The dental hygienist has an important role in the detection of occlusal abnormalities and jaw dysfunction. The application of true prevention principles includes attention to the form and function of all aspects of the head and neck. Form is the morphology of the teeth, bones, and temporomandibular joint (TMJ), whereas function includes the jaw muscles and neuromuscular system. Form and function are also important in the masticatory system, a complex apparatus that has an amazing adaptive capacity to function. However, when the masticatory system’s adaptive capacity is exceeded, dysfunction can range from discomfort to debilitating pain. Good oral health requires the functional harmony of the teeth, muscles, and TMJ.
Bacterial plaque biofilm is the causative factor in periodontal diseases. However, numerous local and systemic factors can affect the response of the body to inflammatory periodontal diseases. This chapter describes the relationship of normal and abnormal form and function to provide a better understanding of occlusal function and dysfunction in periodontal treatment. In addition, it describes a method of screening for temporomandibular disorders (TMDs). The classification and treatment of these disorders are also discussed. The role of the dental hygienist is to recognize the signs and symptoms of pain and dysfunction, record the parameters of these signs and symptoms, and refer the patient for diagnosis and treatment.
The oral cavity in occlusal function—during talking, chewing, and swallowing—is in a dynamic rather than a static state. Orthofunction is a state of morphofunctional harmony in which the forces developed during function are within an adaptive physiologic range. In orthofunction, which means health and comfort for the patient, there are no pathologic changes in the oral tissues. Another term used to describe a range of morphologic variability is physiologic occlusion.1,2 This term indicates psychologic and physical comfort for the patient, a normal adaptive situation. An occlusal relationship that functions for the patient is considered optimum and does not follow a particular occlusal configuration. For example, a malocclusion, although not ideal, can still be in orthofunction.
Dysfunction is a state of morphofunctional disharmony in which the forces developed during function cause pathologic changes in the tissues. These changes result in abnormal function or pain. The degree of dysfunction can be slight, with no great disturbance to the patient, or significant, making daily activity difficult or impossible.
The range of morphofunctional harmony to disharmony is dependent on the adaptive capability of the oral system.1,3–6 At one end of the spectrum is the normal range, orthofunction. When the forces directed through the teeth and periodontal attachment in function and parafunction exceed what an individual system can handle, dysfunction may result. This trauma occurs where the greatest force is exerted against a weakened periodontal apparatus. Axial forces directed along the tooth and periodontium usually meet the demands necessary for normal function. Parafunctional activity, such as grinding or clenching, can stress this system. Antiaxial forces directed along the tooth and periodontium can cause resorption or a hypertrophic response. For this reason, some areas in the oral cavity will break down as a result of these forces, whereas other areas will not show any injury.7
Certain factors affect the response of the teeth and periodontal structures to normal and abnormal function. These factors include the size and shape of the roots, the quantity and quality of the alveolar bone, and the presence of microbial plaque biofilm. Oral habits and other occlusal situations, such as missing or shifting teeth, can increase the frequency and force on the teeth. When periodontal disease has weakened the periodontium, these forces may exceed the individual’s adaptive capability, causing injury. At this point, a treatment intervention can correct an existing problem and prevent further damage. An occlusal contact relationship that is harmonious does not produce a painful response in the masticatory system.
When the condyles of the TMJ rest in the normal closed superoanterior position and the mandible has a well-distributed, even contact with the maxilla, the maxillary system is in a stable relationship. This situation allows the TMJ system to tolerate such activities as hyperfunction and possibly some trauma. The structures of the masticatory system can tolerate a certain amount of functional change. When functional changes exceed a certain level, alteration to the tissues may begin. This structural breakdown will vary depending on the individual and on systemic and local factors.5
The area of occlusion and study of occlusal harmony have been surrounded with controversy and confusion. Therefore, it is important to recognize that each component of the masticatory system must be understood within its functional relationship, not as a separate element.2,4
A traumatic occlusion is an occlusion that has caused injury to the teeth, muscles, or TMJ.2,5,6 A classification of primary traumatic occlusion is made when heavy occlusal forces exceed the adaptive range in a normal periodontium, causing injury to tissues and bone. A classification of secondary traumatic occlusion is made when normal occlusal forces exceed the capability of a periodontium that is already affected by periodontal disease. Trauma from occlusion does not initiate gingivitis and periodontal disease. When inflammation is present, occlusal trauma can increase tissue attachment loss and supporting bone destruction. Therefore, occlusal trauma is of interest in the diagnosis and treatment of periodontal disease.
Traumatic occlusion does not refer to a malocclusion, as described by Angle’s three classifications. Angle’s Class I, II, and III occlusion classifiy and describe the skeletal relationship of the maxillary to the mandibular teeth. Because malocclusion of the teeth may interfere with the removal of bacterial plaque, it is a factor in the attainment of good oral hygiene. Common terms used to describe mandibular function and dysfunction are listed in Box 11-1.
