Dental Dominion: ARTICULATORS- A note

ARTICULATORS

o Definition
o Purpose
o Uses
o Requirement
o Advantages
o Limitations
o Classification
o component
o Commonly used articulator
o Selection of an articulator
o Mounting of cast
o conclusion

DEFINITION An articulator may be defined as a mechanical device that represent the temporomandibular joint and jaw members to which maxillary and mandibular casts may be attached to simulate jaw movement.

PURPOSES

o To hold the maxillary and mandibular casts in a determined fixed relationship
o Mounting of dental casts for diagnosis treatment planning and patient presentation.
o To simulate the jaw movement like opening and closing.
o Fabrication of occlusal surfaces for dental restoration.
o Arrangement of artificial teeth for complete and removable partial denture.

USES

o To diagnose the state of occlusion in both the natural and artificial dentition.
o To plan the dental procedures based on the relationship between opposing natural and artificial teeth.

Ex. Evaluation of the possibility of balance occlusion.

o 4.To aid in the fabrication of restorations and prosthodontics replacements.
o 5.To correct and modified complete restorations.
o 6.To arrange artificial teeth.

REQUIREMENTS

Two Types of Requirements

a. Minimal requirements

b. Additional requirements

Minimal requirements

They are necessory for the fabrication of complete denture to the patients centric position.

They are –

1. It must be accurately maintain the correct horizontal and vertical relationship of the patient’s casts.

2. The casts should be easily removable and attachable to the articulator without loosing their correct horizontal and vertical relationship

3. The articulator should have an incisal guide pin with a positive stop, that is adjustable and caliberated.

4. The articulator should be able to open and closed in a hinge like fashion.

5. The articulator should accept a face-bow transfer utilizing an anterior reference point.

6. The construction should be accurate, rigid and of non corrosive material.

7. The moving parts should move freely without any friction.

8. The non moving parts should be of a rigid construction.

9. The design should be such that there is adequate distance between the upper and lower members.

10. The articulator should be stable on the laboratory bench and not too bulky and heavy.

ADDITIONAL REQUIREMENT

1. The condylar guides should allow right lateral, left lateral and protrusive movement.
2. The condylar guides should be adjustable horizontally.
3. The articulator should have provision for adjustment of Bennett movement.
4. The incisal guide table should be mechanical table that can be adjusted in thesagittal and frontal planes or a table that can be customised with autopolymerizing resin or by grinding.

ADVANTAGES

1. Properly mounted casts allow the operator to better visualize the patients occlusion, especially from lingual view.

2. Patient cooperation is not a factor when using an articulator. once appropriate interocclusal records are obtained from the patient.

3. A reduces the chair time, patient appointment time.

4. The refinement of complete denture occlusion in the mouth is extremely difficult because of shifting denture bases and resiliency of the supporting tissue.

Inter occlusal records can be obtained and complete denture occlusion can be refined outside the mouth on an articulator.

5. More procedures can be delegated to auxillary personnel when utilizing an articulator for development of patients occlusion.

6. The patients saliva, tongue, and cheeks are not factors when using an articulator.

LIMITATIONS

o Metal,plastic articulators show errors in tooling, (manufacturer).
o It not exactly simulate the intraborder and functional movements of the mandible.
o Errors in jaw relation procedure are reproduced as errors in the denture occlusion. Articulators do not have any provision to indicate or correct these errors.

CLASSIFICATION OF ARTICULATORS

Several basis of classification of articulator were proposed, some of them are as follows.

o Based on the instruments function.
o Based on theories of occlusion.
o Based on the type of inter occlusal record used.
o Based on the adjustabililty of the articulator
BASED ON INSTRUMENT FUNCTION / ABILITY TO SIMULATE JAW MOVEMENTS:-

At the international prosthodontic workshop on complete denture occlusion at the university of Michigan in 1972, the articulators classified based on instrument capability, intent, recording procedure and record acceptance

Class I : Hinge Type

Class II : Arbitrary – type A

type B

type C

Class III : Average -

type A

type B

Class IV : Special –

type A

type B

CLASS I (Hinge Type)

These are simple articulator (Simple holding instruments) capable of accepting a single static registration.

Only Vertical motion possible.

Important features are positive stops and locks at the mounted position

Use in cases where a tentative jaw relation is done.

Class I instruments are suitable for crown and bridge, and operative instruments.

Subdivision A: vertical motion is possible. Ex: Corelator, Venticulator.

