Retention & Stability of Complete Dentures

Question 1

What is retention in complete dentures?

Answer 1

Retention is the resistance of a denture to vertical movement away from the tissues.

Question 2

Define stability in the context of complete dentures.

Answer 2

Stability is the resistance of a denture to displacement in a horizontal direction caused by functional forces.

Question 3

List the forces that can displace dentures.

Answer 3

Gravity
Muscle activity
Sticky foods
Functional forces

Question 4

What is adhesion in denture retention?

Answer 4

Adhesion is the physical attraction between unlike molecules, such as:

Saliva and mucous membrane
Saliva and denture base

Question 5

How does cohesion contribute to denture retention?

Answer 5

Cohesion involves the physical attraction between similar molecules, such as salivary film, which helps keep the denture in place.

Question 6

What roles does saliva play in denture retention?

Answer 6

Saliva enhances adhesion between the mucous membrane and denture base and contributes to interfacial forces.

Question 7

Why is a border seal important in denture retention?

Answer 7

A border seal ensures atmospheric pressure contributes to denture retention, especially in maxillary dentures.

Question 8

Explain the importance of interfacial surface tension in denture retention.

Answer 8

A thin fluid layer between the denture and mucosa creates interfacial force, with better retention achieved when the salivary film is thin and well-adapted.

*Viscous force falls rapidly as the thickness of the liquid increases
*Need good adaptation between denture and mucosa to keep salivary film thin

Question 9

What are the three critical surfaces to optimize for denture retention and stability?

Answer 9

• Fitting (basal) surfaces
• Polished surfaces
• Occlusal surfaces

Question 11

Why is full coverage of the denture-bearing area important? (fitting basal surface)

Answer 11

Full coverage maximizes the base extension and stability of the denture, particularly in the maxilla.

Question 12

What is an important feature in the maxillary denture fitting surface?

Answer 12

adequate post dam seal

Question 13

What is an important feature in the mandibular denture fitting surface?

Answer 13

adequate extension into the retromylohyoid fossa (lingual pouch)

Question 14

How do undercuts affect denture retention?

Answer 14

Utilizing labial and bilateral soft tissue undercuts improves the mechanical retention of dentures.

Question 15

Name factors that can challenge denture retention and stability.

Answer 15

• Atrophic ridges
• Incomplete palate (e.g., congenital cleft)
• Mobile soft tissue
• Natural lower teeth
• Insufficient saliva (e.g., due to salivary gland disease)
• Patient who cannnot tolerate base extension
• Cobalt – Chromium base plates adapt less well than acrylic resin

Question 16

What factors influence the effectiveness of occlusal surfaces in denture stability?

Answer 16

• Arch form
• Occlusal plane level
• Tooth position relative to the edentulous ridge and oral musculature (tongue control)
• Errors in tooth positioning

Question 17

Why are polished external surfaces important?

Answer 17

Properly contoured polished surfaces allow the tongue and cheek muscles to guide and stabilize the denture, improving retention and comfort.

Poorly designed polished surfaces may lead to instability, discomfort, and difficulty in controlling the dentures during use.

Question 18

Why is a balanced occlusion important and why is it debated?

Answer 18

• Errors in tooth positioning, like lingual overhangs, can destabilize the denture. A balanced occlusion reduces forces that might displace the denture, ensuring it stays seated properly.
• Some argue that natural chewing patterns do not always involve uniform contact on both sides, so its clinical significance may vary based on the patient’s specific needs and habits.

Question 19

What happens when there is a lingual overhang in tooth positioning?

Answer 19

Lingual overhangs can make dentures unstable, leading to compromised function and comfort.

Question 20

What aids can improve denture retention?

Answer 20

• Denture adhesives
• Linings
• Implants

Question 21

Summarize the key factors for achieving successful denture retention and stability.

Answer 21

• Good adaptation (good impressions)
• Good extensions (know your anatomy & look)
• Tooth position (over ridge on lower? crossbite)
• Muscle activity and denture shape
• Patient factors