DMS

Question 1

what are some patient concerns about amalgam?

Answer 1

• aesthetics
• discolouration of tooth
• mercury poisoning
• metal allergy
• environmental impact
• pregnancy concerns

Question 2

what reassurance can you give pt about amalgam use?

Answer 2

• has been used for many years
• v effective in purpose
• metal compound so mercury not the same as in elemental state
• mercury in very small amounts

Question 3

what aspects of cavity prep allow for i) removal of all caries
ii)ensure restoration is fully cleansable

Answer 3

i) remove enamel to identify extent of lesion at adj and smooth enamel margins
progressively remove caries at adj and then circumferentially deeper. only then remove deep caries overlying pulp chamber.

ii) no overhangs, smooth margins, smooth occlusal surface

Question 4

describe the mechanism by which composite bonds to dentine

Answer 4

acid etch: dentine conditioner.

• removal of smear layer
• decalcifies dentine
• exposes collagen network

dentine bonding agent: bivalent molecule. hydrophilic end bonds to dentine through penetration and micromechanical retention into dentine tubules and collagen. hydrophobic end bonds to resin in adhesive

Question 5

What are the ideal properties of a denture base? (6)

Answer 5

dimensionally accurate
high softening temperature
high hardness
biocompatible
high thermal conductivity
easy/inexpensive to make and repair

Question 6

What are the constituents of PMMA?

Answer 6

powder -> benzoyl peroxide, PMMA particles, plasticisers, pigments, co-polymer
liquid -> methacrylate monomer, hydroquinone, co-polymer

benzoyl = initiator
hydroquinone  = inhibitor

Question 7

Give 4 possible faults during production of acrylic baseplate and explain why they occur?

Answer 7

contraction porosity - too much monomer
gaseous porosity - monomer boiling in thicker areas
granularity - too little monomer
crazing- cooling too quickly, internal stress caused

Question 8

4 advantages of CoCr as a denture baseplate

Answer 8

high softening temperature
high thermal conductivity
high youngs modulus YM -rigid
radiopaque

Question 9

Give 4 disadvantages of CoCr as a denture baseplate

Answer 9

aesthetics
costly to make
difficult to modify
difficult to make

Question 10

What undercuts are required for SS, Gold and CoCr clasps?

Answer 10

0. 75 SS
1. 5 gold
2. 25 CoCr

Question 11

What are the ideal properties of an impression material? (6)

Answer 11

no dimensional change
high wettability
high surface reproduction
high tear strength
good operator convenience
acceptable taste and smell
biocompatible
compatible with lab materials/ gypsum

Question 12

Name 2 non elastic impression materials

Answer 12

impression compound

impression paste

Question 13

Give 4 types and names of elastomers

Answer 13

• polyether - impregum
• addition silicones - PVS
• condensation silicones - lab putty
• polysulfide -

Question 14

Name 2 hydrocolloids

Answer 14

agar

alginate

Question 15

Constituents of alginate

setting reaction

Answer 15

sodium alginate, calcium sulphate, trisodium phosphate

sodium alginate + calcium sulphate -> sodium sulphate + calcium alginate

Question 16

2 pros and 2 cons alginate

Answer 16

:)
cheap
user friendly
high elasticity

:(
poor tear strength
poor storage - imbibition and syneresis

Question 17

2 uses alginate

Answer 17

primary imps dentures
imps for study models
wash impression

Question 18

3 advantages elastomeric impression materials over alginate

Answer 18

better tear strength
better accuracy
better surface reproduction
better storage - does not dry out

Question 19

Pros of using RMGI as liner over GI liner

Answer 19

on demand set
higher mechanical strength
lower solubility

Question 20

What is different about GI used for restorations over GI used as luting cement

Answer 20

shorter working time in filling GI

Question 21

Luting cement used for metal post core

Answer 21

GI luting cement

Question 22

Luting cement used for porcelain veneer

Answer 22

resin luting cement w/ silane coupling agent

Question 23

Luting cement used for carbon fibre post

Answer 23

DUAL CURE comp resin cement

Question 24

Ideal properties of luting cements (6)

Answer 24

high tensile strength
high compressive strength
easy to use
thickness <25 microns
RADIOPAQUE
low solubility
CARIOSTATIC

Question 25

Negative of RMGI as luting cement

Answer 25

HEMA absorbs water + swells

cytotoxic to pulp

Question 26

Process of bonding porcelain veneer?

Answer 26

etch with hydrofluoric acid, then use silane coupling agent to allow c=c bonds with comp resin cement

hydrophobic c=c from c-oh hydrophilic

Question 27

Process of bonding non-precious metal?

Answer 27

sandblast with aluminium oxide

use MDP or 4META

Question 28

Components of temp bond

Answer 28

ZOE based

base - zinc oxide, starch, mineral oil
accelator - EBA, eugenol, carnuba wax

Question 29

How is zirconia retained?

Answer 29

micromechanical retention

cannot be etched therefore cannot be chemically bonded

Question 30

Pros of lithium disilicate crowns

Answer 30

crystals stop crack propagation
high flexural strength

used for posterior crowns

Question 31

Why apply vaseline on top of GI restorations

Answer 31

after hardening, fresh cement is highly prone to crazing and cracking due to drying of loose water particles.