Subdivision B: vertical motion is joint related. Ex: Centric Relator

Examples of Class I :- Slab articulator

Hinge joint articulator – J.B. GARIOT (1805)

Barn door articulator

Gysi Simplex (Alfred Gysi, Zurich, 1914)

CLASS II (Arbitary)

These articulator permits horizontal and vertical movements but they do not orient the movement to TMJ a face-bow. They are –

è TYPE A :-

Eccentric motion is unrelated to patient motion.

Permit limited eccentric motion based on averages.

Do not permit face-bow transfer.

The condyles are on the lower member of articulator.

( Based on Bonwill’s triangle)

Ex. Mean-Value articulator - GYSI

è TYPE B :-

Permit limited eccentric motion based on arbitrary theory of motion .

Do not accept a face-bow transfer.

(? Based on spheric theory of occlusion).

Ex. Monson’s articulator / Spherical Theory Articulator – Fournet & Hageman articulators

Hall’s articulator / Conical Theory Articulator

Shofu Handy II

è TYPE C :-

Permit limited eccentric motion based on engraved records obtained from the patient.

Do not accept a face-bow transfer.

Ex.:- House’s articulator (1920)

Gnathic Relator

CLASS III (Average)

They permit horizontal and vertical motion

Do accept face-bow transfer but these facility is limited.

Do Not / Cannot allow total customization of condylar pathways.

They simulate condylar pathways by using average or mechanical equivalents for the whole or part of the condylar motion.

They allow for joint orientation of the casts and may be arcon or nonarcon instruments. All the examples are arcon instruments, accept facebows, and have mounting plates for unlimited case load.

These instruments can fulfill the requirements for complete denture construction.

Desirable features would be good centric lock, progressive and immediate side shift controls, protrusive inclination, intercenter distance adjustment, a simple mounting procedure, a good sturdy design, and an arcon arrangement

They are – Type A

Type B

è TYPE A :-

Accept static protrusive interocclusal records / registrations + Accepts a face-bow transfer

Uses equivalents for other types of motions.

Exp. Hanau H articulator ( RUDOLPH HANAU , 1923) NON-ARCON

Hanau H2 articulator – NON ARCON

Bergstrom articulator (ARCON)

Dentatus (1944, Sweden)

è TYPE B :-

Accept a Static Lateral protrusive interocclusal records + face-bow transfer

Use equivalents for other types of motions

Exp. Trubyte articulator - (GYSI, 1926) – NON ARCON

Tripod articulator - STANSBERRY

Ney articulator - (De Pietro , 1960) - ARCON

Hanau (130-21) - (Richard Beu & James Janik .1964)

Tele Dyne articulator - (Richard Beu ,1975) - ARCON

Pandent articulator - Robert Lee - ARCON

Denar Mark II

Whipmix

Case Articulator Simulator

TMJ Mechanical fossa Instrument

CLASS IV (Special)

These articulator accept three dimensional dynamic registration.

They are capable of accurately reproducing the condylar pathway for each patient.

They allow point (?joint) orientation of the casts using Face Bow Transfer

They allow for orientation of the cast to the temporomandibular joints and replication of all mandibular movements.

These articulators are the instruments of choice for complete reconstructions.

These instruments should hold adjustments, contain good centric locking mechanism, versatile incisal guide tables, and stable mounting features, and be precision engineered.

They are – Type A

Type B

è TYPE A :-

Accept three dimensional dynamic registration + utilise a face-bow transfer.

Condylar pathways are formed by registration engraved by the patient.

This path is non - modifyable

Exp. TMJ articulator – Kenneth Swanson (1965)

Stereograph

è TYPE B :-

Accept three dimensional dynamic registration + utilise a face-bow transfer.

Condylar pathway can be selectively angled and customized / modified.

The procedure utilise the pantographic tracing.

EXP. Pantronic acticulator – Dener (1982)

Gnathoscope - Charls Stuart

Denar D 4A & D 5A - Niles Guichet, 1968

Denar Model SE

Simulator - Earnest Granger

• BASED ON THEORIES OF ARTICULATOR

è Bonwill theory Articulators

Known as theory of equilateral triangle.

Allow lateral movement & permit movement in horizontal plane.

Always model the upper wax (record base) first, judging the length of incisors and trial placement of anterior teeth for shade, shape, length and width. To articulate the lower cast, use a pair of dividers four inches apart with the center of the lower teeth at the median line just four inches from the condyles on either side

è Conical Theory Articulators

Designed b R.E. Hall (Hall, 1918 : adjustable 3D anatomic articulator; universal mandibular movements, adjustable incisal guide )

Lower teeth move over the surface of the upper teeth as over the surface of a cone generating an angle of 45 degree.

