CHAPTER 6 DENTAL IMPLANT THERAPY FOR MEDICALLY COMPLEX PATIENTS
This chapter focuses on a number of systemic factors that have an impact on the indications, contraindications, and success rates of endosseous implants. The results of this modern treatment approach—implants—are different when applied to a health-compromised patient or, more accurately defined, a medically complex patient. It is of the utmost importance that the treating dentist consider the interaction between “local” and “systemic” factors. This chapter will address the latter.1
The number of medically complex patients, together with the aging population, is constantly growing. Dentists should be aware of this change in the population profile, which ensures an increase or at least prevents a decrease in their patient pool. Increased attention to the patient’s general health becomes mandatory in the medically complex patient. The patient’s medical history plays a central role in dental treatment planning, and monitoring devices for blood pressure, pulse, oxygen saturation, and temperature have become imperative in every dental office that provides implant-supported oral rehabilitation. Because implant dentistry is a medical dental discipline required for the general population, but mainly for medically complex patients, a basic knowledge in internal medicine is becoming a sine qua non subject in the education program of every dentist. Statistical data accentuate the need for this approach. By the year 2020, 17.7% of the population in the United States will be over 65 years old, and 85% of this population will have at least one chronic disease and will be taking between two and eight medications. Cooperation with the patient’s physician and the provision of full information relating to the physiological implications of implant treatments are basic requirements for patient selection, treatment planning, and follow-up. However, it is the dentist’s responsibility to make the final decisions and to intelligently apply them.
Nonetheless, several studies relating to the risk factors associated with dental implants for medically complex patients are encouraging. The perioperative morbidity and the rate of implant failure are not higher for medically complex patients in terms of age, diabetes, or the use of steroids. Local anesthesia, anxiolytics, and analgesic medications do not appear to increase the rate of complications.
Unfortunately, there is little evidence-based data on dental implant treatment for medically complex patients; guidelines are inadequate and perioperative recommendations are sparse, resulting in unclear protocols. This chapter presents the current knowledge that will help to facilitate this multifaceted decision-making process, thereby improving both treatment outcome and patient satisfaction. The topics to be covered include the following: dental implant therapy for the diabetic patient, the hypertensive patient, the patient with an increased bleeding tendency, and the patient treated with bisphosphonates; the use of adrenaline in local anesthesia; and the implications of radiotherapy and chemotherapy.
Dental implants are one of the treatment solutions for patients with advanced periodontal disease. Understanding the pathological process is crucial for devising a sound and well-informed treatment plan. The results of basic science studies are proof of the dental-medical symbiosis. For example, C-reactive protein (CRP) blood levels are an indicator for a systemic inflammatory response. CRP is elevated in patients with acute myocardial infarction (AMI). It was found that the CRP level in patients with both periodontal disease and AMI was 50.7 mg/L compared with 30.7 mg/L in patients who did not have periodontal disease. Atherosclerosis is considered a chronic inflammatory process, so a reduction in inflammatory markers such as CRP could have an impact on cardiovascular disease. This accentuates the need for the eradication of periodontal disease and reinforces the central role played by dental implant treatments.
Between 6% and 7% of the U.S. population are affected by this metabolic disease (Figure 6-1).2 With this prevalence, every dental practice would have 60 to 70 diabetic patients for every 1000 persons, but half of them would be undiagnosed.
Figure 6-1. Dental implant therapy for the diabetic patient. A 64-year-old woman diagnosed with IDDM. The control of the disease proven by a HbA1c level of 6.5%. The four implants were inserted in the upper jaw 5 months before for an implant-supported denture.
(Courtesy the Happy Dental Clinics for Oral Health, Israel.)
Diabetes mellitus affects the metabolism of carbohydrates, proteins, and lipids. The resulting hyperglycemia affects all the tissues in the body, resulting in multiple complications including those in the micro- and macrovasculature. The glucose blood level is affected by different hormones: insulin is the only one that lowers it, whereas glucagon, catecholamines, glucocorticoids, growth, and thyroid hormones increase it.
