Articulator Crown &Bridge / orthodontic courses by Indian dental academy

Articulators

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Articulator is defined as “A mechanical device which represents the temporomandibular joints and the jaw members to which maxillary and mandibular casts may be attached to simulate jaw movements”.


Purpose of an articulator • To hold the maxillary and mandibular casts in

a determined fixed relationship. • To simulate the jaw movements like opening

and closing. • To produce border movement (Extreme lateral

and protrusive movements) and intra border movements (within the border movement) of the teeth similar to those in the mouth.


Uses of an articulator • To diagnose the state of occlusion in both the

natural and artificial dentitions. • To plan dental procedures based on the

relationship between opposing natural and artificial teeth. example evaluation of the possibility of balanced occlusion.

• To aid in the fabrication of restorations and prosthodontic replacements.

• To correct and modify completed restorations. • To arrange artificial teeth


Classification Several classifications of articulators were

proposed. The most popular methods of classifying articulators are :

• Based on the theories of occlusion • Based on the ability to simulate jaw

movements. • Based on the adjustability of the articulator.


Articulators based on theories of occlusion Bonwill theory articulators • This articulator was designed by WGA Bonwill. • Bonwill’s theory is also known as the Theory of

equilateral triangle according to which, the distance between the condyles is equal to the distance between the condyle and the midpoint of the mandibular incisors (incisal point).

• Bonwill articulators allow lateral movement and permit the movement of the mechanism (joint) only in the horizontal plane.


Conical theory articulators • The conical theory of occlusion proposed that

the lower teeth move over the surfaces of the upper teeth as over the surface of a cone, generating an angle of 45º with the central axis of the cone tipped 45º to the occlusal plane.

• The Hall automatic articulator designed by RE hall follows the conical theory of occlusion.


Spherical theory articulators • The spherical theory of occlusion proposed

that lower teeth move over the surface of upper teeth as over a surface of sphere with a diameter of 8 inches.

• The centre of the sphere was located in region of glabella. The surface of sphere passed through the glenoid fossa and along with the articulating eminences.

• The articulator devised by G.S. Monson operated on the spherical theory of occlusion.


Based on the ability to simulate jaw movements:

some articulators show three dimensional movements but some show only single dimensional movements. At the international Prosthodontic Workshop on complete denture occlusion at the University of Michigan in 1972, the articulators were classified based on the instrument’s capability, intent, recording procedure and record acceptance. This is the most widely used classification.


Class I These are simple

articulators capable of accepting a single static registration. Only vertical motion is possible. These articulators are used in cases where a tentative jaw relation is done, e.g. Slab articulator, Barn door hinge articulator


Class II These articulators permit

horizontal and vertical movements but they do not orient the movement of TMJ with a face bow.

Type A: Limited eccentric motion is possible based on the average values. Example: Mean – value articulator (Gysi simplex )


Type B: Limited eccentric motion is possible based on theories of arbitrary motion. Example: Monson’s articulator, Hall articulator.

Type C: Limited eccentric motion is possible based on engraving records obtained from the patient. Example: House’s articulator.


Class III These articulators permit horizontal and

vertical movements. They do accept face bow transfer but this facility is limited. They cannot allow total customization of condylar pathways. These instruments simulate condylar pathways by using average or mechanical equivalents for the whole or part of the condylar motion.


Type A: They accept a static protrusive registration, and they use equivalents for other types of motion.

Example : Hanau H, Hanau H2, Bergstrom articulator.

Type B: They accept static

lateral protrusive registration, and they use equivalents for other types of motion. Example : Panadent, Trubyte, Teledyne Hanau University series.


Class IV

These articulators accept three dimensional dynamic registrations. They are capable of accurately reproducing the condylar pathways for each patient. They allow point orientation of the casts using a face bow transfer.


Type A: The condylar path is determined by the engraving registrations produced by the patient. This path cannot be modified. Example: TMJ articulator.

Type B: They are similar to type of A but they allow angulations and customization of the condylar path. Example: Stuart instrument, Gnathoscope.


Based on the adjustability of the articulator

Based on the adjustability, articulators can be classified as

• Non-adjustable • Semi-adjustable • Fully adjustable


Non adjustable articulators • They can open and close in a fixed horizontal

axis. • They have a fixed condylar path along which

the condylar ball can be moved to simulate lateral and protrusive jaw movement.

• The incisal guide pins ride on an inclined plate in a fixed inclination.


Semi adjustable articulators They have adjustable horizontal condylar paths,

adjustable lateral condylar paths, adjustable incisal guide tables and adjustable inter condylar distances. The degree and ease of these adjustments differ. There are two types of semi adjustable articulators.

• Arcon articulators • Non-arcon articulators


Arcon articulators The term ‘arcon’ was derived by Bergstrom from the

words articulator and condyle. Example : Hanau University series and Whip mix articulators. The condylar element is attached to the lower member of the articulator and the condylar guidance is attached to the upper member. This articulator resembles the temporomandibular joint. (Here, the condylar guidance is the mechanical analog of the glenoid fossa).

Advantages of arcon articulators The face bow transfer, occlusal plane and the

relationship of the opposing casts are preserved when the articulator is opened and closed.


Non-arcon articulators • These articulators have the condylar elements

attached to the upper member. • The condylar guidance is attached to the lower

member. • This articulator is the reverse of the

temporomandibular joint. • Some examples include Hanau H series,

Dentatus and Gysi.


Fully adjustable articulators They are capable of being adjusted to follow the mandibular movement in all directions. These articulators have numerous adjustable readings, which can be customized for each patient. They do not have condylar guidance instead they have receptacles in which acrylic dough can be contoured to form a customized condylar and incisal guidance. They are not commonly used due to their complexity. Example: Stuart instrument gnathoscope, simulator by E. Granger.


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Articulator Crown &Bridge / orthodontic courses by Indian dental academy

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