This document summarizes the shift in the conceptualization and treatment of temporomandibular disorders (TMD) from a dentally-based model to a medically-based model over the past 40 years. It describes early research at the University of Illinois that conducted controlled clinical trials testing single-modality treatments for TMD, including medications, physical therapies, oral appliances, TENS, and psychological therapies. The studies found high placebo response rates of 35-60% across treatments. Placebo treatments like sham prescriptions, placebo splints, and mock occlusal adjustments were also effective for many patients, demonstrating the strong psychological factors involved in TMD. The results challenged traditional dental concepts and treatment of TMD,

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