ARTICULATORS

INTRODUCTION

In the fabrication of indirect dental prosthesis a

mechanical device is used to relate opposing casts called

an articulator

DEFINITION

An articulator is mechanical device which represents TMJ

and jaw members to which maxillary and mandibular casts

may be attached

Primary function of articulator is to simulate patient

in the absence of patient.

An articulator can simulate but they can not

duplicate all mandibular movement

Articulators: Minimal Requirements

It should hold casts in the correct horizontal and vertical relationship

It should provide positive anterior vertical stop

It should accept a face bow record

It should open and close in a hinge movement

The moving parts should move freely and be machined accurately

The non-moving parts should be a rigid construction

It should allow protrusive and lateral jaw motion

Articulator : uses.To open and close in a hinge manner

Hold opposing casts in a predetermined manner

To produce border and intra border movements like in

the mouth

To diagnose dental occlusal conditions in natural and

artificial conditions

To plan dental procedures

To aid in the fabrication of the prostheses

To correct and modify complete restorations

As a teaching aid to study occlusion and mandibular

movements

Articulators: Advantages over mouth

On patients co-operation

To rely No need Allow operator to view patients occlusion from

the lingual side

Refinement of patients occlusion can be easily be done on the

articulator than in the patients mouth

Saves a lot of chair side time

More procedures can be delegated to auxiliary personals when

using an articulator

The patients saliva, tongue and cheek are not factors when using

an articulator.

Articulators : Classification

Based on theories of occlusion

Based on type of inter occlusal records

Based on ability to simulate jaw movements

(IPWS classification)

(Heartwell and rahn classification)

Based on the adjustability of articulators

Bonwill theory articulators

Designed by WGA Bonwill

The teeth moves in relation to each

other as guided by condylar and incisal

guidance

Also known as theory of equilateral

triangle

Distance between the two condyles

is equal to the distance between

midpoint of the mandibular incisors

and condyle

Conical theory articulatorLower teeth move over the surface of the upper teeth as over the

surface of the cone generating an angle of 45° with the central axis

of the cone tipped 45° to the Proposed by RE Hall

occlusal plane.

Spherical theory articulatorLower teeth move over the surface of the upper teeth as over the

surface of the sphere with a diameter of 8“ with the center located

at the glabella

The surface of the sphere moved over the glenoid fossa &

articulating eminences.

Disadvantages of articulators based on the theory of occlusion

These are based on theoretical concepts

There is no provision for variations from the theoretical relationships

that occur in different persons

Articulators based on the type of record used for their adjustment.

Inter occlusal record adjustment

Made of base plate wax, zinc oxide eugenol, POP & acrylic resin

Graphic record adjustment.

Records of extreme border positions of mandibular movements.

Face bow pantograph can be attached

Hinge axis location for adjusting articulators

HEARTWELL AND RAHN CLASSIFICATION

Class I

These are instruments that receive and reproduce stereogram

These articulators can be adjusted to permit individual

condylar movement in each of the three planes they are capable

of reproducing the timing of the side shift of the orbiting

(balancing) side and its direction on the rotating side

Hence these articulators are called as four dimensional

instruments.

Eg: McCollum gnathoscope, Granger gnathoscope, Hanau

kinoscope, Cosmax, Aderer simulator, Ney articulator, Stuart

gnathoscopic computer, TMJ streographer, Denar D5A

CLASS IIThese instruments will not receive stereogram

Some have fixed controls, others are adjustable but usually in no more

than two planes a close approximation of condylar movements patterns

can be determined quickly and the information permits better

adjustments to the condylar control or the selection of a guidance fossa

that will closely match the condylar element movement gained from

stereograms

Gnathology is defined as the science which deals with the masticatory

apparatus as a whole including morphology anatomy histology

physiology pathology and therapeutics

Referred as `gnathalogic’ instruments

o Stuart Articulator - Charles Stuart 1955

o Denar D4A - Denar D5A

o Simulator

Has four types

TYPE I (HINGE)

Capable of opening and closing in hinge movement

Some permits limited non adjustable excursive like movements

eg: The barn door hinge, Trubite, Gariot, Twinstage occluder, Hageman

balancer, Bonwill, Gysi simplex and adaptable, The centric relator

Stephens models, Crescent models, Gysi, Acme

TYPE II (ARBITRARY)

Depends on specific theories of occlusion

eg: Monson, Handy II, The correlator, Transgraph, The gnathic relator,

Verticulator

TYPE III (AVERAGE)

Designed to provide condylar element guidance by means of

average positional records or mini recorder system

Horizontal or lateral guidance can be adjusted

Accepts face bow transfer

eg: House, Dentatus, Hanau, Whip mix ,Denar mark II and omni

TMJ, Panadent

TYPE IV ( SPECIAL)

Designed primarily for complete denture

eg : Stansberry tripod, Kile Dentograph, Irish Duplifunctional.

