Prosthodontics

Question 1

Definition of support ?

Answer 1

Resistance to occlusal directed forces towards the tissues.

Question 2

Definition of retention ?

Answer 2

Resistance to vertical displacing forces.

Question 3

Definition of indirect retention ?

Answer 3

Resistance to rotational displacement.

Question 4

Definition of path of insertion ?

Answer 4

Path the denture takes from first making contact with the teeth to then being fully seated.

Question 5

Definition of path of displacement ?

Answer 5

Direction of displacement during normal function.

Question 6

Definition of bracing ?

Answer 6

Resistance to horizontal functional forces.

Question 7

How do rests work ?

Answer 7

Transfer forces down the long axis of the tooth.

Question 8

Requirements for rests ?

Answer 8

To be large and placed centrally (on midline) on the tooth to ensure forces are transferred down the long axis of the tooth.
Shouldn’t interfere with occlusion so tooth preparation or be careful with positioning.

Question 9

How do clasps work ?

Answer 9

Terminal 1/3 of the clasp engages undercut - area below the maximum bulbosity of the tooth (0.25mm for CoCr).

Question 10

Clasps should …

Answer 10

• Sit passively when in situ in the undercut to prevent stress on the tooth.
• Should be 15mm long.

Question 11

Where are undercuts typically found on canines and premolars ?

Answer 11

Buccal or labial surface.

Question 12

Where are undercuts typically found in maxillary molars ?

Answer 12

Mesial/distal buccal surface - depending on the tooth in question.

Question 13

Where are undercuts typically found on mandibular molars ?

Answer 13

Mesial lingual surface.

Question 14

What is the purpose of a major connector ?

Answer 14

• Join all components of a denture.
• Extension of connector aids bracing.
• Can provide indirect retention.

Question 15

What is an RPI system ?

Answer 15

Stress relieving clasp system used on abutment teeth for free end saddles.

Question 16

What is the purpose of an RPI system ?

Answer 16

Prevent torquing and tilting of the abutment tooth on a free end saddle.

Question 17

What are the components of an RPI system ?

Answer 17

Mesial rest, proximal plate, I-bar gingivally approaching clasp.

Question 18

What is the purpose of the I-bar clasp and proximal plate in the RPI system ?

Answer 18

Move downwards and forwards in compressive forces allowing saddle area to sink into undercut, reducing stress on the abutment tooth.

Question 19

What is the requirements of the mesial rest in an RPI system ?

Answer 19

Should be rounded and prepared to allow rotation.

Question 20

What are the advantages of an RPI system ?

Answer 20

• Prevent torque of abutment tooth during compression of mucosa and free end saddle.
• Protects PDL and ultimate tooth loss.

Question 21

What are the disadvantages of an RPI system ?

Answer 21

• Creates windows for mesial rest which can cause food trapping.
• No limitation on free end saddle so can accelerate bone resorption.

Question 22

Kennedy classification I ?

Answer 22

Bilateral free-end saddle areas.

Question 23

Kennedy classification II ?

Answer 23

Unilateral free-end saddle area.

Question 24

Kennedy classification III ?

Answer 24

Bounded saddle.

Question 25

Kennedy classification IV ?

Answer 25

Anterior bounded saddle that crosses the mid-line.

Question 26

Craddock classification 1 ?

Answer 26

Tooth borne i.e. Kennedy Class III or IV unless bounded saddle is >3 teeth (Craddock class 3).

Question 27

Craddock classification 2 ?

Answer 27

Mucosa borne i.e. only full dentures.

Question 28

Craddock classification 3 ?

Answer 28

Mucosa and tooth borne i.e. Kennedy Class I and II and inc. Kennedy Class III if saddle area is greater than 3 teeth.