CHAPTER 3 Evaluation and Selection of the Implant Patient
INTRODUCTION TO PATIENT SCREENING AND MEDICAL EVALUATION
Implant dentistry has progressed amazingly during the past 20 years. Every aspect, whether scientific or clinical, is taught in academic institutions around the world with a discipline and demands equal to those of other types of surgical instruction. However, one vital element that has been underemphasized is the meticulous physical evaluation of patients before, during, and after implant treatment. This element is becoming increasingly important because, as mentioned previously, life expectancy in the industrialized nations is increasing, and a growing number of elderly patients will have implant-supported prostheses.
Absolute Contraindications
Absolute contraindications arise from health conditions that may jeopardize the patient’s overall health and seriously compromise the survival of implanted systems, resulting in residual chronic complications (Table 3-1).
Table 3-1 Systemic Absolute Contraindications to Implant Surgery and Their Impact on Predictability
| Health Condition | Risks for Patient’s General Health | Severity of Immediate Implant Complications | Long-Term Predictability of Implant System |
|---|---|---|---|
The number of + relates to the degree of gravity of the complications associated with implant and graft surgery. One + is the least complicated (least predictable), and four ++++ is the most complicated (most predictable). Zero corresponds to total unpredictability.
1. Recent myocardial infarction. Contemporary cardiology, including the use of nonsurgical interventions, has greatly improved the care and treatment of patients who have had a myocardial infarction (MI). Permanent use of potent anticoagulants is required much less frequently, whereas the cardiovascular protectors are used extensively; these include beta-adrenergic blocking agents, antihypertensive drugs, and antiplatelet agents (aspirin, clopidogrel bisulfate [Plavix]). Patients who have had an MI usually reach stable condition 6 to 12 months after initiation of primary care. However, it is important to avoid any surgical stress that could trigger uncontrolled vasoconstriction, with possible tachyarrhythmias, until the stable condition has remained unchanged for at least 3 to 6 months. In addition, if the patient has been prescribed anticoagulants or antiplatelet agents, interrupting administration of these drugs in the early stages of the disease may prove extremely dangerous.
2. Valvular prosthesis. The onset of bacteremia in patients fitted with valvular prostheses constitutes a major threat to the longevity of the cardiac valve. The oral cavity traditionally has been recognized as the principal gateway for such infections. Consequently, no implant surgery should be planned until the patient has reached stable condition, which usually occurs 15 to 18 months after cardiac surgery. Depending on the type of valve used (i.e., a mechanical valve), the patient may be required to take potent anticoagulants permanently. Any planned procedure must take into consideration surgical stress, anticoagulant imbalance, and the risk of an infection that in extreme cases may lead to endocarditis and loss of the artificial valve. All patients with prosthetic cardiac valves require prophylaxis with antibiotics before dental procedures that would result in manipulation of the gingival tissue or the periapical region of the teeth, or interruption of the mucosal surfaces.
3. Coronary stents. The incidence of cardiac disease seems to be on the rise, and more and more patients are undergoing percutaneous coronary angioplasty, with or without placement of coronary stents, instead of open heart surgery. Symptomatic cardiac conditions no longer are the primary indication for interventional therapy. In the absence of symptoms, if patients have a significant family history of cardiac or coronary artery disease or a lifestyle that puts them at risk for such disease, early intervention is recommended, through lifestyle changes with or without medications. Coronary artery disease may be detected in these asymptomatic patients through a positive stress test result. In other cases, coronary artery disease is diagnosed in patients who seek treatment for acute coronary syndrome (unstable angina), which may result in urgent angioplasty and the placement of stents. Coronary stents also are placed when arterial occlusions are identified during an angiogram after an MI. These patients undergo aggressive antiplatelet therapy for at least 6 months and sometimes for an indefinite period. Therefore, no implant surgery should be planned for at least 6 months after placement of the stents, because the stress of surgery on the healing but damaged myocardium may compromise it further, resulting in a dysrhythmia during implant surgery. In addition, achieving proper hemostasis during and after dental surgery could be challenging and could result in significant loss of blood volume or the development of a hematoma, which may compromise the viability of the surgical area.