Based on the adjustability of the articulator.

Arbitrary articulators

Can open and close only about a fixed horizontal axis

Fixed condylar paths

Incisal guide pin glide on an inclined plate on a fixed inclination

Semi adjustable articulators

They have adjustable horizontal and lateral condylar and incisal

paths, inter condylar distances. 2 types: Arcon and Non arcon

Fully adjustable articulators

Capable of adjustment in all directional movements of mandible.

Do not have condylar guidances; receptacles are present to becontoured into customized condylar and incisal guidances.

Eg.Stuart instrument, Gnathoscope, Simulator

Based on plane of orientation

The Articulators which are based on the

Camper's line.

Kavo, Stratos,

The Articulators which are based on the

Frankfort horizontal plane.

Hanau, Dentatus, Whip-Mix,

Denar Mark II, Stuart

Based on the ability to simulate jaw movement

The INTERNATIONAL PROSTHODONTIC WORKSHOP

on Complete Denture occlusion at the University of Michigan in 1972,

an articulator classification was developed.

This classification was based on articulator’s function, capability, intent and

registration acceptance

Class I simple holding instrument capable of accepting a single

Interocclusal record eg. Garriot’s Hinge, Barn hinge door.

Class II Instrument that permit horizontal as well as vertical

motion but don’t accept face bow transfer

Type A- eccentric motion is based on average or arbitrary values

eg.Grittman’s articulator, Gysi’s Simplex

Type B- Eccentric motion permitted is based on theories of arbitrary motions

eg. Maxillomandibular instrument

Type C- eccentric motion permitted is determined by patient’s engraving methods

eg. House’s articulator

Class III permit horizontal and vertical movements, do accept face

bow transfer but facility is limited. Simulate condylar pathways using

average or mechanical equivalent for the whole or part of condylar

motion but cannot allow total customization

Type A - they accept a static protrusive record and they use

equivalents for other types of motion

eg . Hanau articulators, Bergstrom articulator

Type B - accept static lateral protrusive record, use other

equivalents for other types of motion

eg. Trubyte articulator, Hanau kinescope, Stansberry tripod,

Neys articulator, Teledyne articulator, Whipmix articulator,

Denar Mark II, Bergstrom’s arcon articulator.

Class IV accept three dimensional dynamic registration they

allow point orientation of the cast using face bow transfer

type A-the condylar path is determined by engraving registrations

produced by the patient this path can not be modified

eg. TMJ articulator by Kenneth Swanson

type B-similar to type A but they allow angulations and

customization of the condylar path

eg. Stuart articulator, Denar D4A, Denar D5A, Simulator

Class ISimple holding instrument capable of accepting a single

interocclusal record vertical movements may or may not be possible

Slab articulator

A plaster extension on distal portion of mandibular cast was

grooved to serve as guide for a plaster extension on the maxillary

cast this constitutes an articulator called slab articulator

Class IIInstrument that permit horizontal as well as vertical motion but

don’t accept face bow transfer

Type A- eccentric motion is based on average or arbitrary

values

eg.GRITTMAN’S ARTICULATOR,

Condyles are on the lower member

and there paths are inclined 15

degree casts are mounted according

to the Bonwill's triangle

eg.Gysi’s Simplex

Condyles are on the lower member and there paths are

inclined 30 degree Incisal guidance fixed at 60 degree

Average value articulator

30° 25°

5°

CLASS II TYPE B

Permits eccentric motion based on arbitrary theories of

motion won’t accept face bow transfer

eg. Monson’s maxillomandibular instrument

Designed by Monson based on spherical theory of occlusion

Lower teeth move over the surface of the upper teeth as over

the surface of the sphere with a diameter of 8” with the center

located at the glabella

The surface of the sphere moved over the glenoid fossae &

articulating eminences.

Upper member of the articulator moves according to Monson’s

spherical theory

CLASS II TYPE CPermits eccentric motion determined by patients engraving methods eg. House’s articulator

A Needle House “chew in” record

4 metal studs in the upper rim against lower compound occlusal rim.

Diamond shaped pathways are generated the instrument.

