dental 5

Question 1

what is an alloy

Answer 1

mixture of metal

Question 2

amalgam

Answer 2

an allow containing mercury and one other metal

dental amalgam- produced by mixing (L) mercury with (S) particles of an alloy containing silver, tin or copper

Question 3

requirements of amalgam alloy

Answer 3

it should primarily consist of copper-silver or tin
can contain a small amount of
indium, platinum, platinum, zinc and mercury

Question 4

classification of alloys

Answer 4

zinc-containing alloys-0.01% or more

low copper alloys- 5% or less
high copper alloys- 13-30%

Question 5

qualities of high copper alloys

Answer 5

13-30%
increase 
strength 
corrosion resistance 
marginal integrity

Question 6

silver alloy amalgam powder

Answer 6

lathe-cut- irregular shape
spherical (cut)
admixed- (mixture of both spherical and lathe cut)

Question 7

dimensional changes during the setting of amalgam

Answer 7

initial contraction- 20min - associated with the solution of the alloy particles in mercury
expansion- due to the reaction of silver and copper and the formation of the matrix phase
the final value is at 24hour-
amalgam doesn’t adhere to tooth structure forming an interfacial gap

Question 8

corrosion

Answer 8

progressive destruction of metal by chemical or electrochemical reaction with the environment
results in loss of strength and marginal integrity

Question 9

bonding of amalgam

Answer 9

amalgam don’t bond to the tooth structure and therefore does not restore the original strength of the clinical crown. adhesive systems attempt to bond the amalgam to the tooth structure

Question 10

trituration

Answer 10

mixing of mercury and amalgam particle
amalgam particles + mercury → dental amalgam + unreacted powder
Ag3Sn + Hg → Ag2Hg3 + Sn7Hg + Ag3Sn​

Question 11

what is ammalgamation

Answer 11

outer silver tin particle dissolve into mercury when coming into contact with mercury

Question 12

dental amalgam

Answer 12

gamma is silver and tin
trituration- mixing of mercury and alloys
silver 65% gamma 1 dissolves first into mercury
tin 29% gamma 2 dissolves second into mercury
after titration gamma 1 and 2 crystals grow and mercury dissolves in the remaining powder (unreacted alloy particles

Question 13

high copper alloys properties

Answer 13

improves 
mechanical properties 
corrosion characteristics are better 
increase marginal integrity 
improved performance in clinical trials

Question 14

2 types of high copper alloy powders

Answer 14

admixed alloy powder

single composition alloy powder

Question 15

admixed alloy powder

Answer 15

79.1 % silver
28.9% copper
sphericle particle
added to low copper lathe cut amalgam particle
admixed particles usually contain 30-55% copper powder

Question 16

single composition alloy powder

η phase (Cu6Sn5)

Answer 16

particles made of the same chemical composition
60%silver 27%tin 13-30%coppper

η phase (Cu6Sn5) occurs when tin amlgum reacts with copper in silver copper
a layer of η phase crystals form around the unreacted silver copper alloy particle

Question 17

resin composite

Answer 17

reinforce polymer system used to restore hard tissue such an enamle and dentin

Question 18

polymer matrix composite (resin composite)

Answer 18

resin composite used to replace missing toothe structures and modify tooth color and contour thus enhancing easthetic
activated by visible wavelengths

Question 19

3 components of rein based composites

Answer 19

matrix- plastic resin materials that forms a coniuous phase
filler -reinforcing particles dispersed in the matrix (strengthen resin composite and provides degree of tranlucency)
coupling agent - promotes adhesion between matrix and filler material

Question 20

hybrid composite

Answer 20

2 types of fillers blended together-
fine particle- size 2 to 4 μm
microfine particle 0.04 to 0.2 μm.

Question 21

microhybris composites

Answer 21

fine particle - 0.04 to 1 μm.
blended with silica microfine particles
contain 60-70% filler by volume
has good clinical wear resistance, mechanical propoties and suitible for stressing application but lose surface polish with time and become dull

Question 22

nanofills

Answer 22

contain nanonmeter size particles 1 to 100μm.throughout resin matrix

Question 23

nanohybrids

Answer 23

consits of large particles 0.4 to 5 μm with added nanometer size particles thus are hybrid materials
surface gradually becomes dull

Question 24

nanoclusters

Answer 24

synthasized from silica sols

size- 5 to 75nm