The SIX DIMENSIONS or Six Degrees of Mandibular Freedom

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What a clinician needs to see and understand to harmonize occlusion in the TMD patient. 

The six dimensions or six degrees of mandibular freedom are:

  1. Vertical relates to the opening and closing dimensional changes of mandibular positioning relative to CO/MIP along the vertical or y-axis.
  2. Antero-posterior (AP) relates to the sagittal positioning of the mandibular body, ramus and both condyles relative to habitual CO along the horizontal x-axis.
  3. Frontal/lateral relates to the mandibular movement laterally left and right when looking at the patient from the front view relative to the midsagittal plane.
  4. Pitch refers to the rotational movements of the mandible about the lateral or z-axis.
  5. Yaw refers to the rotational movements of the mandible about the vertical y-axis.
  6. Roll refers to the rotational movements of the mandible about the horizontal x-axis.

Does the clinician adjust the bite/occlusion to the habitual trajectory ignoring the unseen spastic musculature (and assume the paining TMD patient’s subjective comments are reliable)?  or does the clinician adjust the bite/occlusion along an isotonic mandibular path of closure keeping in mind the six dimensions of mandibular freedom (deprogrammed hyper muscle activities) so the mandible with all the teeth can close evenly and precisely with even balanced force along a physiologic myo-trajectory in the 6 dimensions?  Vertical, AP, frontal/lateral, pitch, yaw and roll.  

Vertical dimension does not only relate to the anterior teeth of the mandible, but dentists must recognize there is also a posterior left vertical dimension of the mandible and a right posterior vertical dimension of the mandible.  The pitch, yaw and roll of the left posterior quadrant often is vertically different than the pitch, yaw and roll of the right posterior quadrants, especially when the TMD patient presents with joint/condylar/disc derangement as well as masticatory muscle dysfunctions (example: tight straining muscles on the left side of the jaw will be different in muscle tonus than the right side of the jaw, thus when the patient is asked to close or bite/occlude their teeth together, the clinician should ASK themselves if the TMD patient is accurately registering the first tooth contact prematurity properly when asymmetric muscle tension and strains exist? I think not.  Thus, the importance to first deprogram the hypertonic muscle activity and bring the musculature toward a neutral isotonic state when establishing or attempting to adjust any occlusion.

Just because a dentist can adjust an occlusion and have the digital occlusal readings appear balanced and the articulating paper marks could appear even in tensity, does not mean the patient is closing properly on a physiologic isotonic path of closure to satisfy all six dimensions of mandibular freedom.  It is easy to make an occlusion look even and balanced, but the marks can also be balanced to the wrong (less than optimal) mandibular position (disc may not be reduced, muscles may not optimally recruit when the vertical dimensions is adjusted to an over-closed position).

The objective of stability is to have the TMD pain patient pain free and comfortable with the ability to close to a terminal contact position at the correct vertical position, to support optimal condylar/disc relationships, along an isotonic mandibular path of closure (myo-trajectory) both AP and frontal/laterally without inducing strains to the teeth, musculature and joints in the pitch, yaw and roll domains up from a stable physiologic rest position.  Occlusal contact forces should be even in intensity to meet all six-dimensions that allow freedom of entry and exit to the terminal contact position that is free of all afferent and efferent noxious stimuli.  These six-dimensions can be objectively measured and determined NOT having to rely on the unseen hypertonic voluntary muscle activities of TMD cases


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