Dental Devices: Facebow and Articulators

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Questions and Answers

What is the primary function of an articulator?

To align dental casts

To measure jaw strength

To create dental impressions

To simulate mandibular movements (correct)

Which class of articulator accepts three-dimensional dynamic registrations?

Class IV articulator (correct)

Class II articulator

Class III articulator

Class I articulator

What distinguishes Class II articulators from Class I articulators?

Class I accepts three-dimensional registrations

Class II can simulate condylar pathways

Class II permits vertical and horizontal motion (correct)

Class I allows only vertical motion

Which of the following is NOT a characteristic of Class III articulators?

Accept only static registrations Signup and view all the answers

What type of motion is possible with a Class I articulator?

Only vertical motion Signup and view all the answers

What is the primary function of a face bow in dental prosthetics?

To record the relationship between the maxilla and the rotational axis of the mandible Signup and view all the answers

Which articulator type is a simple hinge type and does NOT simulate condylar pathways?

Simple hinge articulator Signup and view all the answers

Which component is NOT part of a mandibular face bow?

Bite fork Signup and view all the answers

What important measurement is used in designing the mean value articulator?

The distance between central points of the condyle and mid incisal point Signup and view all the answers

What distinguishes a kinematic face bow from an arbitrary face bow?

It can locate the exact terminal hinge axis Signup and view all the answers

Which type of articulator is considered a simplest form that can take a single static registration?

Class I articulator Signup and view all the answers

What is the role of the infra-orbital pointer in an arbitrary face bow?

To relate the base plate to the patient’s frankfort plane Signup and view all the answers

Which type of face bow uses a universal joint to attach components?

Both A and C Signup and view all the answers

What two measurements does the maxillary face bow primarily record?

Maxillary and mandibular relationship relative to the rotational axis Signup and view all the answers

How does the clamp function in a mandibular face bow?

Attaches the bow to the mandible Signup and view all the answers

What is a common mistake regarding the relationship between the maxillary and mandibular face bows?

They are identical in structure and function Signup and view all the answers

What is the purpose of adjusting the condylar rods on the maxillary face-bow?

To align with the condylar axis points. Signup and view all the answers

What is a key benefit of using a face-bow during denture fabrication?

It minimizes errors in anatomical closure axis alignment. Signup and view all the answers

What do arbitrary face-bows rely on to record the position of the maxilla?

Facial and anatomical landmarks. Signup and view all the answers

In what scenario is a face-bow recording considered unnecessary?

When vertical dimension changes are avoided. Signup and view all the answers

How often do arbitrary face-bows achieve positioning within 6 mm of the true hinge axis?

About 80% of the time. Signup and view all the answers

What does the type of occlusal scheme influence during denture fabrication?

The need for interocclusal records. Signup and view all the answers

What tool is utilized as a posterior reference point in the ear piece face-bow?

External auditory canal. Signup and view all the answers

What component is essential for mounting the upper cast in denture fabrication?

Bonwill triangle. Signup and view all the answers

What geometric shape is used for mounting the upper cast in Gysi articulator?

Equilateral triangle Signup and view all the answers

Which record is necessary to adjust the horizontal condylar path in a semi-adjustable articulator?

Protrusive record Signup and view all the answers

What formula is used for adjusting the lateral condylar path in a semi-adjustable articulator?

L = H/8 + 12 Signup and view all the answers

What type of articulator allows both horizontal and lateral inclinations to be adjusted?

Fully-adjustable articulator Signup and view all the answers

Which record is NOT required for mounting casts in a fully-adjustable articulator?

Patient bite record Signup and view all the answers

What is the average angle range of the condylar path in the articulators?

33° to the horizontal plane Signup and view all the answers

Which of the following articulators is an example of a semi-adjustable articulator?

Hanau (Model H) articulator Signup and view all the answers

Which statement about the Bonwill triangle is accurate?

It connects the condyle and lower incisors. Signup and view all the answers

What is a key reason for the difficulty in achieving extreme accuracy with articulators for complete denture patients?

The record bases are somewhat mobile resting on movable tissues. Signup and view all the answers

Why is perfecting denture occlusions intra orally not always necessary for edentulous patients?