Lipid deposition will result in atherosclerosis and microangiopathy observed in the systemic vascular bed, including the alveolar bone and periodontal tissues.3 Hyperglycemia also results in the accumulation of advanced glycation end-products, which will impair the collagen metabolism and bind to monocyte and macrophage cell membranes, thus altering the wound-healing process and promoting infectious inflammatory processes.4 In light of these effects, it becomes clear that the complex process of implant treatment for diabetic patients demands special considerations.
Close monitoring of glucose blood levels is mandatory before, after, and even during surgery in prolonged cases. The normal plasma glucose level is 80-120 mg/dL, whereas a fasting value of more than 126 mg/dL and a 2-hour postprandial value of more than 200 mg/dL are considered diagnostic criteria for diabetes. A more indicative test is the glycosylated hemoglobin assay, which does not relate to a momentary value but indicates the long-term control of glycemia for 30-90 days prior to the test. The higher the plasma glucose level during that period, the greater the percentage of glycated hemoglobin. HbA1c is the common indicator, and a value of 6%-6.5% is considered normal. A value of more than 8% positions the patient in the poorly controlled group and mandates a change in his or her management.
The first line of management in the diabetic patient is diet control. The central role of a healthy and functional masticatory apparatus is obvious and concurs with the objectives of the present chapter. The insulin-dependent diabetes mellitus (IDDM) patient is controlled with daily injections or with the help of a subcutaneous insulin infusion pump. The latter has shown significant amelioration of both symptoms and systemic complications.5 Non-insulin-dependent diabetes mellitus (NIDDM) patients are controlled with different oral agents that stimulate insulin secretion, prevent glycogenolysis in the liver, increase tissue sensitivity to insulin, decrease hepatic gluconeogenesis, or slow the digestion and absorption of glucose from the intestine. It is essential that the dentist be familiar with their effects and side effects because the length of action differs between the different agents. This information should be sought from the literature or from the patient’s physician.
Insulin is also available in a variety of preparations. Its action could be long (active for 20-30 hours), intermediate (16-20 hours), short (4-12 hours), or rapid-acting (less than 5 hours). Not being experts in these advanced methods of treatment, dentists must communicate with the diabetologist to best design the treatment plan, especially once implant placement has been scheduled. Implant surgery should be scheduled according to the expected length of time a specific medication is active. In general it is preferable to treat these patients in the late morning hours after the administration of their medication and an appropriate meal. This will prevent the most common in-office medical emergency: hypoglycemia. Moreover, the length of the procedure and the difficulty of food intake for hours (hopefully not days!) following the procedure require special attention, possible changes in medication, and close monitoring to prevent an imbalance in the plasma glucose level.
The application of antimicrobial therapy and antiseptic mouth rinses has been shown to improve outcome. However, more failures were seen in type 2 diabetic patients, a fact to be seriously considered when designing the treatment plan.
In diabetic animal models a reduced bone-implant contact and bone density was shown.7 It appears though that the success of osseointegration is greater in the mandible, as shown by a meta-analysis of two implant systems revealing a 3.2% early failure rate, increasing to 5.4% for the late failures.8 Success rates of up to 94.3% have been reported in diabetic patients.9 Interestingly, reports by Olson et al.10 and Fiorellini et al.11 did not show a direct correlation between the success rates of implants and diabetes control, as indicated by the glucose and HbA1c levels.
The use of antibiotics, although controversial in implant therapy, seems to be beneficial in diabetic patients. Prophylactic antibiotics will result in high tissue concentration levels, thus preventing wound infection. Bactericidal low-toxicity antibiotics are recommended, such as penicillin or amoxicillin. Clindamycin, metronidazole, and cephalosporin are also effective.6 Significantly fewer failures occur when preoperative antibiotics are used.12
Additional support for implant therapy indications in both type 1 and type 2 diabetic patients comes from the study of Farzad et al.13 They followed 25 patients with 136 implants and noted a 96.3% success rate during the healing period and 94.1% 1 year later even though the patients were managed by appropriate diabetes control and administration of prophylactic antibiotics.
