Artículo referente ala ATM

1. Orthodontic dental casts: The case against
routine articulator mounting
Donald J. Rinchusea
and Sanjivan Kandasamyb
Greensburg, Pa, and Midland, Western Australia, Australia
T
here is no doubt that dental casts, whether
plaster or digital, are one of many important
tools routinely used in orthodontics for assess-
ing dentitions or malocclusions. Unfortunately, to
this day, a convincing case has still not been made
for the routine mounting of all casts on articulators.
Drs Martin and Cocconi, however, would like you to
believe otherwise. The issue of articulator mountings
in orthodontics must be considered within the broad
framework of orthodontic gnathology. Under the
premise of pursuing “what is best for the patient,”
Drs Martin and Cocconi have conveniently left out
the term “gnathology” in their “Point” article; how-
ever, the principles of gnathology (right or wrong)
form the basis of their argument for using articula-
tors. We have written and expressed the evidence-
based view on gnathology and articulator mounting
in orthodontics several times and advise the reader
to review relevant literature for a more thorough un-
derstanding on this topic.1-11
Drs Martin and Cocconi make many unsupported
claims in their article. Statements such as the articu-
lator “is just another tool . . .” an orthodontist can
do good orthodontics without using an articulator,
but an articulator can help him or her to provide bet-
ter treatment in many clinical situations,” and
“whether research is always good for clinical prac-
tice” fly in the face of evidence-based practice and
the basic tenets of science. With comments like
these, are they really putting forward an intellectual
and scientific discussion on the use of articulators
in orthodontics?
Clearly, several issues need to be discussed: artic-
ulators in relation to centric relation and records,
centric slides, occlusion and temporomandibular dis-
orders, and occlusion and periodontal disease.
Articulators can play a role in prosthodontics,
restorative dentistry, and orthognathic surgery to main-
tain a certain vertical dimension for laboratory purposes.
For some orthodontists, mounted dental casts help eluci-
date various 3-dimensional and static jaw and occlusal
relationships and deviations. Nonetheless, using articula-
tors as a routine diagnostic aid in orthodontics appears to
be a perfunctory exercise. The premise for the use of ar-
ticulators dates back to well over a half century ago,
when occlusion and condyle position were believed to
be the primary cause of temporomandibular disorders.11
However, the modern view is that specific occlusion, con-
dylar position, and jaw alignment factors are no longer
considered the primary causes of temporomandibular
disorders.6,12-18
The diagnosis and treatment for
temporomandibular disorders has changed from a den-
tal-based model to a biopsychosocial model that inte-
grates biologic, behavioral, and social factors to the
onset, maintenance, and mitigation of temporomandib-
ular disorders.12,19-30
A medical orthopedic approach
that focuses on the biomedical sciences and musculo-
skeletal treatments similar to those for chronic pain are
the current approaches for temporomandibular disor-
ders. Biopsychosocial treatment approaches such as
cognitive-behavioral therapies and biofeedback are con-
temporary treatment modalities for temporomandibular
disorders. The exciting future research topics for tempo-
romandibular disorders are genetics (vulnerabilities
related to pain), central-brain processing, imaging of
the pain-involved brain, endocrinology, behavioral
risk-conferring factors, sexual dimorphism, and psy-
chosocial traits and states.12-15,19-30
Conservative and
reversible forms of temporomandibular disorder treat-
ments are preferred (at least initially) over aggressive
and irreversible forms. In the evidence-based view, or-
thodontics is considered temporomandibular disorders
neutral— ie, orthodontics does not cause and will not
necessarily correct or improve a patient’s temporoman-
dibular disorder condition now or in the future.31-34
Because orthodontics has not been demonstrated to
a
Professor and graduate orthodontic program director, Seton Hill University,
Greensburg, Pa.
b
Clinical senior lecturer in orthodontics, Dental School, The University of West-
ern Australia, Nedlands, WA, Australia; visiting assistant professor in orthodon-
tics, Center for Advanced Dental Education, St. Louis University, St. Louis, Mo;
private practice, Midland, WA, Australia.
Reprint requests to: Donald J. Rinchuse, Seton Hill University, Center for Ortho-
dontics, 2900 Seminary Drive, Greensburg, PA 15601-1599; e-mail, rinchuse@
setonhill.edu.
Am J Orthod Dentofacial Orthop 2012;141:8-16
0889-5406/$36.00
Copyright Ó 2012 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2011.11.008
American Journal of Orthodontics and Dentofacial Orthopedics January 2012 Vol 141 Issue 1
POINT/COUNTERPOINT 9

2. cause temporomandibular disorders, this further sup-
ports the notion that occlusion and condyle position
do not cause temporomandibular disorders: ie, the
premise that orthodontics could cause temporoman-
dibular disorders is grounded in the dental-based
model.
