Articulators Crown &Bridge / orthodontic courses by Indian dental academy

ARTICULATORS ARTICULATORS

INDIAN DENTAL ACADEMY

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Basic Out LineBasic Out LineNeed for articulatorsNeed for articulatorsDefinition, classification, parts, Definition, classification, parts,

advantages, disadvantages of advantages, disadvantages of articulatorsarticulators

Definition, classification, parts, Definition, classification, parts, advantages, disadvantages and advantages, disadvantages and purpose of face bow transferpurpose of face bow transfer

Mean-value articulator, parts, Mean-value articulator, parts, measurements.measurements.


ARTICULATORSArticulator 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" GPT

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..•To aid in the fabrication of restorations and prosthodontic replacements. .•To correct and modify completed restorations.•To arrange artificial teeth.


Requirements of an Articulator Minimal Requirements. It should hold casts in the correct horizontal relationship.. It should hold casts in the correct vertical relationship.. The casts should be easily removable and re attachable.. It should provide a positive anterior vertical stop (Incisal pin).. It should accept face-bow transfer record using an anterior reference point. . It should open and close in a hinge movement. . It should be made of non-corrosive and rigid materials that resist wear and tear. . It should not be, bulky or heavy. . There should be adequate space present between the upper and lower members.. The moving parts should move freely without any friction.. The non-moving parts should be of a rigid construction.


Additional Requirements

•The condylar guides should allow protrusive and lateral jaw motion.

•The condylar guide should be adjustable in a horizontal direction.

•The articulator should be adjustable to accept and alter the •Bennett movement.

•The incisal guide table should be customizable


Advantages of Articulators

. Properly-mounted casts allow the operator to visualize the patient's

occlusion, especially from the lingual view.

. Patient cooperation is not a factor when using an articulator once

the appropriate inter occlusal records are obtained from the patient.

. The refinement of complete denture occlusion in the mouth is

extremely difficult because of shifting denture bases and resiliency of

the supporting tissues. This difficulty is elimi nated when articulators

are used.

. Reduced chair time

. The patient's saliva, tongue and cheeks are not factors when using

an articulator. www.indiandentalacademy.comwww.indiandentalacademy.com

Limitations of an Articulator

. An articulator may be made of metal or plastic. Metal

articulators show errors in tooling (manufacture) or errors

resulting from metal fatigue.

. The articulator may not exactly simulate the intraborder

and functional movements of the mandible.

. Errors in jaw relation procedures are repro duced as

errors in the denture occlusion. Arti culators do not have

any provision to indicate or correct these errors.www.indiandentalacademy.comwww.indiandentalacademy.com

ClassificationSeveral classifications of articulators were pro posed. The most popular methods of classifying articulators are:. Based on the theories of occlusion.. Based on the type of inter-occlusal record used. . Based on the ability to simulate jaw movements.. Based on the adjustability of the articulator.


Articulators Based on Theories of Occlusion

Bonwill theory articulators According to the Bonwill's theory of occlusion the teeth move in relation to each other as guided by the condylar and the incisal guidances. Bonwill's theory is also known as the Theory of equilateral triangle according to which, an equilateral triangle is formed between the two condyles and the incisal point. Theore tically, the dimension of the equilateral triangle is 4 inches 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 45-degrees

with the central axis of the cone tipped 45° to the occlusal

plane. The Hall automatic articulator designed by RE Hall

follows the conical theory of occlusion.


