TMJ & Orthodontics: Patient Individuality & Joint Function

PECIAL ARTICLES
The individuality of the patient and the
emporomandibular joints. Part I
John R. Thompson, DDS, MSD, MS
Buchanan, Mich.
[This is the first of three articles to be published in the
'OURNAL. ]
T h i s clinical report uses the individual case
9eport method of clinical research. It is directed toward
he-individual variations in growth of the mandibular
:ondyle and the behavior and pattern of growth of the
'acial skeleton, focusing on the influences on ortholontic treatment and temporomandibular joint dys'unction.
9Faulty intercuspation of the teeth and dental intru;ions into the freeway space are two of the many eti)logic factors that may lead to joint dysfunction and its
;equelae. lntercuspation of the teeth, which operate
hrough the proprioceptive functions of the periodonium, can be a major influence on mandibular position
n closure after initial contact. Faulty intercuspation can
)verload a joint in various ways. Dysfunction of the
oints and musculature may occur before orthodontic
reatment, during treatment, or anytime after treatment
aas been completed. Whether related directly to treatnent or not, the orthodontist must be alert to recognize
;uch dysfunction and intervene whenever it may occur.
The primary team for management and treatment
ffthese conditions is the orthodontist and the restorative
tentist. One or the other or both, combining their ef:'orts, can correct a majority of these problems related
:o abnormal occlusal function. On some occasions, sur;ical intervention may be required to reposition the
naxilla or correct other skeletal deformities, but surgical revision of the joint itself is seldom required in
ldults and never in young persons.
The role of the orthodontist in correcting a mal9cclusion is a complex one that requires moving teeth
:o a desired dental occlusion in harmony with normal
:elations of the joint structures, and this is best accomalished in a growing face where relationships among
ill of the components are in a continual state of flux.
rhe ultimate goal is optimal intercuspation of the teeth
tnd normal temporomandibular joint (TMJ) function
AM J St-x: Dr~,-ror^c OwnloP 1994;105:83-7.
Copyright 9 1994 by the American Association of Orthodontists.
0889-5406194151.00 + 0.10 811137117
after the major growth of the mandibular condyles has
been completed.
This can be difficult to achieve because the orthodontist must deal with some factors like growth of the
mandibular condyle, which cannot be predictably influenced or controlled by orthodontic tooth movement.
Even though the best orthodontic results can usually be
achieved by instituting treatment at a time of active
facial growth, this must be done with the understanding
that natural variability demands a continual alertness to
the need for adapting to the occasional slow response
to mechanical therapy.
PART 1. GROWTH OF THE MANDIBLE
The mandibular condyle is an important primary
growth center. Condyle growth may vary over a broad
range, from none at all to too much, and either extreme
can cause abnormal TMJ function.
No growth
One of the two growth extremes is no growth at the
moment of treatment. If the condyles are not growing
upward and backward at the time of orthodontic tooth
movement, the body of the mandible will not be projected downward and forward with the rest of the face,
and the normal dental freeway space can be lost. The
result is downward and backward rotation of the mandible, which may cause clicking and other symptoms
in the joint.
Any horizontal or vertical movement of a functional
buccal tooth will cause interferences and some loss of
freeway space that should be temporary. In cases of
abnormally wide freeway space (6 to 7 mm), the orthodontically induced eruption or interference of posterior
teeth may not intrude into the normal "freeway space;
it merely reduces the wide freeway space toward the
average 2 to 3 mm. This is within the range of muscular
rest position, so trauma to the teeth, supporting tissues,
or the joints is unlikely.
As long as tooth movement does not encroach excessively on the nomlal freeway space envelope, simultaneous condylar growth can provide new space to
enlarge the envelope. When clicking occurs during
treatment and there is no obvious cause (such as
overerupting lower second molars), it is quite possible
83
Zhottlpson
that either facial growth is inadequate or the orthodontic
changes have been too rapid for compensation.
A new lateral cephalometrie radiograph will probably show the current mandibular position and any rotation or posterior displacement that may have occurred
since an earlier film.
The no growth problem is demonstrated in the case
reports in part 3 of this series (to be published at a later
date).
Protracted condyle growth
Too much growth can be just as serious as too little.
Additional condyle growth after other facial growth has
stopped is a special concern because it can alter the
occlusion and joint function. There may be no joint
clicking or other symptoms at 12 or 14 years of age,
yet pronounced symptoms 5 years later. Every patient
should be checked regularly, especially through the
years immediately after other growth has essentially
ceased. The orthodontist should continue to be responsible for this supervision of orthodontic patients. Continuing observation at least once or twice a year is an
additional professional service not entirely related to
treatment that should be explained before treatment is
started. The orthodontist should be the first to detect
any clicking or dysfunction, understand the problem,
and know how to control it.
