1. Journal of Dental Research
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Temporomandibular Disorders: Moving from a Dentally Based to a Medically Based Model
Charles S. Greene and Daniel M. Laskin
J DENT RES 2000 79: 1736
DOI: 10.1177/00220345000790100101
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2. E1- 1
Charles S. Greene and Daniel M. Laskin* Temrporomand ibu ar
Department of Oral & Maxillofacial Surgery, University of Illinois,
College of Dentistry, Chicago, IL 60612; and *Department of Oral & Disorders: Moving
Maxillofacial Surgery, Virginia Commonwealth University, School of
Dentistry, Richmond, VA 23298-0566; *corresponding author,
Dlaskin Cden .den.vcu.edu
from a Dentally Based
J Dent Res 79(10): 1736-1739, 2000
to a Medically Based Model
INTRODUCTION etiology, and treatment. Originally, Laskin had no particular
bias for or against any of the popular etiologic theories of the
The year 2000 marks the end of a century in which many
time, but he was impressed by the findings of Laszlo
I traditional dental concepts were subjected for the first time
Schwartz and his colleagues at Columbia University
to some type of systematic inquiry. This kind of investigation
(Schwartz, 1959). Their research had indicated that most so-
produces results that differ considerably from the results of called "TMJ pain and dysfunction" was probably myofascial
"Discovery" experiments (such as those often described in this in origin, and their etiologic perspective emphasized
section of JDR), in which new diseases or new diagnostic psychological stress rather than occlusal disharmony as the
modalities are brought to light. This essay describes the primary cause of the problem.
background of nearly 40 years of systematic inquiry into the By 1965, the University of Illinois Temporomandibular
subject of temporomandibular disorders (TMD), much of Joint and Facial Pain Research Center was established, and
which was directed at questioning the validity of the traditional Charles Greene joined the group as clinical director. From the
concepts in this field, and how this eventually changed the beginning, one or more psychologists were always included on
clinical management of patients. It also recounts the struggle to the team. Most of the oral and maxillofacial surgery residents
persuade the dental profession to move from the past into the also contributed to many of the studies as part of a Master of
modem arena of TMD diagnosis and treatment. Science degree program. The collaboration between Laskin
and Greene began a working relationship that has continued to
SINGLE-MODALITY TREATMENT EXPERIMENTS this day.
In 1963, the University of Illinois College of Dentistry submitted In the early 1960s, conventional wisdom held that all
an application to the National Institute of Dental Research for a "TMJ" patients had more or less the same kind of problem,
five-year program-project grant to study the various aspects of usually referred to as "TMJ syndrome". This oversimpli-
temporomandibular joint (TMJ) growth and development, fication generally was accompanied by the concept that this
anatomy, physiology, and pathology, as well as the various clinical condition was caused by some type of occlusal/skeletal
disorders. The co-principal investigators were Seymour Yale, who disharmony and, therefore, proper treatment inevitably would
had recently become Chairman of the Department of Oral require the correction of these morphofunctional faults. This
Radiology, and Daniel Laskin, who was an associate professor in mechanistic viewpoint had previously been challenged by
the Department of Oral and Maxillofacial Surgery with an interest Laszlo Schwartz and his co-workers (most notably by the
in the role of the mandibular condyle in facial growth. Included as psychiatrist, Ruth Moulton), who believed that myofascial
co-investigators were Milton Engel, Allan Brodie, and E. Lloyd pain and psychological stress were important etiologic factors.
DuBrul. This grant was subsequently funded for $872,000, the However, they had not made many converts by 1966, which
largest grant that the dental college had received up to that time. was when our work began.
