Response to Behavioral Mechanisms in the Pathophysiology of TMJ: Barry R. Dworkin In the peripheral nervous system stimulation of a sensory receptive field can elicit a reflex motor response proportional to the degree of sensory activation. For example, irritation of certain sensory fields in the mouth activate motor patterns in the jaw muscles. While it is tempting to hypothesize that such simple mechanisms could be the basis of important pathology, Dr. Yemm's scholarly review argues convincingly that simple peripheral sensory-motor reflexes do not adequately explain temporomandibular joint syndrome (TMJ) and bruxism. In contrast to this clear and specific but probably incorrect hypothesis, several very elaborate psychosomatic mechanisms have been proposed. The most common of these attributes the pathology to diffuse environmental or psychological stress. In a hydraulic metaphor the stress squeezes and the pathology oozes out. This model alone does not explain the specificity of psychosomatic symptoms. Some patients have elevated blood pressure, others develop gastric ulcers, or suffer from temporomandibular joint syndrome and still others undergo psychotic deterioration. We must assume that for certain individuals some organ systems are genetically more vulnerable to stressful stimuli than others. However, hypotheses which do not explicitly describe the functional link between the manifest symptom and the pathogenetic force also fail to suggest specific modes of therapy. While general therapeutic recommendations such as reducing stress may be otherwise desirable and theoretically correct, the prescription may be difficult or impossible to fill. I believe that there is an intermediate level of analysis between the simple specific peripheral sensory-motor reflex and the complex catch-all combination of stress plus genetic predisposition. A behavior or motor response can sometimes modify the conditions at the sensory receptive field which initiated it. When this happens, the effect or consequence of initial components of the response revises the subsequent execution of the remaining components. Depending upon whether the response increases or diminishes the sensory stimulus, the revising effect of this feedback will either amplify or attenuate the later components. If the response diminishes the stimulus, the result is regulation: the effect of subtractive or negative feedback is to reduce stimulation at the receptive field to a minimum level. For example, a minor irritation in the mouth may reflexively elicit a particular posturing of the jaw. If the elicited posture avoids further irritation the process soon comes to a successful conclusion. The irritation subsides and the oral posture returns to normal. In contrast, if the response increases the sensory stimulation, the result is opposite: positive or additive feedback does not lead to stability and control, but instead to an amplification of any initiating action. Thus, if the elicited oral posture exacerbated the irritation of the initiating receptive field instead of reducing it, the patient could become trapped in a vicious circle or spiral of increased irritation and more exaggerated response. Untreated, this condition would progressively worsen. Effective treatment is, however, at least in theory, straightforward: interrupting the behavior for a period of time would allow the irritation to heal, thus removing the initiating stimulus. Some biofeedback therapists have claimed that even a relatively brief course of jaw muscle relaxation training can be effective and orthodontic appliances, if intelligently used, can be helpful as well. Pathogenetic mechanisms are not necessarily limited to innate responses. Learned behavior can also have physiologically adverse consequences. In the instrumental learning paradigm, a response which is promptly and consistently followed by a rewarding reduction in aversiveness is strengthened with each occurrence. Thus, if a particular behavior immediately reduces a source of irritation, that behavior will intensify with time. Furthermore, since instrumental learning is primarily governed by immediate reduction of pain and is indifferent to delayed or nonpainful injury, a patient may learn to adopt an oral posture which reduces the discomfort of some chronic irritation, but that posture may coincidentally result in insidious damage to another structure. Once a learned behavior is established it has an extraordinary stability and resistance to intervention. left alone the palliative response will probably not become stronger, but intentional blocking of the palliative response will exacerbate the patient's discomfort and increase his motivation. The growing motivation will evoke increasingly more powerful responses until the therapeutic "obstacle" is overcome. The diagnosis may be complicated because the primary irritation can be anatomically distinct from the pathology which produced the complaint; nevertheless, the only correct therapy for this type of disorder is to identify and eliminate the original irritation, and thus, to remove the motivational basis which is maintaining the pathogenetic behavior. The learned palliative response can reduce the discomfort of the primary irritation in different ways. The most direct is to remove the source of irritation. For example, if the patient has bitten his tongue, he may adopt an oral posture which keeps the injured edge of his tongue from between his teeth. Another, less obvious way of reducing a localized discomfort or pain is through stimulation of an adjacent receptive field. Most sensory receptive fields have inhibitory surrounds which can attenuate the output of the central region. Scratching a mosquito bite is one common example. Electrical stimulation for the relief of pain and possibly certain types of acupuncture analgesia are others. Sometimes the painful area and the inhibitory surround are so intimate that vigorous stimulation of the surround unavoidably exacerbates the primary irritation. Mosquito bites itch, but if they are not scratched the itching stops. Nevertheless we learn to scratch mosquito bites because scratching produces a counterstimulation which momentarily but immediately relieves the discomfort. However, scratching at the same time irritates and sensitizes the receptive field, increasing the motivation for scratching. Because the course of learning is most determined by immediate consequences, the delayed effects of irritating the mosquito bite do not interfere with the instantaneous reward produced by scratching. Thus, as in the earlier example of an innate response producing a viscious circle of increasing irritation, the instrumental learning paradigm may similarly ensnare the patient. Fortunately, intrinsic inhibitory mechanisms exist for most responses. When irritation reaches a sufficient level, then scratching a mosquito bite begins to hurt. Pain exceeds relief, punishment