W1: Matrix Systems Flashcards
What types of matrix are there?
contoured and non contoured
avoid flimsy for post.
Which wedge is not apart of system?
fender wedge, which is used for prep stage
Order of sectional matrix
matrix
wedge
ring
use explorer to check gaps in gingival margin (impossible to remove excess material)
If you detect gap in gingival margin what must you do?
don’t proceed. potential for secondary caries and periopocket
MOD, what should you do?
use 2 matrix systems, complete mesial matrix, wedge and ring, repeat for distal
where does ring orient?
outside of mouth
What should we use for amalgams?
tofflemire
tofflemire placement
parallel to arch
slots of tofflemire should be facing which side?
always gingivally, facial side
Metal band types
- simple
- gingival ext, goes into deep prox box
closing metal will make narrow and wider circumference, narrow part goes gingivally to follow crown which is narrower gingivally
How do you orient the tofflemire band?
big up, small down
Use of Tofflemires. Do they replace wedges?
Yes, can be used for MOD, but also MO or DO
Automatrix is limited how so?
‘flat’
Retainerless matrices limitation
can be bit big, need wedge
When to use?
to recreate contour of proximal surfaces (cervical class V also, used to contour and adapt material more easily, prevent moisture)
Direct placement of comp in comp veneers, which matrix do we use?
clear strip
Why use matrix?
- contour
- proper filling, no gaps
- no excess
- contact
- moisture prevention
What is proper anatomic contour for tooth we are restoring?
consider embrasures on surfaces in 3D.
Matrix must be placed beyond where? and why?
beyond cavity margin
- optimise bonding
- prevent ledges (AVOID LEDGES- would be really hard to remove, hard to clean, biofilm risk and result in secondary caries, or periodontal disease)
Why are wedges used and where would they be placed?
- used to stabilise matrix in cervical area, though teflon can be used alternatively
- PLACE below contact area either Buccal or palatially (effects seal)
- some plastic wedges have concavities which lets it sit over papilla with low impact and helps it be inserted for better seal
How do you create contour on tofflemire matrix which is flat?
‘burnishing.
use ball burnisher, identify from inside towards out where contact is and press few times to create contour.
if you do it outside it won’t be as precise.
For proper contour you must….
ensure clearance of contact so matrix can fit
- if no clearance= no matrix can fit
Flat vs precontoured matrix
flat= large space, food impaction, contact is too high, slight occlusal embrasure needs to be proper
to deflect food when masticating,
precontour= contact point more natural position
Cons of V3 matrix
some matrix like V3 can make concavities. should be convex.
Adv of wooden vs plastic wedge
wooden= can adapt, if too big can make it thinner.
plastic= not possible to adapt
cross section resembles area under contact point. make sure base of triangle goes gingival
how to place wooden wedge?
tip goes through. triangle fits IP area with BASE to gingival, top point of triangle to contact area
A matrix should be selected
such that it ….
- covers. extends beyond the extent of the
cavity - sits. can be engaged and stabilised.
- bulges right place. maximum convexity of the matrix should be positioned against and in contact with the maximum convexity of the intact adjacent tooth to create an appropriate contact area
- fits. The matrix should be able to be
placed passively, unimpeded by contact with the adjacent tooth.
material excess can lead to
food impaction
happens when we don’t place wedge far enough to pt where we feel tension/position.
What is a solution to gaps in matrix?
teflon tape
Comment on this placement of matrics:
Sectional matrices are good for maintaining contact area however if matrix is distorted it can form a concavity (don’t want that, will be hard to clean and harbor bacteria causing caries)
Fig. 3 a, b, c, d) Tooth restored using sectional matrix and separating ring. Very tight contact,
with peripheral ledging and concavity at contact area and beyond. Concavity only evident
when tooth removed
which one is correct placement of matrix? A or B?
B is correct
A the matrix is not in contact with neighbouring tooth.
I.e:
a) Matrix with insufcient occluso-cervical curvature not contacting adjacent tooth following appropriate wedging.
comment on this matrix position (different views)
good contact area, but probs should position more downwards
i.e:
b, c) Matrix with
increased occluso-cervical curvature resulting in acceptable positioning of contact (potentially slightly coronal). However, adaptation occlusal
to the contact area is sub-optimal, potentially requiring increased fnishing. Repositioning the matrix more apically may address these issues.
This may require adjustment of the matrix cervically
C,D image is ideal
Comment on D,E matrix position
- more curve up down so contact is good
- adaptation of occlusal to contact is good
con
- bc it’s more curved this could lead to distorted placement.
comment
a) an eliott sep
b & c) the wedge is not high enough to seal cervical area, you can see lil gap palatally
d,e) better seal by placing 2 wedges
fgh) teflon tape pack for seal
ij) teflon wrapped around floss. technique for seal. pulle dsame time in opp directions to make a seal.
What happens if you apply force to a matrix?
causes distortions
- gaps leading to ledges or loss of contact area
Comment
Comment
wedge= prevent distortion/ moving
problem sometimes, add ring= more distortion
use wooden wedge
i.e.
“Anecdotally, rigid metal matrices lend
themselves to a degree of self-stabilisation
coronally, which facilitates their use without a separating ring in many situations. When a ring is not used, separation with a frmly
placed wooden wedge or mechanical separator is required.”