The temporomandibular joints are the only joints in
the body under such precise discipline as that imposed
by two rigidly attached, separate but interdependent
articulations, and these must also coordinate with the
dental occlusion. Every movement of one joint imposes
movements and loads on its contralaterai antimere. As
the jaw closes and teeth come into contact, the third
articulation of this triumvirate becomes dominant. Proprioceptive feedback from the intercuspation of the
teeth can then become the primary influence on the
position of the condyles in their fossae from initial
contact to full closure.
Control over jaw movement, however, does not extend to control over condyle growth. Continuing condyle growth will alter occlusal relationships, which in
turn will alter joint relationships, but most occlusal
relationships cannot be expected to influence condyle
growth. Weinmann and Sicher state: "While the dependence of bone growth upon the development of teeth
is slight, the reverse relation, that is, the dependence
of tooth development and especially, tooth eruption
upon growth of bone and bones is considerable.'" That
statement remains true.
This unique three-way articulation makes the temporomandibular joints the only joints in the body that
can grow into an internal displacement (Fig. 1). Com-
American Journal of Orthodontics and Dentofacial Orthopedics
January 1994
parable growth in an elbow or a knee would simply
result in a longer arm or leg, because those joints do
not have to content with restricture feedback from another articulation such as the teeth. The cartilage growth
centers of the long bones can abut against each other
with no problem, but there are compressible, nonarticulatory soft tissues behind and above the cartilage
growth centers of the mandibular condyles. These tissues provide a limited measure of adaptability, but they
are also subject to injury from excessive functional
loads.
To fully appreciate the growth pattern of the face,
one can refer to the classical studies of Broadbent, 2. 3
Brodie, 4 and Weinmann and Sicher, I which remain the
foundation pillars of scientific orthodontics.
Broadbent,s 2. 3 study and compilation of the cephalometric radiographs of a large group of children in
the Bolton Study showed th e unfolding of a stable
growth pattern. From his composite tracings he created
an average face for the various ages (Fig. 2).
Brodie4 followed with his serial cephalometdc radiographic studies, and he too demonstrated the basic
stability of the normal enlarging facial pattern (Fig. 3).
At the same time, anatomist and histologist SicheP
explained the biologic mechanisms of facial growth.
This was an epochal blending of research to explain
how the face grows, and his explanation of cartilage
growth in the mandibular condyle is particularly appropriate to this report (Fig. 4).
Figure 1, A shows the direction of normal condyle
growth at ages 8, 10, and 12 years. Fig. 1, B shows
normal repositioning of the body of the mandible in
response to the growth at the condyle. Fig. 1, C illustrates this normal condyle growth at ages 17 and 18
years and the resulting mandibular repositioning, and
Fig. 1, D shows how such condyle growth can produce
posterior displacement with resultant clicking when the
dental occlusion restricts the normal downward and forward repositioning of the body of the mandible
(Thompsonr-S).
In considering condyle growth, great care is required in the interpretation of temporomandibular joint
radiographs taken before and after a protrusive type of
orthodontic treatment of Class II malocclusions, as with
a functional appliance. Before treatment radiographs
taken with the appliances in place will typically show
the condyles to be downward and forward of their normal relation to the articular eminences. After treatment
radiographs may show the condyles to be again in their
normal positions in the fossae. It is my opinion that
this is essentially growth that would also have occurred
without treatment of the dental malocclusion; radiographs made with a new protrusive appliance fitted at
rnerican Journal of Orthodontics and Dentofacial Orthopedics
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Thompson
85
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8Y
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8,
IOY
B
A
12u
clir
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17y
18jY " ~ - ~ - - -
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Fig. 1. Growth of mandible. A, The direction of normal condyle growth at ages 8, 10, and 12 years.
B, Repositioning of the body of the mandible in response to the condyle growth. C, Normal condyle
growth at ages 17 and 1B years, with normal repositioning of the mandible. D, Condyle growth producing
posterior condyle displacement (clicking) should the dental occlusion prevent the normal downward
and forward repositioning of the mandible. This repositioning occurs as normal at rest position, but
now there would be an abnormal upward and backward path of closure from rest position to the occlusal
position.
his stage would present a picture similar to the original
~retreatment film. Cephalometric radiographs show
imilar progressive downward and forward positioning
if the mandibular body in a normal growth pattern. The
ontroversy exists over the magnitude of potential
:rowth enhancement during therapy.
It is my opinion that correction of occlusion with
hese appliances is accomplished through disengagenent of the occlusion, which allows the growth changes
o alter interocclusal relationships that would otherwise
~e carried along unchanged with growth. This same
:ffect is seen with a broad spectrum of treatment ap-
proaches; the significant factor is occlusal disengagement, not the particular means by which it may have
been achieved.