Of note, the evidence-based view does not argue
that occlusion and condyle position have no relation-
ship to temporomandibular disorders and that ortho-
dontists should ignore them. The gross evaluation of
the patient’s occlusion still are useful: “assessment of
occlusion is necessary as part of the initial oral exami-
nation to identify and eliminate gross occlusal discrep-
ancies.”35
The amelioration of gross occlusal
interferences that cause tooth mobility, fremitus, and
deviation or deflection on mandibular closure and
movement are within the scope of the evidence-based
paradigm.
Because there has been a paradigm shift regarding
the etiology, diagnosis, and
treatment of temporoman-
dibular disorders away from
occlusion and condyle posi-
tion, occlusionists and gna-
thologists should reconsider
and abandon age-old views
and techniques that are not
supported by science and ev-
idence. Certainly, the
evidence-based view on the
role of occlusion in relation to temporomandibular dis-
orders should have had a negative impact on the rou-
tine use of articulators in orthodontics.4,12
Greene16,17
wrote: “I would encourage orthodontists
to be somewhat flexible in applying the standards of
ideal jaw relationships as well as ideal occlusion rela-
tionships to their finishing of patients . . . we should
not have conversations about tenths of millimeters
when discussing where the condyle should be. . . .
The failure to produce some expert’s version of a so-
called good/ideal occlusion or CR position is not
a risk for developing TMD.” Does it make sense to focus
and study occlusion and condyle position the same way
that we did more than 50 years ago?
The belief that centric occlusion or (or maximum in-
tercuspation or intercuspal position) should be coinci-
dent with an arbitrary centric relation position is not
evidence-based. The preponderance of evidence sug-
gests that for the population at large there is a range
of acceptable positions and not 1 centric relation posi-
tion that is optimal for every patient.5
That is, a partic-
ular 3-dimensional position of the temporomandibular
joint condyles in the glenoid fossa has not been found
to predict temporomandibular disorders.5
Johnston36
wrote: “I know of no convincing evidence that condyles
of patients with intact dentitions should be placed in
CR or that once placed or that once having been placed
there, the resulting improvement on nature will be sta-
ble.” Interestingly, centric slides greater than 4 mm that
have been found to be associated with temporoman-
dibular joint arthropathies are most likely the result
of the temporomandibular disorders rather than the
cause, contrary to the beliefs of Drs Martin and Coc-
coni.32
Many of the problems we have with articulators as
diagnostic aids in orthodontics start before the articu-
lator is actually used (Fig 1). Centric relation records
can be demonstrated to be reliable, but there is no ev-
idence to support their validity.5
Nonetheless, proper
attention to an orthodontic patient’s centric records
is an important consideration in orthodontics and all
of dentistry. We do know that
doctor-generated patient cen-
tric records are more reliable
than patient-generated re-
cords, but they are also less
valid (physiologic).5
In addi-
tion, the same bite registra-
tions used to make dental
casts should be consistently
used throughout all the pa-
tient records—dental models,
photographs, cephalometric radiographs, and so on.
And, to merely ask orthodontic patients to bite on their
back teeth will not always provide an accurate centric
bite registration, and one might miss diagnosing
a “Sunday bite.”
Gnathologic centric records are static and not func-
tional (Fig 1). Patients are not asked to exercise any rel-
evant physiologic mandibular movements to generate
centric relation records. Chewing kinematics are not
evaluated, such as chewing pattern dynamics, which
might determine whether a patient is more or less a ver-
tical or horizontal chewer.4,37
Furthermore, the harsh-
est occlusal forces are those generated via
parafunctional mandibular movements, such as brux-
ing and clenching. These movements and forces are
not evaluated by centric relation records and articulator
mountings.4
Based on information from the study of Alexander
et al,38
clinicians, in general, cannot predict where con-
dyles are positioned and recorded based on their partic-
ular type of centric bite registration. This makes it
imperative that orthodontic gnathologists provide
The premise for the use of articula-
tors dates back to well over a half
century ago, when occlusion and
condyle position were believed to
be the primary cause of temporo-
mandibular disorders.
Counterpoint 11
American Journal of Orthodontics and Dentofacial Orthopedics January 2012 Vol 141 Issue 1

3. magnetic resonance imaging research data of the tem-
poromandibular joints that substantiate that the sub-
jects’ condyles are actually placed and recorded in
positions determined by such registrations. In addition,
the difference between gnathologic and nongnatho-
logic diagnostics is on average as little as 1 mm or
less, and this is mostly in the vertical dimension.39
Are such minor differences really a health concern?
