O ne of the most difficult problems to manage in dentistry is an odontogenic infection. These infections may range from low-grade, well-localized infections that require only minimal treatment to severe, life-threatening fascial space infections. Although the overwhelming majority of odontogenic infections are easily managed by minor surgical proce-
dures and supportive medical therapy that includes antibiotic administration, the practitioner must con-stantly bear in mind that these infections occasionally become severe in a very short time.
This chapter is divided into several sections. The first section discusses the typical microbiology involved in odontogenic infections. Appropriate therapy of odonto-genic infections depends on a clear understanding of the causative bacteria. The second section discusses the natu-ral history of odontogenic infections. When infections occur, they may erode through bone and into the overly-ing soft tissue. Knowledge of the usual pathway of infec-tion from the teeth and surrounding tissues through the bone and into the overlying soft tissue planes is essential when planning appropriate therapy. The third section of this chapter deals with the principles of management of odontogenic infections. A series of principles are discussed, with consideration of the microbiology and typical path-way of infection. The chapter concludes with a section on prophylaxis against infection. The prophylaxis of wound infection and of metastatic infection is discussed
MICROBIOLOGY OF ODONTOGENIC
The bacteria that cause infection are most commonly part of the indigenous bacteria that normally live on or in the host. Odontogenic infections are no exception, because the bacteria that cause odontogenic infections are part of the normal oral flora: those that comprise the bacteria of plaque, those found on the mucosal surfaces, and those found in the gingival sulcus. They are primarily aerobic gram-positive cocci, anaerobic gram-positive cocci, and anaerobic gram-negative rods. These bacteria cause a vari-ety of common diseases, such as dental caries, gingivitis, and periodontitis. When these bacteria gain access to deeper underlying tissues, as through a necrotic dental pulp or through a deep periodontal pocket, they cause odontogenic infections.
Many carefully performed microbiologic studies of odontogenic infections have demonstrated the microbio-logic composition of these infections. Several important factors must be noted. First, almost all odontogenic infec-tions are caused by multiple bacteria. The polymicrobial nature of these infections makes it important that the cli-nician understand the variety of bacteria that are likely to
cause the infection. In most odontogenic infections the laboratory can identify an average of five species of bacte-ria. It is not unusual for as many as eight different species to be identified in a given infection. On rare occasions a single species may be isolated.
Odontogenic infections have two major origins: (1) peri-apical, as a result of pulpal necrosis and subsequent bac-terial invasion into the periapical tissue, and (2) peri-
odontal, as a result of a deep periodontal pocket that allows inoculation of bacteria into the underlying soft tis-sues. Of these two, the periapical origin is the most com-mon in odontogenic infections.
Necrosis of the dental pulp as a result of deep caries allows a pathway for bacteria to enter the periapical tis-sues. Once this tissue has become inoculated with bacte-ria and an active infection is established, the infection will spread equally in all directions but preferentially along the lines of least resistance. The infection will spread through the cancellous bone until it encounters a cortical plate. If this cortical plate is thin, the infection erodes through the bone and enters the soft tissues. Treat-ment of the necrotic pulp by standard endodontic thera-py or extraction of the tooth will resolve the infection. Antibiotics alone may stop the infection, but the infec-tion is likely to recur when antibiotic therapy is ended and the tooth is not treated.
When the infection erodes through the cortical plate of the alveolar process, it appears in predictable anatom-ic locations. The location of the infection from a specific tooth is determined by the following two major factors: (1) the thickness of the bone overlying the apex of the tooth and (2) the relationship of the site of perforation of bone to muscle attachments of the maxilla and mandible.
PRINCIPLES OF THERAPY
OF ODONTOGENIC INFECTIONS
This section discusses the management of the odonto-genic infection. A series of principles are discussed that are useful in treating patients who come to the dentist with infections related to the teeth and gingiva. The cli-nician must keep in mind the information in the pre-ceding two sections of this chapter to understand these principles.
Principle I: Determine Severity of Infection
Most odontogenic infections are mild and require only minor therapy. When the patient comes for treatment, the initial goal is to assess the severity of the infection. This determination is based on a complete history of the current infectious illness and a physical examination.
Complete history. The history of the patient's infec-tion follows the same general guidelines as any history. The initial purpose is to find out the patient's chief com-plaint. Typical chief complaints of patients with infec-tions are, "I have a toothache," "My jaw is swollen," or "I have a gum boil in my mouth." The complaint should be recorded in the patient's own words.
The next step in taking of the history is determining how long the infection has been present. First, the dentist should inquire as to time of onset of the infection. How long ago did the patient first have symptoms of pain, swelling, or drainage, which indicated the beginning of the infection? The duration of the infection is then dis-cussed. Have the symptoms of the infection been con-stant, have they waxed and waned, or has the patient
Principle II: Evaluate State of Patient's Host Defense Mechanisms
Part of the evaluation of the patient's medical history is designed to establish the patient's ability to defend against infection. Several disease states and several types of drug use may compromise this ability. Compromised patients are more likely to have infections, and these infections often become serious more rapidly. Therefore to manage their infections more effectively, it is impor-tant to be able to discern those patients who may have a compromised host defense mechanism
Principle III: Determine Whether Patient Should Be Treated by General Dentist or Specialist
Most odontogenic infections seen by the dentist can be managed with the expectation of normal rapid resolution. Odontogenic infections, when treated with minor surgical procedures and commonly used antibiotics, almost always respond rapidly. However, some odontogenic infections are potentially life threatening and require aggressive medical and surgical management. In these special situa-tions, early recognition of the potential severity is essen-tial and these patients should be referred to a specialist, usually an oral-maxillofacial surgeon, for definitive man-agement. For some patients, hospitalization will be required, whereas others will be managed as outpatients.
When a patient with an odontogenic infection comes for treatment, the dentist must have a set of criteria by which to judge the seriousness of the infection (Box 15-2). If some or all of these criteria are met, immediate referral must be considered
. Principle IV: Treat Infection Surgically
The primary principle of management of odontogenic infections is to perform surgical drainage and removal of the cause of the infection. Surgical treatment may range from something as simple as the opening of a tooth and extirpation of the necrotic tooth pulp to treatment as complex as the wide incision of soft tissue in the sub-mandibular and neck regions for a severe infection.
The primary goal in surgical management of infection is to remove the cause of the infection, which is most commonly a necrotic pulp or deep periodontal pocket. A secondary goal is to provide drainage of accumulated pus and necrotic debris.
When a patient has a typical odontogenic infection, the most likely appearance will be a small vestibular abscess. With this presentation the dentist has the three options for surgical management of endodontic treat-ment, extraction, or I&D. If the tooth is not to be extract-ed, it should opened and the pulp removed, which results in elimination of the cause and obtaining limited drainage. If the tooth cannot be salvaged, it should be extracted as soon as possible.