Lec 8 3 (hard)

Prosthodontics Lecture 8 & 9 - Denture Bearing Areas

• Topic: Denture bearing areas of maxilla and mandible
• Lecturer: Dr. Vinothkumar Sengottaiyan (@Dr_VK)
• Institution: Oman Dental College

Learning Outcomes

• Differentiate denture bearing areas (supporting, relief, limiting) of maxillary and mandibular arches
• Plan and condition denture bearing areas for complete dentures
• Understand preprosthetic surgeries for denture construction
• Identify situations needing specialist referral

Support - Definition

• General: Foundation area for a dental prosthesis, resisting occlusal/functional forces
• Complete dentures: Area of mouth available for support
• Other: Areas in the mouth for absorbing mastication forces

Parts of Complete Denture

• Denture base/foundation: Part of the denture contacting supporting areas (impression surface, intaglio surface, support areas, relief areas, and peripheral seal/border areas)
• Denture flange: Surface outside denture base, called cameo/art surface, aesthetically developed by the dentist (doesn't affect function).
• Occlusal surface: Formed by artificial teeth, creating balance during mastication

Denture Bearing Area

• Refers to surfaces contacted by the denture base.
• The denture base (fitting surface) contacts oral tissues.
• Denture bases are typically made of hard materials like acrylic, and don't change shape during function.
• All occlusal forces are transferred to denture bearing areas by the denture base

Forces in Complete Dentures

• Forces perpendicular to the occlusal plane during mastication are transmitted to underlying supporting tissues as compressive forces.
• These forces cause bone resorption in bone and ischemia (reduced blood flow) in tissues.
• Bone resorption and ischemia can result in long-term problems.
• However, in some instances, short-term pain, ulceration, and irritation could occur.

What Happens When We Make an Impression

• A dental impression records the anatomy of the oral cavity using impression trays and appropriate materials.
• Pressing the material against oral structures is compression.
• The denture base applies similar force during impression making.
• Some structures (teeth, bone) can withstand pressure longer; others (mucosa, muscle attachments) can't.

How to Manage Compression in Denture Bases

• Fabricate a customized tray contacting only pressure-resistant areas.
• Use a first duplicate (primary cast) from the preliminary impression.
• Place wax sheets (relief wax) in areas needing reduced pressure during impression making.
• Create a special tray with acrylic, removing the wax after the final impression.
• Relief holes can further reduce pressure inside the tray.

Anatomical Landmarks

• Visible/palpable structures within the oral cavity (edentulous patient).

• Important for understanding how to classify structures.

• Support classification helps create custom trays for selective pressure during impression making.

• Support areas: Primary and secondary

• Relief areas:

• Border/peripheral seal areas:

Tissues of Edentulous Oral Cavity

• Mucosa:
  • Keratinized attached mucosa: Present on residual ridge and palate
  • Non-keratinized unattached mucosa: Vestibule, cheeks, floor of mouth, soft palate, uvula, and tonsillar pillars
• Submucosa: Fibrous, anterior palate, tuberosities, residual ridges
• Fatty/glandular: Posterior palate, some floor of mouth areas
• Muscular: Along vestibule, cheeks, floor of mouth
• Bone:
  • Cortical bone: Most areas except crest of residual ridges
  • Medullary bone: Crest of residual ridges

Favourable Characteristics of Supporting Areas

• Thick cortical bone: Avascular, resists resorption (excellent support)
• Thick keratinized attached mucosa: Resists trauma/ulceration from denture movements.
• Direction relative to occlusal plane: Maximum support/resistance when parallel or perpendicular to occlusal forces.

Maxillary Anatomical Landmarks

• (List of specific landmarks - see the text)

Mandibular Anatomical Landmarks

• (Refer to the text, list mandibular Landmarks)

Preprosthetic Surgeries

• Alveoloplasty (invasive): Reduces sharp bony extensions of alveolar ridge.
• Vestibular extension/Sulcus deepening: Increases sulcus depth, usually achieved with skin or mucosal grafting.
• Tuberosity reduction: Creates vertical space in posterior ridge.
• Debulking of flabby tissues: Achieves firm mucosal support.
• Ridge augmentation: Increases height of the alveolar ridge for improved denture stability and possibly, implants instead of removable dentures.

Textbook for Reference

• Zarb, G.A., 2012, Prosthodontic Treatment for Edentulous Patients: South Asia Reprint-E-book, Elsevier Health Sciences.