Clinicians and researchers are increasingly concerned about the overuse of antibiotics and the resulting development of resistant strains of microorganisms.⁶ Although the use of prophylactic antibiotics in dentistry is not a major contributing factor to the problem of overuse, the current situation clearly requires judicious and prudent consideration before antibiotic therapy is administered.⁷ In this article, we review the literature regarding the scientific rationale for antibiotic prophylaxis and develop a series of practice guidelines to use in making clinical decisions.

	CLINICIAL SITUATIONS CONSIDERED FOR ANTIBIOTIC PROPHYLAXIS

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Infective endocarditis. IE, also known as acute or subacute bacterial endocarditis, is defined as an exudative and proliferative inflammatory alteration of the endocardium; it is characterized by vegetations on the surface or within the endocardium that are caused by an infection with microorganisms. A heart valve is commonly involved and proliferation also may occur in the inner lining of the cardiac chambers.^8,9 It is well-recognized that IE arises from the colonization of a preexisting lesion, usually composed of fibrin and platelets, that develops from the disruption of the endothelial lining via abnormal development, disease or presence of foreign bodies and turbulent blood flow. This accumulation of fibrin, blood products and platelets, known as nonbacterial thrombotic endocarditis, or NBTE, adheres to the damaged endothelium. The endothelium is later colonized by bacteria, which, in turn, stimulates further platelet aggregation and the bacteria become incorporated into the vegetations of the lesion.

Congenital or acquired cardiac defects and abnormalities may predispose the heart to endothelial damage and formation of NBTE.⁴ Researchers have suggested that these conditions may alter the hemodynamics of the heart, causing turbulence, which, in some way, increases the exposure of predisposed cardiac endothelium to bacterial infection (usually streptococcal).

The current AHA recommendations for the prevention of IE are significantly changed in respect to patients with various cardiac conditions (Box, "Cardiac Conditions Considered for Prophylaxis").¹⁰ In general, the trend has been to more specifically describe those conditions that pose significant risk for patients and to delineate low- or negligible-risk situations. As a result, antibiotic prophylaxis is now recommended for fewer conditions. These changes also reflect improvements in the understanding of these disease processes and changing attitudes toward the use of antibiotics. The most notable among these changes include reducing the oral dose of amoxicillin from 3 grams to 2 g, recommending that a follow-up dose of antibiotic be discontinued, and replacing erythromycin with other antibiotics as alternatives to the penicillins.^10,11 Dajani and colleagues¹² have reported that 2 g of amoxicillin provides several hours of antibiotic coverage. Table 1 shows the new recommendations for prophylactic coverage for certain dental procedures.

The current American Heart Association recommendations for the prevention of infective endocarditis are significantly changed in respect to patients with various cardiac conditions.

Patients often indicate on a health history form the existence of a heart murmur at some time without having any further knowledge of the nature or extent of the cardiac defect. Because of concerns about the overuse of antibiotics, it is prudent for the dentist to ask for medical evaluation before continuing dental care, rather than to simply prescribe antibiotic prophylaxis when in doubt. Similarly, if a dentist is treating a patient with MVP, it may be reasonable to contact the patient’s physician to determine the specific cardiac anomaly before making a decision about antibiotic prophylaxis.

Patients with prosthetic joints. Prosthetic joint replacement is becoming increasingly common, especially in developed countries with an aging population. It has been estimated that more than 120,000 hips and knees were replaced in 1990 in the United States.¹⁵ In 1997, approximately 450,000 joints of all types were replaced, reflecting an increasing annual trend.¹⁶ Infections of the prosthetic joints may be classified as early- and late-onset.⁹

Early prosthetic joint infection is presumed to occur after microbial contamination of the surgical site during placement of the prosthesis. Late prosthetic joint infection, or LPJI, typically occurs three or more months after surgery and may involve delayed infection from microorganisms introduced at the time of surgery or via hematogenous spread from a distant site, such as the mouth. With devastating morbidity and a mortality rate of 18 percent, orthopedic surgeons are justified in their concerns about LPJI.¹⁷ The incidence of LPJI associated with dental procedures is extemely low. In a review of 2,693 patient records, Jacobson and Matthews¹⁸ found only one instance (0.04 percent) of LPJI that could be even temporally related to dental treatment.

