Failure of composite and amalgam

Question 1

Time dependent change in the form of amalgam under constant loads and temperature

Answer 1

creep

Question 2

how to overcome creep in amalgam

Answer 2

High copper amalgam shows lower creep values

Question 3

breakage of a thin edge of a restoration creating an irregular
V-shaped crevice.

Answer 3

Marginal degradation ( ditching, Fracture, Crevicing )

Question 4

one of the causes of Marginal degradation is depletion of support at margins , it may be due to ?

Answer 4

Excessive expansion resulted from:
-Under trituration —Excess mercury. -Moisture contamination (causes delayed expansion)

Question 5

one of the causes of Marginal degradation is insufficient bulk at margins , it may be due to ?

Answer 5

l. Beveling of CSA.
2. Over carving.
3. Leaving thin marginal flashes.

Question 6

one of the causes of Marginal degradation is voids, it may be due to ?

Answer 6

l. Inadequate condensation force. 2. Too dry amalgam mix.
3. Moisture contamination of zinc containing amalgam.
4. Corrosion.

Question 7

one of the causes of Marginal degradation is excess mercury
, it may be due to ?

Answer 7

1.Wrong proportioning of alloy / mercury ratio.
2. under trituration and squeezing.
3. Inadequate condensation force.

Question 8

Isthmus outline especially … wall of …….. are more common sites for marginal ditching?

Answer 8

buccal wall of lower first molars

Question 9

walls should be made in the form of reverse curve to provide CSA 90 ° to avoid what

Answer 9

marginal ditching

Question 10

treatment of Very small ditching

Answer 10

Resurfacing with finishing bur.

Question 11

treatment of moderate ditching

Answer 11

repair with amalgam

Question 12

treatment of gross ditching

Answer 12

Total replacement of the restoration is indicated.

Question 13

the narrowest junction between
the principle portion (occlusal) and the auxiliary portion (buccal, lingual or proximal).

Answer 13

Isthmus

Question 14

A fracture of compound
amalgam restoration at the junction between the principle portion and the auxiliary portion of the cavity.

Answer 14

Isthmus fracture

Question 15

The causes or factors contributed to isthmus fracture may be:

Answer 15

• Factors that decrease flexural strength
• Factors that increase flexural stresses

Question 16

one of the Factors that increase flexural stresses is Incorrect-resistance and inadequate retention to avoid it we should have?

Answer 16

1.Flat pulpal floor and gingival floor perpendicular to the
direction of force.
2.Walls parallel to the direction of masticatory force.
3. CSA 90°.

Question 17

one of the Factors that increase flexural stresses is Excessive occlusal forces it may be duo to?

Answer 17

1) Presence of premature contact due to:
A. Under carving of the marginal ridge.
B. Misplacement of marginal ridge.
C. Sudden biting on a hard object. D. Presence of protruded or over erupted opposing plunger-
cusp.

2) Biting on amalgam before sufficient setting.

Question 18

one of the Factors that increase flexural stresses is Surface and structural discontinuities it may be duo to?

Answer 18

1) Poor polishing leaving the surface rough and full of
pits and scratches.

2) Over carving into deep grooves not only creates
stresses, but also weakens the restoration by decreasing
its bulk.

3) Presence of internal voids due to corrosion ,moisture
contamination ,too dry amalgam mix and lack of forceful condensation.

Question 19

one of the Factors that decrease flexural strength is insufficient bulk of the amalgam it may be duo to?

Answer 19

Over carving,

decreased cavity depth.

Question 20

one of the Factors that decrease flexural strength is excess mercury , what dose it cause?

Answer 20

lowers the strength of amalgam

Question 21

one of the Factors that decrease flexural strength structural discontinuities: it may be duo to?

Answer 21

Corrosion,
moisture contamination,
dry mix,
lack of condensation forces.

Question 22

Formation of a surface film of discoloring oxides and
sulfides

Answer 22

tarnish-loss of surface luster-

Question 23

tarnish is due to

Answer 23

Excess Hg, under trituration,
improper condensation, Lack of finishing, moisture
contamination, and bad oral hygiene.

Question 24

Actual disintegration of the bulk of amalgam.

Answer 24

Corrosion-rough pitted amalgam surface-

Question 25

Chemical corrosion is due to

Answer 25

lack of polishing

Question 26

The amalgam shown through
enamel.

Answer 26

amalgam blue-dark bluish discoloration-

Question 27

amalgam blue is due to

Answer 27

-Thin or undermined enamel that shows dark blue discoloration of amalgam.

-Penetration of metallic ions and corrosive products of amalgam through the dentinal tubules.

Question 28

how to fix tarnish

Answer 28

re-polishing

Question 29

how to fix corrosion

Answer 29

may require removal of old restoration

Question 30

how to fix amalgam blue

Answer 30

may require removal of old restoration

Question 31

marginal discoloration is due to ?

Answer 31

1.Gross marginal leakage of environmental fluids and stains

2. Poor application of bonding systems.
3. Moisture contamination.
4. Excessive thinning out of margins, premature polishing
   may cause crevicing
5. Softening of composite due to hydrolytic instability, and
   degradation increases their tendency to marginal
   discoloration- especially- at the gingival margins where
   local acidity tends to increase.

Question 32

surface discoloration is due to

Answer 32

The rougher the surface the more dull it appears and the greater is its tendency to retain food and stains and get discolored

Question 33

bulk discoloration can cause?

Answer 33

Excessive porosity is a most common attribute for bulk discoloration thus, trapped air voids , cause unfavorable changes of optical characteristics.

Question 34

treatment of surface discoloration?

Answer 34

polishing

Question 35

treatment of slight marginal discoloration?

Answer 35

if not complicated by any caries recurrence may be repaired in the same shade composite

Question 36

treatment of bulk discoloration

Answer 36

replacement of the restoration