è Spherical Theory Articulators

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

The center was located in the region of glabella.

BASED TYPE OF INTEROCCLUSAL RECORDS USED:

Eccentric pathways can be dynamically registered either graphically (pantographic method) or stereographically (engraving method), positionally registered (checkbite method), determined by the articulator (mechanical equivalents), or adjusted entirely on the patient.

BASED ON THE ADJUSTABILITY

Three Types :-

a. Non – Adjustable

b. Semi – Adjustable

c. Fully – Adjustable

NON – ADJUSTABLE A.

Can open and close in a fixed horizontal axis.

Have a fixed condylar path.

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

Can accept one or two of the following records: Face bow, centric jaw relation or protrusive record.

A class I articulator is a nonadjustable articulator.

SEMI ADJUSTABLE A.

Have adjustable horizontal condylar paths, adjustable lateral condylar path adjustable incisal guide table and adjustable inter condylar distance.

The degree and ease of these adjustments differ.

Can accept all three of the following records: Face bow, centric jaw relation or protrusive record.

A class II or III articulator is a semiadjustable articulator.

Two Type:-

Arcon Type

Non arcon Type

è ARCON Type

The term “Arcon” was derived by Bergstrom from the words Ar- Articulator & Con – Condyle

This articulator resembles the TMJ.

The Condylar Element / analogue / sphere àattached to – Lower Member (Movable)

The Condylar Guidance (~Glenoid Fossa) à attached to – Upper / Cranial Member (immovable)

Advantage: The Face Bow transfer, occlusal plane, and relationship of the opposing casts are preserved when the articulator is opened and closed.

Examples :- Whipmix , 8500 ( DR. Charles Stuart, 1963)

Hanau H@, Arcon

Dentatus, ARA

Ney articulator - (De Pietro , 1960)

Tele Dyne articulator - (Richard Beu ,1975)

è Non-Arcon type

This articulator is the reverse of the TMJ

The Condylar Element / analogue / sphere àattached to – Upper Member (Movable)

The Condylar Guidance (~Glenoid Fossa) à attached to – Lower Member (immovable)

Examples:- Hanau , 96h20

Hanau, University

Gysi, adjustable

Trubyte articulator - (GYSI, 1926)

Dentatus, ARL

Hanau, Kinoscope

House, Rotary Grinder

FULLY ADJUSTABLE A.

Capable of being adjusted to follow the mandibular movement in all direction.

They have numerous adjustable readings which can be customized for each patient.

They donot have a condylar guidance instead they have receptacles, in which acrylic dough can be contoured to form a customized condylar & incisal guidance.

Can accept the following five records: Face bow, centric jaw relation, protrusive, lateral records, and intercondylar distance record.

They are not commonly used due to their complexity.

A class IV articulator is a fully adjustable articulator

Examples:- Pantronic acticulator – Dener (1982)

Gnathoscope - Charls Stuart

Denar D 4A & D 5A - Niles Guichet, 1968

Simulator (by Ernest Granger)

Gnatholator (by Granger)

Board Questions

Alfred Gysi was the first to produce an articulator which could reproduce downward and forward movements.

The first articulator to record downward and forward motion at the condyles was the Balkwill articulator.

William Walker developed an adjustable articulator for individual mandibular movements, making registrations of the inclinations of individual condylar paths extraorally.

The Fournet and Hageman articulators are examples utilizing the spherical theory.

Instruments that encompass the "terminal orbital function" are the Gnathoscope, the Wadsworth articulator, the Transograph, the Denar D-5A, and the Stuart

Gnatholator, Denar, and Stuart are fully adjustable articulators

Hanau, Whip-Mix, and Dentatus articulators are semi adjustable.

The Whip-Mix, Hanau University, and Stuart are examples of articulators with adjustable intercondylar distance.

Walker first recorded mandibular movement

BASIC COMPONENT OF AN ARTICULATOR

o Upper member – Represent maxilla
o Lower member – Represent mandible
o CONDYLAR TRACK –
o CONDYLAR ELEMENT-
o Vertical Rod (Incisal Pin)
o Incisal guide table

SOME COMMONALY USED ARTICULATOR

o Mean-Value Articulator
o Hanau wide VUE articulator
o Whip – mix articulator
o Denar articulator
o Panadent articulator
o TMJ articulator

MEAN-VALUE ARTICULATOR

Triangular frame

Vertical Rod with thumb screw.

