3. Matrix and Retainer Systems Flashcards
What are the purposes of having a matrix with amalgam
- Confine amalgam so adequate forces can be applied
- Reestablish contact
- Establish Physiological contour of proximal contact
- Prevent extrusions and overhangs
Describe the properties on a prep for an amalgam restoration that make it successful
- box like
- confining walls and floors
A properly placed matrix should have what properties
- Rigid against existing tooth
- proper anatomic contour
- Prevent gingival overhang
- easily removed
- restore correct proximal contact
list the four different parts of the tofflemire retainer
- head
- slide or vice
- rotating spindle
- set screw or locking nut
the head should be held with the slots facing (occlusally/gingivally) when placing the band in but (occlusally/gingivally) when placed on the tooth
occlusally….gingivally
When is a matrix needed
when a restoration goes from one surface to another
The purpose of the slots in the head are for…
positioning the matrix band
The diagonal slot on the slide is meant to hold - mm of the round ends of the matrix beyond the slot
1-2
the extent to which the matrix surpasses the diagonal slot of the slide/vice depends on what variable
size of the tooth
There should be more band extending out of the slide for a PM or a molar
PM
For band installation where is the slide positioned relative to the head
next to it
What does the rotating spindle do
adjusts the distance between the slide and head and thus adjusts the size of the band
what is the role of the set screw/locking nut
locks and unlocks the matrix band in the slide
What are the two types of matrix retainers
- straight
- contra-angled
The names for the two different matrix retainers are based on what processes
-the angle between the head
contra-angled are good for what types of restorations
ones that are on the lingual surfaces of teeth
What are the three different flat band thicknesses
- 0.001 inch
- 0.0015 inch
- 0.002 inch
What is the difference between the thick and thin flat bands
thin establish a tighter contact and thicker are more rigid for condensation forces
What are the three different types of flat bands and describe them
- # 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
The #2 band is better for (molars/PMs) verses #3 which is better for (Molars/PMs)
molars….PMs
What is the name of the pre contoured bands
Getz contour
Why must you be careful when removing the pre contoured bands
need to make sure you don’t break the marginal ridge
When would you want the band to project from the retainer straight
when restoring anterior teeth (posterior should be angled left or right)
Which quadrants should the band be turned left for? right?
- Left= 1 and 3
- Right= 2 and 4
The loop of the matrix should be shaped like a funnel- the wider part should point
occlusally
Why do you use a wedge with a matrix
prevent gingival overhang, makes tight proximal contact to compensate for the thickness of the matrix
Which embrasure should you place the wedge in
the largest embrasure (lingual for posterior teeth)
If the base of the wedge can’t be placed gingival to the prep what will happen
a concavity will develop in the matrix
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
- surgically reflect the dental papilla
- use a rigid bladed instrument to hold the matrix gingival to the prep
How should you burnish the matrix
-burnish on a cushioned surface with the back of a spoon excavator or ball burnisher
How should a retainer and matrix be removed
- Loose the slide and set screw
- Pull retainer occlusally
- Pull distal matrix occlusally and lingually
- Pull mesial matrix occlusally and facially
(T/F) You can reuse a matrix band
F- one time only
The band should extend _-_mm above the marginal ridge and cavosurface margin and why?
1-1.5… need to overpack restoration with amalgam
The gingival portion of the band should be _ mm below the gingival
0.5 mm
How do you tighten the matrix band
- 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
Automatrixing systems are good for what kind of amalgam restorations
-complex ones and core build ups
What is the major advantage of the automatrixing system
has its own built in retainer that is smaller than a tofflinmyer
What is the advantage of a denovo matrix system
pre welded band with specific sizes and no retainer is needed
How is a denovo matrix system removed
-bur is used to cut the welds
Describe the T band matrixing system
- simple and inexpensive
- built in retainer- smaller than toffelinmire
Describe palodent matrixing system
- precontouring and no need for matrix when restoring one proximal surface
- 2 proximal surface you need 2 small retainers, 2matrices, two wedges
Under what cases is reinforcing matrices with modeling compound not needed
when the matrix is supported by adjacent teeth
How can you prevent the matrix from coming into contact with resin from bonded amalgam
coat with wax/crayon
