Lateral Pterygoid Muscle: It’s Relevance to Clinical Dentistry

Anatomy and Function of the Lateral Pterygoid

Originally published 2008 · Last updated May 2026

The lateral pterygoid is one of the muscles that controls mandibular position and function. It controls the opening and closing paths of the condyles and articular disc complex, as well as the protrusive and lateral movements of the mandible.

The lateral pterygoid is innervated via the lateral pterygoid nerve of the anterior division of the mandibular branch of the trigeminal nerve (V). The muscle is comprised of two distinct muscle bodies:

🔹 The superior division (smaller) arising from the infratemporal surface and crest of the greater wing of the sphenoid bone

🔹 The inferior division (larger) arising from the lateral surface of the lateral pterygoid plate

Spasm and shortening of the lateral pterygoid can result in losing coordination of the condyle, articular disc, and musculature. Clinical experience and observations have confirmed the role of spasm in the lateral head, as well as clicking and popping of the TM Joint. The lateral pterygoid is prone to muscular pain and tenderness, resulting in compromised mandibular movements and restrictions when strained or placed in a compromised position.

How the Two Heads Function Reciprocally

The superior head exerts forward traction on the articular disc during closure of the mandible. This displaces the disc forward and impedes the return of the disc to its normal position in relation to the condyles as the jaw closes. The superior head is active when the mandible closes but inactive when the mandible opens. The spastic foreshortening of the superior head is the chief suspect in the majority of anteriorly displaced discs (McCarty, 1980).

The inferior head allows for opening of the jaw, protrusion of the jaw, and lateral movements of the mandible. Significant EMG activity occurs in the inferior head during mandibular opening, as referenced in Moyers’ 1950 analysis. The inferior head pulls the condylar head down and forward so the condyle can translate along the posterior surface of the articular eminence when opening wide. Studies have shown both pterygoid heads function reciprocally during vertical and horizontal jaw movements.

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The Question Skeptics Have Raised for Decades

Can J5 Dental TENS relax the masticatory muscles of the head and neck region when EMG studies after TENS relaxation do not directly monitor the lateral pterygoid muscle?

This argument has been used for years in opposition to the science of neuromuscular and Gneuromuscular dentistry. The debate continues as long as dentists ignore the objective measured science of how this exquisite neuro-muscular masticatory system actually works.

This page answers that question with anatomical, neurophysiological, and clinical evidence — and explains how the GNM Optimized Bite protocol resolves the apparent contradiction.

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Recording the Lateral Pterygoid

The lateral pterygoid is a muscle that cannot easily be measured with surface EMG. The anatomic placement of the muscle behind the ramus makes surface EMG impossible. As such, one cannot easily know if the lateral pterygoid is physiologically relaxed with low muscle activity without alternative measuring methods.

Needle EMG studies of the lateral pterygoid have been done correlating surface activity of other muscles, as reported in Masticatory Muscle Function: A Multichannel Electromyographic Investigation by Paul Koole, a Danish dentist-researcher. His research is published, detailed, and thorough.

Needle electromyography, as utilized in medical neurological testing, is employed to test the neural conduction capacity from one point to another. This mode of testing is designed to diagnose neural conductivity. Testing of a single nerve fiber or muscle unit is of no value in the analysis of muscle function or dysfunction when associated with myogenous TMD or with the analysis of dental occlusion. Hiraba and colleagues, in their classic needle EMG studies, correlated opening, closing, and protrusive EMG signaling patterns for both the superior and inferior head of the lateral pterygoid muscle.

In contrast, electromyographic techniques using bipolar (paired) silver-silver chloride surface electrodes placed along the long axis of muscle groups provide data related to the collective electrical activity of a large group of muscle fiber units. This is valuable in the muscle activity associated with dental occlusion, whether temporomandibular disorders exist or not.

🔹 Treacy (1999, p. 283) reported: “The pterygoid-masseter muscles are here seen as a unit in accordance with the findings of Hickey, Woelfel & Reiner (1957) that suggest overlapping electrical fields of the lateral pterygoid and masseter when surface EMG is used on the masseter muscle.” This study confirmed that placing surface EMG electrodes on the masseter muscle yields information regarding the masseter as well as the pterygoid muscles.

🔹 Other investigators have reported correlation of the lateral pterygoid muscle groups with the masseter, temporalis, and digastric/suprahyoid muscle groups.

One note of interest: if hundreds of universities around the world that have access to TENS, needle EMG, and patients have not published on the correlation of TENS and lateral pterygoid, how can clinicians who acknowledge neuromuscular science and computerized electro-diagnostic instrumentation be expected to have done so?