4. Severe renal disorder. Severe renal disorder is probably the most important single contraindication to any form of implant or bone graft surgery. It has a number of possible causes; the most common are hypertensive vascular disease, diabetic nephropathy, polycystic kidney disease, glomerulonephritis, recurrent kidney infections (pyelonephritis), malignant or voluminous benign tumors, and complications arising from kidney stones. Most recently in Europe and other industrialized countries, the reappearance of tuberculosis of the kidneys has further expanded the list of potential complications. In all events, damage to the kidneys may cause bone destruction through reduced gastrointestinal (GI) absorption of calcium and excessive urinary calcium loss as a result of decreased kidney production of the active metabolite of vitamin D. In patients with renal insufficiency, retention of phosphate further triggers excessive production of parathormone (PTH), which aggravates bone demineralization. The combination of vitamin D deficiency and excessive production of PTH can rapidly result in metabolic osteopenia. The uremic environment further compromises the body’s resistance, resulting in an increased risk of odontogenic infections.
Fig. 3-1 illustrates daily calcium metabolism. The kidneys initially filter about 10 g of calcium a day into the primary urine.
5. Treatment-resistant diabetes. Treatment-resistant diabetes is confirmed, severe diabetes that does not respond to treatment. The complications that arise with this disorder are related to the serum hyperosmolarity (e.g., sugar, urea), metabolic disorders (e.g., sodium [Na+], calcium [Ca++], phosphate [PO4–], and magnesium [Mg++]), dehydration, and microdisease or macrodisease. These metabolic and vascular derangements predispose the patient to tissue degeneration, compromised healing, and a higher risk of infection.
6. Generalized osteoporosis. Generalized osteoporosis is an anatomic and a structural syndrome involving significant loss of bone mass and bone volume, which leads to rarefaction of cancellous bone and thinning of the cortical plates. Bone becomes devoid of osteoid and shows osteoclasia and medullary fibrosis. Consequently, nonintegration of endosseous implants results. A useful screening tool for evaluating the extent of osteoporosis is bone densitometry (dual photon absorptiometry). Bone densitometry studies can identify individuals with osteopenia (modest-risk patients) and those with osteoporosis (high-risk patients). It should be performed regularly on all patients with clinical signs of bone fragility like spontaneous fractures (hip, vertebrae, femur).
7. Chronic or severe alcoholism. Chronic or severe alcoholism is a major health disorder that frequently leads to liver disorder, cirrhosis, and medullary aplasia. These in turn give rise to a cascade of possible complications, such as platelet diseases, distress infarction, aneurysm, and the risk of insidious hemorrhage. In patients with severe alcoholism, healing often is retarded, which is aggravated by malnutrition, psychological disorders, inadequate hygiene, and the risk of a major infection. For the purposes of implant surgeons, the most common tests for hepatic disorders measure the following:
• γ-Glutamyl-transpeptidase (γ-GT): (Normal: <25 mU/mL). Elevated values may be seen in alcoholic cirrhosis (to 50 mU/mL), hepatitis (to 100 mU/mL), jaundice (to 200 to 300 mU/mL), and pancreatic cancer (to 1000 mU/mL).
• Serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT): (Normal: SGOT, 5 to 35 IU; SGPT, 5 to 25 IU). SGOT and SGPT are elevated in hepatic cytolysis, infectious and toxic hepatitis, and prolonged salicylic treatment. With myocardial infarction, SGOT alone is elevated.
• Bilirubin: (Normal: Total <10 IU). Bilirubin is elevated in cases of hemolysis, cholestasis, and jaundice.
• Alkaline phosphatases: (Normal [pH of 9.2]: 13 to 39 IU, or 0.22 to 0.65 mmol/sec/L). The alkaline phosphatases are elevated with hyperparathyroidism, Paget’s disease, hepatic disorders, and bone metastases.
• Prothrombin time (international normalized ratio) (PT/INR): (Normal: 11.5-13.5 seconds). The prothrombin time (PT) is a coagulation indicator (it also is reported as the international normalized ratio [INR]). Vitamin K participates in coagulation with factors II, V, VII, IX, and X. The PT measures the activity of factor VII, the factor with the shortest serum half-life, and reflects the overall integrity of the coagulation cascade. This provides an accurate indication of the synthetic function of the liver.
8. Treatment-resistant osteomalacia. Rickets resulting from vitamin D deficiency is a rare disease in the industrialized countries and is seldom seen in adults. In more than 95% of cases, this mineralization deficit (hypophosphocalcific bone with osteoidosis), which leads to demineralized osteopathy (soft bone), responds favorably to vitamin D therapy coupled with calcium supplementation. However, if the treatment fails, osteomalacia may lead to nonintegration of an implant and a higher risk of infection.
9. Current radiotherapy. Radiotherapy results in a number of insults to the body, primarily disruption of defense mechanisms, compromise of the endosseous vascular system, and inhibition of osteoinduction. The periosteum is the principal “organ” in which physiologic activities are almost completely disrupted. Depending on the proximity to the irradiated zone, this may lead to soft and hard tissue necrosis, risk of a major infection, and disruption of osteoconduction.