RE HALL ARTICULATOR BASED ON CONICAL THEORY


Spherical theory articulatorsSpherical theory articulators

The spherical theory of occlusion proposed that The spherical theory of occlusion proposed that lower teeth move over the surface of upper teeth as lower teeth move over the surface of upper teeth as over a surface of sphere with a diameter of 8 inches over a surface of sphere with a diameter of 8 inches

The centre of the sphere was located in region of The centre of the sphere was located in region of glabella. The surface of sphere passed through the glabella. The surface of sphere passed through the glenoid fossa and along with the articulating glenoid fossa and along with the articulating eminences. The articulator devised by C.S. Monson eminences. The articulator devised by C.S. Monson operated on the spherical theory of occlusionoperated on the spherical theory of occlusion


ARTICULATOR BASED ON SPHERICAL THEORY


Disadvantages of articulators based on Disadvantages of articulators based on theory of occlusiontheory of occlusion

These articulators are based on theo retical These articulators are based on theo retical concepts. There is no provision for varia tions from concepts. There is no provision for varia tions from the theoretical relationships that occur in the theoretical relationships that occur in different persons.different persons.


Articulators Based on the Type of Record Used for Their Adjustment

Articulators are specifically designed to accept different jaw relation records. Based on the type of record accepted by the articulator, they are classified as:

Interocclusal record adjustment Most articulators are adjusted by some kind of interocclusal records. These records are made of base plate wax, Plaster of Paris, zinc oxide eugenol paste or cold cure acrylic resin.


Graphic record adjustmentGraphic record adjustment Graphic records consist of records of the extreme Graphic records consist of records of the extreme

border positions of mandibular movements. These border positions of mandibular movements. These articulators are capable of accurately reproducing articulators are capable of accurately reproducing the border movements of the mandible. The face the border movements of the mandible. The face bow and Jaw-writing apparatus (pantograph can be bow and Jaw-writing apparatus (pantograph can be attached to transfer the records)attached to transfer the records)

Hinge-axis location for adjusting articulators: A Hinge-axis location for adjusting articulators: A transographic record can be used to record the transographic record can be used to record the accurate location of the hinge axis in an articulator.accurate location of the hinge axis in an articulator.


Based on the instrument's capa bility, intent, recording procedure and record acceptance.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 articulator.

Class II: These articulators permit horizontal and vertical movements

but they do not orient the movement to TMJ with a face-bow.

•Type A: Limited eccentric motion is possible based on the average

values. E.g.: Mean-Value articulator

•Type B: Limited eccentric motion is possible based on theories of

arbitrary motion. E.g.: Monson's articulator, Hall articulator.

•Type C: Limited eccentric motion is possible based on engraving

records obtained from the patient. E.g.: House's articulator.www.indiandentalacademy.comwww.indiandentalacademy.com

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 regis tration, and they use equivalents for other types of motion. E.g:Hanau H, Hanau II Bergstrom articulator.•Type B: They accept static lateral protrusive registration, and they use equivalents for other types of motion. E.g.: Panadent, Trubite ,Hanau university series.


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

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

Type BType B: They are similar to type A : They are similar to type A but they allow but they allow angulations and customization of the condylar path. angulations and customization of the condylar path.

E.g.: Stuart instrument gnathoscope.E.g.: Stuart instrument gnathoscope.


Based on the Adjustability of the Articulator. 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 intercondylar distances. The degree

and ease of these adjust ments differ.

There are two types of semi adjustable articulators:

. Arcon articulators

. Non-arcon articulators.


Arcon articulators (Fig. 10.6) the term 'arcon' was Arcon articulators (Fig. 10.6) the term 'arcon' was derived by Bergstrom from the words articulator and derived by Bergstrom from the words articulator and condyle. E.g. Hanaucondyle. E.g. Hanau University series and Whip-mix University series and Whip-mix articulators.articulators.

The condylar element is attached to the lower member The condylar element is attached to the lower member of the articulator and the condylar guidance is attached of the articulator and the condylar guidance is attached to the upper member. This articulator resembles the to the upper member. This articulator resembles the temporomandibular joint. (Here, the condylar guidance temporomandibular joint. (Here, the condylar guidance is the mechanical analog of the glenoid fossa).is the mechanical analog of the glenoid fossa).

Advantages of arcon articulators; The face-bow Advantages of arcon articulators; The face-bow transfer, occlusal plane and the relationship of the transfer, occlusal plane and the relationship of the opposing casts are preserved when the articulator is opposing casts are preserved when the articulator is opened and closed.opened and closed.