Shortly thereafter, Yale became the dean of the college, and the We decided to conduct a series of single-modality
responsibility for being the principal investigator and implementing treatment experiments, using placebo controls in each one,
and administering the grant fell to Laskin, who continued to direct to see which of the existing therapeutic procedures might
the program and to secure NIDR funding for 23 consecutive years. have "real" effectiveness. In these studies, we looked at
Although Laskin's original interest in the several medications (Greene and Laskin, 1969, 1972; Ryan
temporomandibular joint was related to craniofacial growth, et al., 1985), various physical therapies (Lerman, 1968;
of necessity this interest soon broadened into the clinical Sutcher et al., 1969; Eisen et al., 1984), oral bite appliances
field of temporomandibular disorders (referred to as TMJ (Greene and Laskin, 1971; Block and Laskin, 1978), TENS
syndrome at that time). He set about establishing a team that (Block and Laskin, 1980; Gold et al., 1983), and even
would subsequently explore both the basic and clinical psychological therapies (Pomp, 1974; Shipman et al., 1974;
aspects of these problems, with emphasis on diagnosis, Dohrman and Laskin, 1978), and found some remarkable
results. Every experiment produced a fairly high (35-60%)
placebo response, with even higher responses produced by
KEY WORDS: temporomandibular disorders, maxillofacial the "real" treatments.
pain, placebo therapies. Nobody had previously conducted any controlled clinical
experiments such as these in this field, despite the fact that a
Received March 28, 2000; Accepted July 10, 2000 "TMJ syndrome" was being diagnosed and treated since the
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3. JDentRes 79(10) 2000 DISCOVERY! 1737
1930s. Our original intent in using placebos in the medication anxiety, depression, coping skills, and similar psychological
studies was entirely traditional, but the high percentage of parameters that were being studied in other kinds of pain
positive outcomes prompted us to develop and use some rather patients (Shipman et al., 1974; Olson and Schwartz, 1977;
innovative placebos in succeeding studies. For example, we Schwartz et al., 1979; Millstein-Prentky et al., 1979; Malow et
decided to try a "realistic prescription" procedure for al., 1980; Malow, 1981; Greene et al., 1982). They also
dispensing a placebo medication rather than using the typical applied various experimental psychophysiologic techniques to
double-blind technique with secret coded numbers on the bottle assess pain tolerance, response specificity, evoked brain
(Laskin and Greene, 1972). We had our University pharmacy potentials, and other parameters of altered mind-body
prepare capsules of lactose that could be obtained only by the relationships (Lupton and Johnson, 1968; Mercuri et al., 1979;
presentation of a written prescription and the paying of a small Malow et al., 1980; Diaz-Clark et al., 1982; Rosenfeld et al.,
fee; the "drug" was given the suggestive name Myolax, and it 1983; Olson and Malow, 1986). The results of these studies
proved to be about 50% more effective than the same placebo contributed to the formulation of Laskin's psychophysiologic
given in a double-blind protocol. theory of myofascial pain etiology (Laskin, 1969). This theory,
We also designed the first "placebo splint", which was along with the work of Schwartz and Moulton, became the
simply an acrylic palatal appliance that did not alter the foundation for much of today's discussions about
patient's occlusion (Greene and Laskin, 1971). This device biopsychosocial concepts, which in turn led to the
was not only quite successful in relieving symptoms, but it development of the Axis I-Axis II dichotomy in the Research
also produced responses from many patients about how their Diagnostic Criteria (RDC/TMD).
jaw and bite felt different while wearing it. Our sham TENS As a result of our initial clinical, psychological, and
procedure used a machine with lights blinking, but with no psychophysical studies, and the subsequent works of others,
electrical current being transmitted through the electrodes TM disorders have been moved away from their traditional
(Gold et al., 1983). niche in the world of dentistry into a more appropriate position.
