matrix band

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

1. circumferential
2. sectional

matrix systems at UM

1. tofflemire metal matrix
2. automatrix
3. composi tight

most common matrix used for class 2 amalgams.
easy to use
inexpensive

reusable, resterilizable

multiple options (sizes)
disposable after use in pt. can reuse in preclinic

4 parts of tofflemire retainer

1. head
2. slide
3. rotating spindle
4. set screw

U shaped end with slots from which the band extends

has a diagonal slot

rotating spindle

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

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

rotating spindle

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

counterclockwise

to retract the slide

set screw turning

righty tighty
lefty loosy

tofflemire characteristics

stainless steel
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

univeral band, 6 mm wide
-routine situations

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)

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

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

precountoured bands

dixieland
-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

band orientation

concave side of band toward gingiva

wider diameter of matrix loop

toward occlusal

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

no retainer
more expensive
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.

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