HANAU SEMI ADJUSTABLE ARTICULATOR


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.

Example; Hanau H series,

Fully Adjustable ArticulatorsThey 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. E.g. Stuart instrument. Gnathoscopewww.indiandentalacademy.comwww.indiandentalacademy.com

FULLY ADJUSTABLE ARTICULATOR


Mean Value Articulator

It is a non-adjustable articulator. This articulator is

designed using fixed dimensions, which are derived from

the average distance between the incisal and condylar

guidance of the population

The condylar guidance (equivalent of glenoid fossa) is

attached to the lower member and the condylar element

(equivalent of the mandibular condyle) is attached to the

upper member, hence, it is a non-arcon articulator.


Upper member It is a triangular frame with the base of the triangle placed posteriorly. The apex of the triangle contains a provision to accom modate the vertical rod (incisal pin). The vertical rod can be locked in position within the upper member with the help of a thumbscrew. Two condylar elements are seen projecting on either side of the base of the triangle. They arti culate with the condylar guidance of the lower member. The maxillary cast is attached to the upper member during articulation.


UPPER MEMBER OF MEAN VALUE ARTICULATOR


Lower memberLower member It is a 'L' shaped frame with a horizontal and a vertical It is a 'L' shaped frame with a horizontal and a vertical

arm. The horizontal arm is triangular in shape. The apex arm. The horizontal arm is triangular in shape. The apex of the triangle of the horizontal arm contains the incisal of the triangle of the horizontal arm contains the incisal guide table. The vertical arm is rectangular containing guide table. The vertical arm is rectangular containing the condylar guidance slot at the upper portion the condylar guidance slot at the upper portion

A fixed metal bar (horizontal bar) is present in the A fixed metal bar (horizontal bar) is present in the

vertical arm of the lower member. The plane of vertical arm of the lower member. The plane of occlusion should coincide with this horizontal bar during occlusion should coincide with this horizontal bar during articulation articulation


Incisal guide table or anterior guidance of the articulator

Incisal guide Table is defined as, "That part of the articulator which maintains the incisal guide angle" - GPT. The incisal guide table gives the incisal guidance of the articulator. The incisal guide table can be described as a very short cylinder whose upper surface is concave. The vertical rod should rest on the centre of the incisal guide table during articulation. The depth of the concavity is designed to have a slope equal to the average incisal guide angle The incisal guide angle is fixed and non-customizable.


INCISAL GUIDE TABLE


Condylar guidance;Condylar guidance;

It is represented by a slot (condylar track) located on the It is represented by a slot (condylar track) located on the upper part of the vertical arm of the lower member. The upper part of the vertical arm of the lower member. The slot is inclined at an angle equal to the average slot is inclined at an angle equal to the average inclination of the condylar guidance in the population.inclination of the condylar guidance in the population.

The condylar element of the upper member passes The condylar element of the upper member passes

through this track. A spring is mounted within this track through this track. A spring is mounted within this track (condylar guidance) to stabilize the condylar elements (condylar guidance) to stabilize the condylar elements and hold them in their posterior most position (centric and hold them in their posterior most position (centric relation) when no movements are made. This condylar relation) when no movements are made. This condylar guidance does not accept face-bow transferguidance does not accept face-bow transfer


Vertical rod or incisal pin

It helps to keep a fixed distance between the upper and lower members at the anterior end. The vertical rod has a pointed tip, which should rest on the center of the incisal guide table during articulation.At the midpoint of the vertical rod a hole is provided to fit the incisal guide pin. The tip of the incisal guide pin is the anterior reference point in this articulator. The incisal edge of the maxil lary incisors at the midline of the occlusal rim should touch the tip of the incisal pin during articulation The upper flat surface of the vertical rod should always be locked flush with the superior surface of the upper member.www.indiandentalacademy.comwww.indiandentalacademy.com


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Articulators Crown &Bridge / orthodontic courses by Indian dental academy