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Author: David M. Hern, D.M.D.

I. Articulator

A mechanical device that simulates, but does not duplicate, all possible mandibular movements. It is an instrument to which maxillary and mandibular casts can be attached in order to simulate these jaw movements.

A. Articulator Function

An instrument that acts as the patient in their absence.

  • We can see the occlusion completely.
  • We can examine the lingual areas.
  • Patient cooperation is not a factor.
  • There is no tissue resiliency to cause sore areas.
  • There is no shifting of record basis that could result in occlusal discrepancies.
  • It is a time-saver.
  • Allows assistants to assume responsibility for some of the procedures.
  • Tongue, cheeks and saliva are not factors.
  • Provides a constant centric relationship.
  • Provides for a constant check of the proper positioning of the T.M.I.

B. Limitation

Articulators cannot duplicate the distance between the condylar heads. They use a median width, which is usually 110 mm.

C. Articulator Requirements

  1. It must accurately maintain centric relation or occlusion.
  2. Casts must be easily attached and removed.
  3. The pin must be adjustable and provide a positive stop.
  4. It must open and close on a hinge.
  5. It should accept a facebow device.
  6. It must have an accurate, rigid and non-corrosive metal construction.
  7. There must be adequate distance between the upper and lower members.
  8. It must be stable on the workbench.
  9. It must not be bulky or too heavy.

D. Types of Articulators

  • Alcon -The condylar head simulation is on the bottom member of the articulator
  • Non-alcon - Not the above
  • Cl. I -Only vertical movement (hinge)
  • Cl. II - Vertical and horizontal movement -no facebow mounting
  • Cl. III - Uses average equivalents for setting the articulator elements and accepts facebow registration
  • Cl. IV - Accepts three dimensional dynamic registrations and requires a facebow mounting

The choice is up to you.

II. Facebow

A caliper-like instrument used to record the relationship of the maxilla to the tempero-mandibular joints (opening axis of the jaws) and to orient this maxillary cast, in the same relationship, to the opening axis of the articulator.

OR

It allows us to transfer the rotational axis of both condyles and an imprint of the maxillary arch (or a maxillary record base and wax rim) as a fixed triad to the articulator.

A. Need for a Facebow

So that slight openings and closing of the mandible can be made with no errors in occlusion. If a facebow is not used, one cannot mill the case (adjust the occlusion) on the articulator nor change the vertical dimension of occlusion.

III. Hinge Axis

A healthy T.M.J. provides a "hinge axis" with an ideal mandibular arc of closure to the centric occlusion or relation. Ideally at this closure are the inter-digitating and non-interfering cusps. Prematurities at this centric will displace one or both of the condyles from their intended condylar head- articular disc-glenoid fossa relationship.

IV. Maxillo-Mandibular Relation Material

An inter-occlusal relation record (a bite) must be made of a material that is dead soft when recording the maxillary/mandibular centric relation. The centric relation must be taken at a near vertical dimension of occlusion (no tissue or tooth contact). It must chill or harden rapidly to a hard state. This will allow the mandibular cast to be accurately occluded with the already (by the facebow) mounted maxillary cast.