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The orientation icons suggest that there are two posterior segments which, over time, can move to an adaptive position along any or all of three axes. The two posterior segments are independent of each other in some functional patterns of engagement, but are very dependent on the ipsilateral side in most mandibular positions. This is the main reason for measuring all contacts in an entire arch during any mandibular movement.
The posterior plane orientation
The term occlusal interference refers to a premature contact which inhibits comfortable mandibular function. An occlusal interference is not determined by occlusal contacts alone, but it also involves the anatomy of the temporomandibular joints, the limiting influence of the ligaments, and the shape and orientation of the occlusal plane. An ideal occlusal plane is only theoretical because all patients have a unique 3-dimensional orientation of their natural or prosthetic teeth in the supportive bone, which may or may not be ideal in shape and/or quality.
Clinicians must understand that bone shape determines the position of the dentition. An interference to a balanced mandibular pathway is often caused by the position a tooth assumes in the bone and within the arch. The occlusal table which is solely the functional portion of the occlusal surface of the posterior teeth is where the interferences appear as a result of poor tooth positioning in the arch. It is also important to realize that an occlusal plane is only acceptable if it permits the anterior guidance to disclude the posterior teeth effectively and rapidly.
Occlusal disharmony is a phenomenon in which contacts of opposing occlusal surfaces are not in harmony with other tooth contacts and/or the anatomic and physiologic components of the craniomandibular complex. A digital occlusal force distribution pattern (DOFDP) can be diagnostic of occlusal disharmony present on the occlusal table by alerting the clinician to exactly which tooth, teeth, or prosthetic replacement(s), cause the interference. It is important to note that asymmetric arch foundations may still achieve a balanced DOFDP if the dentition and/or prosthetics have been corrected to compensate for the skeletal asymmetry.
The two posterior occlusal planes are a 3-dimensional representation of what controls the vertical and transverse force that occurs during mandibular engagement with the maxilla. To prevent functional codependency, micro trauma, interference, or occlusal deflection, each plane must meet the conditions of the first and second determinants of occlusion. In theory, during function, the x-y-z axes of the occlusal plane (the transverse, sagittal, and horizontal posterior planes) of the static upper arch should match the mandibular posterior spatial orientation.