Lec 8 3 (easy)

Module: Prosthodontics 3 (BDS IV/Semester 7)

• Lecture covers Denture bearing areas of maxilla & mandible
• Lecturer: Dr Vinothkumar Sengottaiyan (@Dr_VK)
• Department: Prosthodontics
• College: Oman Dental College

Learning Outcomes

• Differentiate denture bearing areas (maxillary/mandibular) into supporting, relief, and limiting areas
• Plan and prepare denture-bearing areas for complete dentures
• Understand pre-prosthetic surgeries needed for denture construction
• Identify situations requiring specialist referral

Support - Definition

• General foundation area for a dental prosthesis
• Resistance against occlusal/functional forces
• In complete dentures, the available mouth area for support
• Supporting areas best suited for absorbing mastication forces

Parts of a Complete Denture

• Denture base/foundation: Contacts the supporting area (impression surface)
  • Three subdivisions: Support areas, Relief areas, Peripheral seal/border areas
• Denture flange: Surface outside the base; "camouflage/artistic" surface influencing aesthetics, not function
• Occlusal surface: Formed by artificial teeth, used to balance dentures during mastication

Denture Bearing Area

• Surfaces contacted by the denture base
• The picture shows the denture base contacting oral tissues
• Hard denture bases (like acrylic) don't change shape during function; occlusal forces transfer to the bearing areas

Forces in Complete Dentures

• Forces perpendicular to the occlusal plane are generated during mastication
• Forces are transmitted to underlying supporting tissues (compressive forces)
• In bone, these forces cause bone resorption
• In tissues, forces cause ischemia (blood flow reduction)
• Bone resorption and ischemia lead to long-term problems; sometimes, short-term pain, ulceration, or irritation is possible.

What Happens When We Make an Impression?

• Dental impressions record oral cavity anatomy using trays and appropriate materials
• Material pressure on structures is compression
• Denture bases apply similar force as impression-making
• Some structures (teeth, bone) withstand pressure longer, whereas others (mucosa, muscles) can be compressed easily.

How to Manage Compression in Denture Bases?

• Custom-made trays only contact pressure-resistant areas
• A primary cast is made from a preliminary impression
• Wax sheets (relief wax) are placed where pressure reduction is needed during the impression-making process
• A tray with acrylic is fabricated
• Wax is removed, and a final impression is taken
• Relief holes in the tray reduce pressure further

Anatomical Landmarks

• Visible/palpable structures in edentulous patients' oral cavities
• Useful for impressions and casts
• Knowledge of classifications is essential for custom trays using selective pressure during impression making
  • Support areas (primary and secondary)
  • Relief areas
  • Border/peripheral seal areas

Tissues of Edentulous Oral Cavity

• Mucosa:
  • Keratinized attached (residual ridge/palate)
  • Non-keratinized unattached (vestibule, cheeks, mouth floor, soft palate, uvula, tonsillar pillars)
• Submucosa: (not in mid-palatine raphe); Fibrous; Fatty/glandular (posterior palate/floor of mouth)
• Muscular: Along vestibule, cheek, and mouth floor
• Bone:
  • Cortical bone (most areas except residual ridge crest)
  • Medullary bone (along residual ridge crest)

Favorable Characteristics of Supporting Areas

• Thick cortical bone (avascular, resists resorption, excellent support)
• Thick keratinized attached mucosa (resists trauma, ulceration from denture base movement)
• Direction relative to the occlusal plane; Maximum support/resistance when parallel/perpendicular to forces

Maxillary Anatomical Landmarks

• Includes various anatomical structures like: Tuberosity, Buccal frenum, Buccal vestibule, Labial vestibule, etc.

Classification of Anatomical Landmarks - Maxilla

• Supporting structures (provide mastication force resistance): Bone (cortical), Mucosa (keratinized, attached), Placed perpendicular to occlusal forces
  • Primary support (posterior 2/3rd palate)
  • Secondary support (anterior 1/3rd, slopes of residual ridge)
• Limiting structures (limit denture base extension): Labial frenum, Labial vestibule, Buccal frenum, Buccal vestibule, Hamular notch, Posterior palatal seal area
• Relief areas (relieving pressure on the denture base): Incisive papilla, Mid palatine raphe, Canine eminence, Pterygoid hamulus, Crest of alveolar ridge
• Border/peripheral seal areas: All with the same meaning of limiting structures

Anatomical Landmarks of Mandible - Self-Assessment

• Students will label diagrams themselves

Classification of Anatomical Landmarks - Mandible

• Supporting structures (resistance to masticatory forces): Bone (cortical), Mucosa (keratinized, attached), Perpendicular to occlusal forces
  • Primary (buccal shelf)
  • Secondary (slopes of residual ridge)
• Limiting structures (limit denture base extension): Labial and buccal frenum and vestibules, Pterygo-mandibular raphe, Lingual frenum and vestibule
• Relief areas (relieving pressure): Mental foramen area, Crest of ridges, Canine/premolar eminences, Genial/mylohyoid ridges

Preprosthetic Surgeries

• Alveoloplasty: reduce sharp bony alveolar ridge extensions
• Vestibular extension/sulcus deepening: increase sulcus depth (skin/mucosal grafting)
• Tuberosity reduction: create vertical space in posterior ridge accommodating posterior denture bases
• Debulking of flabby tissues: achieve a firm mucosal support
• Ridge augmentation: increase alveolar ridge height, enhancing denture stability (possibly with implants)

Textbook for Reference

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

Test your knowledge on the denture bearing areas of the maxilla and mandible as covered in Prosthodontics 3. This quiz will assess your understanding of supporting, relief, and limiting areas, as well as the preparation of these areas for complete dentures. Explore concepts related to pre-prosthetic surgeries and when to refer to specialists.