months to 7.4 years. In a meta-analysis of 8 primary studies involving 1090 implants in bisphosphonate users and 3472 implants placed in healthy controls, Ata-Ali and colleagues reported only 1 study that offered statistical evidence that bisphosphonates reduce dental implant success, with an overall OR of 1.43 (95% CI, 0.87–2.34; P = .156). Together, these data indicate that patients taking bisphosphonates are not at higher risk of implant failure. This finding is consistent with a recent study published by Al-Sabbagh and colleagues who reported no increased risk of implant failure among patient with osteoporosis who took oral bisphosphonates.
There are no SRs available on RANKL inhibitors or antiangiogenic medications as of this date. Accordingly, dental practitioners should be cognizant of the current evidence and review the medical status of each patient before beginning a procedure for dental implant placement in a patient who uses or has received antiresorptive medications. If necessary, the patient’s medical practitioner should be consulted.
Radiation therapy
It is estimated that 51,540 new cases of oropharyngeal cancer will be diagnosed in 2018 and an estimated 10,030 lives will be lost because of this disease. Most oropharyngeal cancer diagnoses occur in persons who are at least 60 years of age; however, at least one-quarter of cases occur in persons younger than age 55 years. Radiation therapy is a common component of the cancer treatment of many of these patients. Radiation therapy is generally administered over a period of 5 to 7 weeks at doses that destroy cancer cells or slow their rate of growth. The high dose of radiotherapy is also damaging to the adjacent tissues and can result in reduced blood supply to bone, bone sclerosis, and reduced ability of osseous regeneration. Accordingly, survival of dental implants is potentially affected in the field of irradiation because of hypovascularization and reduced regenerative ability, which can affect the osseointegration process.
There are 5 SRs on radiation and implant failure. These SRs evaluated 58 primary studies, and more than 10,000 dental implants over a 23-year period. Most primary studies were retrospective and only 1 study was a randomized trial. Evidence from these SRs indicate a higher rate of failure (15% to 25%) in irradiated jaw areas compared with nonirradiated areas (5%) over a 60-month period. In an analysis based on random effect, the RR of failure was higher (RR, 2.63; 95% CI, 1.93–3.58; P <.001) in irradiated patients versus nonirradiated patients. Risk seems to increase when the radiotherapy dose is more than 50 Gy ; however, most SRs did not analyze the dose received as a confounder.
The anatomic location is also a consideration. Evidence from a recent SR indicates a higher survival rate of dental implants in irradiated mandible than in irradiated maxilla (OR, 3.67; 95% CI, 2.81–4.79; P <.0001). This finding is also reported in the SRs by Shugaa-Addin and colleagues and Schiegnitz and colleagues ; however, not all primary studies have reported this finding. Hyperbaric oxygen is a consideration when a dental implant is planned for a region that has received greater than 50 Gy; however, consensus is lacking on the need for this treatment. The accumulated evidence from these SRs indicates that irradiated areas in the maxilla or mandible may receive dental implants, but strict evaluation that includes information on the radiation dose received in the site planned for the dental implant, informed consent that includes risks involved, as well as monitoring of the area are needed.
Introduction
Dental clinicians on a daily basis should be mindful of the indications, precautions, and contraindications of treatment in order to achieve the best patient outcomes. Indications for treatment generally are considered when a patient initially presents with a problem or complaint. After the indication, the precautions and contraindications should be considered as balancing components of the decision-making and informed consent process. Precautions and contraindications involve taking into account the relative seriousness of a particular treatment and when specific treatment would be inadvisable because of the harm or serious adverse outcome that may, or is likely to, occur. A precaution indicates that there is ability to prevent or mitigate the adverse event. In contrast, a contraindication is a more serious situation in which the likelihood and severity of the adverse event outweighs any potential benefit to the patient ( Fig. 1 ).
Contraindications are recognized as being either absolute or relative. An absolute contraindication indicates that the procedure could cause a life-threatening event or the risk of the procedure clearly outweighs any possible therapeutic benefit. A relative contraindication indicates that caution should be exercised and it is likely that the benefit of the procedure outweighs the risks involved.
