Terms in this set (76)
purpose of matrix and wedge
1. provide external wall for appropriate condensation
2. provide physiologic contour for proximal surface
3. reestablish contact with adjacent tooth
4. restrict extrusion of amalgam beyond the margins (to prevent overhangs)
5. provide appropriate surface texture to the proximal surface where it cannot be carved and burnished
matrix systems general
thin and pliable pieces of metal held adjacent to the proximal portions
2 types of matrix systems
matrix systems at UM
1. tofflemire metal matrix
3. composi tight
most common matrix used for class 2 amalgams.
easy to use
multiple options (sizes)
disposable after use in pt. can reuse in preclinic
4 parts of tofflemire retainer
3. rotating spindle
4. set screw
U shaped end with slots from which the band extends
has a diagonal slot
adjusts the distance between the slide and the head, increasing or decreasing the size of the band loop
tightens the band in the slide; adjustment for holding band in place
U shaped end
has slots from which the matrix may extend in one of 3 directions
1. straight forward
2. angled 90 deg to right
3. angled 90 deg to left
oped side of U must face??
gingiva to allow removal from an occlusal direction
the slot holds the ends of the matrix band
- ends of band extend 1-2 mm beyond the slot
-slide is near the head when inserting the band so the band is secure in the slot
-both ends of band are in the slot
adjusts distance between the slide and the head (increases or decreases the matrix loop)
how to hold spindle
hold the head and slide with thumb and forefinger of one hand while turning the rotating spindle with other hand
to advance the slide
to retract the slide
set screw turning
flat (many shapes and sizes)
dead soft metals (no memory, retains shape)
precountoured (rounded contour)
0.001, 0.0015, 0.0020 inches
resist condensation better but make it harder to get proximal contact
before or after placing with large convex instrument (burnishing) avoids flat, straight proximal contour and pin point contact area
no 1 band
univeral band, 6 mm wide
no 2 band
MOD band 10 mm wide; humps on gingival side; allow greater width of matrix band for deep proximal boxes (where universal band would not extend)
no 3 band
MOD band 6-7 mm wide
narrow width for shorter teeth
matrix band MUST extend past the gingival margin of the box for an adequate seal
when to use no 2 and 3 bands
do not use unless extra width of band is needed for deep box
-if band extends too high above marginal ridge it will obscure access
-shape of band creates funnel shaped proximal contour
cut off hump
if only one box of MOD is deep or if only one proximal surface is restored
if band too wide where extra width is not needed
bumps into gingiva and will not seat down far enough at the deep box
-fits into tofflemire retainer
-final contours more physiologic and less funnel
-thin and dead soft (holds shape, doesn't spring back)
when to use dixies?
when proximal contact is difficult, minimal tooth structure remains
-also works well for class 2 composites
concave side of band toward gingiva
wider diameter of matrix loop
how to insert band into retainer
fold the 2 ends of band together to form a loop.
insert flat ends together into the slide.
insert the loop into the correct slot in the head for the desired direction in which it should extend (stright, R or L)
set screw aimed
toward anterior of mouth
retainer position on
buccal side usually
when not to use buccal side
when buccal surface is being restored it is fine to place on the lingual side (anterior teeth may interfere)
once band is seated on tooth
tighten the band on the tooth by turning the rotating spindle
is fine where band fits intot he retainer head
cut a piece of band
to seal the area better if needed
if band doesnt pass through contact?
go back and break contact with bur or hand instrument
if band doesnt slide through contact on the other, non restored side
get a new band
try a thicker band if possible
separate teeth with a wedge
use sectional matrix
sectional matrices designed for class 2 composite.
can be used for amalgam
useful when opposite contact will not allow circumferential band to pass through
cut band to remove
useful such as extensive missing tooth structure
pick a size and shape that corresponds to size and shape of gingival embrasure.
too small wedge
may not seal margin well
too large wedge
may not fit in embrasure far enough to seal margin and may not stay in place
purpose of wedgin
1. adapt and seal the matrix at the gingival margin
2. stabilize matrix band
3. establish SHAPE of gingival embrasure
4. SEPARATE teeth slightly to compensate for the thickenss of the matrix
how to insert wedge
inserted from the side of the tooth with the largest embrasure: lingual side; but can be inserted on buccal or lingual side if convenient
wedge base must be
gingival to the gingival margin of the prep.
must be tight to be effective. warn pts of pressure
if precountoured matrix not used,
contour band with a convex instrument before or after placement. burnish matrix band against proximal contact
band must extend past
1 mm and SEAL gingival margin of prep
band must extend 1 mm HIGHER than
the HIGHEST point occlusally to be restored to allow for overpacking
band properly CONTOURED
to reestablish physiological tooth contours
band should establish
proximal CONTACT with the adjacent tooth
band wedged and
what if band is hung up on the gingival margin of the prep?
margin is unsealed and improperly contoured
what is band is short of gingival margin of prep?
RD visible, meaning amalgam will extrude, causing and overhang, if not corrected gap will be present while condensing
how to prevent overhangs
check that all margins are sealed by matrix band
what if RD or gingiva caught in between band and gingival margin of prep?
corrected by loosening the matrix, stretching the RD and depressing it, repositioning matrix.
if uncorrected will leave open marginal gap
what if band does not completely seal gingival margin of prep
often due to fluting of root concavity
- if uncorrected, will result in amalgam overhang if not carved away
try different wedging technique
try different matrix band
try buttering the wedge with warm compound
if wedge is improperly placed?
1. unsealed margin
2. matrix band unstable and may dislodge
3. may leave matrix improperly contoured
what if band not tall enough occlusal-gingivally to allow for overpacking of amalgam?
1. insufficient occlusal height of amalgam (poor anatomy)
2. fracture of marginal ridge upon band removal or carving
3. correct by using a wider band
what if band placed upside down on tooth?
1. difficult to seal gingival margin
2. poor anatomical contours
if band comes loose or dislodges during condensation?
remove band, amalgam and start all over
unless it is a rare case of very deep gingival margins
RD selection is
what type of clamp?
flat pronged clamp, W3
restoring adjacent class 2's
more efficient and kinder to pt to restore multiple teeth in one area of the mouth at the same time.
-saves multiple injections and RD applications
how to restore 2
1. do not apply 2 adjacent matrix bands
2. restore SMALLEST PREP (BL) first to maintain open proximal contacts for the second one
3. pack cotton pellets in the adjacent proximal box after the matrix is placed. Provides some resistance against displacement of the matrix band during condensation
4. carve first restoration to establish proper proximal contour prior to restoring second one.