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The Significance of Recording Lateral Pterygoid Activity

Determining a physiologic mandibular position has given rise to the question of whether to treat from a centric relation or muscularly-based position. This challenge results from the lack of convenient procedures to quantify the horizontal mandibular position. Treatment concepts in dentistry are generally based on a preconceived “normal” state derived from clinical observations and theories rather than scientific objective evidence.

Drs. Mazzocco and Hickman at the West Virginia University School of Dentistry completed a thorough literature search regarding the lateral pterygoid. They reported: “The literature is generally ambiguous regarding the true role of the pterygoid complex; however, there does seem to be some consensus that a relaxed masseter will be coincident with a relaxed lateral pterygoid.” They further indicated they found no sources reporting a method of determining lateral pterygoid status without needle EMG. Without confirming evidence, those who theorize have no objective means to directly confirm its status.

The needle EMG technique has its limitations with respect to determining lateral pterygoid status at any given point in time, especially when determining an optimal physiologic mandibular position as a starting point for treatment.

The “bone-braced CR” concept has classically been substantiated by views that the lateral pterygoid is important in maintaining a CR position to record a hinge-axis position as a starting point for diagnosis and treatment. Both the neuromuscular and gnathologic camps recognize that there is very little written in the scientific literature regarding the lateral pterygoid as it pertains to mandibular positioning and activity. There is much ambiguity regarding this subject.

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Centric Relation (CR) and the Lateral Pterygoid

Some advocates in dentistry claim the lateral pterygoid will only be relaxed if the condyles are seated in a CR position. The question that must be asked is: in what position in the glenoid fossa are the condyles “seated”?

There are seven official CR positions and twenty-six unofficial positions documented in the literature. Depending on which occlusal “camp” one believes, one’s view of the precise position varies. The occlusal definition of CR shows no valid consistency.

Charles McNeill, Professor of Clinical Dentistry, Department of Restorative Dentistry, Director of the Center of Temporomandibular Disorders and Orofacial Pain at the University of California, San Francisco, acknowledges in his Quintessence publication: “Unfortunately, the definition of centric relation keeps changing in the literature. However, the changes simply relate to improvements in jaw manipulation techniques and new knowledge regarding the anatomic and physiologic position of the condyle.” He further states: “Because tomographic surveys of nonsymptomatic subjects have shown great variation in condylar position, this functional definition may be more accurate than the one based on anatomic relationships that cannot be proven.”

If one accepts that the mandible is suspended by muscle and that the position of the mandible in space is controlled and governed by the muscles of mastication, then many of the gnathologic concerns related to condylar position, hinge-axis records, and centric relation become non-issues for the GNM-trained clinician.

There is no reliable method — neither using a millimeter ruler nor “romantic” hands manipulating the mandible — by which one can determine the resting tonus of muscles. Returning the muscles to a physiologic resting position allows muscle to operate at its optimum physiologic length.

Dr. Peter Dawson stated: “The most common shortcoming in analyzing or treating occlusal relationships is failure to consider all the parts of the masticatory system. We are prone to many mistakes if our understanding of occlusion is limited to occlusal contacts alone. The teeth are merely a part of the total system. There is no way to evaluate occlusal relationships until we ascertain TM articulation. There can be no occlusal harmony when any part of the masticatory system is at war with muscle.”

Mazzocco stated: “The only way to verify muscle activity is via EMG. That is why the EMG-guided bite registration is such a breakthrough. By using EMG we are able not only to establish the maximum physiologic opening or closing, but coupled with a myo-trajectory, we are able to establish a vertical position which represents a balanced A-P muscle position. As long as we are able to return the patient to physiologic rest — which we can measure via EMG — then it is possible to identify the physiologic range of motion. This will be consistent because when muscles are at maximum physiologic opening they will be at their maximum physiologic length, which is genetically determined for that individual.”

Further support is found in the work of Melvin Moss concerning the functional matrix.

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How Muscles Can Relax While in Opposition

A thoughtful question deserves a thoughtful answer: how can the lateral pterygoid contract to hold a position along the eminence at closure — which would seem to assure isometric antagonistic muscle activity directly opposing the elevator group — and yet relax under TENS?

A related question: does one’s evaluation method have the ability to discern the activity of the superior belly of the lateral pterygoid? It may not be painful, but may create instability as it pulls anteriorly on the disc assembly, potentially causing deformation of the posterior bands.

