Odontogenic Infection 1

2024 Microbiology Odontogenic infections are caused by bacteria that are part of the normal oral flora: (bacteria of plaque, those on mucosal surfaces, and those found in the gingival sulcus). These bacteria are primarily aerobic gram-positive cocci, anaerobic gram-positive cocci, and anaerobic gram-negative rods 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. As the infection progresses more deeply, different members of the infecting flora can find better growth conditions and begin to outnumber the previously dominant species. Almost all odontogenic infections are caused by multiple bacteria (anaerobic and aerobic bacteria) 50% are caused by anaerobic bacteria 44% are caused by mixed bacteria (aerobic & anaerobic) 6% are caused by aerobic bacteria Odontogenic infections pass through 4 stages 1- Inoculation Stage The predominant aerobic bacteria in odontogenic infections are the Streptococcus milleri. These facultative organisms (can grow in the presence or the absence of oxygen), may initiate the process of spreading into deeper tissue Inoculation Stage initial stage Periapical Periodontal if see early infection >> inculaton or celibus mainly aerobic late > anarobic Page 1 2024 2- Cellulitis Stage nsky After initial inoculation into deeper tissues, the S. milleri can synthesize hyaluronidase, which allows the infecting organisms to spread through connective tissues, initiating the cellulitis stage of infection, several infection 3- Abscess Stage favourable Streptococci create a favorable environment for the growth of anaerobes as they release of essential nutrients, lower pH in the tissues, and consume local oxygen supplies The anaerobic bacteria are then able to grow and predominate and cause liquefaction necrosis of tissues by their synthesis of collagenases. Localization of spread infection As collagen is broken down and invading WBCs necrose and lyse, clinically recognizable abscess forms. In the abscess stage, anaerobic bacteria predominate. 4- Resolution Stage If occurs when the abscess drains spontaneously through skin or mucosa, or it is surgically drained. Page 2 2024 Direction of Spread of Infection Odontogenic infections have two major origins a) Periapical: as a result of pulpal necrosis and subsequent bacterial invasion into the periapical tissue, and b) Periodontal: as a result of a deep periodontal pocket that allows inoculation of bacteria into the underlying soft tissues. Removing of the cause Treatment of the necrotic pulp by endodontic therapy or extraction of the tooth should resolve the infection. Antibiotics alone may arrest, but do not cure, the infection because the infection is likely to recur when antibiotic therapy has ended without treatment of the underlying dental cause. The infection spreads 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 surrounding soft tissues The location of the infection arising from a specific tooth is determined by the following two major factors a) The thickness of the bone overlying the apex of the tooth b) The relationship of the site of perforation of bone to muscle attachments. A) The thickness of the bone overlying the apex of the tooth When infection starts, it spreads along the lines of least resistance. If the labial bone overlying the apex of the tooth is thinner than palatal bone infection spreads through labial soft tissues. If the tooth is severely proclined (Palatal bone is thinner than labial bone) infection spreads through palatal bone into the soft tissue "palatal abscess" Page 3