Quartz 4

L1 Articulators

14 min read

Articulators1

Dr Matsubara

Learning Outcomes2

  1. Explain the importance of the articulator for oral rehabilitation
  2. Describe the classification of articulators
  3. Understand the difference between ARCON and NON-ARCON articulators
  4. Describe the Facebow recording and its clinical importance
  5. Describe bite registration in CR and when to mount in CR or MIP
  6. Describe the programming of a semi-adjustable articulator

Articulator Elements - Terminology3

  • Bennet angle: Adjustability in the angle formed between the sagittal plane and the condylar track in the nonworking side.
  • Bennett movement: lateral shift of the mandible resulting from the movements of the condyles along the lateral inclines of the mandibular fossae during lateral jaw movement
  • Intercondylar distance: Refers to the distance between the vertical axes of rotation
  • Horizontal axis of rotation: Mandibular movement around the horizontal axis is an opening and closing motion.
  • Incisal guidance: The simulation of anterior guidance in the natural dentition.
  • Condylar & glenoid fossa components: Variability in the angle of the eminentia; the directional condylar guidance provided by the medial, superior and posterior walls of the glenoid fossa; and the ability to simulate laterotrusive and protusive movements.

Articulators1

”A mechanical instrument that represents the TMJs and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements”

Glossary of Prosthodontic Terms 9th ed.

Function4

  • To evaluate the patient’s occlusion (simulate mandibular movements and hold casts in a determined fixed relationship)
  • To allow most of the prosthetic work to be done without the presence of the patient
  • Dental laboratory can then design the prosthesis (occlusal surfaces) to be in functional harmony with the patient’s movements
  • To reduce clinical time needed for adjustments of restorations

Assist In:

  • Diagnosis & treatment planning
  • Fabrication of restorations

Limitations5

  • Due to their inflexible mechanical nature, articulators cannot simulate the complex tissues, joints; and neuromuscular control that influence mandibular movements.
  • Even the most advanced and expensive articulator, can only be customised to simulate, but still not fully replicate, all possible combinations of movements in the patient

Info

The human masticatory system remains the “ultimate articulator,” and fine adjustments must always be finalized in the mouth.

Indications for Mounting Models6

When should you mount the models on articulators?

  • To assess occlusion (Diagnostic Articulation)
  • Diagnostic wax up
  • More than two single crowns / Bridge
  • Removable partial dentures
  • Complete dentures
  • Immediate dentures (partial or complete)
  • Cases where increase of VD is necessary (wax up)
  • Occlusal splints (if not using CAD-CAM)
  • Single crowns ??

Note on Single Crowns

Mounting may be optional if the patient has stable occlusion and a "confirmative" approach is used.

Diagnostic Articulation During Treatment Planning7

  • Tooth alignment
  • Prosthetic/interocclusal space
  • Occlusal contacts
  • Occlusal plane
  • Enough space for restorations
  • Shape, morphology and size of artificial teeth (Partial dentures and immediate dentures)
  • Occlusal rest (guide planes, adequate height of contour, undercuts – surveyor)
  • ==Cobalt Chrome Dentures: Assessing space for occlusal rests and guide planes.==

Complete Denture Considerations8

Do you need to mount study models on articulator for Complete Denture treatment plan?

  • No, we can change all those parameters in a complete denture.
  • Note: Edentulous patient with severe class II or III, you may need to mount the models to assess ridge relationship.

Exception

For severe Class II or III cases, mounting may be required to assess ridge relationships for potential pre-prosthetic surgery.

Classification of Articulators9

Based on:

  • Instrument function
  • Adjustability

Classification Based on Instrument Function10

• Capacity to simulate mandibular movements

  • Class I: Hinge type
  • Class II: Arbitrary
  • Class III: Average
  • Class IV: Special

Class I: Hinge type11

  • Simplest instrument
  • Accept a single static registration
  • Only vertical motion is passible
  • Cannot accept a facebow
  • Limited use: very simple restorations

Class II: Arbitrary12

  • Articulator that allow horizontal and vertical movements but it does not orient the motion of TMJs

Info

It does not allow adjustment of condylar guidance or Bennett angle.

