**5. Pathway of facial and cervical infections of odontogenic origins**

#### **5.1. Fascial infections derived from mandibular odontogenic origins**

diaphragm, providing a pathway into the posterior mediastinum and pleural spaces. Infec‐ tions of danger space most commonly occurs when an abscess in the retropharyngeal space

Invasive dental manipulation is known to cause bacteremia and generally considered highrisk procedures for the spread of infection in susceptible patients.[31-48] Sato et al., has shown that the main origin of maxillofacial infections were odontogenic (79.31%), fol‐ lowed by trauma (10.7%), immunosuppression (1.6%), pathologies (1.6%), and other causes (8%).[49] Seppänen et al., also reiterated that the most common dental procedures that precede odontogenic infection complications are: tooth extraction (60%), endodontic treatment (20%), dental implant surgery (8%), restorative treatment (8%) and dental plaque

Lower third molars are more frequently involved in odontogenic infections when compared with other teeth. Flynn et al., presented in their prospective study with 37 consecutive hospitalized patients, a 68% prevalence rate of this group of teeth in association with odonto‐ genic infections, followed by other lower posterior teeth (premolars, first and second molars), without anterior teeth involvement.[13] Third molar removal is one of the most regular dentoalveolar surgical procedures.[10, 26, 52-65] With an 80% prevalence of retained third molars in the adult population,[23] appropriate treatment, and especially prophylactic third molar removal remains a key focus of interest in healthcare with both medical and economic dimensions. It is generally accepted that substantial risks may arise both from third molar removal,[6, 29, 37, 60, 66, 67] as well as from a "wait and see "policy.[4, 11, 14, 25, 33, 44, 65]

The severe infections of odontogenic origin frequently involve a complex polymicrobial mix of aerobes, facultative aerobes and strict anaerobes working together. Some species like *Peptostreptococcus, Staphylococcus, Lactobacillus, Prevotella, Treponema, Fusobacterium, Veillonella, Actinomyces, Bacteroide s*sp. and oral *Streptococcus* sp. are frequently associated with infections of odontogenic origin.[13, 36, 43, 46, 48, 56] Sakamoto et al., reported 17 different species collected from a single surgical site.[48] Flynn et al., isolated 90 different strains of microor‐ ganisms in 37 patients, and of these, 17 were penicillin-resistant.[13] Other species can be easily found at the infection sites, but generally, they reflect the indigenous microflora of the oral cavity. Routine culture and sensitivity testing for minor oral infections does not appear to be justified, however, when an infection involves anatomic spaces of moderate or greater severity, or when there is significant medical/immune compromise, the tests become important to the

ruptures through the alar fascia.[21, 23-31]

344 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

and calculus removal (4%).[50-52]

**4. Microbiological involvement**

outcome.

**3. Teeth involved in fascial infections**

Infections originating in the facial planes of the head and neck spread downward along the cervical fascia, facilitated by gravity, breathing, and negative intrathoracic pressure. Knowl‐ edge of the facial spaces and fascial planes is essential for understanding the propagation, pathways, symptoms, and complications of cervical infections.[4, 47] Although the pattern of spread varies among patients, a relatively constant trend in the distribution of infection into the spaces seem to be evident. Some studies clearly demonstrated that the masticatory space is the most prevalent site for odontogenic infection spread. Taken together with the finding that the masticatory space encompasses the posterior mandibular body, ramus, and a part of the alveolar bones of the maxilla, this suggests that the masticatory space may be the initial site of spread of odontogenic infection. This contention was further supported by the finding that mandibular infection more frequently involved the masseter and medial pterygoid muscles (located in the lower compartment of the masticatory space where the mandible is included) than the temporalis and lateral pterygoid muscles (located in the upper compart‐ ment of the space where part of the maxilla is included).[3]

