Bds2 Revision

Question 1

What is support?

Answer 1

Resistance of the denture to the occlusally directed load

Question 2

What are the 4 Kennedy classifications?

Answer 2

Class 1 - bilateral free end saddle
Class 2 - unilateral free end saddle
Class 3 - unilateral bounded saddle
Class 4 - anterior bounded saddle across midline

Question 3

What is retention?

Answer 3

Resistance of the denture to vertical displacement (away from tissues)

Question 4

What components of RPD provide support?

Answer 4

Rest seats (tooth support)
Mucosal support

Question 5

What are the 3 types of retention and how are they achieved?

Answer 5

Mechanical - clasps
Muscular - shape of denture to allow control eg enough room for tongue
Physical - mucosal coverage

Question 6

How are clasps successfully retained?

Answer 6

Clasp flexes over the maximum bulbosity of the tooth into the undercut (this force is greater than the force dislodging the denture)

Question 7

What is the minimum undercut and length for cobalt chrome clasp?

Answer 7

Undercut - 0.25mm
Length - 15mm

Question 8

What is the minimum undercut for a gold clasp?

Answer 8

0.5mm

Question 9

What is the minimum undercut for a stainless steel clasp?

Answer 9

0.75mm

Question 10

What are the components of an RPI?

Answer 10

Occlusal Rest (R)
Distal guide Plane (P)
Gingivally approaching I bar clasp (I)

Question 11

What is indirect retention? And how is it achieved?

Answer 11

Resistance to rotational displacement of the denture .

Clasps engage with rotational displacement, resulting in rests acting as a point of pivot.
Therefore move the point of pivot further away from clasp axis by using components which usually provide support.
eg. Cingulum rest on canine/ lingual plate

Question 12

Why is an occlusal rest recommended where placement of clasp?

Answer 12

To prevent the clasp sinking towards gingival margin

Question 13

Which part of the clasp engages in the undercut?

Answer 13

Terminal third

Question 14

What is reciprocation and why is it important?

Answer 14

Addition of a component to the opposite side of clasped tooth to resist horizontal load (or clasp can act as ortho appliance to move the tooth)

Question 15

What is the most favourable pattern of retention?

Answer 15

Triangular

Question 16

How much of a load can a healthy tooth carry?

Answer 16

It’s own load + one and a half similar teeth.

Depends on perio attachment

Question 17

How is mucosal support achieved?

Answer 17

By covering as large an area as possible (reduction from the occlusal table). B

Question 18

What are the areas of primary and secondary support in upper arch?

Answer 18

Primary- hard palate
Secondary - alveolar ridge, rugae

Question 19

What are the areas of primary and secondary support in the lower arch?

Answer 19

Primary - buccal shelf, posterior ridge, pear shaped pad
Secondary - anterior ridge, buccal sulcus

Question 20

Why is it better to have a larger rest seat?

Answer 20

Directs force down long axis of tooth rather than applying large forces per unit

Question 21

Where is a rest seat placed for a free end saddle and why?

Answer 21

Rest seat is placed mesial of tooth
Movement of the saddle can rotate towards tissue and cause stress of abutment tooth.

Question 22

What are the two types of connectors and their functions?

Answer 22

Minor- joins denture components eg rests to major connector
Major - joins componentes on each side of arch, provides bracing and indirect retention

Question 23

What are the 4 properties of minor connector design?

Answer 23

Should be rigid
Finish above the survey line
Cross the gingival margins at right angles
Cover as little gingival tissue as possible

Question 24

What are some major connector designs for upper arch?

Answer 24

Anterior plate
Mid palatal plate
Ring design (anterior and posterior design)
Horseshoe
Posterior bar

Question 25

What are some major connector designs in the lower arch?

Answer 25

Lingual plate
Lingual bar
Dental bar
Sublingual bar

Question 26

What are the advantages of plate major connectors?

Answer 26

Thinner in cross section (0.5mm)

Question 27

What is the advantage of a bar connector?

Answer 27

Less mucosal coverage

Question 28

How much space is required for a lingual bar connector?

Answer 28

8mm

3mm below gingival margin, height of bar is 4mm, 1mm clearance of floor of mouth

Question 29

What is RPI?

Answer 29

A stress relieving clasp commonly used in distal extension saddles.
Made up of a mesial rest, proximal guide plate, gingivally approaching I bar clasp.
Protects the abutment tooth as during occlusal load, the only component on the tooth is the mesial rest.