Odontogenic infections are among the most frequently encountered infections that patients can be afflicted with. They can be acute, intensifying in severity very quickly over hours or days; or chronic, persisting over several weeks or even months. They can range from low-grade, well-localized infections that require minimal treatment to severe, life-threatening infections that can be among the most difficult conditions to manage in all of dentistry or medicine. The mechanism for why odontogenic infections occur is very well understood and is concisely presented to the dental practitioner. Most odontogenic infections are clinically minor in nature and resolve by treatment of the offending tooth either by endodontic (root canal) treatment or removal of the tooth, with or without the addition of antimicrobial therapy. Early recognition of odontogenic infections and aggressive surgical and/or medical management with antimicrobial therapy is essential. Targeted therapeutic antimicrobial treatment is discussed in an effort to help the dental health care team prevent odontogenic infections from progressing to a dangerous and more complicated level.
Introduction
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Commonly arise from the teeth and have characteristic flora.
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Caries and periodontal disease lead to pulpitis and apical periodontitis that can spread to the alveolar process as well as the deeper tissues of the face, oral cavity, head, and neck.
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May range from low-grade, well-localized infections that require only minimal treatment to severe, life-threatening deep fascial space infections.
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Although the majority of infections are managed by minor surgical procedures and antibiotic administration, sometimes these infections can occasionally become severe and life-threatening in a short time.
Microbiology of Odontogenic Infections
Microflora Activity
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When the bacteria gain access to deeper tissues, such as a necrotic dental pulp or a deep periodontal pocket, they can cause odontogenic infections.
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As the infection progresses deeper, different members of the infecting flora may find better growth conditions and outnumber the previously dominant species.
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Each infectious disease process is unique and differs according to:
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Orofacial infections are unique and do not mimic infections in other locations. These may be:
Aerobic Versus Anaerobic
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An important factor is oxygen tolerance of the bacterial species.
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Aerobic bacteria alone account for 6% of all odontogenic infections.
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Anaerobic bacteria alone are the reason for 44% of odontogenic infections.
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Infections caused by a mixed population of anaerobic and aerobic bacteria comprise 50% of all odontogenic infections.
Pathophysiology of Odontogenic Infections
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The mechanism by which mixed aerobic and anaerobic bacteria cause infections has been established.
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After initial inoculation into the deeper tissues, the facultative S. milleri organisms can synthesize hyaluronidase which allows them to spread through connective tissues and initiate a cellulitis type of infection.
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Metabolic by-products from the streptococci then create a favorable environment for the growth of anaerobes.
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As collagen is broken down and invading white blood cells necrose and lyse, microabscesses form and may coalesce into a clinically recognizable abscess.
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In the abscess stage, the anaerobic bacteria predominate and may eventually become the only organisms found in culture.
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Early infections (cellulitis) may be characterized as aerobic streptococcal infections; and late, chronic infections (abscess) may be characterized as anaerobic infections.
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Clinically, this progression from aerobic to anaerobic seems to correlate with the swelling that can be found in the infected region.
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During the first 3 days, a soft, mildly tender, doughy swelling represents the inoculation stage, in which the invading streptococci are just beginning to colonize the host.
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After 3 to 5 days, the swelling becomes warm, hard, red, and acutely tender as the infecting mixed flora stimulates the intense inflammatory response of the cellulitis stage.
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At 5 to 7 days, the anaerobes begin to predominate, causing a liquefied abscess in the center of the swollen area. This is the abscess stage.
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Finally, when the abscess drains through skin or mucosa or it is surgically drained, the resolution stage begins as the immune system destroys the infecting bacteria and the processes of healing and repair ensue (▶ Table 7.1).
Spread of Infection
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The infection spreads through the cancellous bone until it encounters a cortical plate.
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If this cortical plate is thin, the infection may erode through the bone and enter the surrounding soft tissues.
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Treatment of the necrotic pulp by standard endodontic therapy or extraction of the tooth typically resolves the infection.
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Antibiotics alone may arrest the infection but usually fail at pathogen eradication because the underlying dental cause has not yet been treated.
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If the infection erodes through the cortical plate of the alveolar process, it spreads into predictable anatomic locations.
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The location of the infection arising from a specific tooth is determined by two major factors:
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Infection typically erodes into the soft tissue through the thinnest portions of cortical bone (path of least resistance):
Fascial Spaces Involved in Odontogenic Infections
(▶ Table 7.2)
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Fascial spaces are potential spaces that exist between anatomic barriers which can be expanded into areas of edema in the presence of infection.
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