Pathway 4
Lingual spread inferiorly beyond the mylohyoid muscle into the submandibular space
This pathway will occur if the tooth apex is closer to the lingual bone cortex (i.e the posterior aspect of the teeth) and so the swelling will be visible on the lingual aspect
General Notes on Infection
The bacteria enters and spreads down to the apex of the tooth, where it eventually erodes its way through the mandibular bone cortex.
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When the apex of the tooth is closer to the lingual bone cortex, the infection will exit lingually.
However, if the roots of the tooth are long and lie inferior to the origin of the mylohyoid muscle, the exit point is usually below this origin, resulting in a submandibular space infection.
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Once the infection is within the submandibular space, it can travel:
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Anteriorly to the submental space
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Posteriorly to the sublingual and pharyngeal spaces.​
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The submandibular space communicates with the sublingual space at the posterior margin of the mylohyoid.
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The infection can travel to the submental space (green highlighted area in diagram) because there is no barrier to the spread of infection anteriorly. This is because it is only the anterior belly of digastric muscle separating the submandibular and submental spaces.
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Therefore the infection can make its way around the muscle, enabling the spread of infection on both sides (i.e bilaterally).​
Anatomy of Infection-Related Spaces
Submandibular Space
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Borders:
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Superior = inferior and lingual surfaces of the mandible mylohyoid muscle
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Inferior = hyoid bone
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Lateral = superficial fascia and the body of the mandible
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Medial = hyoglossus and mylohyoid muscle
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Anterior = anterior belly of digastric muscle
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Posterior = posterior belly of digastric muscle and the stylohyoid muscle
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Contents = facial artery and vein, marginal mandibular nerve, mylohyoid nerve, submandibular gland, and lymph nodes
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Infection signs and symptoms = swelling at the inferior border of the mandible that extends medially to the2
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anterior digastric muscle and posteriorly to the hyoid bone
Green area highlighting the submandibular space.
Submental Space
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Located adjacent to the mandibulae midline, under the chin and is between the anterior belly of digastric muscle.
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Superiorly - myolohyoid muscle
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Inferiorly - platysma muscle
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Contents = anterior jugular veins and lymph nodes
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Infection signs and symptoms = submental oedema and erythema
Green area highlighting the submental space.
Parapharyngeal Space
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This space is continuous with the submandibular space anterior and the retropharyngeal space posteriorly
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It runs from the base of the skull to the hyoid bone – i.e superior and inferior borders
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Medial border = buccopharyngeal fascia
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Lateral border = investing fascia of deep cervical fascia
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The parapharygenal space includes the lateral pharyngeal space and the retropharyngeal space,
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These spaces form a “ring” around the pharynx and act as a pathway for spread of infections from the orofacial region to the neck and mediastinum
Pathway 4 - Clinical Considerations
Similar to pathway 3, if the infection spreads to the sublingual space, the increased swelling of these areas leads to the tongue being elevated and reduces the function of the muscles of mastication.
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This causes trismus ("lock-jaw") and even asphyxia due to swelling of the laryngeal inlet.
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Clinically, an infection in the parapharyngeal space will cause trismus and lateral neck swelling.
Ludwig’s Angina
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This is life-threatening cellulitis of the soft tissue involving the floor of the mouth and neck
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It involves 3 compartments/spaces (perimandibular spaces) = sublingual, submental and submandibular space.
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This is because the spread of infection from the submental space posterolateral to the anterior digastric muscles allows for direct bilateral extension of infections to the submandibular and sublingual spaces.
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When the perimandublar spaces are bilaterally involved in an infection, it is known as Ludwig’s angina
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The infection is rapidly progressive, leading to potentially fatal airway obstruction.
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Severe swelling is almost always seen, with elevation and displacement of the tongue, and tense, hard, bilateral induration of the submandibular region superior to the hyoid bone.
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The patient usually has trismus, drooling, difficulty swallowing and difficulty breathing.
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Cervical Fascia Spaces
Include the parapharyngeal, retropharyngeal, prevertebral spaces
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If infection spread to cervical fascia spaces, they can cause symptoms such as:
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Pain
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Trismus – this is muscle spasms in your TMJ and so your jaw becomes so tight that you can’t open it ("lock-jaw")
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Swollen soft palate with deviated uvula
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Difficulty swallowing and speaking
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Inability to locate the angle of the mandible
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They can also track down towards the mediastinum
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If this occurs, infection spreads inferiorly by the cervical fascia spaces to the mediastinum potentially causing mediastinitis (inflammation of the mediastinum)
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This condition can lead to sepsis and organ failure.
Stages of Infection
In a healthy tooth crown is made up of the dense mineralised outside layer of enamel, supported by the sensate less well mineralised layer that is dentine which contains dental tubules which connect to the pulp chamber in the middle of the tooth. The vital part of the tooth which is not mineralised is call the pulp chamber contains the blood vessels and nerves which supply the tooth and this vital material extends into the roots of the tooth as the root canal. The nerves and vessel exit the tooth via the apex of the tooth and join the structures within the periodontal ligament that surrounds the tooth and anchors it to the alveolar bone of the socket.
During the initial stages of the tooth infection, the healthy tooth gets invaded by bacteria contained in plaque, which thrive off the carbohydrates in the mouth and produce acid, which slowly destroys the enamel layer.
When the bacteria gain access to the dentine, they invade the dentinal tubules and in this way gain access to the pulp chamber in the middle of the tooth. Within the pulp chamber, the bacteria incite an acute inflammatory reaction which causes an increase in the hydrostatic pressure within the tooth and leads to hypoxia and this leads to destruction of the contents of the pulp and roots canal system, effectively killing the tooth.
It is here, within the pulp chamber, that most of the bacteria will reside, and having destroyed any access for white blood cells normally carried in the blood vessels, makes eradicating the bacteria difficult without either extracting the tooth itself or at least removing the dead contents of the pulp and root canal system and sterilising this area to kill the bacteria. The presence of bacteria means that their by-products/ toxins can leak out of the apex of the tooth, where the nerve would normally exit, and these insight an inflammatory response in the body, which causes a build-up of pressure within the apical tissues of the periodontal ligament, instigating bone resorption.
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If the roots of the tooth are long and lie below the origin of the mylohyoid muscle, then the exit point of the infection is usually below the origin of the mylohyoid muscle and results in submandibular space infection.
If the roots of the tooth are long and lie below the origin of the mylohyoid muscle, then the exit point of the infection is usually below the origin of the mylohyoid muscle and results in submandibular space infection. The infection can travel to the submental space because there is no barrier to the spread of infection anteriorly – this is because it is only the anterior belly of digastric muscle separating the submandibular and submental spaces so the infection can just make its way around the muscle and so this enables spreading of the infection on both sides (i.e bilaterally).
If the roots of the tooth are long and lie below the origin of the mylohyoid muscle, then the exit point of the infection is usually below the origin of the mylohyoid muscle and results in submandibular space infection. The infection can travel to the submental space because there is no barrier to the spread of infection anteriorly – this is because it is only the anterior belly of digastric muscle separating the submandibular and submental spaces so the infection can just make its way around the muscle and so this enables spreading of the infection on both sides (i.e bilaterally). This leads to facial swelling under the chin and around the neck.