|
The Parafunctional Nature of Articulators |
|
|
|
When trying to replicate mandibular movements, dentists hold the incisal guidepin so as to move the maxillary cast.
Pushing the incisal guidepin backwards demonstrates mandibular protrusion.
Pulling the guidepin forwards demonstates mandibular retrusion.
Elevating the maxillary cast demonstrates mandibular depression (opening).
By default, mounted models left alone on an articular are constantly clenching.
James P. Boyd, DDS
In order to evaluate the vertical dimension of rest, the incisal guide pin can be re-set.
Gravity and the practitioner's pull on the pin can then provide the illusion that an anterior midline point stop, such as the NTI-tss device, and allow for "distalization of the condyles", thereby putting the tissues posterior to the condyle at risk.
James P. Boyd, DDS
Some practitioners claim that a full-coverage splint provides "posterior support for the joint". While the term is meaningless, it is also derived from the misinterpretation of the articulator. The animation below demonstrates how the full coverage splint prevents the maxillary cast from slipping down and forward, thereby creating the illusion of the condyle being "distalized" up and back into the fossa:
Other than the posterior temporalis, there are no muscles to distalized the mandible.
If a patient has an NTI-type device whose Discluding Element is angled similar to the example at the top page, the patient will avoid traumatizing their incisor by retruding their mandible, thus irritating any inflamation or swelling posterior to the condyle(s).
However, during sleep, the directional pull of the anterior temporalis and masseter during clenching events overwhelms any attempt by the posterior temporalis to retrude the mandible, resulting in a sore and tender incisor. The patient typically refuse to continue to use the NTI-type device until it has been adjusted by the provider.
|
  |
| An incisal pin is used on an articulator just as an NTI device is utilized for a TMD patient. Both limit occluding forces and can keep canine and posterior teeth from occluding in excursive movements.
The nature of the typical articulator set-up has provided the term, "canine rise". On the articulator, it is the maxillary canines that rise up the buccal surface of the lower canines in excursive parafunctional movements (instead of how the mandibular canines move down and away from upper canines as in real life).
Essentially, it is the adoption of the workings of an articulator that has allowed dentistry to stipulate chronic clenching (and therefore assume it couldn't be treated) and further succumbs to the inevitability of its intensity by the inclusion of the incisal pin.
|
|
Education 