Two Condylar elements

L Shaped frame with horizontal and vertical arm.

Horizontal arm is triangular and its apex contains incisal guide table.

Vertical arm is rectangular containing condylar guidance slot at upper portion.

Contain very short cylinder whose upper surface is concave.

Vertical Rod should rest on the center of the incisal guide table during articulation.

Represent by a slot ( condylar track)

o Condylar element of upper member passes through this track.
o A spring is mounted within this track to established the condylar element.

Helps to keep a fixed distance between the upper & lower member at anterior end.

The pointed tip of vertical rod should rest on the center of incisal guide during articulation.

Present at the mid point of vertical rod.

The incisal edge of the maxillar incisors at the mid line of the occlusal rim should touch the tip of incisal pin during articulation.

It present the anterior reference point.

HANAU ARTICULATORS

o Hanau wide VUE articulator.
o Hanau wide VUE II articulator
o Hanau H2 articulator
o Hanau ARCON articulator
o Hanau Redialshift

HANUA WIDE VUE A.

Semi adjustable

ARCON type

Accept a Face-bow transfer

Capable of hinge & lateral movements.

Upper Member : T.Shaped with vertical & horizontal arm.

Condylar guidance attached to this.

Mounting dowels present the center of under surface.

Orbital indicator present near dowel.

Lower Member - L-Shaped with horizontal & vertical arm.

Horizontal arm is rectangular metal strap.

Dowel present center of the lower member for mounting ring & also a stand of pivot.

Vertical arm slope outword.

Upper portion of vertical arm contains a roll pin. Which project on the outer surface.

The condylar shaft attached to inner surface of the vertical arm 12-13 mm anterior to the roll pin.

The condylar element (metal ball ) is attached to the free end of the condylar shaft.

It is circular structure with a slot in the center

The condylar element of lower member articulate with this slot also called condylar track.

The poterior end of this track has a component known as centric stop.

The condylar element should contact the centric stop during articulation.

The condylar guidance can be rotated around the vertical axis to set the Bennett angle.

Bennett angle(L) = H/8+12

H = Horizontal condylar inclination

It has a customised incisal guide table.

The slope of the incisal guide table can be changed in the antero posterior direction & can lock in position with a lock nut.

During articulation it should be flat & the incisal pin should be at in center.

A pair of lateral wings is present around it.

It is a double sided pin.

One end is sharp but chisel like with flat edge. The other end tapers to a pointed tip.

Usually the flat end is used.

The incisal pin has series of markings closely placed in one end & two widely spaced marking in other end.

The upper member of the articulator should be at the level of the darkest marking of the close markings.

The space out markings acts as the anterior reference point in the absence of face-bow transfer.

HANAU H2

o It is non arcon type articulator.
o It has a fixed intercondylar distance of 110 mm. & does not accept a face-bow transfer.
o Four different face-bow can be utilised –

1. Facia face-bow
2. Earpiece face-bow
3. Twirl face-bow
4. Adjustable axis face-bow

HANAU RADIAL SHIFT

Structure is almost same as Hanau series articulator.

It has right & left Centric Latches & the upper member is easily removed for waxing.

The radial shift adjustment has a 3mm radius and allow upto 3 mm.of radial shift before intercepting preadjusted prograssive Bennett angle.

HANAU WIDE VUE II

The only difference between Hanau wide vue & vue II that the wide vue has way closed condylar track.

The closed condylar track does not allow the upper member to be removed, Whereas the open condylar track allow the upper member to be removed for waxing.

WHIP-MIX ARTICULATOR

It is an arcon articulator.

The upper & lower member are mechanically attached by means of a spring latch assembly.

The original model is 8500.

The condylar elements on the lower frame & adjustable to three position

1. Small (S) – 96 mm

2. Medium (M)–110mm

3. Large (L) – 124 mm.

* Two Different face-bows can utilised.

o Quick mount or earpiece face-bow for complete denture.
o The adjustable axis for fixed prosthodontics.

* The intercondylar distance is determined from the scale on the face-bow S.M.L.

Ø The articulator has pins on the outer flanges of the condylar guides correspondingholes on the medial side of the earpieces of the face-bow make for easy transfer of the face-bow record to the articulator.

