Extensive Amalgam Restorations

Question 1

3 reasons to restore cavities

Answer 1

• restore integrity of tooth surface
• restore function of tooth
• restore aesthetics of tooth

Question 2

what method of retention does amalgam use

Answer 2

macromechanical

Question 3

define retention and resistance

Answer 3

retention: ability to withstand forces in long axis of tooth
resistance: ablility to withstand dislodgement in all other directions

Question 4

what is meant by auxillary retention?

Answer 4

other aids used to aid retention

Question 5

3 methods of auxillary retention used in EARs

Answer 5

• cavity design features
• pins
• adhesives

Question 6

4 elements of cavity design which offer additional resistance form

Answer 6

BAPS:
Boxes
Axial grooves
Pits
Slots

Question 7

maximum size of slots and pits

Answer 7

depth no greater than 1mm

width little more than instrument used to prepare them

Question 8

name a disadvantage of slots and pits

Answer 8

sharp internal form –> increases stresses within tooth and material but necessary to provide resistance form

Question 9

3 types of pins

Answer 9

• cemented
• friction grip
• self-threading

Question 10

which type of pin is the most retentive and most common?

Answer 10

self-threading pins

Question 11

how many pins should be used per

a) missing cusp
b) missing line angle
c) missing proximal surface

Answer 11

1 for each

Question 12

measurements for placement of self-threading pins

Answer 12

1-2mm inside DEJ/CDJ
2mm in to dentine, amalgam
2mm from opposing tooth

Question 13

why should pins be used with caution?

Answer 13

weaken tooth and restoration

Question 14

what are EARs used instead of?

Answer 14

cast restorations (crowns, inlays, onlays etc)

Question 15

2 possible outcomes of incorrectly placed pins

Answer 15

• insert in to pulp –> pulpitis, post-op sensitivity

- insert in to periodontal tissues –> post-op sensitivity

Question 16

2 adhesives used with pins in EAR

Answer 16

4META (AmalgamBond)

MDP (methacryloyloxydecyl dihydrogen phosphate, Panavia)

Question 17

advantages of adhesives

Answer 17

-conserve tooth structure
-increase retention
BUT no evidence that it increases survival

Question 18

2 ways restorations fail

Answer 18

• new disease (secondary/recurrent caries, pulpal problems)

- technical failure

Question 19

4 possible routes to technical failure of EARs

Answer 19

• defective contact points
• overhanging restoration
• non-retentive (falls out)
• fractured restoration

Question 20

outcome of technical failure of EAR

Answer 20

secondary caries, periodontal disease

Question 21

is repair of replacement of EAR preferable and why

Answer 21

repair: conservative, quicker, cheaper, less traumatic, poss no LA

not replacement: inadvertent removal of tooth tissue, increase in cavity size, pulp damage, development of clinical symtoms

BUT depends on clinician, circumstance, pt preference