Biomechanics of Complete Denture

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Questions and Answers

What does retention in complete dentures primarily refer to?

The ability to remain stable during chewing

The horizontal stability of the denture

The resistance to removal away from the tissue (correct)

The support provided to the jaw

Which factor does NOT affect the stability of a complete denture?

Size of the denture bearing area

Resistance to vertical forces

Quality of the denture bearing area

Viscosity of saliva (correct)

Which anatomical feature leads to greater retention in complete dentures?

Larger denture bearing area (correct)

Higher quality tissue in the bearing area

A smoother denture surface

Increased viscosity of saliva

How does saliva contribute to the adhesion of complete dentures?

By forming a thin film between mucosa and denture Signup and view all the answers

What is the role of cohesion in the context of complete dentures?

It acts within the film of saliva to enhance stability Signup and view all the answers

What happens when more tissue is displaced during the impression making process for a denture?

Retention may be compromised during denture use Signup and view all the answers

Which of the following factors can lead to compromised retention in complete dentures?

Ropy saliva accumulation between tissue and denture Signup and view all the answers

What does support in complete dentures refer to?

Resistance to vertical forces from occlusion Signup and view all the answers

How does atmospheric pressure assist in the retention of dentures?

It acts to resist dislodging forces applied to dentures. Signup and view all the answers

Which factor is directly proportional to the retention produced by atmospheric pressure?

Denture base area Signup and view all the answers

What is the function of the peripheral seal in denture retention?

It prevents air entry between the denture and soft tissue. Signup and view all the answers

Under which condition will unilateral undercuts aid in denture retention?

When the ridge is not resorbed Signup and view all the answers

Which type of denture adhesive is NOT mentioned as a form of denture adhesive?

Tablets Signup and view all the answers

What has led to the avoidance of suction chambers in modern maxillary dentures?

Risk of palatal hyperplasia Signup and view all the answers

Which aspect is NOT important for the vertical height of the residual ridge to ensure good denture stability?

Shape of the denture base Signup and view all the answers

What should an accurate impression do for achieving good denture stability?

Duplicate all details without voids Signup and view all the answers

Study Notes

Biomechanics of Complete Denture

The presentation discusses the biomechanics of complete dentures, covering retention, stability, and support, and factors influencing all three.

Retention

Retention is the resistance to removal in the opposite direction of insertion (vertically, away from tissues).

Stability

Stability refers to the denture's ability to withstand horizontal forces, providing firm and steady support during functional use. It accounts for resistance to both horizontal and rotational forces.

Support

Support is the resistance to vertical forces of mastication, occlusal forces, and other forces directed towards the denture bearing area . Forces are ultimately transmitted through the mucosa and supported by bone.

Factors Affecting Retention, Stability, and Support

Presented factors impacting these elements are categorized as:
- Anatomical factors
- Physiological factors
- Physical factors
- Mechanical factors
- Neuromuscular factors

1- Anatomical Factors

A- Size of the denture-bearing area: Larger areas generally provide greater retention. The maxillary denture covers approximately 24cm², while the mandibular covers roughly 14cm².
B- Quality of the denture-bearing area: Retention is influenced by how easily tissues can shift, affecting how the denture adheres. Displaced tissues during impressions can lead to rebound and loss of retention.

2- Physiological Factors

Saliva viscosity significantly impacts retention. Sticky saliva tends to accrue between the denture and palate, hindering retention. Conversely, thin saliva can compromise retention.

3- Physical Factors

A- Adhesion: The attractive force between unlike molecules is crucial; saliva plays an important role, wetting tissue surfaces and attaching the denture to the mucosa. Adhesion proportionally matches the denture base area.
B- Cohesion: The force holding like molecules together, within the saliva film, enhances retention, and effectiveness increases with broader denture-bearing areas.
C- Interfacial surface tension: This property resists the separation of liquids between well-fitted surfaces. A well-fitting denture base and mucosa maximize this force. Palate shape (high/vaulted vs. flat) affects how easily the denture might shift.
D- Atmospheric pressure and peripheral seal (intimate contact): Effective border seals use atmospheric pressure to resist dislodging forces, with greater retention proportional to a larger denture base area.
peripheral seal: The contact area between the denture borders and surrounding tissues prevents air pockets forming.

4- Mechanical Factors

A- Undercuts: A unilateral undercut can enhance retention, but bilateral undercuts prevent insertion requiring surgical correction.
B- Magnetic forces: Intra-mucosal magnets assist retention for extremely resorbed ridges.
C- Denture adhesives: creams, gels, or powders applied to tissue prior to denture placement increase adhesion/cohesion, reducing voids between the denture base and the underlying tissues.

5- Neuromuscular Factors

Muscles, such as buccal and tongue muscles, assist in holding the denture in place.
Best retention is achieved when the artificial teeth align with the neutral zone to balance the muscular forces.
Occlusal plane should be parallel to the ridge to prevent reduced stability from sliding forces.

Factors Affecting Complete Denture Stability

1-Vertical height of the residual ridge: Sufficient vertical height is essential for stability. Resorbed ridges offer reduced stability.
2-Quality of soft tissue: A firm soft tissue base improves stability. Adequate sub-mucosal tissue is also crucial.
3-Quality of the impression: Impressions should be precise, smooth, and void-free.
4-Occlusal plane orientation: Parallel alignment with the ridge resists lateral forces thus enhancing stability.
5-Arrangement of teeth: Balanced occlusion distributes forces evenly. Teeth should ideally be positioned in the neutral zone.
6-Contour of polished surfaces: Smooth surfaces prevent interference with oral musculature movements.

Support of Complete Denture

The resistance to vertical forces, like mastication and occlusal forces, is considered as support. The forces are transmitted via the mucosa and supported by bone.
Factors influencing support include anatomical and histological ridge characteristics. The pressure distribution along the ridge during impression procedures significantly influences support. Adequate coverage maximizes force distribution, distributing forces throughout a large area.

Factors Affecting Support of Complete Denture

Ridge shape and density (anatomical and histological characteristics).
Pressure distribution during impression procedures.
Denture's coverage and wide distribution of forces.
Compact bone support covered with fibrous connective tissue.

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Description

This quiz explores the essential concepts of biomechanics related to complete dentures, focusing on the aspects of retention, stability, and support. Dive into the factors that influence these characteristics and their implications for effective denture functionality. Test your understanding and application of these principles in dental practice.