RPD design

Question 1

What is the system of design for RPDs?

Answer 1

Saddles
Support
Retention
Bracing and reciprocation
Connector
Indirect retention
Review of denture design

Question 2

What is an RPI?

Answer 2

Stress-relieving clasp system used in free-end mandibular saddles
R - rest mesial to saddle area
P - proximal guide plate
I - I-bar gingivally approaching clasp

Question 3

What is BRACING?

Answer 3

When denture is fully seated, components that prevent horizontal movement. Can usually be offered from acrylic denture base during lateral excursion movements

Question 4

What is RECIPROCATION?

Answer 4

Resistance to pressure from clasp arms acting to move the tooth. Offered by reciprocating clasp arm on opposite side of tooth to retentive clasp engaging undercut.
Occurs when when retentive clasp is moving over the bulbosity of the tooth e.g. during insertion and removal

Question 5

What is a benefit of a ring connector?

Answer 5

Less coverage on the palate - good for first-time denture wearers as more tolerable
Touches the palatal part of anterior teeth - can easily add teeth if patient loses any more

Question 6

What is a benefit of a palatal strap major connector?

Answer 6

Better for periodontally involved teeth

Question 7

How much height and width is required for a lingual bar and why?

Answer 7

7mm total height
lingual bar is 4mm in height and must be 3mm away from the gingivae

2mm thickness

Question 8

What is a disadvantage of a lingual bar?

Answer 8

Can’t add teeth on
Quit invasive down into FOM
May interfere if patient has tori

Question 9

What size of undercuts do you need for gold, CoCr, and stainless steel respectively?

Answer 9

Gold - 0.75mm
CoCr - 0.25mm
Stainless steel - 0.5mm

Question 10

What is a galvanic reaction and what is the solution to this problem?

Answer 10

When you’ve got 2 metals against each other - e.g. gold clasp on buccal amalgam filling - gives patient zingy feeling due to electrical currentdue to difference in metals corrosion potentials

Change either the clasp to acrylic or the filling to composite

Question 11

What is the minimum length of clasp arm for CoCr?

Answer 11

15mm

Question 12

What is the minimum length of clasp arm for stainless steel and gold?

Answer 12

7mm

Question 13

If a clasp snapped off your patient’s partial denture and you wanted to add a new one without re-making the whole denture how would you do it?

Answer 13

Take alginate impression with denture in situ. Leave denture in impression if comes out with it - send to lab and they with add

Question 14

Give examples of supporting areas in the maxilla?

Answer 14

Rugae
Posterior palate
Maxillary tuberosity

Question 15

Give examples of supporting areas in the mandible?

Answer 15

Buccal shelf
Alveolar ridge

Question 16

When in function what features of the RPI prevent the FES from damaging the periodontium of the tooth?

Answer 16

The rest mesially acts as an axis of rotation.
As the proximal plate and I bar
rotates downwards and mesially around the axis of rotation during occlusal load.
The I bar and proximal plate disengage from the tooth/undercuts, thus avoiding
potentially traumatic torque.