4 Components of RPD

Question 1

Components of an RPD (6)

Answer 1

1. Major connector
2. Denture base
3. Direct retainers
4. Indirect retainers
5. Guide planes
6. Minor connector

Question 2

The six components of an RPD provide what six features?

Answer 2

1. Support
2. Stability
3. Retention
4. Resistance
5. Reciprocation
6. Passivity

Question 3

Major Connector - Features (3)

Answer 3

1. Connect parts of prosthesis from one side of dental arch to the other
2. All other parts are directly/indirectly attached
3. Provides “cross-arch stability” and resists displacement from functional stresses

Question 4

Major Connectors - Single Palatal Bar - Bar is less than __ mm in width (half oval __ gauge thickness)

Answer 4

8 mm

Half oval 6 gauge thickness

Question 5

Major Connectors - Palatal strap - Strap is __ mm or greater in width and can be thinner (__ gauge)

Answer 5

8 mm

24 gauge

Question 6

Major Connectors - AP strap

- AP strap is minimum __ to __ wide and Lateral strap are __ to __ wide

Answer 6

AP strap: 8-10 mm

Lateral strap: 7-9 mm

Question 7

Major Connectors - at least __ mm away from free gingival margins

Answer 7

6 mm away

Question 8

Major Connectors - Palatal plate

• Recommended in Class __ RPD’s when canine or premolar is the most M/D? abutment
• Maximizes support and __

Answer 8

1. Class I RPD’s

2. Support and rigidity

Question 9

What major connector should be used as a last support?

• Why?
• What situations warrant its use?

Answer 9

1. Horseshoe / U shaped
2. Lacks rigidity and support
3. Great when inoperable torus or Kennedy Class III/IV

Question 10

Mand. Major Connectors: Lingual bar

• What shape is the bar and how tall?
• How far away from free gingival margin?

Answer 10

1. 1/2 pear shaped and 4 mm tall

2. 3-4 mm away from free gingival margin

Question 11

Sublingual bar

• What shape is the bar?
• Used when you have too much or too little distance to floor of mouth? How much?

Answer 11

1. 1/2 pear shape

2. Too little (less than 7-8 mm, because you need 4 mm from FGM)

Question 12

Lingual plate

• Used when you have too much or too little distance to FOM?
• What shape is the bar?
• You must have what design feature at the end of the plates?

Answer 12

1. Too little (less than 7-8 mm)
2. 1/2 pear shape
3. Rest seats at terminal ends of plate

Question 13

Cingulum bar (located on cingula of anterior teeth)
 - Indicated when? (3)

Answer 13

1. Indicated if too much blockout for lingual bar or if open embrasures of plate visible from anterior
2. Also indicated to avoid large inoperable lingual tori

Question 14

What mandibular major connector is used as a last resort?

Answer 14

Labial bar

Question 15

Requirements of a clasp assembly (6)

Answer 15

1. Support
2. Stability
3. Retention
4. Resistance
5. Reciprocation
6. Passivity

Question 16

Rest Seat Purpose (3)

• Provides __
• Maintains __ in their planned positions
• Maintains occlusal relationships by preventing __

Answer 16

1. Provide support
2. Maintains components in their planned positions
3. Maintains establish occlusal relations by preventing settling of the denture?

Question 17

Rest seats

• Outline is what shape?
• Width?
• Depth?
• Angle formed by occlusal rest and vertical minor connector should be greater/less than 90 degrees to direct forces where?

Answer 17

1. Rounded triangle
2. 2.5 mm width
3. 1.5 mm depth
4. Less than 90 degrees to direct along long axis

Question 18

Embrasure rests

- M-D dimension should be __ mm or big enough to hold two __ gauge wires

Answer 18

a. 2.54 mm

b. two 18 gauge wires

Question 19

Cingulum rests

• Incisors or Canines preferred?
• Keep far away or close to gingiva?
• Max or Mand canines have thin enamel?

Answer 19

1. Canines preferred
2. Keep close to gingiva
3. Mand canines have thin enamel

Question 20

Cingulum rests

• M-D dimension
• F-L dimension with __ depth

Answer 20

a. M-D: 2.5 to 3 mm

b. F-L: 2 mm with 1.5 mm depth

Question 21

Circumferential clasp - Adv (3) and Disadvantage (4)

Answer 21

1. Retentive, stable, simple
2. Covers more tooth than bar type, more metal display, adds bulky contour to tooth, and in 1/2 round profile, adjustments are difficult

Question 22

Ring clasp

• Infra or supra bulge
• Adv (1) and Disadvantages (3)

Answer 22

1. Supra
2. Flexibility due to greater length, must incorporate bracing strut to reduce flexibility, covers too much tooth structure

Question 23

Embrasure clasp

• Infra or supra bulge?
• Advantage (1)
• Disadvantages (4)
• Depth of prep

Answer 23

1. Supra
2. Allows cross-arch clasping when no mod. space
3. High failure rate, significant tooth reduction, opposing teeth frequently interfere, and requires rests on both teeth
4. 2.54 mm to fit two 18 gauge wires

Question 24

What clasps are great when the only available undercut lies close to the proximal plate?
- Disadvantages (4)

Answer 24

Reverse action clasp

1. Covers a lot of tooth structure
2. Food trap
3. Generally widens occlusal table
4. Unesthetic

Question 25

Bar clasp - Adv/disadv (2)

Answer 25

Adv: Less tooth coverage and more esthetic Disadv: Tissue undercuts may require a lot of blockout causing food trap - Length of clasp arm may be too flexible

Question 26

Utilization of an RPI changes the Class I lever to a Class __?

Answer 26

Class 2 lever

Question 27

RPI Designs - Kratovil | - Guide plane

Answer 27

Long guide plane, engaging as much tooth structure as possible

Question 28

RPI designs - Krol | - Guide plane

Answer 28

Guide plane contacts plate 1 mm of the gingival portion (approximately the junction of the occlusal and middle thirds of the crown)

Question 29

RPI designs - Demer | - Guide plane

Answer 29

Minimal guide plate prep and contacts 1 mm at height of contour (as occlusal as possible)

Question 30

RPA clasp (Eliason) - M/D rest? - What kind of clasp? - Used for Kennedy class? - Proximal 2/3rd of clasp arm MUST do what?

Answer 30

1. M rest 2. Aker's clasp 3. Kennedy Class I/II 4. 2/3rd of arm must be on height of contour

Question 31

Twin flex clasp - CC or WW? - Used in distal extension and/or tooth borne? - Kennedy class? - Disadvantage?

Answer 31

1. WW in 0.010"" 2. Tooth borne 3. Class IV, sometimes III 4. Difficult to adjust

Question 32

Features of ideal denture base material (9)

Answer 32

1. Tissue adaptation accuracy 2. Dense, non-irritating surface 3. Thermal conductivity 4. Low specific gravity 5. Sufficient strength 6. Easily kept clean 7. Esthetic acceptability 8. Future reline potential 9. Low initial cost

Question 33

Acrylic denture base (ANSI/ADA Spec #12) - Adv (2) - Disadv (4)

Answer 33

1. Able to reline and flanges can be contoured better | 2. No thermal conductivity, less wear/abrasion resistance, requires bulk for strength, porosity

Question 34

Metal denture base (ANSI/ADA Spec #14) - Adv (4) - Disadv (

Answer 34

1. Accurate, naturally cleaner, better thermal conductivity, less weight/bulk, acrylic retentive features 2. Poor esthetics, cannot reline