Also employs a rotatory grinder on the upper member for milling in a 40/1000 inch elliptical areas so as to free the occlusion in centric occlusion

CLASS IIIPermit horizontal and vertical movements, do accept face bow transfer

but facility is limited. Simulate condylar pathways using average or

mechanical equivalent for the whole or part of condylar motion but

cannot allow total customization

HANAU MATE ARTICULATOR

It is an arcon instrument accept a

face bow transfer it has average

condylar guidance of 30°

Bennett angle 15° incisal guide table

is 10° in both protrusive and lateral

movement

They won’t accept a static

protrusive record

Class III TYPE AType A -they accept a static protrusive record and they use

equivalents for other types of motion

eg. Dentatus, Hanau articulators,

DENTATUS

• It is Designed in Sweden 1944

•Similar to Hanau but it is unique

in that the relationship between

upper and lower can be

standardized with a gauge block

so that cast can be transferred

one to another articulator without

changing the relationship

Mounting procedureMounting the maxillary cast

Attach face bow to the articulator

Maxillary cast is attached to the articulator using orientation jaw relation record .

Support the bite plane with a cast support to carry the additional

weight..

Maxillary cast is made flat and v-shaped notches are prepared on the

mounting surface at the periphery. This surface is lubricated with thin

coating of petroleum jelly.

The cast is then securely seated in the denture base with the occlusal

rim firmly resting in bite fork imprint.

Mixture of stone is placed on the cast, the upper member is swung

back to embed the mounting plate and to bring the incisal pin into

contact with the incisal guide.

Mounting the mandibular cast

Mandibular cast is mounted after recording tentative and centric jaw

relations.

Articulator with mounted maxillary cast is inverted to aid in mounting

the Mandibular cast.

Maxillary occlusal rim is placed on the cast, mandibular occlusal rim is

positioned over the maxillary occlusal rim without using the centric

relation record and mandibular cast is placed in the lower rim measure

and note the X dimension.

Now centric relation record is interposed and maxillary and mandibular

occlusal rims with there casts are luted.

Adjust the pin so the X dimension us same.

Stone is placed on the cast and lower member is swung back to embed

the mounting plate and incisal pin touching incisal guide.

Adjustment of lateral condylar guidanceCan be adjusted according to the Hanau’s equation for lateral

condylar guidance or with lateral relation record.

Hanau`s equation L=H/8+12

L=Lateral condylar guidance

H=Horizontal Condylar guidances

Mathematical Study of Hanau Articulators

Average anatomic location of hinge axis

For average anatomic location of hinge axis a Max error of 5 mm is

considered .If the relation of the jaws to the hinge axis of the patient

differ from relation of the casts to the hinge axis of the instrument,

when a 3mm wax centric record is removed and articulator is closed

an anteroposterior error of approximately 0.2mm would be produced

.

Arbitrary location of anterior point of reference

An elevation of anterior part of the face bow decreases the protrusive

condylar reading & vice versa.

Any of the commonly used arbitrary point of reference can change

vertical height of the face bow mounting not more than + 16 mm .

When the face bow mounting is oriented 16mm high , there is reduction

of 9°in condylar reading making it 31° from the lower member.

The effect of change in condylar inclination

on occlusion

Working cusp inclines

The working condylar motion of Hanau is built into the

machine & is dependent on the balancing condylar motion.

A difference of 10 degree in the working condylar inclination

produces approximately a 1.3° change in the Bennett angle the

net effect is practically immeasurable at the working condyle

and half again as much at the 2nd molar working cusp inclines

BALANCING CUSP INCLINES

The hypothetical patient

has a 40° cuspal inclines .

The 9° reduction in the

protrusive reading due to

elevation of the face bow

decreases the second molar

balancing cusp inclination

to 35.5°, this error is of 0.2

mm for 3 mm cusp.

STRAIGHT CONDYLAR PATH

The average Hanau articulator has a straight condylar slot

rather than a curved path.

condylar path follows a curvature of ¾ inch radius. With

static records , only the centric relation & eccentric positions

are recorded.

The midpoint of the

excursion produces the

maximum error with a

straight condylar slot.

The maximum difference

between a straight condylar

path & one that is having

½ inch radius is 0.4 mm a

maximum error of 0.4 mm

produces 0.2 mm error at

second molar. This is for a

3mm cusp height with a

constant incisal guidance.

