Occlusion for partial dentures; Problem denture design

Question 1

Define “occlusion” as per the Glossary of Prosthodontic Terms.

Answer 1

Occlusion is the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or their analogues.

Question 2

Compare Intercuspal Position (ICP) and Retruded Contact Position (RCP) in terms of stability, reproducibility, and anatomical dependence.

Answer 2

ICP:

Best fit of teeth, regardless of condylar position

Tooth-determined position

Stable if sufficient index teeth

May change over time

RCP:

Most retruded position of condyles in joint cavities

Condyle-determined, not tooth-dependent

Most reproducible position

Useful when occlusion is unstable or lacks index teeth

Question 3

What are “index teeth” and why are they important in partial denture occlusion?

Answer 3

Index teeth are teeth with contacting facets in the ICP. They are essential for establishing a stable and reproducible occlusal relationship, especially in conforming to existing occlusion.

Question 4

Differentiate between conforming and changing occlusal schemes in RPD fabrication.

Answer 4

Conforming:

Used when stable ICP exists with sufficient index teeth

Aim is to maintain existing occlusion

ICP is usually used

Changing:

Necessary when occlusion is unstable or index teeth are insufficient

Often use RCP as reference

Requires more challenging occlusal records

Question 5

List and describe three types of interocclusal records used for recording occlusion.

Answer 5

Bite Registration Paste: Silicone-based material, accurate and easy to use.

Wax Wafer: Traditional modelling wax, easy to adapt.

Modified Wax Wafer (e.g., Alminax): More rigid/stable, can better resist distortion.

Question 6

Describe how articulated study casts can differ depending on the presence or absence of sufficient teeth.

Answer 6

Sufficient index teeth: Casts may be articulated without a formal interocclusal record.

Insufficient index teeth: Require use of record blocks to accurately register occlusion.

Question 7

How are record blocks fabricated and adjusted in the clinic?

Answer 7

Fabricated in the lab to standard sizes using wax

Adjusted chairside using wax knives, hot plates, or heat to accurately record jaw relationships.

Question 8

List two alternatives to wax record blocks for recording occlusal registration.

Answer 8

Melted Wax: Manually adjusted molten wax applied for registration.

Bite Registration Paste: Used instead of wax for a faster, cleaner technique.

Question 9

How does modifying the survey line improve denture design?

Answer 9

By altering the contour of tooth surfaces (e.g., with composite), the survey line is shifted to enable better clasping, which enhances retention and stability.

Question 10

What are precision attachments, and what is an example?

Answer 10

Precision attachments are mechanical devices (usually intra-coronal or extra-coronal) used for retention and support.

Example:

Ball on post (fixed to tooth)

Diaphragm or socket in denture receives the ball

Variants: Tubelock attachments

Question 11

What are the advantages and disadvantages of precision attachments?

Answer 11

Advantages: Improved aesthetics and retention

Disadvantages: Technically demanding, difficult to repair or replace

Question 12

Describe a two-part denture and its indication.

Answer 12

A two-part denture is used when there is gross soft tissue loss or different paths of insertion.

First part: Cobalt-chrome base with split pins

Second part: Acrylic portion slots into pins following a separate path

Question 13

Explain how a swinglock denture functions and its main considerations.

Answer 13

Utilizes a labial or buccal swinglock bar to engage undercuts on both hard and soft tissues for retention

Has a hinge and locking mechanism

Allows use in cases with poor abutment teeth

Requires excellent oral hygiene

Technically complex to fabricate

Question 14

When is a connector for lingually tilted teeth indicated, and what is a design solution?

Answer 14

Used when teeth are severely lingually inclined, making conventional clasping difficult

Solution: A buccal bar connector can be used to avoid impinging on the tongue space while engaging undercut

Question 15

How can dentures be modified for bruxist patients?

Answer 15

Use metal backing on teeth to improve durability

Cross-linked acrylic teeth for better wear resistance

Cobalt-chrome frameworks to resist fracture

Add metal occlusal surfaces

Incorporate acrylic postdam to increase retention