articulator

-II- ARTICULATORS

Dr. Monia M.N. Kandil

Articulator

The articulator: Is a mechanical instrument that represents the temporomandibular joints and jaw members, to which maxillary and mandibular casts may be attached to simulate some or all- mandibular movements

Articulators

The non-adjustable articulator
Semi-adjustable articulator
Fully adjustable articulator
Arcon
Non- Arcon
Mean Value
Hinge
Panto-graphic tracing
Sterio-graphic

Non Adjustable Articulators

Hinge articulator

Mean Value articulator

Semi Adjustable Articulators

Some of semi-adjustable articulators (for example, the Hanau H series, the Dentatus, and the Gysi) have the condyles attached to the upper member of the instrument (non-arcon), whereas others have the condyle attached to the lower member as occurs in nature (arcon)

Arcon articulator

Non Arcon articulator

Difference between Arcon & Non arcon articulators

Fully Adjustable Articulators

Fully adjustable articulator

Deficiencies and inherent inadequacies of articulators
As the mandible closes around hinge axis (mha), the cusp tip of each mandibular tooth moves along an arc.

The distance between the teeth and the axis of rotation on the small instrument is consider shorter than it is in the skull with a resultant less of accuracy.
If the location of the axis of rotation relative to the cusp tip differs markedly from the patient to the articulator, the radius of the arc of closure of the cusp tips may be different producing an error.
The large dissimilarity between the (aha) and (mha) will produce a large discrepancy between the arc of closure of the articulator and of the mandible.

What if patient doesn’t match articulator? Articulator

Patient

Articulators

mha
aha
Patients

Therefore the distance from the condyle to the teeth is crucial

We obtain a measurement of this distance with a facebow
aha
mha

Records needed for mounting on a Semi-adjustable Articulator:

I-Face Bow record or by Bonwill triangle
II-Centric relation record III-Eccentric relation records
a-Protrusive Record b-Lateral Excursion Records ??

Semi-adjustable Articulator

Can be programmed to reproduce some mandibular movement capabilities; usually limited to straight line movements
Remember

Fully-adjustable Articulator

An articulator that allows replication of three dimensional movement of recorded mandibular motions:



Fully-Adjustable Articulator
• It is the most accurate instrument.• It is designed to reproduce the entire character of the mandibular border movements, including: immediate and progressive lateral translation, and the curvature and direction of the condylar inclination.• Intercondylar distance is completely adjustable. The tracing of condyle path way is accomplished by helping of a pantographic tracer.

The techniques required for its use demand a high degree of skill & are time consuming to accomplish. This type of instrument is expensive. For these reasons, they are used primarily for extensive treatment, requiring the reconstruction of an entire occlusion. Unavoidable errors that occur in recording the angulation of the condyle paths on using such instruments make their value doubtful.
Limitations of Fully adjustable condylar path articulators

Articulators of the fully adjustable type include for example:

Stansbery tripod articulator. Hanau Kinoscope articulator. The Denar articulators. H.O. Beck and Coworkers have developed an experimental articulator that takes the factor of time into account by correlating the time of movement in each of the three planes of the skull. Fully Adjustable PROTAR (9) articulator.

Stansbery tripod articulator

Hanau Kinoscope articulator
Denar II
Denar V

Fully adjustable H.O. Beck experimentalarticulator

Fully Adjustable PROTAR (9)
This class of articulators accepts registration of all anatomic determinant of occlusal morphology, and accept a “hinge axis” kinematic transfer bow.The incisal guidance can closely simulate the paths of natural dentition.This class is fully utilized in extensive restorative procedures, as well as adjunct to diagnostic determinations of TMJ dysfunction.


Records needed for mounting on a Fully Adjustable Articulator
Centric Relation Record
Hinge axis location and Face bow record
Pantographic tracings
Stereographs

A- Hinge axis location and Face bow record

Face bow record has to be made in relation to the actual terminal hinge axis. This should first be located using a Kinematic face bow.

B- Centric Relation Record:

Since the use of such an articulator would be limited to those cases that need full reconstruction and rehabilitation  It can be done byBut it prefers more sophisticated methods, such as:- Electronic recording techniques- Intraoral gothic arc registration Classic centric records

C- Pantographic tracings

Tracing the exact movements made by the mandible to register the exact direction and path and amount of those movements.
A pantographic tracing is made by the use of the pantograph, to record lateral and protrusive excursions

The pantograph

Consists of two facebows, one affixed to the maxilla while the other to the mandible, with the use of clutches that are attached to the teeth.



The tracings are made by styli attached to one member and small tables upon which the tracings are drawn attached to the other member, opposite the styli. There are posterior vertical and horizontal tables on both right and left sides. The patient is instructed to move his mandible through protrusive, right and left lateral excursion movements, while the styli scribe on their opposing tables the paths followed by the condyles in those movements.


When the pantograph is attached to the articulator, adjustments and alterations are made to the movements of the articulator follows the same paths that was scribed by the styli on their tables, that is following the paths of the condyles in their movements. Computerized systems have also been developed. A print out is obtained and used to program the articulator. The computerized systems closely resembles the manual pantograph and are much more economical as regards time, as the transfer stage is eliminated.

Pantographic recording

For fully adjustable articulator

Pantograph Computerized systems

D- Stereographs:
This is another method for programming the fully adjustable articulators. Clutches are made to fit the teeth, and the patient is instructed to perform lateral and protrusive excursions, during which, studs in one clutch cut into the opposing one.


For programming the articulator, the clutches are transferred to it, and it is moved to follow along the paths formed by the cut out areas. The condyles of the articulator are made to mold auto-polymerizing resin, previously placed in the articulator fossae. This enables the original jaw movements to be reproduced when the clutches are removed.

Summary

The choice of articulator depends upon such factors as; Intended use - Skill of the technician Availability of equipment - Expense Patient's occlusion - Skill of the operator The more closely the articulator matches the patients anatomy, usually the better the outcome and the less adjustment is required at chairside on fitting prostheses.