The oral motor apparatus is involved in routine yet intricate functions (speech, posture, mastication, and swallowing). Regulation of these activities may occur at three levels: the local neuromuscular unit, central neuronal pathways, and systemic influences. While aging is associated with changes in neuromuscular systems, animal studies suggest that age-associated deficiencies in motor function are unrelated to the composition and contractile function of skeletal muscles. Rather, these changes probably are related to other factors such as neuromuscular transmission and propagation of nerve impulses.
Dentition status (the number of teeth) and not age, influences mastication. While older adults with an intact dentition prepare food more slowly for swallowing than do younger individuals, and minor alterations in performance (mastication, swallowing, oral muscular posture, and tone) can be expected with increased age, changes are more common among completely or partially edentulous persons rather than among persons with a natural dentition. Any diminution in masticatory efficiency can be exacerbated in individuals with a compromised dentition (persons with dental caries, periodontitis, missing teeth, and removable dentures).
Swallowing changes in older persons are usually caused by sensory, muscular, and neurologic deterioration. A thorough review of swallowing problems in older people is provided in Chapter 36. Normal aging has minor adverse effects on swallowing, although in a healthy older person, even advanced age does not appear to cause any clinically important dysfunction. However, a host of conditions common in the older adult population can cause clinically significant swallowing deficiencies. Salivary hypofunction (described earlier) impairs swallowing times and under severe conditions increases the likelihood of aspiration. Patients with neuropathies have been reported to have oral swallow times four- to sixfold longer than those in healthy controls; these persons may not even be able to produce the recognizable characteristics of an oral swallow. Neurovascular conditions (eg, cerebrovascular accidents, dementia, motor neuron disease) are likely to cause dysphagia and predispose a person to the danger of aspiration.
The temporomandibular joint (TMJ) is located between the glenoid fossa and the condylar process of the mandible, and exhibits a functionally unique gliding and hinge movement. It is of particular interest to clinicians, for it is the focus of several craniofacial pain disorders. Radiographic and postmortem evaluations suggest that the components of this joint undergo degenerative alterations with increasing age. However, TMJ functional impairment is not a “normal” age-associated event. Rather, temporomandibular disorders (TMD) in older adults are linked with many common oral and systemic conditions. Orofacial pain in an older patient may be a result of a variety of problems of the craniomandibular-oral complex and other extraoral diseases, making diagnosis and treatment challenging and frequently requiring a multidisciplinary approach.
In general, two types of pathology are associated with the TMJ: articular, related to the joint itself, and nonarticular, pathology occurring in structures unrelated to the joint but causing similar or referred symptomatology. Articular abnormalities common to all joints may also affect the TMJ, for example, trauma, ankylosis, dislocation, and arthritis. Nonarticular disorders may result from trigeminal neuralgia, headache, migraine, otitis, dentoalveolar pain/infection, and masticatory myalgia. Orofacial habits (eg, jaw clenching and tooth grinding) and poor head and neck posture can produce muscle fatigue and spasm. Psychological conditions (stress and depression) can exacerbate underlying articular and nonarticular disorders. Clinically, the patient will present with pain in many regions: TMJ, temporal, neck, masticatory muscles, and the oral cavity. Diagnosis is challenging because symptoms primarily occur in any of these sites with regular, irregular, or no pain referred to the TMJ region. Limited jaw opening (< 40 mm from the maxillary central incisor to the mandibular central incisor) and pain on mastication or during jaw movements may be indicative of TMD. Treatment, as with other arthritic or muscular disorders, requires the elucidation of an appropriate diagnosis and ranges from conservative and reversible regimens (anti-inflammatories, analgesics, muscle relaxants, physical therapy, oral bite splints) to more invasive procedures for unresolved painful conditions (eg, TMJ surgery). Pain in the jaws and/or face is present in 3% to 6% of persons age 65 and older.
Speech is another function of the oral structures; speech undergoes changes with increasing age, including shape of the tongue and its function during sound production and frequency variability. Among healthy older persons, these changes do not compromise or alter speech in any perceptible way. Tongue strength decreases with age, even among healthy adults, yet tongue endurance is similar between younger and older persons. There are also age-associated alterations in intraoral and maxillofacial posture. Drooping of the lower face and lips in the older adult results from the loss of supporting hard tissues and diminished tone of the circumoral muscles. The latter changes may elicit esthetic concerns and can lead to embarrassment from drooling or food spills caused by the inability of an older individual to close the lips competently while eating or speaking. Often, drooling caused by reduced circumoral muscle tone can result in complaints of excess salivation. Finally, oral motor disorders also may result from a number of therapeutic drug regimens, such as the frequent association of tardive dyskinesia with phenothiazine therapy. These dyskinesias may include diminished performance and speech pathoses as well as alteration in movement (eg, chorea).