Class III: Average13

  • Simulates condylar pathways by using averages or mechanical equivalents for all or part of the motion
  • Allows vertical and horizontal motion
  • Use of face-bow transfer
  • Does not allow total customization of condylar pathways

Tip

Facebow use is recommended with class III articulators.

Class IV: Special14

  • Accept three dimentions dynamic registrations
  • Use of facebow transfer
  • Capable of accurately reproduce the condylar pathway
  • Able to adjust multiple angles

Info

These accept three-dimensional dynamic registrations, such as pantographic tracings.

Classification Based on Adjustability15

  • Nonadjustable articulator
  • Semi-adjustable articulator
  • Fully-adjustable articulator

Nonadjustable Articulator16

  • Class I articulator
  • Open and close in a fixed horizontal axis
  • Indication: simple cases (e.g. single crown)

Risk

The short distance between the restoration and the hinge axis often results in "high" restorations and premature contacts in the mouth.

Semi-adjustable Articulator17

  • Class III articulator
  • Condylar guidance incline, Bennet angle, incisal guidance, inter condylar distance*
  • Two types:
    • Arcon articulator
    • Non-arcon articulator

ARCON Type18

This type resemble the TMJ:

  • Ar – articulator

  • Con – condyle

  • Condylar element (sphere) is attached to the lower member of the articulator

  • Mechanical fossae is attached to the upper member

  • Simulated the correct anatomical position of the TMJ elements

  • Example: Kavo Protar, Whip Mix

Advantage

The angle between the condylar guidance and the maxillary occlusal plane remains constant regardless of the opening.

NONARCON Type19

  • Condylar element (sphere) is attached to the upper member of the articulator
  • Mechanical fossae is attached to the lower member
  • Upper and lower components are rigidly attached – easier to handle
  • Example: Hanau, Dentatus articulator

Disadvantage

The condylar angle changes as the articulator is opened, which can introduce errors during eccentric movement checks.

ARCON vs NONARCON Comparison20

ARCON ArticulatorNONARCON Articulator
• Condylar inclination is at a fixed angle to the maxillary occlusal plane• the angle changes as the articulator is opened results in errors to program protrusive record

Semi-Adjustable Types21

  • ARCON
  • NONARCON

Clinical Impact of Adjustability22

  • A) Semi-adjustable articulator
  • B) Nonadjustable Articulator Type I
    • Premature contact, interference

Info

Using a semi-adjustable articulator reduces the risk of occlusal interferences because the arc of closure more closely matches the patient's actual radius of movement compared to a non-adjustable hinge.

Fully Adjustable Articulator23

  • Class IV articulator
  • Capable of being adjusted to follow the mandibular movement in all direction
  • Condylar guidance, Bennet angle, Fisher angle, intercondylar distance, anterior guide
  • Not commonly used due to its complexity

Info

It is typically used for severe malocclusions or for teaching purposes.

  • The articulator is an essential tool in successful denture manufacturing that allows for the correct positioning of artificial teeth, which in turn result in balanced articulation and a successful prosthodontic appliance.

Facebow2425

Aim: to record the anteroposterior and mediolateral spatial position of the maxillary occlusal plane in relation to horizontal axis of rotation of the mandible during opening and closing, and to the cranial base.

Kavo Protar Facebow26

Definition

A facebow is a caliper-like instrument used to record the relationship of the maxillary arch to the horizontal hinge axis and the base of the skull.

OVD Reduction: Model Mounted with Facebow27

  • Model mounted with facebow

Info

When the Vertical Dimension (OVD) is reduced on the articulator (e.g., by 3mm at the pin), the reduction in the posterior and anterior regions will accurately reflect the patient's mouth because the distance from the hinge axis is correct.

