1. The document discusses the relationship between malocclusion and temporomandibular joint dysfunction (TMD). While some studies have found a correlation, others have found no relationship or a minor contribution of malocclusion to TMD. 2. Certain types of malocclusion like increased overjet, unilateral posterior crossbite, and skeletal open bites have been associated with higher rates of TMD in some studies. However, other research has found a wide variation in occlusal characteristics in both TMD and non-TMD groups. 3. The temporomandibular joint has a high ability to adapt to different occlusal changes, making it difficult to definitively link specific malocclusions to

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Dr. Mohammed Alruby
Temporomandibular joint dysfunction
and malocclusion
Prepared by:
Dr Mohammed Alruby
The effect of malocclusion on TMJ has been a matter of controversy since many years, the
problem is often related to the path of mandibular closure from the initial contact to centric
occlusion

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Dr. Mohammed Alruby
It has been noted that, the path of mandibular closure from rest position to initial contact is
essentially normal in most pt, the most of difference occurs from the point of initial contact to
centric occlusion
In normal individual, the rest position, centric relation, initial contact and centric occlusion
should be coincident. However, malocclusion may provide a change in the initial contact position
because of the premature points of contact and teeth guidance problems, the mandible may be shift
from the ideal acclusal to the usual occlusal position.
Arc of closure:
= the mandible usually closes with lower incisors follow an arc in upward and forward direction.
This arc of closure is abruptly disturbed at the point of initial contact of prematurity or teeth
guidance problem exist. This arc of closure may become vertical, upward and backward or lateral
shift depending on the type of tooth guidance.
Since, the articular disc is held in its position by the external pterygoid muscle which prevent it
from being further retruded. In some cases, such as Class II divi 2 when the mandible closed, it
will be guided backward by the effect of retroclined maxillary incisors. The condyle forced upward
and backward, and may rides the posterior tip of articular disc and in some instances become
imping on the post articular connective tissues.
Initiation of the opening movement may result in:
1- The articular disc pulled forward by contraction of external pterygoid muscle and the
condyles snap over the disc periphery against the post articular connective tissue. Then the
condyle starting late but moving forward rapidly, riding over the posterior margin of the
disc into more normal position.
2- The posteriorly displaced condyle, move forward riding over the posterior lip of the disc
In all instances, snap or pop sensation is felt by the patient, pain or limitation of movement may or
may not occur depending upon the type of disharmony and resistance of patient
Definition: TMD: disorders with common signs and symptoms affecting the joint, facial muscles
or both
: limited opening of mandible < 40mm in males and <45mm in females
: Joint noise and pain, tender muscle of mastication, popping or tinnitus of the ears, and
headaches
Etiology:
- Multifactorial
- Inflammatory
- Degenerative
- Dysfunction
- idiopathic
Clinical studies:
== studies suggesting positive correlation:
Moteg et al 1992 keeling 1994 Tanne et al Brand et al 1995
 Tanne et al reported the incidence of TMD in his untreated sample was 19%, however no
other epidemiologic studies were available to support this finding

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Dr. Mohammed Alruby
 It was found that, the incidence of TMD increase as the age of the patient increase, however
Keeling et al found no such age difference in their sample (3742) pt
 It was evident from the results of the previous studies that, certain type of malocclusion may
induce TMD more frequently than other type, and not all types of malocclusion should be
considered responsible for the occurrence of TMD.
TMD according to the previous studies was found to be associated with one or more of the
following occlusal features:
1- Increase in anterior dimension of the face and skeletal open bites (Pullinger et al, Tann et
al) however Keeling et al found no significant correlation between increase LAFH and TMD
2- Over jet more than 6 mm ----- Pullinger et al, Tann et al
3- Occlusal slide more than 2mm Pullinger et al
4- Extracted no restored posterior tooth Pullinger et al
5- Unilateral posterior cross bite Pullinger et al, Tanne et al
6- Increase maximum opening Keeling et al
7- Skeletal deep bite Tanne et al, Keeling wt al
8- Crowding Keeling wt al
9- Decrease maxillary and Mand Corpus length Brand et al
10-Edge to edge bite
11-Mandibular prognathism Tanne et al
12-Class II div 2 and postural Class III
 Mac Namara et al in their review article, concluded that, the relationship of malocclusion
to TMD is minor but, the major question is how to investigate this minor contribution in
TMD pt
== Studies found no correlation between malocclusion and TMD:
= On the other hand, De-Boever et al and Tankineshita et al found no significant correlation
between malocclusion and TMD.
They found a wide range of variation in the occlusal characteristic in both TMD and TMD free
groups
No one in occlusal factor in TMD group could be correlated to the condition, these finding
indicated the higher power of adaptation of TMJ to various occlusal changes.
= Sadowsky concluded that, these finding should not be surprising for 2 reasons:
1- TMD is multifactorial
2- TMJ have a higher power of adaptation to various occlusal changes
Effect of different forms of malocclusion on TMJ
1- Unilateral cross bite ----- interfere with lateral movement------- abnormal distribution of
biomechanical stresses with TMJ, the funcyional adaptation to unilateral cross bite comes
on the expenses of articular dis derangement
2- Centric occlusion- centric relation slide: the slide from the point of initial contact to centric
occlusion------ malposition of condyle dis assembly --------- stress the joint --------- internal
derangement which may progress to arthrosis.
3- Excessive over jet ------ dual bite ----- stress the muscle of mastication and load the TMJ
ligament
4- Crowding -------- many occlusal interference + occlusal slides from the initial contact to
centric occlusion.