Although the use of implants remains controversial, it appears that highly trained and experienced operators can ensure successful treatment in diabetic patients as in the general population. The procedure should be postponed for uncontrolled diabetic patients until better control is achieved.14
The prevention of stress, or at least its minimization, is crucial because the stress hormones—endogenous epinephrine and cortisol—elevate the glucose level. Profound local anesthesia will eliminate pain during the procedure and reduce the resulting stress. The small amount of 1 : 100,000 adrenalin in a 1.8-mL cartridge of local anesthesia (18 mcg) does not have a significant effect on plasma glucose level. The total amount of local anesthesia in diabetic patients, to be discussed later, is not different from what is allowed for healthy patients. For patients diagnosed as anxious, the use of anxiolytic means such as nitrous oxide is highly recommended. It is the safest and simplest sedation technique. Sedative drugs such as diazepam or midazolam can be given to the diabetic patient the night before and/or the morning of the procedure to ensure a good night’s rest and stress reduction. Hepatic and renal impairment as well as advanced age require caution and possible consultation with the physician.
The most common emergency scenario is hypoglycemia. It is easily recognizable when the following signs and symptoms develop: confusion, sweating, tremors, agitation, anxiety, dizziness, tingling, and tachycardia. It is preferable to use a glucometer to determine the glucose plasma level. In addition, the dentist should administer 15 g of carbohydrate per os, or in extreme cases 25-50 mL of a 50% dextrose solution intravenously. The emergency situation should resolve within 10-15 minutes.
Hypertension is the most common primary diagnosis in the United States, affecting 50 million Americans.15 In order to apply invasive dental treatments such as osseointegrated implants to this very large segment of the population, a basic knowledge about hypertension and its complications, treatment, and side effects is mandatory. According to the new national guidelines on hypertension summarized for dentistry by Herman et al.,16 “for people older than 50 years a systolic blood pressure greater than 140 mmHg is a much more important risk factor for cardiovascular disease than is elevated diastolic pressure.” Previously, a diastolic blood pressure of 90 mmHg defined hypertension.
Dentists can play an important role in the detection and management of hypertension when the primary goal of therapy is a maximal blood pressure of less than 140/90 mmHg and 130/80 mmHg for diabetic patients. Hypertension may be asymptomatic for years, but it may present with headache, visual blurring, dizziness, and fatigability—all of which can be diagnosed by the dentist.
Uncontrolled blood pressure increases the risk for cardiovascular conditions such as angina pectoris, myocardial infarction, or cerebrovascular accident during dental care, mainly during prolonged stressful situations. Because 30% of hypertensive patients are unaware of their condition, blood pressure readings should be taken for every new patient. Hypertensive patients should have their blood pressure measured before undergoing major dental procedures such as implant placement.
The recommendations presented here were extrapolated from studies based on oral surgery patients as specific studies on hypertension and dental implant therapy were not available. Patients with well-controlled hypertension and patients with stage 1 hypertension (140-159/90-99 mmHg) are considered treatable for all dental procedures.17 However, particular risk assessment is mandatory especially when complex surgical procedures such as sinus lifts, bone augmentation, and multiple implants are anticipated.18
On many occasions dentists are given advice from physicians: “This patient is hypertensive. Avoid using adrenaline in local anesthesia.” This certainly is a matter for debate. Bader et al.19 conducted an extensive review of the cardiovascular effects of epinephrine in dental local anesthesia and did not find sufficient evidence to totally avoid its use. They reviewed 373 papers on this subject. Only 6 studies with 177 hypertensive patients met the inclusion criteria. The patients received anesthesia with 1 : 100,000 epinephrine for dental extractions. In hypertensive patients the systolic blood pressure increased by 4 mmHg, the heart rate increased by 6 beats/minute, and the diastolic blood pressure decreased by 1.0 mmHg. In none of the studies did any patient report adverse events. However, two electrocardiographic studies associated premature ventricular contraction with epinephrine and one reported atrial fibrillation in a patient with cardiac disease.