MODIFICATIONS

o Articulator model 9600 is similar to model 8500 except the lower frame is ½ inches taller to provide more space for mounting the mandibular cast.
o Mode 8800 provides an additional ½ inches space to mount the maxillary cast.
o Model 9800 is combines the upper frame of model 8800 with the lower frame of model 9000 to provide the greatest distance between the upper & lower frames.
o Model 8340 assure that cast can be interchanged between any model 8340 articulator without loss of accuracy.

DENAR ARTICULATORS

DENAR MARK II

Arcon type

The articulator is a two piece instrument incorporating a possitive locking machanism that can hold the two member together by means of centric latch.

The condylar elements are at a fixed 110 mm intercondylar distance however an adjustable distance (110 to 122) mm option is available.

Four types of face-bow can be used :-

- Facia face-bow

- Earpiece face-bow

- Sidematic face-bow

- Adjustable axis face-bow

o The sidematic face-bow has a feature of unique slide gear machinasm which make it easy & quick to assemble.
o The mark II can be programmed using anatomic averages positional records or with a mini recorder.

OMNI

It is a newest Denar articulator.

The design allow one to easily exchange closed fossa for open fossa with a positive locking latch.

The purpose of this model is an attempt to better meet the requirments for complete denture, removable & fixed partial denture fabrication in one articulator.

When the articulator is equipped with the open fossae which is identical to mark II fossa it is called omni mark.

When it is utilised with closed track fossa called omni track.

TMJ ARTICULATOR

Designed by (1965) Kenneth Swanson.

The articulator has a spring loaded latch to help return the upper frame to the centric relation position.

There is curved incisal guide pin with both a plastic & adjustable machanical incisal table.

Small version of the articulator is available & is called the mini articulator.

Its intercondylar distance is limited & has a straight incisal guide pin.

DENTATUS

It is a shaft type instrument.

The condylar element attached to the upper member & the condylar path is straight.

The intercondylar distance is fixed.

The articulator received a hinge axis face-bow.

The features are similar to Hanau model.

SELECTION OF AN ARTICULATOR

One should not used too complex instruments for a simple case or too simple articulator for a complex case.

The following factors pertinent to the understanding and selections.

Articulator movements of the condylar elements do not reproduced condylar movementin the temporomandibular joint.

The goals of articulation is to duplicate tooth movements along border path ways in at least to planes of space.

The most important requirment of an articulator are to maintain centric relation & the vertical dimension of occlusion.

4. Fixed condylar elements at 110mm are all that is neccesary. An adjustable inter condylar capability may permit more records to be accepted.

5. The articulator should be able to receive a face-bow transfer record,.

6. The articulator should have the capability of adjustment for precurrent or immediate side shift upto atleast 2.5 mm.

§ An adjustable mechanical incisal guide table can not reproduce the natural guidance of the anterior teeth.

§ A sterograph ( pantograph) has limited value for all but a few types of prosthodontics situation.

§ The sophistication of articulators should not exceed the level of training & ability of the personnel that will be fabricating the restorations.

MOUNTING PROCEDURE

Mounting of maxillary cast

o Maxillary cast is attached to the articulator using the orientation jaw relation record.
o Procedure of transferring the orientation jaw relation to the articulator is called face-bow transfer.
o The anterior reference point should be positioned by making the orbital indicator contact the orbital pointer of the face-bow.
o A pivot stand attached to the lower member of the articulator also helps toprevent vertical displacement of the occlusal rim during articulation.

Mounting of mandibularcast

o Tighten the centric lock on each enclosed condylar track mechanism to ensure that the articulator is capable of nothing but a hing opening.
o Invert the articulator on the benchtop resting it on the three thumnutsprotruding from the upper member of the articulator.
o Place the centric relation interocclusal wax record on the teeth of maxillary cast.Be sure that the teeth seat completely into wax record.
o Place the mandibular cast into interocclusal record.
o There should be no contact between the maxillary and mandibular cast.
o Remove the mandibular cast and soak it for about 2 minute in slurry water.
o Reseat the soaked mandibular cast into the record and mount it by plaster/stone.

è Inspect the articulated cast:-

The condyle is in the retruded position in its condylar track mechanism.

Both casts are seated completely in the interocclusal wax record.

Mounting stone is securely attached to both casts and mounting plates.

CONCLUSION

An articulator is an important device that mechanical analogues the temporomandibular joint & upper and lower dental arches.

A device to which maxillary and mandibular casts can be attached,with the intent of simulating the functional & para functional contact relationships of one arch to the other.

Dental Dominion

Wednesday, 26 October 2011

ARTICULATORS- A note

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