10. Severe hormone deficiency. Patients with a severe hormone deficiency have more than two different families of hormone disorders. The endocrine systems most affected that may be screened are the thyroid and parathyroid, pancreas, gonads, and adrenal and pituitary systems.
11. Drug addiction. Most drug addicts suffer from loss of a sense of priorities, low resistance to disease, predisposition to infection, malnutrition, psychological disorders, lack of hygiene, and difficulty with follow-up.
12. Heavy smoking habits. Heavy smoking (more than 10 cigarettes a day) was added to the list of absolute contraindications in 1996 because of the occurrence of a number of long-term implant complications in heavy smokers who had no other systemic disorders. In addition to poor healing in the early stage, problems arose as a result of relatively accelerated bone loss (possibly because of altered vascularity) and inflammatory diseases related to poor oral hygiene.
13. Pregnancy. Most medications used before, during, and after surgery are listed as category D for pregnant women: There is positive evidence of possible fetal risk, but the benefits from use in pregnant women outweigh the risk. According to current obstetric practice, no good reason can be advanced for performing implant or any elective surgery on pregnant patients.
Relative Contraindications
Patient selection with regard to relative contraindications is much more subtle, and among all the criteria, the dental practitioner’s judgment remains the critical factor. If the practitioner is not medically oriented, the patient may need to be referred to a specialist. If a disorder has been adequately corrected, the dental practitioner can carry out the treatment plan; otherwise, treatment should be postponed until optimal conditions prevail. Table 3-2 presents the possible effects of relative contraindications on the success of implant and bone graft surgery.
Table 3-2 Systemic Relative Contraindications to Implant Surgery and Their Impact on Predictability
| Health Condition | Risks for Patient’s General Health | Long-Term Implant Predictability in Absence of Proper Diagnosis or Treatment | Patient’s Possible Response to Medical Treatment Before Implant Surgery | Long-Term Implant Predictability After Proper Diagnosis and Treatment |
|---|---|---|---|---|
(2) ++
++
++
+++
The number of + relates to the degree of gravity of the complications associated with implant and graft surgery. One + is the least complicated (least predictable), and four ++++ is the most complicated (most predictable). Zero corresponds to total unpredictability.
1. Acquired immunodeficiency syndrome (AIDS) and other seropositive diseases. A patient who is seropositive (i.e., tests positive for the human immunodeficiency virus [HIV]) may be considered normal, because the current statistical life expectancy after primary infection is 15 to 20 years. In a patient confirmed to have AIDS, the indications for an implant procedure are evaluated according to the classification system established by the federal Centers for Disease Control and Prevention. The stage of disease development and the patient’s life expectancy and wishes are important considerations. Careful assessment for possible systemic complications from the disease may contraindicate any form of surgery or may dictate a pragmatic treatment plan with more realistic objectives based on function, comfort, and relief.
2. Prolonged use of corticosteroids. Prolonged use of corticosteroids often is associated with retarded healing, disorders of calcium and phosphate metabolism (osteopenia and osteoporosis), and medullary aplasia. A number of authors also have reported bone fragility, adrenal deficiency, metabolic disorders (including disorders of blood glucose metabolism), and fluid retention. Prolonged corticosteroid use also may inhibit bone formation. Therefore, it is important that the dental practitioner determine the reason for corticosteroid treatment and evaluate the patient’s response to it. If corticosteroids are used exclusively for their antiinflammatory properties, resolution of this contraindication may be as simple as changing the medication to one of the many newer nonsteroidal antiinflammatory drugs.
3. Calcium and phosphate metabolism disorders. An imbalanced diet (e.g., excessive protein, inadequate calcium and/or vitamin D intake) may lead to such disorders. Also, minor hormone deficiencies (especially during menopause) in conjunction with systemic disorders and an unhealthy lifestyle may bring about a calcium and phosphate imbalance. A typical example is a patient with a disorder of the GI tract, such as inflammatory bowel disease or chronic diarrhea, which may be corrected or contained by carefully planned, long-term treatment. If such problems cannot be managed effectively, daily calcium and phosphorus absorption may be disrupted completely, leading to metabolic bone disease and poor quality of mineralized bone.