The occlusal relationship of the teeth is not a predictor of pain or problems in the TMJ. Common occlusal features, such as intercuspal position or midline discrepancies, do not provide the dominant factors in defining populations with TMDs.8,9
Controversy regarding the clinical significance of trauma from occlusion has existed for some time. It is now widely accepted that in the absence of marginal gingival irritation, trauma from occlusion does not produce gingival inflammation. Trauma associated with orthodontic movement of teeth is self-limiting. Self-limited mobility is greater than normal, but is based on the adaptive capacity of the periodontium. Thus, the increased mobility of the teeth is handled through periodontal adaptation to the excessive forces without causing trauma from occlusion.1 Dentists may use this rationale when selectively grinding (adjusting) the occlusal surfaces of the teeth after periodontal therapy to create a dentition that does not produce injury. The goal is to establish an occlusal relationship that will foster a favorable periodontal response. True trauma from occlusion (trauma that exceeds the adaptive capacity of the periodontium) increases bone loss and pocket depth formation. This situation may occur with bruxism in a periodontal patient.
Certain tooth relationships can also be detrimental to the attainment of good periodontal health. Open contacts or faulty contacts between teeth can cause areas of food impaction. Food impaction is the forceful wedging of food into the periodontium by occlusal forces. The self-cleansing aspects of the dentition do not exist in these situations, and food impaction can be a contributing factor in periodontal disease.
The dental hygienist must carefully complete the clinical assessment of the patient, noting all of the gingival conditions and determining the reason for the condition, if possible. In the past, certain gingival conditions, such as recession, clefting, or thickening of the gingival margin, were thought to be caused by trauma from occlusion. These causative relationships have not been supported by research.4
Understanding the multifactorial origin of jaw dysfunction and how it relates to the treatment of the periodontal patient is important. When an individual can attain and maintain good oral hygiene, malocclusion is of no periodontal significance.1,5 However, most patients have difficulty with plaque removal, making malocclusion a factor to be considered in the progression of periodontal disease.
TMDs are a grouping of musculoskeletal conditions that produce pain or dysfunction in the masticatory system. When the disorder involves the muscles and not the joint, it is referred to as extracapsular. A problem occurring within the TMJ is known as intracapsular. The percentage of people who have signs or symptoms of a functional disorder can be as low as 5% or as high as 60%, making the prevalence of TMDs significant.5,10–14 However, it is generally agreed that only 5% to 7% of these patients are in need of TMD intervention therapy.2,5
Historically, TMDs have been described with a number of labels, such as temporomandibular joint syndrome and myofascial pain dysfunction syndrome. Most orofacial clinicians and researchers agree that the term TMD accurately reflects the scope and complexity of the conditions.3,8 A diagnosis of a subcondition, such as myofascial pain or arthritis, further describes the problem. It is important for the dental hygienist to remember that there are many orofacial pain problems in addition to TMDs.
The etiology of TMDs is multifactorial. Because of the many causes, TMDs are frequently difficult to diagnosis and treat. Stress is often a factor in TMDs and patients with TMDs may have a history of other diseases, such as arthritis and psychological problems. In determining the causes of TMDs, a history of macrotrauma or microtrauma may be discovered by the clinician. A macrotrauma is usually a single event that may have caused damage to the masticatory system. Such an event could be a sports-related injury, a whiplash accident, or a fall. The patient may not relate such an event to later occlusal or TMJ pain and discomfort. Microtrauma is a number of minor habits or events that cause damage to the masticatory structures. Examples of microtrauma include bruxism and postural and oral habits.
There are four main diagnostic categories for TMD, which are listed in Box 11-2. These categories are based on criteria derived from the signs and symptoms gathered in the comprehensive TMD evaluation.3,5,11 The first category is muscle and fascial disorders of the masticatory system. This group includes myalgia (pain in the masticatory muscles), trismus (spasm in the masticatory muscles), dyskinesia (incoordination of the jaw), bruxism (clenching or grinding), and other muscle disorders. Disorders of the TMJ, the second category, include internal derangements that impair mechanical function of the TMJ, such as arthritis. The third category includes disorders of mandibular mobility, such as ankylosis, muscular fibrosis, internal derangement, and adhesions in the joint. The fourth category, disorders of maxillomandibular growth, is less common. These disorders include neoplastic and nonneoplastic conditions.
Oral habits can contribute to periodontal and dental damage in the oral cavity. Oral habits are repetitive masticatory activities outside the normal range of function. These parafunctional activities can involve tooth to tooth contact or contact with foreign objects. The amount of damage is related to the intensity and duration of the habit. Oral habits can lead to tooth damage, muscular hypertrophy, muscular pain and tenderness, and periodontal tissue injury. Bruxism is the most frequently described oral habit.
Bruxism is clenching or grinding of the teeth, not including chewing or swallowing. Bruxism can occur as rhythmic side to side movements or as a sustained clench. Clenching is continuous or intermittent closure of the jaws under vertical pressure.6 Grinding and clenching are parafunctional habits that are involuntary and may be destructive. Bruxism is further categorized into nocturnal (nighttime) and diurnal (daytime) types. Bruxism can be identified by the presence of wear facets that are not caused by masticatory function. The results of bruxism may be tooth wear, tooth fracture, restoration fracture, myalgia, hypertrophy of the masticatory muscles, and headache. Bruxism or periodontal disease can cause mobility in the teeth. Researchers have found that bruxism does not cause damage to the periodontium and that periodontal disease and bruxism seldom occur in the same individual.12
The prevalence of bruxism is difficult to estimate because most patients are unaware that they grind their teeth. Stress may contribute etiologically to bruxism. Other causes may be neurologic or occupational. Bruxism is common in children between the ages of 3 and 12 years and disappears as they age.