Finally, we were ready for "the big one"-we pretended to Instead of being considered as mechanical morphofunctional
adjust the bite (equilibrate) in a series of 25 TMD patients after problems, it is now clear that they are orthopedic,
doing a thorough occlusal analysis and discussing it with the musculoskeletal conditions usually featuring pain as the
patient. Little did we expect that we were about to set our all- dominant symptom, with significant psychological associations
time high placebo response record: 64% of these patients that affect their etiology and management. Yet, treatment of
reported a major or total improvement after only two sessions these disorders remains within the dental profession as one of
of mock equilibration (Goodman et al., 1976), and most of our primary responsibilities, so that it becomes necessary for
them were quite happy with the "improvement" in how they dentists to learn how to care for TMD patients within this new
were biting. paradigm. To do so, they must use their training in oral
The results of these studies demonstrated that many TMD medicine rather than the more traditional morphofunctional
patients are strong placebo responders and that such effects, treatment approaches.
plus the procedural aspects of the doctor-patient relationship,
have a strong influence on the outcome of various rational CURRENT STATUS OF THE TMD FIELD
therapeutic approaches. They also explained why certain other After 35 years of research that has been conducted around
treatments can sometimes be effective, even though they lack a the world, a scientific foundation for the TMD field has been
scientific basis. In essence, they showed that with TMD established. Converging information from several diverse
patients it is often not what is done for them, but how it is done, disciplines has contributed to this foundation, so that today
that is important. we speak of TM disorders in terms of orthopedic principles,
neurophysiology of pain, molecular pathophysiology of
PROFESSIONAL CHALLENGES joints and muscles, and behavioral aspects of chronic pain.
Naturally, the first challenges to our results came from various We diagnose and classify TMD patients within a
members and groups within the "occlusion-changing" biopsychosocial framework, and we treat many of them
community of dentists. They insisted that we were merely successfully with empirically validated, conservative
producing short-term successes, which would quickly fade therapies.
once we stopped "manipulating" these patients, because we Unfortunately, these conclusions are not yet universally
were not correcting the underlying dental causes of their endorsed or even accepted by all members of the dental
problems. In both 1974 (Greene and Laskin) and 1983 (Greene profession. In this regard, dentistry remains a somewhat
and Laskin), we published our long-term follow-up data on the fragmented profession, with each discipline having its own
use of conservative and reversible treatments (including viewpoint about many TMD issues. Because these disorders
placebos). Analysis of these data showed not only that most of clearly do not belong to any single dental specialty, they end
our positive treatment effects were enduring, but also that up being treated by almost everybody. As a result, the
positive placebo responders did just as well over the years as special interests and training of each group become imposed
the real treatment patients. on the patients. The old joke says that the fate of a TMD
During the same period when we were conducting these patient is determined by the floor at which the elevator stops
TMD treatment studies, our research team also was studying in a professional office building-not a good state of affairs.
psychologic and psychophysiologic issues in these patients. A These traditional differences among dental subgroups have
series of outstanding behavioral researchers who worked in become accentuated in recent years through the emergence
our Center looked at personality characteristics, stress, of competing TMD academies and societies, and many TMD
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4. 1738 Greene & Laskin J Dent Res 79(10) 2000
patients today remain at risk of being treated with incredibly patients (abstract). IADR Progr & Abstr: 198.
complex and invasive therapies, instead of getting the kind Dohrnann RJ, Laskin DM (1978). An evaluation of electromyographic
of conservative (and effective) care that is currently biofeedback in the treatment of myofascial pain-dysfunction
supported by the body of scientific evidence. syndrome. JAm Dent Assoc 96:656-662.
Nevertheless, there currently is much about which to be Eisen RG, Kaufman A, Greene CS (1984). Evaluation of physical
positive in the TMD field, and the core of fundamental therapy for MPD syndrome patients (abstract). JDent Res 63(Spec
knowledge continues to grow through research. The Iss):344.