Placing a dental implant is an elective procedure that requires consideration for the desires, oral anatomy, potential trauma, and healing capacity of the patient. Hence, indications, precautions, and contraindications are key components of the diagnostic work-up. During the planning phase, health conditions and medical comorbidities are to be respected, and caution should be used before engaging in a procedure or treatment to ensure that the benefits are likely to outweigh the risks.
Expert opinion suggests that there are few situations or medical conditions that create an absolute contraindication for placing a dental implant. Relative contraindications are those situations associated with patients who are categorized with a health condition that may increase the risk of an adverse event, implant failure, or postoperative problem. These patients include those categorized as American Society of Anesthesiology patient status IV or higher (eg, oropharyngeal malignancies, recent cerebrovascular accidents and myocardial infarction, uncontrolled or poorly controlled epilepsy, diabetes mellitus or psychiatric illness, risk of osteoradionecrosis, bleeding disorders, profound immunosuppression, drug and alcohol abuse, active cancer chemotherapy and receiving intravenous antiresorptive medication, or conditions that may jeopardize the life or lifespan of the patient). However, little evidence exists to date to support contraindications to placing a dental implant, but there are contrasting opinions that exist among practitioners. Readers are referred to other publications on this topic for additional perspectives.
In the context of decision making and dental implants, evidence suggests that 90% to 95% of dental implants are successfully maintained for 10 years and 51.97% to 75.8% survive at 16 to 20 years. The most common causes for failure of a dental implant include peri-implantitis, peri-mucositis, failure of osseous integration, placement error, anatomic anomalies, persistent pain, and breakage caused by force applied during function.
In as much as dental implants have a high rate of success and few contraindications for placement, this article focuses on conditions associated with increased risk of dental implant failure, generally defined as cases in which the implant is removed because of disease, pain, or mobility. In this article, our opinions focus on systematic reviews (SRs) of the literature because this is the highest level of evidence. Readers are referred to primary studies on proton pump inhibitors and selective serotonin reuptake inhibitors as well as case series regarding chronic pain and neuropathic pain following implant placement for additional information on this topic. Readers are cautioned that although SRs provide a high level of evidence for decision making, SRs are not without flaws and some are better than others. Detailing the limitations of SRs is beyond the scope of this article, and the authors do not attempt to analyze the quality of the SR. Readers should be aware that SRs can vary at many levels, including whether investigators of the primary studies or the SR used accurate and consistent definitions of disease or proper inclusion/exclusion criteria; measured publication bias, type, and frequency of treatment provided; or measured the outcome domains (ie, success, survival, failure). For this report, risks for dental implant failure have been categorized into local factors, behavioral factors, and medical factors.
Local
Periodontal disease
Periodontal disease is a global disease that is a diagnostic consideration for patients seeking a dental implant. Both a history and the presence of periodontal disease are well-recognized risk factors for periimplant disease and implant failure. The increased risk may be caused by compromised bone level; reduced bone quality; immune dysregulation; or concurrent exposures, such as poor oral hygiene, tobacco use, or persistent periodontal pathogens. At present, there are 10 SRs on periodontal disease and dental implants. Both aggressive and chronic periodontitis have been evaluated in SRs.
There are 2 SRs on the topic of aggressive periodontitis and dental implants ( Table 1 ). In the Al-Zahrani SR, 9 primary studies involving 72 patients who had a history of aggressive periodontitis were evaluated. These patients, in general, received periodontal treatment for several years before implants were placed. There were 4 case reports and 5 longitudinal studies. Patients ranging from 17 to 82 years of age received more than 260 dental implants and were followed for 2 to 36 months. More than 90% of the dental implant survived 24 to 36 months; however, patients with a history of aggressive periodontitis showed greater periimplant crestal bone breakdown than patients without a history of periodontal disease. Hazard ratios were not calculated, and the primary studies were not evaluated for level of evidence or publication bias.
