Musculoskeletal Unit

The mandible is formed by two rami that divide into a horizontal and an ascending portion. The horizontal portion forms the body of the mandible. The ascending ramus divides into the coronoid process anteriorly and the condylar process posteriorly. The temporomandibular articulation is unique because it consists of a bilateral joint, or diarthrosis, between the mandibular fossa and articular eminence of the mandible’s temporal bone and condyle (Fig. 70-1). An intervening layer of fibrous connective tissue separates the articulating surfaces. A fibrous capsule also surrounds the temporomandibular joint (TMJ) and is reinforced by capsular ligaments that help limit mandibular range of motion. Functionally, when the mandible opens, the condyles move inferiorly and anteriorly down the eminence; during closure, the mandible moves posteriorly along the eminence and superiorly into the fossa.

The muscles of mastication are divided into the mandibular elevators (the supramandibular group) and depressors (the inframandibular group). The elevators, or masseteric sling, consist of the masseters, medial pterygoids, and temporalis. The posterosuperior movement of the condyle during mandibular closure is the result of bilateral, simultaneous movement of this group. The muscles involved in the opening or depression of the mandible include the lateral pterygoid, digastric, geniohyoid, and mylohyoid. Bilateral activity of these muscles results in opening; unilateral contraction causes the mandible to deviate to the opposite side. At rest the mandible assumes a position in which the mandibular and maxillary teeth are separated by a few millimeters of space. During functional activity, mandibular closure occurs as the action of the elevators predominates.

Teeth

The pulp is the tooth’s center and serves as its neurovascular supply. The primary purpose of the pulp is to provide sensation and to produce dentin, a microtubular structure that hydrates and cushions the tooth during mastication. The part of the tooth normally visible in the oral cavity is the coronal portion covered with enamel, the hardest substance in the body. The part that is not normally visible and anchors the tooth is called the root. The root is covered with cementum, which is much softer than enamel and not designed for exposure in the oral cavity (Fig. 70-2).

The normal primary, or deciduous, dentition consists of 10 mandibular and 10 maxillary teeth. The primary dentition is important for mastication, cosmesis, and growth and development and functions as a physiologic space maintainer. Starting at the midline and moving posteriorly in any quadrant, the normal dentition consists of a central incisor, lateral incisor, canine, and two primary molars. The lower central incisor is the first tooth to erupt, at approximately 6 months of age; all primary teeth should be present by 3 years of age. If not, further investigation for developmental or endocrine abnormalities is warranted. The permanent dentition begins to erupt at approximately 5 to 6 years of age with the appearance of the first molar. Normally, the permanent dentition consists of 32 teeth: the central incisor, lateral incisor, canine, two premolars, and three molars. The third molars are the last to erupt, appearing at approximately 16 to 18 years of age, and are commonly called “wisdom teeth.” The primary molars are replaced by the permanent premolars. There are many numbering systems for teeth, but none are universal. Perhaps the most common system for the permanent dentition consists of numbering the teeth from 1 to 32, starting with the upper right third molar (1) and moving to the upper left third molar (16), to the lower left third molar (17), and to the lower right third molar (32). The starting point for this numbering system can be recalled by the mnemonic “upright.” Because there may be congenital absence of teeth or additional, supernumerary teeth, it is perhaps best for practitioners to describe anatomically which tooth is involved—for example, the upper left second premolar or the lower right second molar (Fig. 70-3).

Specific terminology is used to describe aspects of dentition. The labial or buccal surface faces outside the oral cavity; the oral, palatal, or lingual surface faces the tongue; the medial surface is toward the midline; and the distal surface is toward the ramus of the mandible. The interproximal surface refers to the contacting area of adjacent teeth, and the occlusal surface refers to the biting area. Finally, apical is in the direction of the root, whereas coronal is toward the crown of the tooth.

Periodontium

The periodontium consists of the gingival unit and the attachment apparatus. The gingiva is covered with keratinized, stratified, squamous epithelium and invests the tooth and alveolar bone. Apical to the gingiva is the alveolar mucosa, which is covered by nonkeratinized epithelium and is more subject to trauma. In healthy individuals the gingiva is attached firmly to the tooth by connective tissue fibers inserting into the cementum, extending coronally from the alveolar bone to the cementoenamel junction. A 2- to 3-mm cuff of tissue, the gingival sulcus, is bordered by the enamel surface of the tooth, the gingival epithelium, and the junctional epithelium at its base (see Fig. 70-2). In a disease state, such as in the presence of the loss of alveolar bone, this cuff increases in depth and is called a “pocket.”

The attachment apparatus refers to the cementum on the tooth, the periodontal ligament, and the alveolar bone. The periodontal ligament is a fibrous structure that surrounds the root of the tooth. It is the key structure that anchors the tooth because it serves as a double periosteum that lays down cementum on the tooth on one side and alveolar bone on its other side.

Fascial Planes of the Head and Neck

The fascial planes of the head and neck are defined as potential spaces filled with loose areolar tissue that separates the layers of fascia of the head and neck. The deep cervical fascia is most important in a discussion of the extension of oral infection to the head and neck (Fig. 70-4). The deep cervical fascia consists of the superficial and investing layer, the pretracheal layer, the prevertebral layer, and the carotid sheath. The superficial and investing layer surrounds the entire neck; it splits as it attaches to the inferior border of the internal pterygoid muscles at the mandible’s ascending ramus. This split forms the masticator space. This space communicates superiorly above the level of the zygomatic arch with the superficial and deep temporal pouches.