Extreme accuracy is not required for establishing occlusion. Signup and view all the answers

What method is used for indexing casts prior to mounting them on an articulator?

Placing grooves or notches in the cast. Signup and view all the answers

What is the primary purpose of using an articulator for final occlusal adjustments in denture fabrication?

To facilitate proper occlusal and aesthetic placement of artificial teeth. Signup and view all the answers

What alignment is necessary when positioning a cast on an articulator?

The occlusion rim midline must align with the incisal indicator pin. Signup and view all the answers

What is an important step before mounting the master cast on a fixed condylar path articulator?

Painting the basal surface of the cast with a separating medium. Signup and view all the answers

Why are complex articulators generally not indicated for edentulous patients?

They complicate the treatment process without added benefit. Signup and view all the answers

What purpose does the wax rim serve when mounting the cast to the articulator?

It helps to temporarily fix the cast to the table during positioning. Signup and view all the answers

Study Notes

Facebow

Definition: A caliper-like device used to record the relationship between the maxilla and the rotational axis of the mandible.
Types:
- Mandibular Facebow (Kinematic Facebow): Records the exact terminal hinge axis of the mandible by using a U-shaped bow with a clamp to attach to the mandible, a universal joint to connect the clamp to the bow, condylar rods connected to the bow and adjusted with screws.
- Maxillary Facebow (Arbitrary Facebow): Records the relationship between the maxilla and the rotational axis of the mandible, transferring this relation to the articulator. Uses a U-shaped bow, a bite fork attached to the bow with a universal joint & clamp, graduated condylar rods, and an infra-orbital pointer.
  - Types:
    - Facial Facebow:
    - Ear Piece Facebow: Uses the external auditory canal as posterior reference points.

Articulators

Definition: A mechanical device that represents the temporomandibular joint (TMJ) and jaw members to which maxillary and mandibular casts are attached to simulate mandibular movements.
Classification:
- Class I (Simple Holding Instrument): Allows for vertical motion.
- Class II (Horizontal and Vertical Motion): Does not orient motion to the TMJ.
- Class III (Average Motion Simulation): Simulates condylar pathways using averages, allowing for orientation of the casts relative to the joints.
- Class IV (Three Dimensional Dynamic Registration): Accepts 3D dynamic registrations, allowing for orientation of the casts to the TMJ and simulation of mandibular movements
Types:
- Simple Hinge Articulator:
  - Records: Centric occluding relation
  - Example: Gariot's articulator
- Mean Value Articulator:
  - Example: Gysi simplex articulator
  - Records: Bonwill triangle, Centric occluding relation.
- Adjustable Articulators:
  - Semi-Adjustable Articulator:
    - Examples: Hanau (Model H), Denar 5a, Denar II - Arcon.
    - Records: Bonwill triangle, Centric occluding relation, Protrusive record.
    - Lateral Condylar Path: Based on Hanau's formula (L=H/8+12; with L being the lateral condylar path and H being the horizontal condylar path).
  - Fully Adjustable Articulator:
    - Examples: Hanau kinoscope, Dentatus articulator.
    - Records: Bonwill triangle, Centric occluding relation, Protrusive record, Right lateral record, Left lateral record.

Mounting the Upper Cast

Indexing: Indexing casts prior to mounting them on an articulator permits removal and accurate replacement. Indexing is important for remounting procedures made for correcting occlusal errors after curing.
Steps:
- Relation the cast to the articulator: The cast should be positioned so that the midline of the occlusion rim aligns with the incisal indicator pin anteriorly and the line drawn on the base is aligned with the marking indicating the midline in the articulator posteriorly.
- Prepare the cast: Apply a separating medium to the basal surface of the cast.
- Secure the cast: Replace the cast and occlusion rim on the occlusion plane table and temporarily fix the wax rim to the table with wax.

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Description

Explore the essential dental devices: facebow and articulators. This quiz covers their definitions, types, and functions, ensuring you grasp the connection between the maxilla and mandible relationships, as well as the mechanisms of articulators. Perfect for dental students and professionals!