Posture training is commonly used to treat poor posture and cervical dysfunction, and many practitioners recommend it as one of the multidisciplinary treatments for TMD.^2,5,22,24 Posture training usually involves exercises that are performed repetitively within the pain-free range to stretch structures that poor posture tends to shorten, strengthen structures that poor posture tends to weaken and create an awareness of the desirable posture.^24,25 Patients are asked to try to maintain this new posture all of the time, which is thought to prevent them from being in positions that cause undue stress, microtrauma and overuse of structures of the head and neck.

We conducted this randomized clinical trial to assess whether posture training may be of benefit to patients with TMD who have a primary masticatory muscle disorder. Subjects who received posture training and TMD self-management instructions were compared with subjects who received only TMD self-management instructions for changes in a modified symptom severity index, or SSI, maximum pain-free opening and pressure algometer pain threshold.

	SUBJECTS AND METHODS

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Subjects consisted of patients who were referred to a TMD specialty clinic, Lackland Air Force Base, Texas, for evaluation and treatment. Inclusion criteria for this study were as follows:

– the patient must have had TMD pain for at least six months;

– the patient must have rated the pain as at least moderate in severity;

– the patient must live within a 90-minute drive from the clinic;

– the patient must not have been receiving any treatment for TMD at the onset of the study (for example, an occlusal splint, prescription medication);

– the TMD pain must have been of masticatory muscle origin.

One of us (E.W.) performed a clinical examination, as described by Dworkin and LeResche,²⁶ to determine the primary source of the patient’s TMD pain and whether the patient met the research diagnostic criteria for TMD. The patient’s primary source of TMD pain was identified as the masticatory muscle or the temporomandibular joint, or TMJ. Digitally palpating the masticatory muscles and TMJs, as described by Dworkin and LeResche,²⁶ was usually sufficient to identify the patient’s primary source of TMD pain, but when necessary, additional tests were performed.²⁷

The study was conducted over 14 months, during which a total of 168 consecutive patients who were not receiving any TMD therapy were referred to the TMD clinic and considered for inclusion. We excluded 43 patients from consideration because their pain had been present for less than six months or they rated it as less than moderate in severity. Another 22 patients lived more than 90 minutes from the clinic and were not considered for inclusion. Of the remaining 103 patients, 33 had TMD pain originating from the TMJ and also were excluded from consideration.

Masticatory muscles. We determined the primary source of pain for the remaining 70 patients to be the masticatory muscles, and all met the TMD research diagnostic criteria for a muscle disorder. These patients were given standard TMD self-management instructions.²⁸ These instructions encouraged patients to rest their masticatory muscles as much as possible; become aware of parafunctional habits, such as teeth clenching, and eliminate them; apply heat or cold to the most painful masticatory areas; and use over-the-counter anti-inflammatory medications. The instructions also stated that improving head and neck posture may improve TMD symptoms and encouraged patients to improve their posture. Sixty-two of these patients stated that they were interested in being taught how to improve their posture by a physical therapist (free of charge) and then were informed of this study.

The patient’s primary source of temporomandibular disorder pain was identified as the masticatory muscle or the temporomandibular joint.

Sixty-one patients agreed to participate in the study (one later withdrew). We did not discuss the self-management instructions any further and the following baseline measures were used to evaluate changes for each subject:

– a modified SSI²⁹;

– maximum pain-free opening^30,31;

– muscle pain threshold assessed with a pressure algometer.³²

The reliability and validity of these standardized outcome measures were demonstrated previously.^29,31,32

The modified SSI used five visual analog scales to identify the level of TMD and neck symptoms independently. We asked patients these five questions:

– How intense are your symptoms?

– How unpleasant or disturbing is your usual level of symptoms?

– How difficult is it to endure the problem over time?

– How often do the symptoms generally occur?

– How long do the symptoms usually last?

Maximum pain-free opening (that is, the widest a patient can open his or her mouth before feeling pain) was measured in millimeters from incisor to incisor. In addition, pain thresholds were measured with a pressure algometer at a pressure rate of approximately 0.5 kilograms per square centimeter per second. The 1.8-centimeter-diameter tip was placed over the right and left midarea of the masseter muscles and midcervical area of the trapezius muscle to measure the point at which the patient first perceived pain.

The subjects were then randomized into two groups: one received posture training and the other served as a control (no therapy was provided). Subjects in the control group received posture training after they completed the study. The examiner (E.W.) was blinded to the assigned groups and the subjects in the treatment group were referred to a physical therapist (M.D.), who also was blinded to the previously collected data.

