BBA Iind SEMESTER EXAMINATION 2008-09 s8

BDS II (Second) Prof. Annual Examination 2014-15

Course Code: BDS203 Paper ID: 0312403

Dental Materials

Time: 3 Hours Max. Marks: 70 Max Marks: 75

Note: Attempt all questions.

Part-A

1. What is the composition of dental ceramics? Explain how metal - ceramic bond is achieved, why does it sometimes fail? Compare the metal - ceramic prosthesis with all ceramic prosthesis. (8)

2. What are the ideal requirements of impression materials? Classify impression materials. Discuss in brief the elastomeric impression materials. (8)

3. Write short notes on: (3x3=9)

a) Compare acrylic resin and porcelain denture teeth

b) List various methods to minimize corrosion of dental alloy restorations

c) What are the advantages and disadvantages of self cure composite resins over light cure ones?

4. Select the best answer for each question:- (2x5=10)

i) Miracle mix contains:

a) 50% amalgam alloy powder + GIC powder.

b) 45% amalgam alloy powder + 55% GIC powder

c) 55% amalgam alloy powder + 45% GIC powder

d) Resin modified GIC

ii) Flow able composites:

a) Have reduced filler content

b) Are used in class II restorations with difficult access

c) Have high fracture toughness

d) All of the above.

iii) Hydrofluoric acid using for etching ceramics for repair is a highly corrosive acid . A topical antidote for HF on exposed skin is:

a) Calcium gluconate gel

b) Ammonium fluoride gel

c) Calcium fluoride gel

d) Sodium bicarbonate

iv) The heat treatment for release of residual stress in strained metal is known as:

a) Galvanization b) Coring

c) Annealing d) Glazing

v) Which of the following cement stimulates secondary dentin formation:

a) ZoE cement b) Ca (OH)2 cement

c) Silicate cement d) GIC

Part-B

1. What is delayed expansion in dental amalgam? Discuss all possible factors affecting the success of amalgam restorations in detail. (8)

2. Write composition, classification and indications for use of composite resins. Also discuss the steps in manipulation of composite resins in brief. (8)

3. Answer the following: (3x3=9)

a) How can back pressure porosity be prevented, during casting procedures?

b) What two properties of stainless steel wires make them quite popular in orthodontic practice?

c) Which dental cement carries the advantage of being anticariogenic? Give its ADA classification.

4. Select the best answer for each question:- (2x5=10)

i) Ortho ethoxy benzoic acid:

a) acts as an accelerator in ZOE impression paste.

b) acts as plasticizer.

c) is a valuable substitute for eugenol in non-eugenol impression paste

d) acts as filler in ZOE paste

ii) The crystalline form of hemihydrates is alpha – hemihydrates in:

a) Dental stone

b) Dental plaster

c) Die stone

d) Both (a) and (c)

iii) The impression material that shows the least dimensional change as a result of disinfection by immersion is:

a) Alginate

b) Addition silicone

c) Polyether

d) Agar – agar

iv) Which statement is true for light cure composites:

a) working time under control of operator

b) less porosity due to readymade mix

c) darker shades require more exposure time

d) all of the above

v) What is not true about direct filling gold:

a) it has excellent resistance to tarnish & corrosion

b) it is bio-compatible

c) very little marginal leakage if compacted well

d) low thermal conductivity so does not require thermal insulation