Complete Denture Retention and Oral Mucosa Anatomy
Support Area and Mucosa Types
Support area: This includes thin, fat, and mucous glandular mucosa.
Anatomical Zones and Peripheral Seal
Neutral marginal zone: This is the mucogingival junction or anatomical area that separates the mobile and stationary mucosa, allowing the tray to function correctly.
Peripheral seal: This is formed by the marginal zone and the rear end zone, also known as the post-damming area.
Lower Jaw Mucosa Classification
The lower jaw constitutes three types of mucosa:
- Inserted or attached: This is the masticatory mucosa.
- Lining mucosa: This corresponds to the buccal and lingual grooves.
- Specialized mucosa: This covers the back of the tongue.
Residual Ridge and Bone Structure
Residual ridge: This consists of the supporting mucosa, submucosa, underlying periosteum, and residual bone.
Residual bone: This is the portion of the alveolar process that remains after losing teeth.
Factors Affecting Complete Denture Retention
- Maximum extension of the teeth/denture base.
- Maximum area of contact between the mucosa and the prosthesis base.
- Intimate contact between the prosthesis base and the basal portion of the mucosa.
- Note: Knife-shaped ridges have a poor prognosis and are prone to ulceration.
Clinical Classification of Mucosa
- Resilient: This possesses a better prognosis because it may be depressed by mechanical forces with easy retrieval of its position.
- Hard: Thin and very tense, it absorbs small defects poorly and has a dubious prognosis.
- Soft: Voluminous and absorbs base defects better, but it is difficult to impress, makes the registration of the centric relation difficult, and resists mechanical stress poorly.
The Ideal Basal Seat and Alveolar Ridge
Basal seat: The ideal prosthesis has a mucosal tissue layer that is more or less soft; ideally, it should be firm or slightly resilient.
Dam area: Includes the peripheral groove, buccal and lingual grooves, and the pyriform papillae.
Characteristics of an Ideal Alveolar Ridge
- Resistant bone quality uniformly coated with healthy mucosa, without depressions or projections.
- Well-defined vestibular and lingual grooves.
- Frenums (braces) that do not start very near the crest.
- A high ridge with a flat top and sides that are parallel or nearly parallel; this ridge type offers maximum support and stability.