Dr. Gary Wolford, a practicing oral-maxillofacial surgeon and expert witness who treated TMD/TMJ/myofascial pain dysfunction cases neuromuscularly and testified in FDA and ADA hearings, submitted the following ten clinical observations from over 1,000 joint surgeries (most performed prior to 1974):

🔹 The articular disc cannot be displaced from the condylar head if the discal ligaments are intact and functional.

🔹 The lateral and medial discal ligaments attach the disc tightly to the condylar head. If the lateral discal ligament is torn, the superior head of the lateral pterygoid will position the disc anterior-medially and there will be a reciprocal click on opening and closing, with the opening click at a greater incisal opening. (This is confirmed with objective sonographic ESG recordings as well as first-hand observations on numerous surgical cases.)

🔹 The same clinical and anatomical findings will be present if both the medial and lateral discal ligaments are torn. Additionally, axially-corrected tomograms will show posterior and posterior-superior positioning of the condyles in the fossa in maximum occlusion.

🔹 If the medial discal ligament is torn alone — which is rare — the disc will be laterally displaced in maximum occlusion. The patient will still have a reciprocal click.

🔹 The posterior ligamentous attachment of the bilaminar zone is never torn in clinical conditions. The bilaminar zone will tear before the posterior ligament. Dr. Wolford reported never seeing the posterior ligament torn in over 1,000 joint surgeries.

🔹 The superior head of the lateral pterygoid can only pull the disc forward if the lateral or medial discal ligaments are torn. Dr. Wolford’s clinical position: the muscle alone cannot tear the discal ligaments if the condyles are centered in the fossa and the patient’s closure trajectory matches the myo-trajectory.

🔹 Pulsing with J5 Dental TENS will let the mandible position anteriorly and inferiorly because of the relaxation of the temporalis muscle — particularly the posterior temporalis — because the posterior temporalis is the only muscle that exerts posterior traction on the mandible. Relax the posterior temporalis and the mandible will position anteriorly and downward in the fossa.

🔹 Patients with myofascial pain (non-infectious) will all close posterior to the myo-trajectory. Relax the muscles with J5 Dental TENS and the mandible will position anteriorly and inferiorly. This is verified with computerized mandibular scanning (Scan 4/5).

🔹 Any manual manipulation of the mandible overrides the physiologic neuromuscular function of the elevator muscles.

🔹 If the discal ligaments are torn, manual manipulation will produce a closing pathway with the disc positioned anteriorly to the condyle.

Studies document that J5 Dental TENS (Myotronics, Inc.) stimulation of the Vth and VIIth cranial nerves occurs through neural mediation. Stimulation and relaxation of the lateral pterygoid by the J5 Dental TENS pulse is inevitable, since neural mediation by definition stimulates all muscles innervated by the Vth and VIIth cranial nerves — including the lateral pterygoid.

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Relaxing Muscles via J5 Dental TENS

The term transcutaneous electrical neural stimulation (TENS) describes two distinct types of medical devices:

🔹 High frequency, low amperage TENS — a pain-suppressor instrument. Its therapeutic effect, according to the Gate Theory of Melzack and Wall, is to block afferent pain pathways to the central nervous system by flooding the system with low-level stimuli.

🔹 Low frequency, low amperage TENS — used to relax the masticatory muscles. By providing pumping intermittent stimulation of the nerve innervating the masticatory muscles, the muscles are debrided of waste metabolites (including ADP and lactic acid), circulation improves with re-stocking of fresh metabolites (ATP), endorphins are released systemically, and muscle contraction is released. This is accompanied by neurologically-mediated pain relief and further muscle relaxation.

The specific TENS instrument — the J5 Dental TENS (Myotronics-Noromed, Inc.) — delivers a repetitive stimulus of 8 to 12 mA for 500 microseconds once every 1.5 seconds. It is applied bilaterally to the area between the temporomandibular joints and the coronoid process of the mandible. A third grounding electrode is placed on the rear of the neck and does not deliver stimulus.

Placement of the bilateral active electrodes is critical, as only at that position is the mandibular division of the trigeminal nerve (V) accessible from the surface of the face. The nerve is located deep to the mandible but accessible via surface application of the subtle stimulus through the soft tissues. In addition to stimulation of the Vth nerve, the facial nerve (VII) — which traverses the same area superficially — is also stimulated. Through this neural route of stimulation, all of the facial and masticatory muscles are stimulated simultaneously.