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Dr. Mohammed Alruby
5- Open bite -------- loss of anterior guidance to protrusive movement ------- increase the range
of border movement ------- stress the TMJ
6- Anterior cross bite ---------- loss of anterior guidance
7- Edge to edge bite ------------ little effect
8- Deep bite ---------------- mandibular over closure forcing the condyle into more retruded
position
TMD and orthodontic treatment:
Roth’s 1973 work demonstrating that, the symptoms of TMD from 9 cases post treatment resolved
once they were equilibrated using positioning splints
TMD and extraction treatment:
Bowbeer 1987: the functional orthodontist believe that extraction cause the condyle to be displaced
distally as the incisors are retracted into extraction spaces
TMD and orthodontic treatment:
Proffit believes that orthodontic treatment reduces TMD symptoms
Sadwsky 1980; TMD reduced in patient have functional appliances and this is not statistically
significant
Kermanak 1992: TMD reduced in patient with functional appliances with small statistically
significant
TMD and orthognathic surgery:
Egermark et al 2000: orthognathic surgery does not necessarily increase or decrease the signs /
symptoms of TMD.
5 years follow post-surgery found that signs / symptoms decrease in some patient and remain the
same in others
Condyle position and TMD:
= Bowbeer 1987: there should be 3mm of joint space behind condyle, they believe that extraction
force the condyle distally and trap the disc anteriorly -------- TMD
= Johnston 1992, Pluinger et al 1987: orthodontic treatment does not force condyle distally infect
it moves temporarily forward 0.7mm in 70% AND: 25% of a symptomatic individual with Class I
occlusion have posteriorly positioned condyles.
How to investigate the TMJ and functional occlusion?
1- Clinical examination;
= assessment of joint sound during occlusion and at different jaw movement
= assessment of masticatory muscles and related muscles for pain and tenderness
= assessment of joint pain and tenderness by palpation
= assessment of jaw movement, range of motion and maximum pain free opening.
2- Radiographic examination:
Panorama, CT, TMJ view, lateral transcranial view, MRI, and electronic thermography
3- Examination of functional occlusion:
Any deviation during function should be detected
a- Interference from initial contact to centric occlusion

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Dr. Mohammed Alruby
b- Balancing side interference
c- Loss of incisal guidance
d- Deviation in path of mandibular closure from maximum opening to initial contact should
be detected
The mandible deviates toward the side of derangement
N: B:
Loss of incisal guidance:
=The movement of lower incisors from occlusion to incision to protrusion, provide a firm basis for
a functional deviation
=An acute V shaped pattern indicate incisor interference, this observation should be coordinated
with the clinical observation of labially inclined pattern of attrition on lower incisors and lingual
wear of upper incisors.
= The upper incisors may also demonstrate palpable mobility on closure
= Straight line pattern of incisors movement downward and forward from full closure indicate
molar interference, the normal path was observed to be a more V pattern between two extremities
Balancing side interference:
= From centric occlusion, the patient in instructed to perform first left and right lateral excursion
to cusp to cusp position
= Functional occlusal contact was recorded as being present or absent, using one thickness of
articulating ribbon on working side and two thickness of ribbon on non-working side (balancing)
= The presence or absence of posterior contact on protrusion was similarly recorded with two
thickness of articulating ribbon.