The spaces adjacent to the masticatory space are the parotid space posteriorly, the paraphar‐ yngeal space medially, and the submandibular and sublingual spaces inferiorly (Figure 1).[48] The parapharyngeal space occupies the central position among the masticatory, parotid, and carotid vascular spaces. Therefore, infections in the parapharyngeal space may originate from any adjacent space. A fascia extends from the posterior superior margin of the medial ptery‐ goid muscle to the base of the skull to separate the masticatory space from the parapharyngeal space.[49] In this way, it is possible to believe that infection spreading from the masticatory space into the parapharyngeal space may pass via the medial pterygoid muscle. Yonetsu et al., found that 100% of patients with parapharyngeal space involvement also had the medial pterygoid muscle affected, and 79% of patients with infection in the medial pterygoid muscle area had concomitant involvement of the parapharyngeal space. However, in none of their cases spread from the submandibular into the pharyngeal spaces.[3]

The parotid space abuts the posterior masticatory space and is enveloped by a layer of the deep cervical fascia.[50] Yonetsu et al., demonstrated that odontogenic infection may extend into the parotid space, via the masticatory space.[3] The retropharyngeal space connects the skull base to the upper mediastinum and contains loose fatty tissue in its infrahyoid portion. Thus, the retropharyngeal space is considered to be important due to its proximity to the airway and because infections in this space may cause mediastinitis, bronchial erosion, and septicemia.[3, 50] The vertebral and vascular spaces are thought to be rarely involved by head and neck infection.[51]

The infection spread occurs when accumulated pus perforates bone at the weakest and thinnest part. In the mandible, the lingual aspect of the molar region represents the easiest way.[4, 52] If odontogenic infection perforates this portion of bone, it will spread into the sublingual or submandibular space. As these spaces are partially separated by a thin sheet of mylohyoid muscle, infection in either space easily spreads into the other. It is generally believed that the midline enables free communication from either the sublingual or submandibular space.[3, 50]

Delineating the maxillary spread pattern is quite difficult, because limited data is available regarding its infections.[3] Nevertheless, it is plausible to consider that the observed difference in the spread profile between maxillary and mandibular infections may be due to differences in the distance between the original focal area in jaw bones and each of the spaces. For instance, maxillary infection was associated with temporalis muscle involvement more often than mandibular infection. Maxillary infection also spreads first to the masticatory space, but the temporalis and lateral pterygoid muscles are predominant targets for the infection. Involve‐ ment of the sublingual and submandibular spaces is rare. Otherwise, odontogenic infection arising in the mandible spreads first to the masticatory space. The masseter and medial pterygoid muscles in the masticatory space are most frequently involved. Thereafter, the infection spreads medially into the parapharyngeal space and posteriorly into the parotid space. Involvement of the sublingual and submandibular spaces seems to occur directly from the primary site of mandibular infection.[3]

There are complex pathways which allow infection to spread along the facial and neck structures. Thus, it is important for dental practitioners to know more about the possibility of a dental intervention to be a cause of severe infections.

#### **The sequence of odontogenic infection spread** that most commonly occurs is:


#### **5.2. Fascial infections derived from maxillary odontogenic origins**

The pattern of maxillary infection spread differs from that of the mandible. Generally, the main maxillary spaces involved were found to be the buccal maxillary (19.05%) and canine (15.24%). [49] According to Yonetsu et al., the temporalis muscle was involved in 100% of the patients with maxillary infection. The involvement of the temporalis muscle in mandibular infections occurred only in 26% of the patients. The downward spread into the sublingual and subman‐ dibular spaces from maxillary infections did not occur. The lateral pterygoid and masseter muscles were frequently involved (86%) as in the cases of mandibular infection. Other spaces were also involved, but less frequently. The buccal space was involved in 57% of the patients with maxillary infection[66] (Figure 2).

**Figure 2.** Different locations of odontogenic infections. (A) Submandibular and sublingual region. (B) Submandibular region. (C) Cervical region. (D) Palate. (E) Orbital region. (F) Submandibular and buccal region.
