Aesthetic Restorative Materials

Question 1

Direct Aesthetic Restorative Materials
Should be

Answer 1

radiopaque to enable detection of secondary caries, identification of overhang ledge and detection of incompletely filled cavities.

Question 2

Lower initial pH in silicate cements , why ?

Answer 2

pulpal protection was required to minimize the irritation

Question 3

Unfilled Acrylic Polymers, Early clinical failure of this material is ..

Answer 3

dimensional instability
(high polymerization shrinkage and thermal dimensional changes).

Question 4

Unfilled Acrylic Polymers
Compositions:

Answer 4

Powder: polymethyl meth-acrylate, initiator benzyl
peroxide and pigment.

Liquid

Question 5

Unfilled Acrylic Polymers
Disadvantage

Answer 5

cause pulpal irritation
Mechanical properties are poor.

Question 6

Composite is

Answer 6

a combination of two or more chemically different materials

Question 7

Composite Compositions

Answer 7

1. Organic matrix .
2. Inorganic filler.
3. Coupling agent binds the inorganic filler to the organic matrix.
4. Initiator activator system.
5. Inhibitor.
6. Ultraviolet.
7. Pigments.

Question 8

Organic matrix consist of

Answer 8

A. high molecular weight monomer (oligomer)
B. Diluents (lower molecular weight monomers)
high molecular weight monomer (oligomer)
1. bisphenol A-glycidyl methacrylate (BIS-GMA)
2. Urethane dimethacrylate (UDMA).

Question 9

Oligomer product are superior to methyl methacrylate monomers by

Answer 9

1. Lower polymerization shrinkage
2. Lower volatility.
3. More rapid hardening.
4. Production of stiffer and stronger resin

Question 10

The urethane dimethacrylates are superior to BIS-GMA by

Answer 10

I. lower viscosity.
II. Lower water sorption.
III. Greater toughness.
IV. Greater susceptibility to visible light curing

Question 11

Diluents , These monomers are included in composite formulation to

Answer 11

reduce the viscosity , and to facilitate clinical manipulation.

Question 12

Modification of resin composite have been made in order to
………of resin such as……

Answer 12

minimize polymerization shrinkage , Ormocers (organic modified ceramic)

Question 13

Silorane (low shrinkage composite)
In this composite, polymerization occur by…..

Answer 13

ring opening polymerization

Question 14

 quartz.
 Borosilicate glass.
 Lithium aluminum silicate.
 Barium aluminum silicate.
 Strontium.
 Colloidal silicate.
These elements contribute to

Answer 14

radiopacity

Question 15

Role of inorganic filler

Answer 15

1- mechanical properties such as compressive strength,
modulus of elasticity and hardness .
2. Reduction in coefficient of thermal expansion.
3. Glass is able to reflect the color of surrounding tooth material
4. Reduction in polymerization shrinkage.
5. Less heat evolve
6. The composite is radiopaque if barium or strontium glasses are used.

Question 16

Classification of composite according to filler

Answer 16

:
1. Smaller filler particles as fine particles (0.5-3µm).
2. Very small micro-fine particles (0.04-0.2µm).
3. Blend (hybrid) containing mixture of (fine and micro-fine).
4. Finally nano-filled composite (2-75nm)

Question 17

Fillers are treated by…..
this compound has two functional group ……….and…..

Answer 17

silane coupling agent

an inorganic group that react with the filler

an organic group that react with the organic matrix

Question 18

The use of coupling agent

Answer 18

1. Improve the mechanical properties of composite by
   transferring the stress from the weak resin to the stronger filler.
2. Reduces early loss of the filler caused by penetration of
   water between resin and filler.

Question 19

chemical activation: (two paste system) in two component chemically polymerized one paste contain …

Answer 19

initiator (benzyl peroxide), the other paste contains activator (tertiary amine).

Question 20

Plastic spatula used instead of metal , Why ?

Answer 20

Metal spatula should not be used since they are easily abraded by the hard fillers of composite and cause discolouration

Question 21

Blue visible light radiations are about

Answer 21

470nm

Question 22

Initiator of chemical cured system is ….
And activator is …

Answer 22

Benzoyl peroxide

Tertiary amine

Question 23

Initiator of Light-cured system is ….
And activator is …

Answer 23

camphorquinon , Aliphatic Amine

Question 24

Disadvantages of light cure are

Answer 24

requiring build up layers of 2mm or less

Poor accessibility in certain posterior and interproximal areas

High cost

Question 25

Factors effecting Depth of cure

Answer 25

1. Shade of composites, darker the shade the longer the exposure time 2. The intensity of light is inversely proportional to the distance (the source be held within 1mm from the surface) 3. The time of exposure not be less than 40 second 4. Each increment of the restoration 1.5-2 mm thick should be cure before another layer 5. Filler size and filer concentration effecting light penetration 6. The concentration of photoinitiator

Question 26

Inhibitors

Answer 26

Hydroquionone, widely used but responsible for causing discoloration. Mono-methyl ether of hydroquinone is now used .

Question 27

Classification according to particle size, shape and distribution

Answer 27

a. Fine composite. b. Micro-fine composite. c. Hybrid composite. d. Nano composite.

Question 28

Composite solubility

Answer 28

very low solubility , lower than the solubility of unfilled acrylic due to loss of residual monomer from acrylics .

Question 29

Thermal conductivity of composite

Answer 29

lower than those for metallic restoration, composite provide good thermal insulation for the dental pulp.

Question 30

Composite materials undergo shrinkage during polymerization , is direct function of

Answer 30

organic matrix

Question 31

Polymerization shrinkage can be reduced by

Answer 31

1. Incremental addition 2. Obtain strong bond between composite filling and the enamel 3. Composite inlay :polymerization of composite outside or inside pt. mouth

Question 32

Aesthetic and Optical properties

Answer 32

can be radiopaque by addition of glasses (barium, strontium and zirconium)

Question 33

Bonding is obtained by

Answer 33

mechanical retention to acid - etched enamel.

Question 34

Bonding agents usually consist of

Answer 34

BIS - GMA or UDMA

Question 35

The most frequently used etchant is

Answer 35

37 % phosphoricacid

Question 36

phosphoricacid MODE OF ACTION ON ENAMEL

Answer 36

1. It creates micro-porosities 2. Etching increases the surface area 3. enamel has a high surface energy, allowing the resin to wet the tooth surface better and penetrate into the micro-porosities.

Question 37

etchant When polymerized, it forms

Answer 37

resin “tags’ which forms a micromechanical bond to the ename

Question 38

EVOLUTION OF DENTIN BOND AGENTS THE VARIOUS GENERATIONS are

Answer 38

First generation , second and third generations had the main problems: 1- They bonded to the loosely attached smear layer . 2-They did not contain a hydrophilic group, (E.g Scotch bond) 3- They showed low bond strength. Fourth generation: Total etch technique, hybrid layer demineralization of the surface and subsurface, followed by infiltration of monomers in to the collagenmesh Fifth generation , bonding into : two steps , the adhesive resin in one bottle but the etchant is in a separate bottle Six generation (self etching primer ) Seventh generation : Attempts to combine all three (etchant, primer and adhesive) selfetchingadhesive(SEA)(onestep) Note : The disadvantages of sixth and seventh generation bonding system are: Most of them have their bond strength values are far inferior from the 4th and 5th generations.