Other spaces of importance in the neck to which dental infection may spread include the lateral pharyngeal or parapharyngeal space, which is lateral to the pharynx and medial to the masticator space; the retropharyngeal space, which is between the deep cervical and prevertebral fascia; and the prevertebral space, which is posterior to the retropharyngeal space. The pharyngomaxillary space extends from the base of the skull to the hyoid bone and is especially important because it communicates with all deep spaces. The mandible itself is divided further by the mylohyoid muscle, which separates the superior sublingual and inferior submaxillary spaces.

Nontraumatic Dental Emergencies

Two pathophysiologic processes affect the dental health of most of the population: (1) dental caries and (2) periodontal disease. Variables related to both disease states include the oral environment, consisting of the teeth and attachment apparatus; the presence of local factors such as bacterial plaque, oral microflora, and substrate; and host states, including immunocompromising diseases and nutritional status. Factors such as water fluoridation, fluoride supplements, and plaque control techniques (e.g., flossing, brushing, orthodontic and dental surgical procedures) have significantly decreased the prevalence of dental caries and periodontal disease. However, the emergency department (ED) is the frequent source of care for dental emergencies, with toothache related to dental caries being the most common complaint. This occurs because of both lack of after-hours access for dental complaints and socioeconomic factors (self-pay and Medicaid). A recent study from Kansas City shows an increased volume from 2001 to 2006 from 13.1% up to 19%.¹

Dental caries is a multifactorial disease involving a susceptible host, cariogenic oral flora, and a substrate. Caries results from the decalcification of enamel by the production of acids from bacteria. In the presence of saliva and a carbohydrate, cariogenic oral flora are able to develop a matrix called dental bacterial plaque. The bacteria metabolize the carbohydrate to form acids that decalcify the enamel. After the carious process has invaded the enamel, the microporous dentin is able to transmit saliva, byproducts of the bacteria, and the bacteria themselves to the pulp. The pulp initially reacts with a hyperemic response, which continues to an inflammatory state, progressing to total degeneration and necrosis.

Pus leaks from the apex of the root and forms an abscess; this is termed a periapical abscess. Periapical abscesses are confined within the alveolar bone (Fig. 70-5). The abscess may break through the cortical plate of either the mandible or the maxilla and spread subperiosteally. Subperiosteal extensions are generally well confined anatomically by muscle attachments; however, if the muscle attachments are violated, either during a surgical procedure or by the natural extension of an infective process, the bacteria can gain access to the fascial planes of the head and neck. Infection extending to the submaxillary, sublingual, and submental spaces with elevation of the tongue is called Ludwig‘s angina. Ludwig’s angina is one of the most serious mandibular infections because of its potential for airway obstruction.

Space infections also may involve the face. The canine space is bounded by the orbicularis oris, the levator labii superioris, and the buccinator; abscessed anterior maxillary teeth commonly involve this space. Infection can extend to the periorbital area. The most serious complication of such space infections is cavernous sinus thrombosis resulting from contamination of the (valveless) facial venous system. The buccal space is superficial to the buccinator and limited by the anterior border of the masseter; maxillary molar infection commonly spreads to this space. The mental space is located at the anterior table of the mandible and often is infected by abscessed lower anterior teeth.

Treatment

Palliative management is indicated for most odontalgia. Systemic analgesics, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or synthetic opioid agents, are indicated. In a meta-analysis of 11 studies comparing flurbiprofen, 65 to 70% of patients experienced 50% pain relief compared with 25 to 30% with placebo; this was similar to findings with comparable NSAIDs, and patients had similar need for rescue pain control at 6 hours.⁴ Although NSAIDs should be sufficient for most pain resulting from carious teeth, a therapeutic dental block may offer immediate relief. Synthetic opioids also are useful and are indicated in some cases but are generally not recommended in chronically carious teeth without an acute process.⁵ A limited quantity of analgesics should be dispensed, which encourages follow-up with a general dentist.

Treatment

Dental abscesses are treated with a conservative incision and drainage (involving blunt dissection with a mosquito hemostat). The gingiva and tooth are anesthetized by apical nerve block or block of the major nerve supplying the area (e.g., superior alveolar, inferior alveolar) as long as this can be accomplished without the needle passing through inflamed or infected tissue, or the gingiva is anesthetized superficially with 2% lidocaine with 1 : 100,000 epinephrine. A stab incision is made toward the alveolar bone and extended through the periosteum; blunt dissection is carried out with a mosquito hemostat. Unlike with other abscess drainage, it is unnecessary to open the abscess from end to end—such a large incision exposes too much alveolar bone. The simple stab incision is sufficient. The cavity is irrigated, and, assuming there is sufficient space, a Penrose or iodoform drain is placed and secured with a No. 4-0 suture.

Standard practice for years included starting the patient on phenoxymethylpenicillin (penicillin V) 250 mg four times daily or doxycycline 100 mg bid for 10 days and warm saline rinses and referring him or her to an oral maxillofacial surgeon or general dentist. Drains are removed in 24 to 48 hours, and antibiotics are continued for 7 to 10 days.⁵ However, recent reviews have questioned the need for routine prescribing of antibiotics if sufficient drainage of pus has been achieved.^6,7

Treatment

More commonly, a patient experiences pain from a periodontal abscess or swelling of the gingiva when food or pus becomes trapped in a “pocket.” In the dental office a periodontal abscess is treated with curettage to establish drainage. (ED management is covered earlier in the discussion of simple dental abscess.) Use of doxycycline 100 mg bid in patients older than 8 years is preferable because it provides better coverage for the gram-negative and anaerobic organisms found in the gingival pocket. The patient should be referred to the general dentist or periodontist for further treatment.