Articulators & face bows

ARTICULATORS & FACE-BOWS

CONTENT

• Articulators

• Uses of articulators

• Requirement of an articulator

• Classification of articulators

• Face-bows

• Articulator:

• It is a mechanical device which represents the tempromandibular joints and jaws to which maxillary & mandibular casts may be attached to simulate some or all mandibular movements.

• The articulator helps to maintain the desired maxillomandibularrelationship of the casts during tooth arrangement.

• It makes it possible to arrange teeth in the absence of the patient.

ARTICULATORS

USES OF ARTICULATORS

1. Diagnose dental occlusal conditions in both the

natural & artificial dentitions.

2. Plan dental procedures that involve positions,

contours & relationships of both natural & artificial

teeth as they relate to each other.

3. Aid in the fabrication of dental appliances & lost

dental parts.

4. Correct & modify completed restorations.

5. Study occlusion & mandibular movements.

REQUIREMENT OF AN ARTICULATOR

1. It should hold casts in the correct horizontal.

2. It should hold casts in the correct vertical relationship.

3. It should provide a positive anterior vertical stop (the incisal pin).

4. It should accept a face-bow transfer record.

5. It should open & close in a hinge movement.

6. It should allow protrusive & lateral mandibular motion.

7. The moving parts should move freely & be accurately machined.


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

construction.

• If your going to choose balanced occlusion, an

articulator should have:

9. Adjustable horizontal & lateral condylar path

elements.

10.The condylar elements as a part of the lower

member & the condylar path elements as a part

of the upper member (Acron-type).


11.A mechanism to accept a third reference point

from face-bow record.

12.A terminal hinge position locking device.

13.Removable mounting plates that can be

repositioned accurately.

14.An adjustable incisal guide table.

15.An adjustable intercondylar width.

CLASSIFICATION OF ARTICULATORS

• The simplest classification system refers to the

degree to which the articulator can be adjusted to

conform to the jaw movements of the patient.

CLASSIFICATION OF ARTICULATORS

Class I Articulators (Non-adjustable)

Class II Articulators (Average-value)

Class III Articulators (Semi-adjustable)

Class IV Articulators (Fully-adjustable)

CLASS I ARTICULATORS (NON-ADJUSTABLE)

• A simple holding instrument capable of accepting

a single static registration. Vertical motion is

possible.

• Defined as:

• An articulator that does not allow adjustment to

replicate mandibular movements.

NON ADJUSTABLE (SIMPLE HINGE OR PLANE-LINE ARTICULATORS)

• It consists of two arms or bows united by a hinge & a stop or screw to hold the bows a fixed distance apart.

• It only simulates the opening & closing movements of the mandible.

• No eccentric movements possible.

• These articulators reproduce only one relation, centric occlusion.

• Therefore, setting the teeth for complete dentures will only be balanced in the centric position.

CLASS II ARTICULATORS (MEAN-VALUE OR AVERAGE-VALUE)

• An instrument that permits horizontal as well as vertical motion but does not orient the motion to the temporomandibular joints.

• Average-value Articulator:

• An articulator that is fabricated to permit motion based on mean mandibular movements.

• They permit not only opening & closing hinge movement around a fixed horizontal axis, but also protrusive, right & left lateral excursions.

MEAN-VALUE ARTICULATOR


• The condylar sphere if present, is normally attached to

the upper member of the articulator & rotates in a

groove in the lower member.

• The condylar path is fixed in 30° angle, this means that

the condylar sphere can be pushed to simulate

protrusive & lateral jaw movements.

• They are provided with an incisal guide pin, it helps:

1. to hold the articulator open at a definite position

2. The teeth are protected against accedental closure


• They have a fixed intercondylar distance.

• It may include some provision for Bennett movements.

• Some can accept a face-bow.

• The relationship of the maxilla to the condyles is

established by aligning the occlusal surface of the upper

occlusal rim with the incisal pin & with the notches or a

bar on the condylar posts at the rear of the articulator in

accordance to Bonwill triangle.

BONWILL TRIANGLE

• A 4 inch equilateral triangle bouded by lines

connecting the contact points of the mandibular

central incisor’s incisal edge ( or the mid line of the

mandibular residual ridge) to each condyle &from

one condyle to the other.

• Cast is mounted in an average position.

ADJUSTABLE ARTICULATORS

• An articulator that allows some limited adjustment in

the sagittal & horizontal planes to replicate

recorded mandibular movements.

Class III

•Semi adjustable

Class IV

•Fully adjustable

CLASS III ARTICULATORS (SEMI-ADJUSTABLE)

• An instrument that simulates condylar pathways by

using averages or mechanical equivalents for all

parts of motion. These instruments allow for

orientation of the casts relative to the joints & may

be arcon or nonarcon.


• They are adjusted so that the articulator

movements will simulate the jaw movements of the

patient.