overpowers the reward, and the behavior stops. Consequently, severe pathology rarely results from scratching a mosquito bite. To relieve discomfort from a minor oral irritation a patient may learn the palliative response of stimulating an adjacent inhibitory field. This behavior may involve bruxing or clenching his jaw. However, if the compensatory oral behavior simultaneously exacerbates the original irritation, then the response will progressively intensify exactly as it did for the innate reflex. The therapeutic approach is to break the pattern by inhibiting the compensatory response and allowing the secondary irritation to subside. Thus, the learned cycle of irritation and response can be treated much like the innate reflex paradigm if the pathology is accurately analogous to a mosquito bite. However, if the primary source of irritation persists, the motivational basis for relearning the original or a new compensatory response will remain and the entire sequelae could reignite. Behavioral Management of Functional Oral Disorders James O. Bailey, Jr. and John D. Rugh The purpose of this paper is threefold. First, a review of the literature is presented with emphasis on the behavioral management of two interrelated functional disorders of the masticatory system: bruxism and a group of multinamed disorders generally known as masticatory pain dysfunction syndromes. The second purpose of the paper is to point to several problems in this sphere of the health sciences research. Problems include (1) the lack of morbidity data, (2) absence of definitive diagnostic tools, and (3) the lack of universally accepted operational definitions of or means of quantifying the behaviors involved, the pathology or the treatment effectiveness. These problems have resulted in a dilemma for investigators who search for etiological information and treatment regimens. Finally, recommendations are made regarding future directions. Bruxism Even from the turn of the century, it has been advocated that psychological variables and bruxism are related in some manner (Marie and Pietkiewicz, 1907). The observation that persons "under tension" tend to press their teeth together has been given in the past as proof of this correlation (Ramfjord and Ashe, 1971). Personality traits, anxiety, frustration, depression, as well as other psychological variables have been reported to be related to bruxism. A review of these studies was recently published by Rugh and Solberg (1976). These studies, although inconsistent and often conflicting, are the basis of the interest in behavioral management of bruxism recently reported in the literature. Bruxism has been defined as "the clenching and/or grinding of the teeth when the patient is not masticating nor swallowing" (Ramfjord, Kerr and Ashe, 1966). Some authors attempt to differentiate between bruxing and clenching (Ramfjord and Ashe, 1971) or between nocturnal and daytime bruxing or clenching (Olkinuora, 1973). The utility of these distinctions deserves further study but cannot be addressed here. It is generally accepted that bruxism is forceful tooth contact for nonfunctional purposes. Concern with bruxism stems from the reported possible sequelae which may result from the behavior itself. Glaros and Rao (1977) reviewed the effects of bruxism which have been reported in the literature. The reported effects of bruxism range from simple tooth wear to peridontal breakdown to head and facial pain. Thus, they state, "Bruxism may have a variety of effects on the individual and these effects range from mild to severe." Ayer and Levin (1973) have pointed out that not all bruxists are in need of treatment. In most individuals, bruxism does not disrupt life or cause sufficient oral pathology to warrant treatment. At this time however, no clear guidelines exist to determine the advisability of beginning a treatment program. Efforts need to be directed at the development of such guidelines. Several strategies have been explored in the clinical management of bruxism and related oral motor disorders. These have included alpha brainwave feedback, meditation, and autogenic training (Cannistraci, 1975), massed practice (Ayer and Levin, 1973), EMG feedback (Soldberg and Rugh, 1972), group therapy (Marback and Dworkin, 1975), hypnosis (Gelberd, 1958), autosuggestion (Boyens, 1940), psychotherapy (Frohman, 1931), aversive conditioning (Heller and Forgione, 1975). Most of these reports have been anecdotal in nature and are difficult to evaluate. Significant experimental literature has developed regarding only two of these procedures. These two procedures, electromyographic biofeedback and massed practice, have been evaluated in sufficient detail to warrant closer study. This review is limited primarily to these therapeutic modes and will conclude with summary comments appropriate to other strategies which have been investigated in less depth. For Biofeedback. Operationally, biofeedback involves a patient being provided information about a body function with the expectation that this information can be used in a therapeutic manner. A common theory is that the patient may learn to reduce activation of a specific organ system via the principles of operant conditioning. There remains much controversy as to what is actually learned and there is little agreement upon a theoretical model to explain biofeedback therapies. example, rather than learning to control a specific response, biofeedback training may be used to increase patient awareness to organ hyperactivity which the patient may then control via previously learned control processes. Alternatively, biofeedback training may serve as a procedure to induce general body relaxation or it may simply serve as a distraction technique. These issues and concerns have been reviewed recently by Black and Cott (1977), Engel (1977), Legewie (1977) and Stoyva (1977). considerations are relevant to biofeedback applications in dentistry and should be of concern to investigators working in the area. Thus far, biofeedback therapy research in dentistry has progressed without the aid of an explicit theoretical model or conceptual framework for guidance. Research often appears random and unsystematic. The area is in need of a theoretical framework to help guide new research efforts. An outline review of several representative studies utilizing EMG biofeedback equipment in the management of bruxism is presented in Table 1. Several features of the studies warrant discussion. Almost without exception, the studies outlined in Table 1 failed to explain or document the subject population and the method utilized to diagnose the bruxist subjects. In most cases, only after baseline data were obtained indicating "increased EMG activity" was the diagnosis "confirmed." This points to the problem of not having definite diagnostic procedures available which would better enable interstudy comparisons to be made, which will be discussed later. |