3. Matrix and Retainer Systems

Question 1

What are the purposes of having a matrix with amalgam

Answer 1

1. Confine amalgam so adequate forces can be applied
2. Reestablish contact
3. Establish Physiological contour of proximal contact
4. Prevent extrusions and overhangs

Question 2

Describe the properties on a prep for an amalgam restoration that make it successful

Answer 2

• box like

- confining walls and floors

Question 3

A properly placed matrix should have what properties

Answer 3

1. Rigid against existing tooth
2. proper anatomic contour
3. Prevent gingival overhang
4. easily removed
5. restore correct proximal contact

Question 4

list the four different parts of the tofflemire retainer

Answer 4

• head
• slide or vice
• rotating spindle
• set screw or locking nut

Question 5

the head should be held with the slots facing (occlusally/gingivally) when placing the band in but (occlusally/gingivally) when placed on the tooth

Answer 5

occlusally….gingivally

Question 6

When is a matrix needed

Answer 6

when a restoration goes from one surface to another

Question 7

The purpose of the slots in the head are for…

Answer 7

positioning the matrix band

Question 8

The diagonal slot on the slide is meant to hold - mm of the round ends of the matrix beyond the slot

Answer 8

1-2

Question 9

the extent to which the matrix surpasses the diagonal slot of the slide/vice depends on what variable

Answer 9

size of the tooth

Question 10

There should be more band extending out of the slide for a PM or a molar

Answer 10

PM

Question 11

For band installation where is the slide positioned relative to the head

Answer 11

next to it

Question 12

What does the rotating spindle do

Answer 12

adjusts the distance between the slide and head and thus adjusts the size of the band

Question 13

what is the role of the set screw/locking nut

Answer 13

locks and unlocks the matrix band in the slide

Question 14

What are the two types of matrix retainers

Answer 14

• straight

- contra-angled

Question 15

The names for the two different matrix retainers are based on what processes

Answer 15

-the angle between the head

Question 16

contra-angled are good for what types of restorations

Answer 16

ones that are on the lingual surfaces of teeth

Question 17

What are the three different flat band thicknesses

Answer 17

• 0.001 inch
• 0.0015 inch
• 0.002 inch

Question 18

What is the difference between the thick and thin flat bands

Answer 18

thin establish a tighter contact and thicker are more rigid for condensation forces

Question 19

What are the three different types of flat bands and describe them

Answer 19

• # 1= universal band- most commonly used
• # 2= MOD band has two projections for deep gingival margins
• # 3= Also has 2 gingival projections but is more narrow than #2

Question 20

The #2 band is better for (molars/PMs) verses #3 which is better for (Molars/PMs)

Answer 20

molars….PMs

Question 21

What is the name of the pre contoured bands

Answer 21

Getz contour

Question 22

Why must you be careful when removing the pre contoured bands

Answer 22

need to make sure you don’t break the marginal ridge

Question 23

When would you want the band to project from the retainer straight

Answer 23

when restoring anterior teeth (posterior should be angled left or right)

Question 24

Which quadrants should the band be turned left for? right?

Answer 24

• Left= 1 and 3

- Right= 2 and 4

Question 25

The loop of the matrix should be shaped like a funnel- the wider part should point

Answer 25

occlusally

Question 26

Why do you use a wedge with a matrix

Answer 26

prevent gingival overhang, makes tight proximal contact to compensate for the thickness of the matrix

Question 27

Which embrasure should you place the wedge in

Answer 27

the largest embrasure (lingual for posterior teeth)

Question 28

If the base of the wedge can't be placed gingival to the prep what will happen

Answer 28

a concavity will develop in the matrix

Question 29

What can you do to get rid of the concavity formed when the base of the wedge can't be placed gingival to the margin of the prep

Answer 29

- surgically reflect the dental papilla | - use a rigid bladed instrument to hold the matrix gingival to the prep

Question 30

How should you burnish the matrix

Answer 30

-burnish on a cushioned surface with the back of a spoon excavator or ball burnisher

Question 31

How should a retainer and matrix be removed

Answer 31

- Loose the slide and set screw - Pull retainer occlusally - Pull distal matrix occlusally and lingually - Pull mesial matrix occlusally and facially

Question 32

(T/F) You can reuse a matrix band

Answer 32

F- one time only

Question 33

The band should extend _-_mm above the marginal ridge and cavosurface margin and why?

Answer 33

1-1.5... need to overpack restoration with amalgam

Question 34

The gingival portion of the band should be _ mm below the gingival

Answer 34

0.5 mm

Question 35

How do you tighten the matrix band

Answer 35

- Turn the rotating spindle to decrease the diameter of the matrix band and tighten it - Place wedge then loosen the matrix band by turning the knob 1/4th a turn to prevent the matrix from being too tight (prevent an open contact

Question 36

Automatrixing systems are good for what kind of amalgam restorations

Answer 36

-complex ones and core build ups

Question 37

What is the major advantage of the automatrixing system

Answer 37

has its own built in retainer that is smaller than a tofflinmyer

Question 38

What is the advantage of a denovo matrix system

Answer 38

pre welded band with specific sizes and no retainer is needed

Question 39

How is a denovo matrix system removed

Answer 39

-bur is used to cut the welds

Question 40

Describe the T band matrixing system

Answer 40

- simple and inexpensive | - built in retainer- smaller than toffelinmire

Question 41

Describe palodent matrixing system

Answer 41

- precontouring and no need for matrix when restoring one proximal surface - 2 proximal surface you need 2 small retainers, 2matrices, two wedges

Question 42

Under what cases is reinforcing matrices with modeling compound not needed

Answer 42

when the matrix is supported by adjacent teeth

Question 43

How can you prevent the matrix from coming into contact with resin from bonded amalgam

Answer 43

coat with wax/crayon