Also, in growing children, the temporomandibular joint
condyle-glenoid fossa complex changes location with
growth; the fossae on average are displaced posteriorly
and inferiorly.40
One would therefore need to perform
new mountings regularly throughout treatment to di-
agnose and maintain their so-called ideal centric rela-
tion position. This however does not occur.
The shortcomings of articulators in orthodontics
were discussed in detail in our article and are listed in
Figure 2.4
Diseases of the temporomandibular joint
such as disc displacement and osteoarthrosis are best di-
agnosed with magnetic resonance imaging of the tem-
poromandibular joints and a clinical examination, and
not with articulators. The major premise for the use of
articulators is based on the incorrect concept of a “ter-
minal hinge axis” of Posselt41
dating back more than
a half century. Posselt conjectured that, in the initial
20 mm or so of opening and closing, the mandible (con-
dyles) only rotates similar to a door hinge (and does not
simultaneously translate). However, Posselt’s theory
was made in the era when centric relation was consid-
ered a retruded, posterior position of the condyles in
the glenoid fossa. During this time period, retruded cen-
tric relation was recorded with distal guided pressure
applied to the chin, a probable reason for Posselt’s find-
ing of a “terminal hinge axis.” In 1995, Lindauer et al42
demonstrated that, during opening and closing, the
condyles not only rotate, but also simultaneously
Fig 1. Limitations of centric relation, condyle position records, and measurements.
Fig 2. Limitations of articulators.
Counterpoint 13
American Journal of Orthodontics and Dentofacial Orthopedics January 2012 Vol 141 Issue 1

4. translate (move downward and forward). They demon-
strated that the terminal hinge axis does not exist, and
their findings support an “instantaneous center of rota-
tion” that varies in every patient and cannot be simu-
lated via an articulator (Fig 2).4
Drs Martin and Cocconi failed to point out that an
association between “occlusal discrepancies and the
progression of periodontal disease” is controversial.
In this respect, they referenced an article by Harrel
et al43
entitled “Is there an association between occlu-
sion and periodontal destruction? Yes—occlusal forces
can contribute to periodontal destruction.” Unfortu-
nately, this was only 1 side of a debate published in
the Journal of the American Dental Association in
October 2006; they neglected to mention the accom-
panying counterpoint article in which Deas and
Mealey44
discussed several clinical studies with results
contradicting those of Harrel and Nunn,45
Nunn,46
Nunn and Harrel.47
As Deas and Mealey44
pointed
out, “the determining factor of whether an occlusal
contact produces occlusal trauma is the presence of
periodontal injury, not the physical manifestation of
the teeth, temporomandibular joints or muscles of
mastication.” Even Harrel et al43
acknowledged the
limitations of their research: “Our study should be
viewed in the context of its design. It does not meet
the level of what is considered the gold standard of
clinical research. . . . Our study was retrospective in na-
ture, a single practitioner performed all evaluations and
data gathering. Furthermore, the patients’ oral hygiene
and maintenance compliance was not standardized. All
these are significant concerns regarding our research
design.” Interestingly, according to the research by
Nunn44
and Deas and Mealey,43
the recording of sub-
jects’ occlusal discrepancies was not determined by the
use articulated mounted dental casts in this research.
So we ask Drs Martin and Cocconi, if they think it so
important to use articulators to deduce occlusal dis-
crepancies, why did they cite and focus on research
that did not use articulators as the clinical tool of
choice for recording such discrepancies?
CONCLUSIONS
If we know that specific condylar positions, slides,
and the minute details of occlusion are not predictive
of temporomandibular disorders, that articulators do
not simulate condylar movements accurately, and that
centric relation records do not really place condyles in
their deemed positions, then what are we actually trying
to achieve by routinely mounting dental casts on artic-
ulators? Such a mechanistic and instrument-oriented
approach to patient diagnosis and treatment planning
is only a disservice to patients. The burden of proof is
and should always lie on those who are advocating
a controversial tool or procedure. So we ask the readers,
did Drs Martin and Cocconi present a convincing argu-
ment for the routine use of articulators in orthodontics
based on scientific and evidence-based considerations
rather than on anecdotes and blind rhetoric? The con-
vincing evidence is against the routine mounting of
casts on articulators. What would William Shakespeare
say, as Hamlet’s famous quote is placed in the context
of this debate on articulators? Perhaps it is whether
one chooses “to believe or not to believe.”
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