TISSUE SPACES AROUND THE JAWS
The dissemination of infection in soft tissues is influenced by the natural barriers presented by bone, muscle and fascia. However, the tissue spaces around the jaws are primarily defined by muscles, principally mylohyoid, buccinator, masseter, medial pterygoid, superior constrictor and orbicularis oris. None of these 'spaces' is actually empty and they should merely be regarded as potential spaces that are normally occupied by loose connective tissue. It is only when inflammatory products destroy the loose connective tissue that a definable space is produced.
The spaces are paired except for the submental, sublingual and palatal spaces.
POTENTIAL TISSUE SPACES AROUND THE LOWER JAW (Fig. 33.43)
Figure 33.43 Potential tissue spaces around the jaws. A, Coronal section showing the sublingual and submandibular spaces in the floor of the mouth and the possible routes for the spread of infections from periapical dental abscesses (left). B, Horizontal section through the mandibular molar region showing the associated tissue spaces. C, Inferior view of the floor of the mouth (suprahyoid region of the neck) showing the position of the submandibular and sublingual tissue spaces. (B and C, by permission from Berkovitz BKB, Moxham BJ 2002 Head and Neck Anatomy. London: Martin Dunitz.)
The submental and submandibular spaces are located below the inferior border of the mandible beneath mylohyoid, in the suprahyoid region of the neck. The submental space lies beneath the chin in the midline, between the mylohyoid muscles and the investing layer of deep cervical fascia. It is bounded laterally by the two anterior bellies of the digastric muscles. The submental space communicates posteriorly with the two submandibular spaces. The submandibular space is situated between the anterior and posterior bellies of the digastric muscle and communicates with the sublingual space around the posterior free border of mylohyoid. The sublingual space lies in the floor of the mouth, above the mylohyoid muscles, and is continuous across the midline: it communicates with the submandibular spaces over the posterior free borders of the mylohyoid muscles.
The remaining tissue spaces are illustrated in Fig. 33.43B. The buccal space is located in the cheek, on the lateral side of buccinator. The submasseteric spaces are a series of spaces between the lateral surface of the ramus of the mandible and masseter: they are formed because the fibres of masseter have multiple insertions onto most of the lateral surface of the ramus. The pterygomandibular space lies between the medial surface of the ramus of the mandible and medial pterygoid, and the parotid space lies behind the ramus of the mandible, in and around the parotid gland. The parapharyngeal space is bounded by the superior constrictor of the pharynx and the medial surface of medial pterygoid. It is restricted to the infratemporal region of the head and the suprahyoid region of the neck and communicates with the retropharyngeal space, which itself extends into the retrovisceral space in the lower part of the neck (the tissue spaces of the neck are described on p. 542 and of the pharynx on p. 626). The peritonsillar space lies around the palatine tonsil between the pillars of the fauces, and is part of the intrapharyngeal space. It is bounded by the medial surface of the superior constrictor of the pharynx and its mucosa.
POTENTIAL TISSUE SPACES AROUND THE UPPER JAW
DENTAL ABSCESS (Fig. 33.43)Abscesses developing in relation to the apices of roots ultimately penetrate the surrounding bone where it is thinnest. The position of the resultant swelling in the soft tissues is largely determined by the relationship between muscle attachments and the sinus (the path taken by the infected material) in the bone. Thus, in the lower incisor region, because the labial bone is thin, abscesses generally appear as a swelling in the labial sulcus, above the attachment of mentalis. The abscess may open below mentalis, when it will point beneath the chin. If an abscess from a lower postcanine tooth opens below the attachment of buccinator, the swelling is in the neck; if it opens above, the swelling is in the buccal sulcus. If an abscess opens lingually above mylohyoid, the swelling is in the lingual sulcus; if it is below, the swelling is in the neck. Third molar abscesses tend to track into the neck rather than the mouth, because mylohyoid ascends posteriorly.
Apart from canine teeth, which have long roots, abscesses on upper teeth usually open buccally below, rather than above, the attachment of buccinator. Because its root apex is occasionally curved towards the palate, abscesses of the upper lateral incisors may track into the palatal submucosa. Abscesses of upper canines often open facially just below the orbit. Here the swelling may obstruct drainage in the angular part of the facial vein which has no valves, and it is therefore possible for infected material to travel via the angular and ophthalmic veins into the cavernous sinus. Abscesses on the palatal roots of upper molars usually open on the palate.
The superficial lamina of deep cervical fascia opposes the spread of abscesses towards the surface, and pus beneath it tends to migrate laterally. If the pus is in the anterior triangle, it may find its way into the mediastinum, anterior to the pretracheal lamina, but because the fascia here is so thin it more often approaches the surface and 'points' above the sternum. Pus behind the prevertebral lamina may extend laterally and point in the posterior triangle, or it may perforate the lamina and the buccopharyngeal fascia to bulge into the pharynx as a retropharyngeal abscess.
Upper second premolars and first and second molars are related to the maxillary sinus. When this is large, the root apices of these teeth may be separated from its cavity solely by the lining mucosa. Sinus infections may stimulate the nerves entering the teeth, simulating toothache. Upper first premolars and third molars may be closely related to the maxillary sinus. With loss of teeth, alveolar bone is extensively resorbed. Thus in the edentulous mandible the mental nerve, originally inferior to premolar roots, may lie near the crest of the bone. In the edentulous maxilla, the sinus may enlarge to approach the oral surface of the bone. Occasional bony prominences termed the torus mandibularis, torus maxillaris and torus palatinus, may lie lingual to the lower premolars or molars, the upper molars. They in the midline of the palate and may need surgical removal before satisfactory dentures can be fitted.
Severe systemic infections during the time the teeth are developing may lead to faults in enamel, which are visible as horizontal lines (cf. Harris's growth lines).