The physical therapist examined the subjects in the treatment group. He used a plumb line, a metric-based carpenter’s tri-square with a line-level attached to the horizontal arm, and a goniometer with a line-level attached to the horizontal arm to make precise measurements. He recorded the posture positions in centimeters for head translation (that is, the distance from the head to the vertical line), shoulder translation (the distance from the shoulder to the vertical line) and the difference between the head and shoulder measurements. The methods used and reliability of these measures have been described elsewhere.⁸

Posture exercises. During a half-hour appointment, the physical therapist gave the subjects posture exercises thought to be effective for improving posture, based on his clinical experience. He taught the exercises to the subjects (Figure, Box ["Exercise Instructions"]), who then demonstrated that they could correctly perform them. The subjects were given a handout of the exercises (Figure) and encouraged to become aware of their posture and to maintain good posture.

View larger version (23K): [in this window] [in a new window]   Figure. Stretching exercises to improve posture. (Detailed instructions appear in the box on page 206.)

All subjects returned to the TMD clinic four weeks after they began posture training or were randomized into the control group. The clinican (E.W.)—still blinded—reexamined the subjects using the modified SSI, pain-free opening and pressure algometer pain thresholds, as described above.

Subjects’ views on symptom improvement. The dentist then solicited opinions from the subjects. He asked them what percentage reduction in TMD and neck symptoms they had experienced. They were then asked to which group they had been assigned. Subjects assigned to the treatment group also were asked the following questions:

– To what extent did they comply with the exercise schedule?

– Why do they think the exercises improved their TMD symptoms (if improvement was achieved)?

– Do they think that the exercises benefited their posture?

– If the physical therapist’s charge for his service had been $100, do they feel the benefit would be worth this charge?

	STATISTICAL ANALYSIS

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To compare changes in the treatment group with changes in the control group, we used Student’s t-tests for all continuous variables and ² analyses for categorical variables. Student’s paired t-tests were used to test for changes in posture in patients in the treatment group. Finally, we used Pearson product-moment correlation analysis to study various relationships between variables. Because only one dentist and one physical therapist participated in the study and they collected different information, calibration between them was not indicated.

	RESULTS

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The treatment group was composed of 30 subjects (26 women, four men); their ages ranged from 18 through 56 years, with a mean age of 32.7 years. The control group was composed of 30 subjects (25 women, five men), whose ages ranged from 18 through 60 years, with a mean age of 30.8 years. In both groups, 28 (93 percent) of 30 subjects reported having neck pain or tightness at the outset of the study. Table 1 lists the SSI, maximum pain-free opening and pressure algometer threshold measurements, as well as the perceived improvement percentages for TMD and neck symptoms. Table 2 lists the mean measurements for posture at the beginning and end of the study.

Within the treatment group, we found significant correlations between improvement in TMD symptoms and neck symptoms (P < .005). We also found significant correlations between improvements in TMD symptoms and the pretreatment difference in head and shoulder posture measurements (the greater the pretreatment difference, the greater the symptom improvement) (P < .05).

Of the 30 subjects in the treatment group, three (10 percent) reported that their TMD symptoms resolved completely and one (3 percent) reported that her neck symptoms resolved completely. Conversely, three subjects (10 percent) in the treatment group reported experiencing no improvement in, or an aggravation of, their TMD symptoms and six subjects (20 percent) reported experiencing no improvement in, or an aggravation of, their neck symptoms. Responses from the remaining subjects were between these extremes.

Compliance with exercise regimen. Patients in the treatment group reported a range of compliance with the exercise schedule from 45 through 100 percent, with a mean compliance of 75 percent. We found no significant correlation between improvements in TMD symptoms and reported compliance with the exercise regimen.

When asked how they thought posture training improved their TMD symptoms, 16 (53 percent) of the 30 subjects responded that the exercises relaxed their neck muscles and thereby caused the masticatory muscles to relax as well. Twenty-seven (90 percent) of the 30 patients in the treatment group thought that posture training improved their posture, and 23 patients (77 percent) responded that if the physical therapist’s charge for this service was $100, the benefit they received justified this expense.

	DISCUSSION

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Within the limits of this randomized clinical trial, the results of this study suggest that posture training and TMD self-management instructions are significantly more effective than self-management instructions alone.