NIH/NIDCR and similar government agencies throughout the Gold N, Greene CS, Laskin DM (1983). TENS therapy for treatment
world have been generously funding both basic and clinical of MPD (abstract). IADR Progr & Abstr:244.
research in this field for many years. Most dental schools Goodman P, Greene CS, Laskin DM (1976). Response of patients with
around the world have established special TMD/Orofacial myofascial pain-dysfunction syndrome to mock equilibration. J
Pain clinics to provide state-of-the-art care for these complex Am Dent Assoc 92:755-758.
pain patients. The dental schools also are providing new Greene CS, Laskin DM (1969). Meprobamate therapy for the
generations of undergraduate and advanced education myofascial pain-dysfunction (MPD) syndrome: a double-blind
students with the latest contemporary information about this evaluation. JAm Dent Assoc 82:587-590.
subject. Advanced training programs lasting up to 2-3 years Greene CS, Laskin DM (1971). Splint therapy for the myofascial pain-
also have been developed in many universities in various dysfunction (MPD) syndrome. A comparative study. JAm Dent
countries to produce "specialists" in the orofacial pain field; Assoc 84:624-628.
the graduates from these programs have become both the Greene CS, Laskin DM (1972). Therapeutic effects of diazepam
community experts for treating complex patients and the (valium) and sodium salicylate in myofascial pain-dysfunction
orofacial pain teachers for the next generation. (MPD) patients (abstract). IADR Progr & Abstr:96.
In the end, we can see that the field of TM disorders has Greene CS, Laskin DM (1974). Long-term evaluation of conservative
undergone significant growth and change during the past 35 treatment for myofascial pain-dysfunction syndrome. J Am Dent
years, and we are proud to have been a part of that evolution. Assoc 89:1365-1368.
We hope that our early commitment to seeking scientific Greene CS, Laskin DM (1983). Long-term evaluation of treatment for
answers to clinical questions, based on applying basic myofascial pain-dysfunction syndrome: a comparative analysis. J
biological principles as well as on following the rules for AmDentAssoc 107:235--238
proper research, has set an example for many of our Greene CS, Olson RE, Laskin DM (1982). Psychological factors in the
colleagues and our students to follow. Today, the field of TM etiology, progression and treatment of MPD syndrome. JAm Dent
disorders is rich with information derived from the research Assoc 105:443-448.
done by us and by so many of our colleagues, and this Laskin DM (1969). Etiology of the pain-dysfunction syndrome. JAm
information has been combined with insights from allied Dent Assoc 79:147-153.
disciplines to produce the current mixture of facts and Laskin DM, Greene CS (1972). Influence of the doctor-patient
hypotheses in this field. Yet, so many important questions relationship on placebo therapy for patients with myofascial pain-
still remain unanswered: Why does the pain become chronic dysfunction (MPD) syndrome. JAm Dent Assoc 85:892-894.
in one person and not in another? Why do joints and muscles Lerman MD (1968). A preliminary study of muscle exercises in
adapt and remodel successfully in some patients and not in treatment of TMJ pain-dysfunction syndrome (abstract). IADR
others? What are the biologic markers, symptom patterns, Progr & Abstr:190.
and behavioral characteristics that will enable us to predict Lupton DE, Johnson DL (1968). The relationship of pain tolerance
responses to therapy? And last but not least, what to personality characteristics among chronic
combination of etiologic factors and host resistance factors temporomandibular joint dysfunction patients (abstract). IADR
determines who gets TMD and who does not? Progr & Abstr:153.
We look forward to the inevitable prospect of seeing these Malow RM (1981). The effects of induced anxiety on pain perception:
and many more questions answered in the not-too-distant a signal detection analysis. Pain 11:397-405.
future. But regardless of how long it takes, one thing is very Malow RM, Grimm L, Olson RE (1980). Differences in pain
clear: The framework for understanding TM disorders will perception between myofascial pain-dysfunction patients and
continue to be developed within a biopsychosocial medical normal subjects: a signal detection analysis. J Psychosom Res
model-not within the traditional mechanistic dental model that 24:303-309.
originated many years ago. Mercuri LG, Olson RE, Laskin DM (1979). The specificity of response
to experimental stress in patients with myofascial pain dysfunction
syndrome. JDent Res 58:1866-187 1.
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Schwartz L (1959). The pain-dysfunction syndrome. In: Disorders of Sutcher 1, Greene CS, Lerman M, Laskin DM (1969). Comparison of
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1
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