OVD Reduction: Model Mounted Without Facebow28

  • Model mounted without facebow

Warning

If the model is mounted too close or too far from the hinge axis, changing the OVD on the articulator will result in incorrect tooth reduction (either too much or too little), leading to restorations that do not fit the patient’s bite.

  • Model mounted without facebow

  • Model mounted without facebow

  • OVD Reduction

  • Reduce more than necessary

Anatomical Reference Points293031

  • 1 - Infra-orbital point + 6 - Porion = Frankfurt Horizontal plane
  • 3 – Subnasal point + 5 - Tragus = 2 Camper’s plane
  • 7 – Hinge axis
  • 4 - Occlusal plane
  • 2 // 4

Kavo Protar Setup

The Kavo Protar setup uses a nasal support which provides an average position between the Frankfurt and Camper’s planes.

Kavo Protar Facebow Setup32

  • Can use either Frankfurt or Camper’s plane
    1. Nasal support

Intercondylar Adjustment3334

  • (Not available on Kavo PROTAR)

Warning

Some articulators allow for Small, Medium, or Large intercondylar distance settings. Incorrect settings can lead to cusp interference during lateral movements.

  • Intercondylar Distance

Facebow Record Procedure3536

1st: Impression of maxillary cusp tips on the fork

| Automixed elastomer | Addition or condensation silicone putty | Impression Compound (not available in the clinic) |

Tip

It is recommended to use the maxillary model to make the indentations in the registration material for better control before taking it to the mouth. | :--- | :--- | :--- | | | | |

2nd: Positioning the Bite Fork37

  • Place the prepared bite fork in the patient’s mouth: patient can hold it against the upper teeth
  • Partial or complete edentulous cases: Need base and wax rim to provide posterior support

Note

The post of the Kavo Protar bite fork is offset to the left, not in the midline.

3rd & 4th: Adapting the Bow38

  • 3rd: Adapt the bow to the width of the patient’s face.
  • 4th: Adjust the nasal support on the nasion and fix it with the lock lever

NOTE:

  • If the Frankfurter horizontal is used, the reference pointer must be inserted above the bow.
  • If the Camper plane is used, the reference pointer must be positioned below the bow.

5th, 6th & 7th: Securing the Assembly39

  • 5th: Shove the bite fork support onto the bite fork ④
  • 6th: Adapt the bite fork support on the facial bow and tighten the the finger screw ①
    • Make sure that the guide pins of the bite fork support engage in the guide groove of the facial bow.
  • 7th: Tighten the knurled screw ②
  • Bite fork support

Bite Registration4041

Clinical Approach: CR vs MIP

Should I use CR or MIP (habitual bite position)?

  • Confirmative approach: patient has stable bite, no symptoms of TMD
    • Prosthetic treatment in MIP, habitual bite position.
  • Reorganized approach: patient with no stable bite, loss of VD, signs and symptoms of TMD
    • Prosthetic treatment in CR
  • Second option for Reorganized approach (Freedom in centric): Reestablish the bite in CR and leave area of freedom in the restoration so that the patient can function anywhere between CR and old habitual position (MIP) if necessary.

Info

CR is a reproducible, tooth-independent position.

MIP (Habitual Bite Position) Technique42

  • Respect working time of bite registration material
  • Do not use a lot of material
  • Check if the patient is contacting upper and lower teeth

Bite Registration in Centric Relation (CR)43

  • RC (Centric Relation): Most posterior position of the mandible in which the condyle is in the most anterior and superior position within the fossa.
  • Manipulating a patient’s mandible
  • Contemporary Fixed Prosthodontics 4th

CR Techniques44

  • Tongue tip to soft palate

  • ==Leaf Gauge: Using a stack of strips between anterior teeth to separate posterior teeth and allow the condyles to seat superior-anteriorly.==

  • (Bite Registration in CR)

The “Lucia Jig”4546

  • Small anterior programming device made of acrylic resin
  • Prevent posterior contact points
  • Help mandible manipulation

Function

It de-programs the muscles of mastication, breaking the "muscle memory" of the habitual bite and allowing the clinician to guide the jaw into CR.