Routine antibiotic prophylaxis for all patients with prosthetic joints is very expensive ($480,000 to prevent one case of LPJI in 1990).¹⁵ Studies of relative risks show that the risk of death caused by anaphylaxis, especially from the penicillins, far outweighed the risks of developing LPJI. These factors have moved the current consensus toward discontinuing routine use of antibiotic prophylaxis. In their advisory statement, the AAOS and the ADA have recommended the use of prophylactic antibiotics only for patients with total joint replacements (not for patients with only pins, screws and/or plates) and compromised immune systems, Type 1 diabetes mellitus, recent (within two years) joint replacement, previous prosthetic joint infections, malnourishment or hemophilia.¹⁶

Dentists still may be faced with the situation in which a physician has recommended antibiotic prophylaxis for a patient that the dentist feels is inappropriate. In such cases, the dentist may choose to consult with the patient’s physician in an attempt to alter that recommendation. In any case, the dental practitioner is responsible for assessing each patient’s situation and deciding whether antibiotic coverage would benefit the patient.

In-dwelling catheters, neurosurgical shunts and other implants. In-dwelling catheters generally do not warrant antibiotic prophylaxis unless the catheter is near the right side of the heart.¹⁹ In cardiac patients with newly placed stents, the initial two weeks after placement is the time of highest risk of infection of the stent. Once an epithelial layer develops, the risks of infection are minimal. For patients in whom catheters are placed to facilitate the administration of systemic medications such as antiviral or chemotherapeutic agents for extended periods, the antibiotic prophylaxis is administered because of the suppressed immune system rather than the catheter itself.

Patients with renal disease who are undergoing hemodialysis constitute another group that warrants some form of antibiotic coverage for dental procedures because of the presence of an arteriovenous shunt for dialysis.²⁰ These shunts may be made from native (autogenous) tissue or from a silastic tube that is implanted. Regardless of type, the shunts are particularly vulnerable to infection, which could be devastating for the patient receiving hemodialysis. Patients receiving continuous peritoneal dialysis, however, do not require antibiotic prophylaxis.

The patient with hydrocephaly poses a different problem because of the placement of shunts.²¹ Patients with hydrocephaly receive shunts to aid in the drainage of cerebrospinal fluid, or CSF. Two types of shunts are used: the ventriculoatrial, or VA, shunt and the ventriculoperitoneal, or VP, shunt. The VA shunt allows drainage of CSF from the lateral ventricles to the venous circulation, whereas VP shunts drain CSF directly into the abdominal cavity.

VP shunts are currently more common than VA shunts. The overall infection rate ranges from 5 to 30 percent, with a mortality rate of up to 40 percent.^22,23 Shunt infections usually will present in the initial two-week postoperative period. The literature suggests that VP shunts carry no higher risk of infection after dental treatment than that before dental treatment, whereas VA shunts are more prone to infection. Therefore, patients with VA shunts should be considered for antibiotic prophylaxis.²³

For other types of implants and devices, such as penile implants, implanted defibrillators and cardiac pacemakers, there is no evidence supporting the routine use of antibiotic coverage for dental procedures.²⁴

	PREVENTION OF LOCAL INFECTION IN SURGICAL OR OPERATIVE SITES IN THE MOUTH

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Surgical procedures in the mouth generally fall into the clean-contaminated category of surgical classification (that is, native organisms are present); this includes routine exodontics, third-molar surgery and orthognathic surgery.²⁵ The incidence of infection after dentoalveolar surgery is very low; for third-molar surgery performed by oral and maxillofacial surgeons, the infection rate is approximately 1 percent.²⁵ Unless the immune system is compromised, antibiotics are not indicated in these cases. For periodontal surgery in which the surgical site is often highly contaminated with microorganisms, antibiotics are usually indicated for most patients with compromised immune systems, for patients at risk of developing IE and for patients with prosthetic joints, especially in the presence of obvious periodontal infections.²⁶

The periodontal literature suggests that localized juvenile periodontitis and other forms of early-onset periodontitis may warrant antibiotic coverage, but there is little evidence to support this view. The American Academy of Periodontology recommends that patients with medical conditions that predispose them to periodontal disease also be considered for antibiotic coverage.²⁷ The use of antibiotic prophylaxis during placement of dental implants is controversial. Preoperative antibiotics appear to decrease the rate of implant failure, but studies have emphasized the prevention of implant failure rather than prevention of the infection itself.²⁸