• The condylar paths have a fixed contour which

cannot be altered & the distance between the

condyles cannot be varied.


• Adjustable horizontal condylar guides.

• Accept centric relation & protrusive records.

• Adjustable incisal guide tables.

• Adjustment for lateral mandibular movements.

• A face-bow to relate the casts to the hinge axis.

• They have a close approximation to the actual

mandibular position.


• Hanau-H series Articulator:

• Accept only one eccentric jaw relationship record, protrusive record.

• The record is then used to adjust the horizontal condylar inclination.

• It is not capable of accepting lateral jaw relation records.

• It is calculated:

• L= H +12

• _____

• 8


• Whip-mix Articulator:

• Accept centric & protrusive jaw records only.

• It has limited three-position adjustment of the

intercondylar width.

ARCON ARTICULATORS

• Articulator + Condyle

• It is used to describe an articulator containing the condylar path elements within its upper member & the condylar elements within the lower member.

• Arcon articulator:

• An articulator that applies the arcon design.

• This instrument maintains anatomic guidelines by the use of the condylar analogs in the mandibular element & fossae essemblies within the maxillary element.

• Examples:

• Hanau university series

• Whip-mix

NON-ARCON ARTICULATOR

• An articulator whose fossae assemblies are part of

the mandibular member& the condylar analogs in

the maxillary member.

• Examples:

• Hanau-H series

• The Dentatus

• Gyzi

CLASS IV ARTICULATORS (FULLY ADJUSTABLE)

• An instrument that will accept three dimensional dynamic registrations.

• Allow for orientation of the casts to the temporomandibular joints & simulation of mandibular movements.

• They have a complex condylar mechanism, it is adjustable in the horizontal, sagittal & frontal planes.

• Replicate 3-D movement of recorded

• mandibular movement.


• They are all arcon, with adjustable intercondylar

distance.

• They all accept arbitrary or hinge axis face-bow

transfers.

• They accept all eccentric jaw relation records.

• They can be adjusted to trace the recordings of a

pantograph.


• Pantograph registers a three dimensional dynamic

registration or tracings (pantograms).

• Then they are transferred to the articulator in the

same relationship in which they exist in the patient.

• Examples:

• Stuart articulator

• Denar articulator

FACE-BOWS

FACE-BOWS

• A calliper – like instrument used to record the spatial

relationship of the maxillary arch to some anatomic

reference point or points & then transfer this

relationship to an articulator.

• The anatomic references are the mandibular

condyles, transverse horizontal axis & one other

selected anterior point.

• It supports the casts while they are being attached

to the articulator.

TYPES OF FACE-BOWS

1. Arbitrary face-bows:

a. Conventional face-bow

b. Earpiece face-bow

2. Kinematic (hinge bow)

ARBITRARY FACE-BOWS

• A device used to arbitrarily relate the maxillary cast to the condylar elements of an articulator.

• They are based on the average location of the hinge axis, has an error of 2mm of the true center of the true center of the opening axis of the jaws.

• The arbitrary rotational center is located over measured points on the face or by some types of earpiece.

• The arbitrary type is considered adequate for complete dentures.

ARBITRARY FACE-BOWS

• Consists of:

• U-shaped bow

• Graduated condylar rods

• Bite fork

• Locking device

ARBITRARY FACE-BOWS

• It is placed on the face, with the graduated

condylar rods located in a line extending from the

outer canthus of the eye to the top of the tragus of

the ear & approximately 13mm in front of the

external auditory meatus.

EARPIECE FACE-BOW (EAR-BOW)

• An instrument similar to a face-bow that indexes to

the external auditory meatus & registers the relation

of the maxillary dental arch to the external auditory

meatus & a horizontal reference point.

EARPIECE FACE-BOW (EAR-BOW)

• Advantages:

1. It is a simple instrument to use

2. Does not require measurements or marks on the

face

3. Consumes less time for its use

4. It is accurate

• Both the face-bow & the ear-bow may use the

infraorbital notch ( infraorbital pointer)or the incisal

plane as the anterior reference point( or the

nasion).

• The anterior reference point along with the two

posterior reference points form the axis orbital

plane, which is transferred to the articulator along

with the maxillary cast.

• The occlusal plane will have a relationship in the

articulator that is similar to that in the patient’s skull.

KINEMATIC FACE-BOW

• A face-bow with adjustable calliper ends used to

locate the transverse horizontal axis of the

mandible.

• It is mostly used with fixed prosthodontic

procedures.

• The patient hinge axis must be located accurately.

• When the hinge axis has been determined, it is

marked on the skin with an indelible pencil.

KINEMATIC FACE-BOW

• The inevitable movement of the record blocks on

the jaws, especially the edentulous mandible,

makes determining the exact center of the opening

axis quite difficult, therefore, the kinematic face-

bow is seldom used for edentulous patients.

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Articulators & face bows

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