Re-establishing Physiologic Vertical Dimension for an Overclosed Patient

The term ‘neuromuscular occlusion’ has been associated with certain limited methodologies that are used to obtain a muscle-compatible occlusal relationship. In reality, there are several different approaches that can be used to determine a neuromuscular maxillo-mandibular relationship, even in a fully edentulous case. Within each method, however the common basis for all muscle-oriented approaches involves determining the resting length of the masticatory muscles.


SIgnS & SymptomS of bIte over-cloSure
When asked, over-closed patients often report symptoms such as frequent headaches, dull pain of the elevator muscles and pain or stiffness in their neck muscles. Ear stuffiness, tinnitus and/or vertigo are also commonly reported. A more subtle symptom, less often reported, is frequent gastrointestinal distress in various forms that has no clear, identifiable cause.
This may also be accompanied by a report of difficulty in chewing and/or swallowing. An overclosed patient will usually report several, but not all, of the following symptoms: However, patients rarely seek dental treatment for any of these objective signs. Instead, they are more likely to seek rehabilitative treatment for headache, jaw-ache, ear-ache, difficulty in chewing/swallowing or for purely esthetic reason.
In other cases they are unaware of their condition, apparently

maxillo-mandibular bite relationships centric occlusion (co):
The maxillo-mandibular position of maximum intercuspation is most often the dental treatment position, primarily by default. This is of necessity whenever single tooth preparations or small restorations are involved, since they must fit within the patients existing occlusal scheme. It is only at times of major reconstructive, orthodontic and/or surgical treatments that the option of opening a bite or establishing a new maxillomandibular relation may present itself. However, many clinicians still prefer to "play it safe" and retain the existing habitual (CO) maxillo-mandibular relationship, even during major rehabilitative procedures. By definition, the use of centric occlusion as a treatment position excludes re-establishing a proper vertical dimension in an over-closed patient. However, if the patient's condition is actively deteriorating this may not be a safe option at all, as the continued physiologic breakdown may lead to failed dentistry and/or a flair up of craniofacial pain.

centric relation (cr):
The concept of centric relation has a very long history and was originally devised, at least in part, to accommodate the use of articulators during prosthodontic treatment. Although we now know that the jaw does not function like a hinge, originally it was convenient to make that assumption when using articulators to make prostheses. Today, one clear difference between centric relation procedures and strictly muscle-oriented methodologies is the priority given by CR methods to evaluating the function of the TMJ. Typically, centric relation operators give first priority to establishing stable joint function, while muscle-oriented (neuromuscular) approaches tend to focus almost exclusively on muscle comfort.

muscle-related centric (mc):
In general, muscle-oriented approaches consider joint position and/or stability secondary to muscle function. In the extreme, it is simply assumed that creating "happy muscles"

ulf-tenS bite registration:
Ultra-low Frequency TENS, originally conceived by Bernard Jankelson, is often used to relax the masticatory muscles. It can also be used to determine a bite registration position, sometimes referred to as myo-centric. After a patient has been "pulsed" for relaxation, usually for about 40 minutes, bite registration material (a quick-cure acrylic) is placed over the mandibular occlusal surface and the ULF-TENS is reapplied to "close" the mandible about 1-2 mm above the rest position.
During this procedure the vertical dimension is usually monitored with a mechanic's inside calipers between marks on the chin and nose. It is a technique sensitive procedure However, once the skill is developed, an operator may produce good consistency. These classic TENS bites ignored the TMJ function in the past, but this should no longer be the case. A final outcome with healthy TMJ and muscles is the goal today.

phonetic bite registration:
As with the previously described muscle-oriented methods, this one begins with muscle relaxation. Then the patient is instructed to speak specific sounds while the anterior teeth are

predicting a patient's response to correcting overclosure
The question is often asked, "How quickly will a patient adapt to a new bite registration?" Even though the object is to "correct" a mal-relationship of the mandible to maxilla, the patient's current relationship still has familiarity. The new relationship, no matter how "perfectly" established, will seem strange to the patient at first. There are many factors that influence patient's adaptation to a new maxillo-mandibular relation. It is possible to estimate a patient's response by considering the following factors: