PRS03 - Lecture 10 - Denture Design Flashcards by Chase B

What are the different kennedy classes?

Kennedy Class I - Bilateral free-end saddles

Kennedy Class II - Unilateral free-end saddle

Kennedy Class III - Unilateral bounded saddle

Kennedy class IV - Anterior bounded saddle (no mods possible)

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Identify the classification of the picture below:

Kennedy Class I Modication I

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Identify the classification of the picture below:

Kennedy Class II Modification I

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Identify the classification of the picture below:

Kennedy Class III Modification I

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What are the 3 support classifications?

Class I - Tooth Supported

Class II - Tissue supported

Class III - Tooth and tissue supported

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What are the functions of rest seats? (2)

Vertical support

Direct functional forces to the long axis of the tooth

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What are the 2 types of rest seats?

Occlusal

Cingulum

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What are major connectors? (3)

Rigid connector that crosses palatally or lingually

Unites and stabilises parts of the prothesis on either side of the arch

By rigid x-arch construction

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What are the 4 types of maxillary major connectors?

Strap

Horseshoe

Plate

Ring

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What are the 4 types of mandibular major connectors?

Lingual bar - pear shaped in cross section

Lingual plate

Buccal bar - labial/buccal sulcus (used when you have lingual undercuts or lingual tori)

Dental bar

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When should you use a lingual bar (over a plate)? (4)

2mm = from gingival margin -> top of bar

2mm = bottom of bar -> lingual sulcus

4mm = depth of bar

8mm = minimum space required from gingival margin -> depth of lingual sulcus

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When would you use a buccal bar?

Lingual tori

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What are minor connectors? (1)

Strong rigid part of the denture that connects other units to major connector

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Give an example of a minor connector

Proximal plate - contacts the guide planes enabling the denture to follow the path of insertion

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What is the function of retainers?

Components that help prevent displacement when under occlusal or masticatory load

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What is retention? (1)

Resistance to vertically displacing forces

Where is direct and indirect retention obtained from? (2:5)

Direct retention (2)

Clasps (predominantly)

Tissue undercuts

Indirect retention (5)

Continous clasp (kennedy bar) - prevents forward rotation

Cummer arm (on canines) - prevents forward rotation

Occlusal rest

Major connector

Denture flange

What is indirect retention? (2)

Extention of the denture base that prevents displacement of the RPD through rotation

Considered for all cases but particularly for kennedy class I and 2 arches

How would you determine where indirect retention will come from? (3)

Pass a line through tips of most anterior and posterior clasps on opposing sides of the arch

Bisect the line (90^o) on opposite side of the arch to the free end saddle

Saddles cannot be displaced by forward rotation due to diagonal opposing contact with natural tooth

What is denture base retention? (2)

Strong, rigid support for attachment of acrylic resin portion that carries artificial teeth

Retention is entirely mechanical

What is denture base material? (2)

Part of the denture that rest on oral mucosa (where there are missing teeth)

Functions to: (3)

Support artificial teeth in desired position

Unite metal base with artificial teeth

Restores contour where natural tissues are lost

What are the 3 components of a clasp?

Retentive

Support

Bracing

What are the different types of clasps? (3:3)

Occlusal approaching clasps

C (or semi-encircling)

Ring (or fully-encircling)

Recurve arm

GIngival approaching clasps

I bar

T (roach)

1/2 T (one armed T roach)

What determines clasp you would use? (4)

Survey lines (4)

High (very deep undercut) -> requires high flexibility class type

Medium -> occlusal + gingival approaching clasps

Low (little or no usable undercut) -> cant use gingival approaching clasps because it would be too close to soft tissues. You can either:

Add composite to create undercut

Create dimple preparation

Diagonal -> suitable for either type of clasp

Describe the arm of an occlusal approaching clasp (2)

**Terminal 1/3** of clasp arm engages with the **undercut area** (retentive) **Remaining 2/3 of** clasp arm lies **on or above** the survey line (non-retentive)

Describe the arm of a gingival approaching clasp (2)

**Whole arm** of clasp is **beneath** the survery line **Terminal tip** is the only part that is in **contact** with tooth

What is the function of the bracing component of the clasp? (4) ## Footnote *(green)*

**1**) When the denture is placed **under load** -\> _retentive_ portion of clasp **flexes** **2**) This will exert **pressure** on tooth -\> possible **movement of teeth** **3**) The bracing component **counters** this movement - action is known as **reciprocation** **4**) This effect can also be provided by the **non-retentive part of the clasp**

What materials are used for clasps? (4)

**Gold** - cast or wrought **Cobalt-chrome** - cast or wrought (wiptam) **Stainless steel** (**SS**) - wrought **Acetyl resin** (dental D)

What are the properties of acetyl resin (dental D) clasps? (5)

Flexible Aesthetic (tooth coloured) Brittle Need to be thick in cross-section Expensive

How does the cross-section of occlusal and gingival approaching clasps differ?

**Occlusal approaching** - D-shape (flat surface against tooth) -\> ↑ Rigid **Gingival approaching** - O-shape (only tip in contact with tooth) -\> ↑ Flexible

Compare the flexibility (modulus of elasticity) of the different clasp materials (6) ## Footnote *(highest to lowest)*

**Wrought gold** **Wrought S.S** **Wrought Co-Cr** **Cast gold** **Cast Co-Cr**

What undercut gauge should be used for the different clasp materials (4)

**Wrought gold** -\> 0.75mm **Wrought S.S** -\> 0.5mm **Wrought Co-Cr** -\> 0.5mm **Cast Co-Cr** -\> 0.25mm (occlusal approaching) + 0.5mm (gingival approaching)

Why should you use a 0.25mm undercut gauge for occlusally approaching Co-Cr clasps that have mesial and distal occlusal rests? (2)

Addition of distal rest ↓ flexibility of clasp by 50% Retentive arm becomes stiffer