An Update on Orofacial Myofunctional Disorders: More Than Tongue Thrust

When you think of orofacial myofunctional disorders (OMDs), the term tongue thrust comes to mind. All of us started out in life with a tongue thrust swallow. By age 6 to 8 years, most of us transitioned out of tongue thrusting into a correct resting tongue posture and swallowing pattern. For those that do not make the transition, thrusting of the tongue becomes the most recognized and discussed component of orofacial myofunctional disorders. You may be surprised to learn that a tongue thrust swallow is probably the least likely OMD to influence or cause changes in tooth position.

The purpose of this article is to review the state-of-the-art of orofacial myofunctional disorders, and to recommend changes in perspectives and terminology that are compatible with accepted dental science. The information herein is currently being reviewed, discussed, and implemented within the International Association of Orofacial Myology (IAOM), which is the ASHA-related professional organization (RPO) for orofacial myofunctional disorders. It is hoped that the speech-language pathologist (SLP) readership of www.SpeechPathology.com will become interested in this exciting area of specialization and seek membership and certification in the IAOM.

What Are OMDs?

Orofacial myofunctional disorders include thumb, lip, tongue, and finger sucking habits; a mouth-open lips-apart posture; a forward interdental rest posture of the tongue; a forward rest position of the tongue against the maxillary incisors; a lateral, posterior interdental tongue rest posture; and thrusting of the tongue in speaking and swallowing. These abnormal habit patterns, functional activities, and postures can open the dental bite beyond the normal rest position. This leads to a disruption of dental development in children and over-eruption of selected teeth in adults.

Over time, dental malocclusion, cosmetic problems, and even changes in jaw growth and position are observed in some patients with OMDs. Examples of changes than can result from a chronic open mouth rest posture include an increased vertical height of the face, a retruded chin, a downward and backward growth of the lower face (rather than downward and forward), and flaccid lips (Proffit, 1986).

Is There Commonality among OMDs?

As you read this, it is expected that your lips are closed but your teeth do not touch; that is, your normal dental rest position is characterized by a small open space between upper and lower teeth. This normal resting space is referred to as the dental freeway space, or inter-occlusal space. It measures 2-3 mm at the molars, and 4-6 mm at the incisors (Sicher and DuBrul, 1970).

The common denominator of orofacial myofunctional disorders is that all OMDs result in a change in the vertical dimension, or freeway space. The OMD, whether digit habit or altered oral posture, causes the mandible to hinge open slightly, while also increasing the resting inter-occlusal space between the upper and lower jaws and teeth. Only a slight increase in resting freeway space for hours per day is needed to initiate continued and unwanted vertical tooth eruption (Mason, 1988).