	PREVENTION OF GENERALIZED SPREAD OF INFECTIONS IN PATIENTS WITH COMPROMISED IMMUNE SYSTEMS

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Patients with compromised immune systems represent a special category for dentists. Because of their illness and/or the treatment rendered for their specific condition, these patients are at higher risk of developing bacteremias, which, in the absence of an adequate host immune system, may rapidly progress to an overwhelming septicemia.^4,29

Patients undergoing chemotherapy are particularly susceptible to systemic infections because their immunosuppressed state is caused by their medications. Not only are these patients at higher risk of developing an infection, but the spread and severity of the infection can potentially be rapid and life-threatening. For these patients, we do not recommend antibiotic coverage for routine dental procedures, but it should be considered for invasive procedures such as dental extractions, deep periodontal scaling and other procedures that cause significant bleeding and seeding of bacteria into the systemic circulation.

Patients with human immunodeficiency virus and AIDS, in the absence of bacterial infection, do not generally require antibiotic prophylaxis.¹⁹ However, a clinical judgment should be made when a bacteremia is likely to occur, such as in cases of extraction of teeth with abscesses. Practitioners should consider the use of antibiotics in these patients because of the higher risk of overwhelming systemic infection and an inability to defend against microbial insult because of a depressed immune system.

The final group in this category of patients with compromised immune systems is the population with diabetes. Diabetics, especially those who are insulin-dependent, have a higher rate of systemic disease and often exhibit some degree of leukocyte dysfunction, which may contribute to higher incidences of infection.³⁰ Insulin-dependent diabetic patients, particularly those with poorly controlled disease, are vulnerable to infections. Therefore, antibiotic coverage for invasive dental procedures is recommended in patients with poorly controlled or uncontrolled diabetes, but is generally not required for those in whom the disease is well-controlled or for those who are not dependent on insulin therapy.³¹

There is some ongoing debate among clinicians and authors over the use of antibiotic coverage for chronic intravenous drug abusers and for patients who have undergone splenectomy.^32,33 The incidence of IE among chronic intravenous drug abusers is several times higher than that seen in the healthy population. Although there is no clear-cut evidence that antibiotics are effective in cases of native valve endocarditis, antibiotic coverage may be warranted until new evidence suggests otherwise.³³ There is also no evidence that patients who have undergone splenectomy are at higher risk of developing infection from dental procedures than is the general population. These patients are, however, more susceptible to infections from encapsulated organisms such as Pneumococcus and Hemophilus type B species; physicians often recommend the use of antibiotic prophylaxis for invasive dental procedures in such cases.^32,34

	DENTAL PROCEDURES AND ANTIBIOTIC PROPHYLAXIS

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The link between dental procedures and IE remains a controversial subject. In 1984, Guntheroth³⁵ reported a low incidence of bacteremia associated with dental procedures and suggested that meticulous oral hygiene was more important in the prevention of IE than any antibiotic regimen. In a population-based control study involving 273 patients with cardiac lesions, Strom and colleagues³⁶ found that dental procedures were not a risk factor for IE, even in patients with valvular abnormalities. Furthermore, even when the recommended antibiotic regimen was administered, it was not 100 percent effective in preventing IE.^36,37

The evidence is now clear that not all dental procedures warrant the use of antibiotic prophylaxis. It is safe to perform dental procedures (such as restorative and prosthetic treatment) in which the potential for bleeding is minimal in at-risk patients without the use of antibiotic prophylaxis. Invasive treatment in which bacteremia is more likely to occur (such as periodontal scaling, periodontal surgery and dental extractions) warrant the use of antibiotic coverage in patients with specific conditions, such as prosthetic heart valves and a history of endocarditis.¹⁴ The box ("Dental Procedures Considered for Antibiotic Prophylaxis in Susceptible Patients"; see page 371) is a proposed guideline for clinical situations in which antibiotic prophylaxis is recommended for invasive dental procedures. Table 2 (see page 372) summarizes our recommendations for administering antibiotic prophylaxis.

	SUMMARY

TOP ABSTRACT CLINICIAL SITUATIONS CONSIDERED... PREVENTION OF LOCAL INFECTION... PREVENTION OF GENERALIZED SPREAD... DENTAL PROCEDURES AND ANTIBIOTIC... SUMMARY REFERENCES

In this article, we have delineated some of the indications for antibiotic prophylaxis in dentistry. Our recommendations can serve as the basis for guidelines for the practicing dentist, with the caveat, however, that guidelines are no substitute for sound clinical judgment.