Denture Bases and Occlusion Blocks

Record Bases and Occlusion Blocks

• Definition: Occlusion blocks are composed of occlusion rims attached to well-fitting trial denture bases.

• Purpose:

  • Establishing facial contours
  • Assisting in tooth selection
  • Maintaining the vertical dimension of occlusion during record taking
  • Making interocclusal records
  • Arranging denture teeth
  • Creating a 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 undercuts to avoid scraping the cast
  • Clean and smooth for patient comfort
  • Proper and uniform thickness (2mm)
  • Easy to construct

Wax Blockout

• Purpose: To protect master casts from tissue undercuts and irregularities.
• Locations:
  • Maxillary casts: Labial of the anterior ridge, rugae areas, sometimes in tuberosity areas laterally.
  • Mandibular cast: Retromylohyoid areas.

Record Base Fabrication

• Master Cast Preparation:
  • The cast is soaked in room temperature water for 5 minutes to expel air and minimize bubble-like defects.
  • A tinfoil substitute is used as a separating medium to protect the cast and ensure separation of the record base.
  • The tinfoil substitute is applied in two thin layers, allowing the first layer to dry before applying the second.
• Record Base Material:
  • Fabricated with autopolymerizing acrylic resin.
• Thickness:
  • Thinner on the crest of the ridges and buccal to the crest of the ridges due to limited space for tooth arrangement.

Occlusion Rims

• Material: Generally made of pink modeling wax.
• Uses:
  • Registration of jaw relationships
  • Tooth selection:
    • Midline determination
    • High and low lip line determination for tooth length
    • Canine line determination for tooth width
    • Distance between the canine line and posterior end of the occlusion rim for posterior tooth width
  • Setting up teeth
  • Support for lips and cheeks

Occlusion Rim Dimensions

• Width:
  • Approximately 8–10 mm in the posterior region
  • 6–8 mm in the anterior region
• Maxillary Occlusion Rim:
  • 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 is about 18mm.
  • Posterior lower region height is equal to two-thirds the height of the retromolar pad (middle to upper third).

Important Considerations

• Patient Communication: Continuously inform patients that the record bases and occlusion rims are not permanent parts of the dentures and may feel loose due to blocked-out undercuts.

Record Bases and Occlusion Blocks

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

Requirements of Trial Denture Bases

• Must be:
  • 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 & smooth for patient comfort
  • Proper & uniform thickness (2mm)
  • Easy to construct

Wax Block Out

• Protect master casts by blocking out tissue undercuts and irregularities with base plate wax
• Maxillary casts are blocked out in locations such as:
  • Labial of the anterior ridge
  • Rugae areas
  • Sometimes in the tuberosity areas laterally
• Mandibular casts are blocked out in the retromylohyoid areas

Preparing the Cast for Record Base Fabrication

• The cast is soaked in room temperature water for 5 minutes to expel air from within the stone and minimize bubble-like defects
• Tinfoil substitute is used as a separating medium applied in two thin layers to protect the cast and allow separation of the record base

Fabricating the Record Base

• Fabricated with autopolymerizing acrylic resin
• Thinner on the crest of the ridges and buccal to the crest of the ridges to allow for space during tooth arrangement

Occlusion Rim Fabrication

• Generally made of pink modeling wax
• Uses:
  • Registration of jaw relationships
  • Choice of artificial teeth:
    • Midline is determined
    • High and low lip lines are determined, indicating tooth length
    • Canine lines are used to determine tooth width
    • Distance between canine line and the posterior end of the occlusion rim determines the mesiodistal width of posterior teeth.
  • Setting-up of teeth
  • Support for lip and cheeks

Width and Dimensions of Occlusion Rims

• Posterior: 8-10 mm in width
• Anterior: 6-8 mm in width
• Maxillary:
  • Labial surface in the central area is approximately 6-8 mm anterior to the middle of the incisive papilla, inclined labially
• Mandibular:
  • Vertical height is about 18 mm
  • Posterior height represents two-thirds the height of the retromolar pad (middle to upper third)

Important Considerations

• Continuously inform patients that record bases and occlusion rims are not part of the completed dentures and may feel loose due to blocked-out undercuts

This quiz explores the essential features and purposes of occlusion blocks and trial denture bases in prosthodontics. It covers the characteristics required for trial denture bases and the importance of wax blockout in protecting master casts. Test your understanding of these fundamental concepts in denture construction.