Pterigoideo Esterno

REVIEW

Australian Dental Journal 2004;49:(1):2-8

The human lateral pterygoid muscle: A review of some
experimental aspects and possible clinical relevance
GM Murray,* I Phanachet,† S Uchida,‡ T Whittle*

Abstract
The clinical notion that some disturbance to the
activity of the lateral pterygoid muscle plays a role in
the aetiology of temporomandibular disorders
(TMD) is still widelyaccepted and influences
management strategies. However, there is no
rigorous scientific evidence to support this clinical
notion and the role of the lateral pterygoid muscle in
normal function is still controversial. The classically
defined functions of each head of the muscle are that
the superior head is active on closing, retrusion, and
ipsilateral jaw movements, while the inferior headis
active on opening, protrusion and contralateral jaw
movements. However, recent data indicate that these
concepts are too simplistic. For example, recent
evidence suggests that parts of the superior head
may also be active on opening, protrusion and
contralateral jaw movements, and that the superior
head may consist of three mediolaterally arranged
functional zones. Given thesecomplexities, the
proposal that clicking and/or locking conditions
arise in the temporomandibular joint through some
form of lack of co-ordination between the two heads
of the muscle needs re-evaluation. Despite earlier
reports to the contrary, both heads of the lateral
pterygoid muscle appear to be electrically silent at
the postural or resting jaw position, and therefore
appear to play no rolein the anteroposterior
positioning of the jaw at the postural position. An
important role has also been demonstrated
electromyographically for progressive changes in
activity in the inferior head as the direction of
horizontal jaw force shifts from one side to the other.
This suggests an important role for the lateral
pterygoid muscle in the generation of side-to-side
and protrusive jawforces. The lateral pterygoid
muscle is likely therefore to play an important role
in parafunctional excursive jaw movements and also
possibly a role in influencing jaw position in patients
where the maxillomandibular relationship records
change from session to session. The above data

*Jaw Function and Orofacial Pain Research Unit, Faculty of
Dentistry, The University of Sydney; WestmeadCentre for Oral
Health, Westmead Hospital, Westmead, New South Wales.
†PhD student, Jaw Function and Orofacial Pain Research Unit,
Faculty of Dentistry, The University of Sydney.
‡Visiting research scholar, Jaw Function and Orofacial Pain Research
Unit, Faculty of Dentistry, The University of Sydney.
2

provide new insights into the normal function of the
lateral pterygoid muscle. Theproposal that the
lateral pterygoid muscle plays some role in the
aetiology of TMD needs now to be rigorously tested.
Key words: Electromyography, temporomandibular
disorders, computer tomography, functional heterogeneity,
jaw movement.
(Accepted for publication 9 September 2003.)

INTRODUCTION
Studies of the anatomy and function of the lateral
pterygoid muscle have had an important influenceon
aspects of dental clinical practice. For example, the
clinical opinion that a disturbance to the activity of the
lateral pterygoid muscle plays an important role in the
aetiology of temporomandibular disorders (TMD) is
still widely accepted.1,2 Patients with TMD complain of
pain in and about the temporomandibular joint and/or
the jaw muscles, and patients may also experience
limitationof jaw movements and/or joint sounds. In
TMD patients, the lateral pterygoid muscle is thought
to become hyperactive, or there is thought to be a lack
of co-ordination between the upper and lower heads of
the muscle, or there is thought to be a disturbance to
the normal postulated role for the muscle in the control
or stabilization of the temporomandibular joint. The
opinion that the...