4. Hematopoietic disorder. The possible complications from hematopoietic disorders in the short and medium terms are not as dramatic as those encountered in other forms of frank bone pathology and osteoporosis. However, satisfactory functioning of the hematopoietic system is an essential factor for long-term success of implant and reconstructive surgery. If a bone marrow disorder is suspected, the maturation cycle of the megakaryocytes (the precursors of platelets) must be explored. It also is important to screen the transformation of the premonocyte lineage to macrophages, osteoclasts, and circulating monocytes. The same attention must be paid to the lymphocyte cycle.
5. Buccopharyngeal tumors. Buccopharyngeal tumors must be analyzed with regard to their malignancy or nonmalignancy, their proximity to the proposed implant site, and the current oncologic treatment. If radiotherapy has been done very close to the planned surgical site, the contraindication becomes absolute. However, routine rejection grafts or implants should be discouraged after resective surgery. If no reason exists to suspect short- or medium-term metastases or extension of the tumor, and the patient otherwise has a satisfactory systemic screening result, the individual patient may be offered improved oral health rather than being required to endure an indefinite waiting period to exclude possible recurrence of a tumor.
6. Current chemotherapy. Few studies in the implantology and bone grafting fields have focused on the role of anticancer drugs in patient screening. Implant and bone graft surgeons frequently have followed a restrictive general guideline, with some ambiguity. In fact, many of the drugs used in contemporary anticancer regimens have a very limited or unknown direct destructive role with regard to implantology. For instance, methotrexate, a common chemotherapeutic agent, is used extensively (in smaller dosage) in contemporary rheumatology. However, when used in massive doses in oncology, it may cause severe thrombopenia and may disturb the osteogenic cycle. The chemotherapy contraindication essentially is related to the damage done to the vital organs, which may also be involved in calcium metabolism. Furthermore, when chemotherapy is administered for bone metastases, patient screening should take into account the extensiveness of the metastasis rather than the drugs used to contain it. An additional factor the dental practitioner should evaluate before performing implant surgery is the patient’s degree of tolerance to the administered drugs. In any event, close collaboration between the implant surgeon and the oncologist is mandatory.
Modern chemotherapy uses a wide range of drugs, which belong to 10 to 12 pharmacologic families. Treatment for each patient may include a complex combination of these drugs. Table 3-3 shows the principal cancer treatments that may present absolute contraindications to an implant procedure during the time they are administered or for up to 6 months thereafter. Table 3-2 also shows a proportionately limited number of drugs that are incompatible with the simultaneous insertion of implant devices. The interpolating agents on the whole, seem to be devoid of adverse effects on implantology. The interferons and interleukins prescribed in advanced stages of pathology, however, are particularly contraindicated.
7. Mild renal disorder. Mild renal disorders are common and frequently are revealed by an initial blood test after the first physical examination. However, such disorders may be predictors of the onset of major renal disorders or other systemic conditions, which then become absolute contraindications to implant and preprosthetic surgery. The wise course, therefore, is to investigate all renal problems and determine whether they are no more than mild disorders that respond to treatment and do not compromise calcium metabolism.
8. Hepatopancreatic disorder. Gallstones and infectious and viral hepatitis (except the severe hepatitis B, C, and E family) are among the liver disorders that have very little negative effect on the long-term success of implant surgery. Nevertheless, further hepatic tests, after a thorough physical examination, may reveal the onset of more serious liver or pancreatic conditions that would be detrimental to the outcome of implant treatment.
9. Multiple endocrine disorder. Multiple endocrine disorder is a complex syndrome. It can involve metabolic loss of calcium, secondary osteoporosis induced by hyperadrenocorticism, glucocorticosteroid disorders (Cushing’s syndrome, Addison’s disease), mineralocorticosteroid syndrome (Conn’s syndrome), and hyperandrogenism, any of which may lead to implant failure.
Table 3-3 Effects of Chemotherapeutic Drugs on Critical Metabolic Functions
| Type of Anticancer Drug or Agent | Drug Family | Commercial Brand | Principal Complications, Disorders, or Affected Organs |
|---|---|---|---|
| Antifolic | Methotrexate | Thrombopenia, osteogenesis | |
| Nitrogen-mustards (III) Nitrogen-urea (IV) Mitomycin |
Ifosfamide Streptozocin Ametycin |
Blood, bone (osteogenesis) Renal, hepatic, blood Renal, hepatic, blood |
|
| Vinca alkaloids (III) | Vincristine | Renal, hepatic, blood | |
| N/A | N/A | N/A | |
| Bleomycin | Bleomycin | Pulmonary fibrosis | |
| Plicamycin | Mithramycin | Renal, hepatic, blood (Ca)++ |
|
| Progestates | Medroxyprogesterone Ethynodiol |
Renal, hep/> |
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