Alternative CR Devices4748495051525354

  • Occlusal splint
  • Kois deprogrammer
  • Anterior jig

Jaw Relation Record Requirements55

  • Requirements:

    • Durability
    • Rigidity
    • Ease of application
    • Ease of transfer

  • For edentulous areas:

    • Stabilizing base and occlusal rim

    • Consider multiple records to ensure repeatability

    For Edentulous Areas V-shaped notches should be cut into the wax to key the registration material.

    When using wax rims,

  • Suitable materials:

    • Wax
    • Silicone
    • ZnO-eugenol
    • Resin

Record Materials56

  • Elastomeric material

  • Acrylic resin record base

  • Partially edentulous

  • (Jaw Relation Record Visual)

Programming the Articulator5758

  • Condylar guidance and Bennet angle
  • MIP/RC
  • Lateral movement to right
  • Lateral movement to left
  • Protrusion

Info

Once models are mounted, the semi-adjustable articulator must be programmed using eccentric bite registrations (Protrusive, Right Lateral, Left Lateral).

  • Condylar guidance and Bennet angle

Condylar Guidance5960

  • PROTRUSION BITE REGISTRATION
  • Return Condylar guidance to 0°

Method

Move the glenoid fossa component until it contacts the condylar sphere (just enough to hold a thin piece of paper).

  • (Condylar Guidance Visual)

Bennet Angle616263

  • Adjust the angle in the non-working side
  • Set Bennet angle = 30°
  • Adjust the angle in the non-working side

Adjustment Rule

To adjust the Right Bennett angle, use the Left lateral registration (non-working side). Set the angle to 30 degrees before adjusting to give the condyle freedom to move.

Adjustment Sequence6465

  • Pre-adjustment for mounting of casts = 0°
  • Pre-adjustment = 30°
  • Final adjustment

Clinical Summary66

  • Needs to be used properly, otherwise errors will be introduced.
  • Potential Issues:
    • Occlusal problems
    • Incorrect articulations
  • Errors mounting models in the articulator lead to treatment delay, addition of appointment

References67

  • Management of TEMPOROMANDIBULAR DISORDERS AND OCCLUSION - JEFFREY P. OKESON, 7th Edition, ELSEVIER
  • CONTEMPORARY FIXED PROSTHODONTICS - Rosenstiel • Land • Fujimoto, MOSBY ELSEVIER, Fourth Edition

Thank you

PROGRAMMING THE ARTICULATOR

Initial Settings and Adjustments

  • Bennet angle
    • Pre-adjustment for mounting of casts = 0°

Articulators1

Programming the Articulator

  • Bennet angle
  • Condylar Guidance
    • Pre-adjustment = 30°
  • Final adjustment

Articulator Usage and Best Practices66

Operational Requirements

  • Needs to be used properly, otherwise errors will be introduced.

Consequences of Improper Use

  • Occlusal problems
  • Incorrect articulations
  • Clinical Inefficiencies
    • Errors mounting models in the articulator lead to treatment delay, addition of appointment

Critical Check

If the mounted models do not look like the patient's mouth, do not send them to the lab. Remount them immediately.

Institutional and Reference Information67

Affiliations

  • THE UNIVERSITY OF WESTERN AUSTRALIA
  • Oral Health Centre of Western Australia
  • Management of TEMPOROMANDIBULAR DISORDERS AND OCCLUSION
    • JEFFREY P. OKESON
    • 7
    • ELSEVIER
  • CONTEMPORARY FIXED PROSTHODONTICS
    • Rosenstiel • Land • Fujimoto
    • MOSBY
    • ELSEVIER
    • Fourth Edition

Thank you

Footnotes

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