Growth is the essential component. If there is little
or no condyle growth during treatment with appliances
that displace the mandible, the result will be some degree of dual bite, with possible joint dysfunction. No
growth during treatment with appliances that disclude
but do not displace the mandible will result in little or
no skeletal change, but with lingual tipping of the maxillary incisors and proclination of the mandibular incisors.
86
Thotllpso/l
American Journal of Orthodontics and Dentofacial Orthopedics
January 1994
Fig, 2. Bolton standards from 1 to 18 years old. Taken from Bolton Standards, Kirtland Enterprises,
Kirtland, Ohio.
S
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\
I
a.,
6
Fig. 4. Sicher's diagrammatic illustration of normal mandibular
growth. I
BRODIE
Fig. 3. Brodie's illustration of enlarging facial pattern, with tracings of films made at birth, 3 years, and 8 years superimposed
on the sella-nasion line. s
My clinical research involving personal tracing of
annual cephalometric radiographs on all orthodontically
treated cases over a 40-year period has clearly shown
that orthodontic treatment with either fixed or removable appliances will not cause the condyles to grow
significantly. The inescapable conclusion is that despite
often spectacular changes in the course of treatment by
various means, treatment can neither start nor stop the
growth of a mandible.
Individual variability in timing and rate of growth.
was very apparent in these studies. It must be concluded
in the majority of cases that growth and treatment were
independent, with concurrent changes the result of coincidence rather than cause and effect. Those cases with
the better results had the benefit of good mandibular
growth at the time of treatment, but orthodontic judgments must not be influenced only by these cases.
Creekmore and Radney 9 make some significant
merican Journal of Orthodontics and Dentofacial Orthopedics
105,No. I
Thompson
87
"olume
tatements in their study of orthodontically treated cases
nd untreated control cases.
I. --individual growth responses were not prediclable.
2. --but looking at individual changes, we see tremeri'.ous variation. These are normal ANB angle changes that
,ccur in untreated persons. Is it no wonder, then, that the
ame orthodontic treatment d6es not elici! the same response
or all individuals since individuals do not grow the same
vithout treatment?'6
Poulton I~ states~ "Upper faci.41 growth (S to N) was
tot critical to treatment speed, but the fast ti'eating
~roup. averaged twice as much mandibular growth as
he slow. This simply reconfirms what has been said
:ountless times regarding the beneficial effects Of manlibular growth during thetreatment of Class II malocclusion. From the data recorded here, it would not
De possible to predict When this growth would occur.
f the study of various maturation criteria eventually
eads to the prediction of facial growth, the efficiency
if orthodontia treatment can be greatly increased."
In 1956 Wylie H stated: "Growth, the best friend the
irthodontist ever had, was all but driven out of the
louse in the forties. Nineteen fifty-five would be an
,ppropriate yeai" to put a light in the window. Maybe
he lady Growth will see it and come home again-his time to stay." Long-range cephalometric radio~raphic evaluation of orthodontically treated cases
:learly sho,;vs that growth has "returned" in its proper
ole of supporting treatment rather than as a variable
esponsive to treatment.
Weitimann and Sicher t have clearlyexplained the
,,rowth mechanisms of the facial structures. The maxIlary and mandibular teeth erupt vertically by growth
ff the alveolar processes. This is appositional growth
of bone tissue. The mandible and maxilla grow in size
by appositional growth of bone tissue. The mandibular
te6th are carried downward and forward with the body
of the mandible by the upward and backward appositional growth Of the condylar cartilage tissue. This
growth mechanism is uniquely characteristic of the
mandible; long bones grow by the different mechanism
of interstitial growth of cartilage. The maxillai'y teeth
are concurrently carried downward and for~vard by sutural growth and alveolar bone growth.
These two different mechanisms of growth, appoSitional cartilage growth in the mandibular condyle and
sut/aral growth in the maxilla, are the basis for many
disproportional relationships between the mandible and
the maxilla. Overretraction of maXillary incisors can
alter the occlusal position of the mandible, initially
creating a functional retrusion and forcing the condyle
to grow into posterior displacement. The rest position
is not altered, so the normal rotary hinge closure from
rest to occlusion becomes a translatory, bodily upward
and backward path of closure because of incisal guidance, with clicking of the joints. It is often a matter of
the relative timing of growth of the condyles and orthodontic treatment that determines the extent o f such lingual incisal movement. It is the interaction of the spatial
relationships (position of the incisors) and time (growth
of the condyle) that ultimately produces either conformity or disharmony (incisal interference).
(This article will be continued in subsequent issues.
References for tlre entire article will appear at the end
of tlre third article.)
Reprint requests to:
Dr. John R. Thompson
3000 White Oaks Ln.
Buchanan, MI 49107