However, opinion leaders recommend limiting the amount of epinephrine used in hypertensive patients. Two to three cartridges of lidocaine with 1 : 100,000 epinephrine (0.036-0.054 mg) are considered safe in ambulatory patients with severe cardiovascular diseases. However, the use of epinephrine-impregnated retraction cords should be avoided.
Hypertensive patients with a systolic blood pressure of 180-209 mmHg or a diastolic blood pressure of 110-119 mmHg, or patients with recent myocardial infarction or unstable angina pectoris requiring close medical attention are not candidates for elective surgical treatments. The use of antihypertensive medications, although vital for the patient, might have side effects with which the dentist must become familiar. Their systemic effects are of key importance to the provision of care, their interaction with the medication that the dentist administers is relevant, and they might induce oral damage.
Mild to moderate hypertension is not an independent risk factor for perioperative cardiovascular complications. Moreover, risk assessment is essential for all patients anticipating complex surgical procedures such as implant therapy.
The stressful situation created by any surgical intervention should be dealt with. Inhalosedation with nitrous oxide oxygen is safe and simple to apply and is thus recommended. Oral sedation with diazepam, 10-mg tablet, both on the night previous to and on the morning of the intervention is advised. For the conscious sedation of anxious patients other drugs can be used, such as triazolam (Halcion) 0.125-0.5 mg or midazolam (Versed) 0.5 mg/kg.
A hypertensive crisis has sequelae that can endanger the patient’s life, namely myocardial infarction, heart insufficiency, or cerebrovascular accident. The management of a hypertensive crisis when blood pressure values reach 250/130 mmHg should include the following steps:
Too often dentists are advised by physicians not to use epinephrine-containing anesthetic solutions for certain patients. Is this advice based on hard data? Should we limit its use? What are the side effects that dentists should be aware of?
The advantages of vasoconstrictors in local anesthesia are obvious and have been widely discussed in the literature. Both the length of time and the level of anesthesia are increased, leading to less bleeding and fewer toxic effects of the anesthetic substance. In a well-designed study Knoll-Kohler et al.24 used articaine 4% with epinephrine 1 : 200,000 and articaine 4% with double the concentration of epinephrine, 1 : 100,000, for the extraction of wisdom teeth. A higher systemic norepinephrine concentration in the former group pointed to the necessity of introducing the vasoconstrictor to reduce pain-induced stress. Their results underline the advantage of using appropriate concentrations of vasoconstrictors, especially for patients with cardiovascular disease for whom stress must be avoided as much as possible. It is of interest to note that the adrenal medulla secretes 2.5-7.5 mcg of epinephrine per minute, whereas during severe stress this secretion increases twentyfold to fortyfold. The sympathetic nervous system is stimulated by pain, resulting in the release of norepinephrine from the nerve endings.
Both norepinephrine and epinephrine affect the cardiovascular system, but in different ways and on different receptors. The stimulation of beta-1 receptors in the heart increases the heart rate, which tends to increase the blood pressure as well, whereas the beta-2 receptors induce pulmonary vasodilatation, which tends to reduce the blood pressure. On the other hand, the alpha-adrenergic system has a mainly peripheral action, inducing vasoconstriction.25 Norepinephrine stimulates mainly the beta-1 receptors, resulting in a significant increase in blood pressure and pulse. It becomes obvious that combining it with local anesthetics is not recommended.
Epinephrine, which stimulates both beta-1 and beta-2 receptors, has a more balanced influence, resulting in minimal if any cardiovascular changes. The pharmacokinetics of epinephrine are also advantageous, since it is metabolized and eliminated from the blood in less than 10 minutes with a plasma half-life of less than 1 minute.26 In other words, even if there are hemodynamic changes, they will be short-lived.
The alpha-agonist effect of epinephrine and norepinephrine is peripheral vasoconstriction with a limited influence on blood pressure. Hersch et al.27 found an increase in the systolic blood pressure, from 125 to 131 mmHg, when injecting local anesthetics with epinephrine 1 : 100,000 and no change with a 1 : 200,000 concentration. The diastolic pressure decreased with both formulations from 73 to 69 mmHg.