Dierct Retainer

Question 1

Factors that determine the amount of retention provided by a particular clasp arm

Answer 1

1. Size of angle of cervical convergence (depth of undercut).
2. How far into the angle of cervical convergence the clasp arm is placed .
3. Flexibility of the clasp arm

Question 2

Contraindications of lingual bar

Answer 2

1.Limited space (less than8mm)

2. Only a few remaining anterior teeth which must be contacted to provide a reference for fitting the framework and indirect retention.
3. Lingually inclined teeth.
4. An undercut of lingual alveolar ridge which would
   result in an excessive space between the bar and mucosa.

Question 3

Purposes of beading:

Answer 3

1. To transfer the major connector design to the investment cast
2. To provide a visible finish line for the casting
3. To ensure intimate positive tissue contact of the major connector with the palatal tissue
4. To reduces food impaction beneath the major connector
   On maxilla only

Question 4

is a mixture of acetone, diethyl phthalate, and cellulose acetate
* Cast must be allowed to dry for a minimum of 5 minutes
Purposes:
1. To seal the cast
2. To protect the design throughout the blockout and duplication procedures

Answer 4

Spraying by surface sealer

Question 5

Arbitrary block out

Answer 5

All gingival margins.
• Spaces between the teeth.
• Tissue undercuts situated below areas involved in the design of denture framework.
• Tissue undercuts distal to the cast framework.
• Labial and buccal tooth and tissue undercuts not involved in denture design.

Question 6

Shaped blockout (ledging)

Answer 6

On buccal and lingual surfaces used as guiding planes. to locate wax patterns for clasp
arms.

Question 7

Proximal tooth surfaces to be

used as guiding planes.
• Beneath all minor connectors.
• Tissue undercuts that are crossed by rigid connectors.
• Tissue undercuts that are crossed by bar clasps.
• Deep interproximal spaces to be covered by minor connectors or
linguoplates.

Answer 7

Parallel blockout

Question 8

Relief only in

Answer 8

Mandibles

Beneath lingual bar connectors

Areas in which major connectors will contact thin tissue.

Beneath framework extensions onto

Question 9

§ It provides stability of the framework during acrylic resin processing

Answer 9

Tissue stop

Question 10

I. Steps Master cast preparation

Answer 10

1. Draw the design on the master cast
2. Beading of maxillary major connector
3. Spraying
4. Blockout
5. Relief

Question 11

Refractory materials (investments) used in RPD frameworks

Answer 11

Phosphate-bonded refractory materials (high heat investments)

1,037°C (1,900°F)
Require a special, silica-containing liquid to mix with the refractory powder

Question 12

Laboratory steps 8

Answer 12

I. Master cast preparation

1. Draw the design on the master cast 2. Beading of maxillary major connector 3. Spraying 4. Blockout 5. Relief

II. Duplication
III. Refractory cast
IV. Wax pattern for the framework
V. Spruing the framework
VI. Investing the refractory cast and burnout
VII. Casting
VIII. Finishing and polishing of the framework

Question 13

Purposes of spruing:

Answer 13

1. Provide a channel for molten metal to enter the cavity of investment mold during casting procedure
2. Provide a channel for the escape of gases and debris during burnout procedure