Working condylar movements

This The effective condylar

movements in Hanau articulator is

upward backward and lateral

movement contains lateral

Bennett shift of 0°

The working cusp inclines at the

2nd molar would be average between

the extreme guidance namely 15°,

hence the articulator would produce

working cusp inclines at the 2nd

molar of 15° while the patient

would require 30°

Hanau Arcon H2 Introduced by Hanau in 1977

IGT is same as H2 mechanical table

in addition to this has ‘’ Pentacrylic”

incisal guide table and pin provided

for customization with acrylic resin

Upper and lower members are

attached to each other by condyles

and their guidances

Accepts face bow transfer primarily

earpiece face bow

For kinematic face bow it condylar

should be equipped with extendible

shaft

Quite simIntrodilar to H2 except it is an Arcon instrument

Hanau radial shiftArcon instrument with fixed

inter condylar distance

The condylar guidance of the

articulator is designed to

incorporate a curved immediate

side shift with an adjustable

progressive Bennett angle. the

radial shift adjustment has a 3mm

radius and allow up to 3mm of

radial shift before intercepting the

pre adjusted progressive Bennett

angle

The condylar guidance is

adjustable horizontally and curved

superior wall with a 0.75” radius

Hanau wide vue articulator

CLASS III TYPE BAccept face transfer Protrusive interocclusal records and some interocclusal record.

Eg. Trubite articulator,

Whipmix articulator

TRUBITE ARTICULATOR

Designed by Gysi in 1926

It is an nonarcon instrument wih a

fixed intercondylar distance

Horizontal condylar inclinations are individually adjustable

Individual bennette adjustments are near the center of intercondylar distance

Incisal guide table is adjusted acoording to the gothic arch angle can accept lateral interocclusal records not all

WHIPMIX ARTICULATORIt is semi adjustable Arcon type of articulator

It is designed by Charles Stuart in 1955

Its intercondylar distance is adjustable at three positions small(S)

96mm medium(M) 110mm, large(L) 124mm by means of removable

condylar guidance spacers along the instruments horizontal axis

Accepts face bow transfer

Horizontal condylar inclinations are set by means of lateral or

protrusive intercondylar record

It is available with either mechanical guide table adjustable in both

frontal and sagittal plane

Or with plastic incisal guide table that can be individually customized

Bennett angulation is set with lateral interocclusal record

the casts are seated in the LI record and medial wall of the condylar

housing is adjusted until they contact the condyles

Incisal guide table

Provided with either with mechanical incisal guide table or plastic

incisal guide table that can be individually customized with auto

polymerizing resin the mechanical guide table has single sagittal table

adjustment right and left frontal adjustment

Incisal guide pin is straight has a one flat end used with mechanical

guide table and one rounded end used with plastic IGT

MODIFICATIONS OF WHIPMIX ARTICULATOR

Condylar thumb lock screw

For stabilization of condyles during hinge movement

Optional immediate side shift guides available from 0.25 mm to 1mm

size is determined by amount of Bennett movement

Curved condylar guides horizontal or medial are designed to reflect

average relationship between condyles and fossa

CLASS IVAccept three dimensional dynamic registration and allow

point orientation of the cast using face bow transfer

Type A-The condylar path is determined by engraving

registrations produced by the patient, this path can not be

modified

Eg. TMJ articulator

Designed by Kenneth Swanson in 1965

Intraoral registration is generated by Studs in auto polymerizing

resin called as stereographic recording this record is placed on the

articulator and used to mold the fossa in auto polymerizing resin

which produces accurate analog of patients TMJ

CLASS IV TYBE B

These instruments will accept three dimensional dynamic records

and utilize face bow transfer. The condylar pathways can be

selectively angled and customized

Arcon vs non arconCondylar articulator or non arcon articulator has

Condylar element attached to the upper member of the

articulator & condylar guidance attached to the lower member

of the articulator. Eg. Hanau H series, Dentatus, Gysi

.

Term coined by Bergstrom in 1950

Arcon means ARticulator and CONdyle

An Arcon articulator has Condylar

element attached to the lower element of the

articulator and condylar guidance attached to

the upper member of the articulator

Resembles the TMJ eg. Hanau University

series, Whip mix

Arcon provides greater accuracy in the

transfer of angle of condyle descent by the

protrusive positional record But in non arcon

instrument the condyle will move distally in

protrusion so this distance will be doubled

SUMMARYThe frequently asked question is which articulator to be used can be

best answered vaguely that how much do you know about it…..

Amount of information required from your patient

Amount and type of restoration planned

Availability of equipments

Late Carl O Boucher stated that it must be recognized that the

person operating the instrument is more important than the

instrument used.

Success or failure of a final restoration us more depends on dentist

rather than the articulator used