All Muscles of Mastication Are Stimulated

When J5 Dental TENS is used, the following muscles are stimulated for group function via the associated cranial nerves:

🔹 Mandibular Nerve (V) — masseter, temporalis, medial pterygoid, lateral pterygoid, tensor veli palatini, mylohyoid, anterior belly of digastric

🔹 Facial Nerve (VII) — muscles of the nose, buccinator, risorius, orbicularis oris, muscles of the lower lip and chin, platysma, posterior belly of digastric

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Scientific Basis for Low-Frequency J5 Dental TENS

Choi and Mitani document that the stimulus from J5 Dental TENS is neurally mediated. All muscles of mastication are pulsed by the stimulus, and muscle relaxation is verified by surface EMG recordings. The stimulus is not selective; it affects all muscles of mastication, including the lateral pterygoid.

Surgical proof from Dr. E. Williamson (orthodontist):

🔹 During surgery, J5 Dental TENS was used to stimulate masticatory muscles 🔹 The oral surgeon administered succinylcholine, which blocked the J5 stimulus 🔹 The oral surgeon then administered Naloxone, which reversed the block, allowing the stimulus to continue

Reference: Williamson E, Marshall D. Myomonitor rest position in the presence and absence of stress. J Facial Orthopedics and Temporomandibular Arthrography, ed. Williamson, Vol. 3, No. 2, 1986.

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J5 Dental TENS and the Lateral Pterygoid: The GNM Resolution

At Occlusion Connections, Dr. Clayton Chan has pioneered a clinical protocol that resolves the apparent contradiction of how low-frequency TENS can relax the lateral pterygoid muscle while at the same time addressing the GNM claim that TENS relaxes muscles. The clinical reasoning is as follows:

🔹 J5 Dental TENS stimulates the superior and inferior heads of the lateral pterygoid in synchrony. This is not physiologic.

🔹 Because the inferior head is working during TENS, it actually projects the jaw forward.

🔹 The superior head is switched off when the mandible is protruding forward (Hiraba et al).

🔹 By advancing the mandible in the GNM Optimized Bite protocol, the activity of the upper and lower heads is balanced into a more physiologic relationship.

🔹 The involuntary contraction of the superior head of the lateral pterygoid is inhibited.

🔹 As the inferior head is brought forward (GNM Optimized Bite protocol using K7 jaw tracking and simultaneous J5 Dental TENS), it is activated while the superior head is inactivated at the proper physiologic balance. This can only be observed using K7 jaw tracking instrumentation following the protocols taught at Occlusion Connections Levels 1–8.

The superior head, during jaw closure, decreases vertical and increases antero-posterior position of the mandible. Each J5 Dental TENS pulse produces an activation of the superior head (jaw-closure response) while the inferior head (jaw-opening response) deactivates and relaxes.

When the jaw protrudes, EMG activity of the superior head diminishes and quiets. Synchronously, the inferior head EMG activates — increasing vertical and AP movement of the mandible.

When the masticatory muscles are TENSed via J5 Dental TENS, the superior head begins to relax, allowing both antagonists with gravity to assist in mandibular repositioning in a down-and-forward direction from the existing habitual bite — and the condyles decompress.

This is a glimpse into the GNM clinical principles Dr. Chan has discovered and pioneered through his clinical practice and OC teachings — what is recognized as Bite Optimization.

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Measuring Muscle Responses via Surface EMG

One can measure the muscle responses affected by the trigeminal nerve via surface EMG recordings, including the anterior temporalis, masseter, anterior belly of digastric, and posterior temporalis. The anatomic placement of the lateral pterygoid behind the ramus makes surface EMG impossible.

It can be anatomically and neurophysiologically concluded that the lateral pterygoid receives the same muscle response, since it is innervated by the same fifth cranial nerve (trigeminal V). Therefore, the responses of the temporalis anterior, masseter, anterior belly of digastric, and posterior temporalis — all supplied by the same mandibular division of the fifth nerve — can be extrapolated into useful clinical information about the lateral pterygoid muscle.

Fujii and Mitani (1973), as well as other studies, have shown that the J5 Dental TENS electrodes placed over the mandibular notch stimulate the Vth and VIIth cranial nerves through neural mediation. Stimulation of the lateral pterygoid by the J5 Dental TENS pulse is inevitable if these studies are accepted as proof of neural mediation. Numerous studies have confirmed the validity and science supporting these neurophysiologic findings. The scientific regulatory boards of the ADA and FDA reviewed and confirmed these facts during the Dental Products Advisory Panel review in 1994.

