Week 5 - Extra RPD components - Clasps

Question 1

What are the 2 types of supra bulge clasps (approaches from the occlusal side)

Answer 1

1. Circumferential (3 arm/Akers) Clasp
2. Ring Clasp

Question 2

What is a circumferential (3 arm/ Akers) Clasp

Answer 2

• most common
  Has 3 components
  1. Occlusal rest
  2. Retentive arm - goes on the undercut
  3, Reciprocal arm

Question 3

What is a ring clasp

Answer 3

Begins from an occlusal rest (usually mesial) then the clasp arm wraps almost 360 degrees around the tooth, and ends in a retentive tip that engages the undercut (often on the mesiolingual side)

Question 4

What are advantages of ring clasps

Answer 4

• Excellent bracing (with support strut)
• Allows use of an available undercut adjacent to edentulous area

Question 5

What are disadvantages of ring clasps

Answer 5

• covers a large around of tooth structure
• high risk of occlusal interference
• very difficult to adjust
• the lower bracing arm should be at least 1mm from the free gingival margin

Question 6

What should supra bulge clasp be used + exceptions for use

Answer 6

Should be used in most tooth borne cases except

Exception
1. Aesthetic concerns
2. Where a posterior abutment is mobile or of questionable prognosis
3. Length of retentive arm is not enough to provide required flexibility

Question 7

What is a RPI clasp

Answer 7

• Type of infrabulge clasp
• design is to protect the abutment tooth and allow some movement of the denture base

components
- rest (typically a mesial occlusal rest)
- proximal plate (contacts the distal guiding plane on the abutment tooth)
- I bar (gingivally approaching retentive arm that engages the buccal undercut)

Question 8

What is an indirect retainer

Answer 8

A part of a removable partial denture that prevent rotational displacement of the denture about the rest of the principal abutment teeth

Indirect retainers usually take the form of rests, on the opposite side of a fulcrum of rotation

Question 9

How do you know which tooth would have an indirect retainer

Answer 9

Draw a straight line between the most posterior teeth on either side of the arch then draw a perpendicular line in the middle - its the teeth which a line with this perpendicular line

Question 10

What are functions of rests (4)

Answer 10

• provide vertical support
• maintains designed position of RPD components
• maintains occlusal relationship by preventing settling of the denture into the soft tissue
• prevents impingement of soft tissue

Question 11

What are 3 types of rests

Answer 11

• occlusal rest
• cingulum rest
• incisal rest

Question 12

What is a occlusal rest

Answer 12

Small metal extension that sits on the occlusal surface of a posterior tooth (premolar, molar)

Question 13

What is a cingulum rest

Answer 13

Metal extension which sits on the cingulum area of anterior teeth

Question 14

What are incisal rests

Answer 14

metal extension that sits on the incisal edge of an anterior tooth