Dental Prosthetics: Occlusion Blocks and Bases

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Questions and Answers

What is the primary purpose of occlusion blocks?

To establish facial contours (correct)

To determine tooth color

To aid in dental hygiene practices

To enhance patient comfort

What is the minimum uniform thickness required for a record base?

3 mm

2 mm (correct)

4 mm

1 mm

Which material is used as a separating medium during the record base fabrication process?

Aluminum foil

Vaseline

Tinfoil substitute (correct)

Liquid paraffin

Which of the following describes a requirement for a trial denture base?

Must be dimensionally stable with minimal warpage Signup and view all the answers

What is the purpose of waxing out tissue undercuts and irregularities?

To protect the master cast and facilitate proper fitting Signup and view all the answers

What is the appropriate width of occlusion rims in the anterior region?

6-8 mm Signup and view all the answers

When should the cast be soaked in room temperature water during the record base preparation?

To minimize bubble formation in the completed record base Signup and view all the answers

How many thin layers of tinfoil substitute should be applied?

Two layers, with drying time in between Signup and view all the answers

Which of the following is NOT a use of occlusion rims?

Measurement of maxillary sinus Signup and view all the answers

How are the record bases designed in relation to the crest of the ridges?

Thinner on the crest Signup and view all the answers

What is a characteristic feature of a record base?

It should be rigid and accurately adapted to the cast Signup and view all the answers

What is the vertical height of the mandibular occlusion rim?

18 mm Signup and view all the answers

What specific feature is determined on the occlusion rim for the arrangement of teeth?

Midline Signup and view all the answers

What is a common misconception regarding record bases and occlusion rims?

They are permanent parts of the dentures Signup and view all the answers

Where is the labial surface of the maxillary occlusion rim positioned in relation to the incisive papilla?

6-8 mm anterior Signup and view all the answers

How far should the posterior lower region height of the occlusion rim be from the retromolar pad?

Two-thirds of the pad height Signup and view all the answers

Study Notes

Record Bases and Occlusion Blocks

Definition: Occlusion blocks consist of occlusion rims attached to well-fitting trial denture bases.
Functions:
- Establish facial contours
- Aid in tooth selection
- Establish and maintain vertical dimension of occlusion during record making
- Make interocclusal records
- Arrange denture teeth
- Waxed-up mold for the external surface of the complete denture

Requirements of a Trial Denture Base

Characteristics:
- Rigid
- Accurately adapted to the cast with proper extensions
- Dimensionally stable with minimal warpage
- Relieved from any undercuts to avoid scraping the cast during insertion and removal
- Clean and smooth for patient comfort
- Proper and uniform thickness (2mm)
- Easy to construct

Wax Block Out

Purpose: Protect master casts, tissue undercuts and irregularities are blocked out with base plate wax.
Locations:
- Maxillary casts: Labial of the anterior ridge, rugae areas, sometimes in the tuberosity areas laterally.
- Mandibular cast: Retromylohyoid areas.

Record Base Fabrication Procedure

Soak Cast: The cast is soaked in room temperature water for 5 minutes to expel air and minimize defects.
Separating Medium: A tinfoil substitute is used as a separating medium to protect the cast and allow separation of the record base.
Tinfoil Substitute Application: It is applied twice, allowing the first layer to dry before applying the second. A thin film is applied to all surfaces of the cast including land areas.
Record Base Material: Autopolymerizing acrylic resin is used to fabricate the record base.
Record Base Thickness: Thinner on the crest of the ridges and buccal to the crest of the ridges because space may be limited for tooth arrangement.

Occlusion Rim Fabrication

Material: Occlusion rims are generally made of pink modeling wax.
Functions:
- Registration of jaw relationships
- Choice of artificial teeth:
  - Midline is determined
  - High and low lip lines are determined to indicate tooth length
  - Canine lines indicate tooth width
  - Distance between canine line and posterior end of occlusion rim determines the mesiodistal (M-D) width of posterior teeth
- Setting-up of teeth
- Support for lip and cheeks

Occlusion Rim Dimensions

Width:
- Approximately 8-10 mm in width posteriorly.
- 6-8 mm in width anteriorly.
Maxillary Occlusion Rim Vertical Height: The labial surface in the central area is approximately 6-8 mm anterior to the middle of the incisive papilla and is inclined labially
Mandibular Occlusion Rim Vertical Height: About 18mm.
- In the posterior lower region, the height is equal to two-thirds the height of the retromolar pad (middle to upper third).

Important Patient Considerations

Information: Patients should be informed that the record bases and occlusion rims are not part of the completed dentures. They may feel a little loose due to the blocked-out undercuts.

References

Rahn, A.O., Heartwell, C.M. (1993). Textbook of complete dentures. (5th ed.). Philadelphia: Lea & Febiger.
Sowter, J.B. (1986). Baseplates. In R.E. Barton (Ed.), Removable Prosthodontic Techniques (Revised edition). Chapel Hill: University of North Carolina Press.
Zarb, G.A., Bolander, C.L. (2004). Prosthodontic treatment for edentulous patients. (12th ed.). St. Louis: Mosby Inc.

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Description

This quiz explores the concepts of occlusion blocks and trial denture bases in dental prosthetics. It covers their definitions, functions, characteristics, and the role of wax block out. Dive into the essential aspects of creating accurate and comfortable dentures.