When muscles innervated by the fifth cranial nerve — including the lateral pterygoid — are physiologically rested via J5 Dental TENS and monitored using surface EMG, the muscles of mastication can be effectively relaxed, allowing the mandible to position to a physiologic down-and-forward position. This is fundamentally different from what has been taught in traditional gnathologic frameworks, which place the condyles in a habitually-strained up-and-back position.

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Why Critics Misunderstand Surface EMG and Neural Pathways

One reason criticism has focused on the lateral pterygoid muscle is the claim that this muscle cannot be measured with surface EMG. While the surface-EMG limitation is anatomically true, critics fail to understand what surface EMG aims to accomplish when applied to monitoring muscle activity and mandibular position.

An understanding of the neural pathways that innervate the muscles of mastication is necessary to fully comprehend the rationale for using surface EMG. By using EMG instrumentation, GNM clinicians can demonstrate physiologic-rested mandibular-to-maxillary relationships. Surface EMG has been well established in the medical and dental literature for determining muscle hyperactivity, as well as muscle rest, function, and comfort.

Understanding which muscles are innervated by the trigeminal nerve (V) and the facial nerve (VII) is paramount to appreciate this technology — and to understand why the lateral pterygoid responds to J5 Dental TENS even when it cannot be directly recorded.

This page addresses one specific skeptical concern — surface EMG and the lateral pterygoid. The wider evidentiary case for GNM, including instrumentation validation, the documented evolution of the field’s own terminology, and the clinical record across decades, is laid out in The Evidence Behind GNM: Objective Measurement and Clinical Outcomes.

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A Final Reflection

The K7 Scan 4/5 evidence is not hidden. It sits in plain view on every objective jaw track displayed on every K7 system in every operatory where this protocol is performed. And yet most CR-trained and classical NM-trained dentists cannot see what they are looking at.

This is not a failing of intelligence or intent. It is the cumulative weight of decades of dogmatic teaching — layers of inherited conceptual frameworks built on retruded condylar positioning, bimanual manipulation, and EMG-as-target thinking — that have shaped how an entire generation of dentists sees the masticatory system.

The GNM Optimized Bite protocol does not ask doctors to abandon what they know. It asks them to see what was always there.

That is the work of OC.

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Frequently Asked Questions

🔹Why can’t the lateral pterygoid be measured with surface EMG?

The lateral pterygoid sits behind the mandibular ramus, making it anatomically inaccessible to surface electrodes. Only needle EMG can directly record its activity — and needle EMG has its own clinical limitations, particularly for ongoing functional assessment.

🔹If the lateral pterygoid can’t be directly measured, how do we know J5 Dental TENS relaxes it?

Through neural mediation. J5 Dental TENS stimulates the Vth and VIIth cranial nerves at the mandibular notch. Because the lateral pterygoid is innervated by the same trigeminal nerve as the masseter, anterior temporalis, and digastric — all of which can be measured via surface EMG — its response is anatomically and neurophysiologically extrapolated. Studies by Choi and Mitani, Fujii and Mitani, and others confirm this.

🔹What is the GNM Optimized Bite protocol’s role in lateral pterygoid balance?

J5 Dental TENS stimulates both heads of the lateral pterygoid in synchrony — which is non-physiologic. The GNM Optimized Bite protocol resolves this by advancing the mandible in a way that switches off the superior head (which is inactive during protrusion) while activating the inferior head, achieving the physiologic balance that pulsing alone cannot produce. This requires K7 jaw tracking instrumentation and is taught at OC Levels 1–8.

🔹How does spasm of the superior head of the lateral pterygoid contribute to disc displacement?

The superior head exerts forward traction on the articular disc during closure. Spastic foreshortening of the superior head is the chief suspect in the majority of anteriorly displaced discs (McCarty, 1980). However, the muscle alone cannot displace the disc unless the discal ligaments are torn — a critical clinical distinction documented across over 1,000 joint surgeries.

🔹Why is centric relation (CR) inconsistent across the gnathologic literature?

There are seven official CR definitions and twenty-six unofficial positions documented. Even Charles McNeill of UCSF acknowledges that CR’s definition keeps changing. Tomographic surveys of nonsymptomatic subjects show great variation in condylar position — meaning a functional definition based on muscle physiology is more reliable than an anatomical one that cannot be proven.

🔹What does the GNM approach offer that traditional CR-based methods don’t?

Objective, measurable verification of muscle physiologic rest using J5 Dental TENS and surface EMG, combined with K7 jaw tracking to confirm mandibular position. This replaces subjective bimanual manipulation with measurable physiologic data — and is the foundation of the GNM Optimized Bite.

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