This study was designed for its generalizability to most general dental practices. Once a diagnosis of TMD is made, we believe that the most common initial treatment protocol is to provide patients with self-management instructions and to schedule an appointment for splint insertion. This study was designed to determine whether posture training during splint fabrication would be a beneficial adjunctive treatment.

We evaluated only patients with TMD who had a primary muscle diagnosis because we speculated that these subjects would be more likely to benefit from posture training than patients with a primary joint diagnosis. In addition, we did not include patients who said they were not interested in improving their posture, because of potential noncompliance with the exercise schedule. We were surprised to find that after reading the self-management instructions, only eight (11 percent) of 70 patients reported being uninterested in improving their posture.

Each subject in the treatment group had two dental appointments and three physical therapy appointments during the study, while subjects in the control group had only the two dental appointments. Because of the interaction between the physical therapist and the subjects in the treatment group, a placebo effect may have developed such that these subjects reported an inflated degree of symptom improvement. We considered providing sham posture instructions or exercises for subjects in the control group, but felt that any interaction emphasizing posture might cause the subjects to develop a greater awareness of their posture, thus creating a treatment effect. We chose this study design because we thought it best mimicked the typical response of a general practitioner (that is, to provide or not provide posture training), affording better generalizability.

We observed that patients in the control group relied on the self-management instructions more than the patients in the treatment group; this was expected since patients in the control group did not receive any other means of helping them control their pain.

Comparing posture training with other TMD therapies. We used the modified SSI to independently assess the masticatory and neck symptoms. Patients in the treatment group experienced a mean reduction of 22.8 in their masticatory score after receiving posture training. Wright and colleages³³ and Shaefer and colleagues³⁴ conducted studies in which they assessed subjects’ masticatory symptoms using this modified SSI measure and reported a mean decrease of 29 after soft-splint therapy among patients with TMD who had a primary muscle disorder³³ and 41 after arthrocentesis among patients with TMD who had a primary joint disorder.³⁴

The mean increase in maximum pain-free opening for patients in the treatment group was 5.3 mm, which compares favorably with the mean increases of 4.9, 5.3 and 12.4 mm reported by three studies evaluating splint therapy.^30,31,33

Even though 90 percent of the patients in the treatment group perceived that their posture had improved, actual changes in posture were not found to be statistically significant. We speculate that the benefit reported by subjects may be associated with their most common response that the exercises caused the neck muscles to relax, thereby relaxing the masticatory muscles as well. A highly significant correlation was found between improvements in neck and TMD symptoms.

We found a significant correlation between TMD symptom improvement and the difference between pretreatment head and shoulder posture measurements. This suggests that patients with TMD who hold their heads farther forward relative to the shoulders have a higher probability of achieving TMD symptom improvement from posture training.

The figure and box provide posture exercises that practitioners can give their patients and/or the physical therapist to whom they most often refer patients with TMD. We recommend that practitioners who instruct their patients in the use of posture exercises follow up with them to ensure that they are complying and properly performing these exercises. In his clinical experience, the physical therapist in this study (M.D.) has found that most patients need some modification of their exercise technique at their first follow-up appointment. If these exercises are done improperly, they may cause the patient’s TMD or neck symptoms to exacerbate. A follow-up appointment (or more than one if needed) also tends to motivate a patient to better comply with the exercise schedule, especially if the patient knows that he or she will be asked about compliance as well as to demonstrate the exercises.

We speculate that the benefit reported by subjects may be associated with their most common response that the exercises caused the neck muscles to relax, thereby relaxing the masticatory muscles as well.

Monitoring posture. Effective posture training also involves instructing the patient to continually monitor his or her improved posture. This can be done in conjunction with other forms of continuous monitoring, such as tongue posture, jaw posture and jaw muscle tension; when warranted, modifications can be made.

It is important to keep in mind that we evaluated subjects in the treatment group after only four weeks of posture training (in addition to having provided them with self-management instructions). The long-term effects of posture training were not evaluated and we recommend that a long-term study be conducted.

	CONCLUSIONS

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The results of this study suggest that posture training may be a beneficial therapy for most patients with TMD who have a primary masticatory muscle disorder and who are interested in improving their posture. On average, subjects who received posture training in addition to self-management instructions reported a 42 and 38 percent reduction, respectively, in their TMD and neck symptoms. Twenty-three (77 percent) of the subjects reported that a $100 charge for physical therapist’s services would be worth the benefit received. We found that patients who hold their head farther forward relative to the shoulders have a high probability of experiencing improvement in TMD symptoms as a result of posture training and being provided self-management instructions.