MYOCENTRIC

In dentistry, ”’Myocentric”’ : synonymous with ”Myocentric Dentistry”.

Refers to that terminal end point in space in which the mandibular jaw is positioned from rest position.  It is a commonly used term of relationship and comparison in dentistry|physiologic rest (an isotonic muscle state) along the myocentric (muscle balanced) trajectory of jaw closure.  It also refers to the initial occlusal contact along the  myocentric trajectory (isotonic closure of the mandible from rest position).

It is defined as, ””That terminal point in space in which, with the mandible in rest position, subsequent colonic muscle contraction will raise the mandible through the interocclusal space along the myocentric (muscle balanced) trajectory. Also described as the initial occlusal contact along the myocentric trajectory (isotonic closure of the mandible from rest position)”. – GPT.”

  • Jankelson B. Dent Clin North Am 1979;23:157-68.
  • Jankelson BR, Polley ML. Electromyography in clinical dentistry. Seattle: Myotronica Research Inc, 1984:52..

This position is used when restoring edentulous patients with [dentures|removable] or [fixed prosthodontics|fixed] prostheses or [fixed orthodontics|fixed] or [functional orthodontics\removable] or either [dental implant|implant]-supported hybrid.  Because the dentist want to be able to reproducibly relate the patient’s [maxilla]] and mandible, but the patient does not have teeth with which to establish his or her own [vertical dimension of occlusion], another method has been devised to achieve this goal.  The muscles of mastication are supported by the myocentric position reproducibly and consistently determined by the dentist with unstrained muscles and condyles in an anterior superior decompressed position within the glenoid fossa.

Myocentric is a concept in dentistry based on a physiologic neuromuscular viewpoint of dentistry. It is a physiologic position and reproducible position determined by the dentist. The Temporomandibular Joint, normally functions in a myocentric physiologic position.  Long centric or adapted centric are terms that describes a centric relation position that patients eventually are restored to when achieving the myocentric position. Myocentric position is a physiologic unstrained position that is inherently stable for both the temporomandibular joints, muscles and [teeth|occlusion].

Myocentric practitioners state that the relationship of the mandible to the maxilla complex are physiologically aligned when the masticatory muscles are supportive of a physiologic rested mandibular position with properly aligned condyle-discs with the glenoid fossa irrespective of Occlusal Vertical Dimension (OVD) or tooth position.  Neuromuscular Dentistry concepts are considered by dentists as far more physiologic than the classical mechanical Centric Relation concepts and slowly advancing with the use of objective measuring instrumentation.

A properly aligned mandible to maxillary relationship in which the muscles of masticatory, temporomandibular joints and teeth function optimally in both resting and functioning modes with no masticatory dysfunction, no joint derangement or temporomandibular joint pain.

Methods of Recording Myocentric:

Objective Methods:

  1. ULF TENS combined with EMGs.
  2. ULF TENS combined with EMGs and Jaw Tracking (Computerized Mandibular Scanning (CMS).
  3. ULF TENS combined Jaw Tracking (Computerized Mandibular Scanning (CMS).

Functional Methods:

  1. # Ultra Low frequency Myomonitor TENS.

Graphic Methods:

  1. Intraoral methd.
  2. # Extraoral method.
  3. * Radiographic Method.

References: 

  1. “Chapter 4: Mandibular Tracking for Diagnosis and Treatment in Clinical Practice”, Neuromuscular Dental Diagnosis and Treatment | Ishiyaku EuroAmerica, In | Jankelson, Robert R. | 1990 | pages175 | isbn:0-912791-49-7.
  2. Glossary of Prosthodontic Terms. http://www.academyofprosthodontics.org/_Library/ap_articles_download/GPT8.pdf
  3. Dinham, GA: “Myocentric A Clinical Appraisal”, ”The Angle Orthodontist”, July 1984. p.211-217. http://www.angle.org/doi/pdf/10.1043/0003-3219(1984)054%3C0211%3AM%3E2.0.CO%3B2

– Clayton A. Chan, D.D.S. – Las Vegas, NV

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MYOCENTRIC