purposes of matrix (5)
1. provide external wall to confine the amalgam so that adequate condensation forces can be applied
2. provide physiologic contour for the proximal surface of the restoration
3. reestablish contact with the adjacent tooth
4. restrict extrusion of the amal
what are the three matrix systems available at UM?
Tofflemire metal matrix
Automatrix
Compsi-Tight (Garrison Dental Solutions)
what is the most common matrix system used for class II amalgams?
tofflemire
2 parts to Tofflemire Matrix
1. retainer - reusable, resterilizable apparatus that holds the band
2. matrix band
4 parts of Tofflemire retainer
1. Head
2. Slide
3. Rotating Spindle
4. Set-Screw
Head
U shaped end
slide
diagonal slot
rotating spindle
adjust distance between the slide and head, increasing or decreasing the size of the band loop
set screw
tightens the band in the slide
head of tofflemire has what options for extension of matrix in what directions?
1. straight forward
2. 90 right
3. 90 left
the open side of the "U" must face
towards the gingiva when placed on the tooth to allow removal from an occlusal direction
the ends of the band extend ____ beyond the slot
1-2 mm
where should the slide be when inserting the band into the retainer slit?
near the head
function of the rotating spindle
adjusts the distance between the slide and the head which increases or decreases the size of the loop of the matrix band
function of set-screw
tightens/locks or loosens/unlocks the matrix band in the slide
original Tofflemire bands made out of
- stainless steel
- flat (various shapes and sizes)
what other type of bands can be used in Toffelmire retainer
1. dead-soft metals (no memory, retains shape)
2. precontoured (rounded)
what are the three thicknesses of Tofflemire bands
.0010, .00150, .0020
thicker bands ---
resist condensation better, but are harder to get into proximal contacts
what does contouring tofflemire do?
avoids flat, straight proximal contour and pinpoint contact area
No. 1 toffelemire
- universal
- most frequently used
- 6mm wide occlusogingivally
No. 2 tofflemire
MOD bands
- 2 humps on gingival side
- 10 mm wide occluso-gingivally
purpose of 2 humps on gingival side of MOD bands?
allow greater width of matrix band for deep proximal boxes where universal band would not extend past gingival margin
contraindications for use of No. 2 and No. 3 bands
do not use unless extra width band is needed for deep box
- is used inappropriately, band extends too high above marginal ridge and obscures access
- shape of band creates "funne" shaped proximal contour
Dixieland Bands fits into ____
Tofflemire retainer
benefits of dixieland bands: final contours
- more physiologic, less funnel-shaped
- thin and dead soft -- hold shape and do not spring back
indications for using Dixieland Bands
- difficult proximal contact
- cinches tighter at gingival margins better than No. 1 band when minimal tooth structure remains
- works well for class 2 composites
concave side of tofflemire is always oriented ____
towards gingiva, towards open end of the retainer head
open side of "U" shaped retainer is always oriented
towards the gingiva
wider circumference of the loop is oriented
towards the occlusal
smaller circumference of the loop is oriented towards
the gingiva
the retainer is always positioned on the tooth so that the set-screw is aimed
towards the anterior of the mouth, buccal side of the tooth
when would lingual placement of the retainer be indicated?
when the buccal surface of the tooth is being restored
orienting the loop at ____ is most common
90
what adjusts the size of the loop?
rotating spindle
options when matrix band will not slide through the contact on the unrestored side of the tooth
- new band
- thicker band
- wedge
- sectional matrix
Composi-Tight
- Garrison dental
- sectional matrix
- class 2 composites
- can also be used for amalgam
-
indications for composi-tight
- improves tightness of proximal contacts
- when opposite contact will not allow circumferential band to pass
automatrix
- no retainer
- requires other equipment
- more expensive
- cut band to remove
indications for automatrix
- useful when tofflemire retainer prevents proper application, such as extensive missing tooth structure
two types of wedges
anatomical
triangular
colored (anatomic) wedge sizes
Largest --> smallest
Natural wood
Pink
Blue
Yellow
Green
Orange
Natural wood
Now Put Big Yellow Gloves On Noam
wedge selection
pick a size and shape that corresponds to the size and shape of the gingival embrasure
if wedge is too small
may not seal margin well
if wedge is too large
may not fit in embrasure far enough to seal margin and may not stay in place
4 purposes of wedging
1. adapt and seal the matrix band against the gingival margin of the preparation
2. help stabilize the matrix band assembly on the tooth
3. establish shape of gingival embrasure
4. separate the teeth slightly to compensate for the the thickness of the mat
wedges are inserted from the ____
side of the tooth with the widest embrasure
- usually the lingual side
- can be inserted on both sides if necessary
MOD wedge situation
both mesial and distal
wedge must be positioned so its base is ____ to the gingival margin of the prep
gingival
- if the wedge is above the margin, it will not seal the margin and it will cave in the matrix band
if a precontoured matrix is not used, the band may be contoured with
a convex instrument before or after placement
- ball burnisher
bad must extent past and seal the
gingival margin of the preparation (by at least 1 mm)
band must extend a minimum of 1 mm higher than
the highest point occlusally (marginal ridge or cusps)
- allows overpacking
band should be properly contoured to reestablish
physiological tooth contours
band should establish
proximal contact with the adjacent tooth
band should be properly ____ and secure
wedged
if band is hung up on the gingival margin of the preparation
amalgam will be short of the true margin, leaving margin unsealed and improperly contoured
if matrix band is short of the gingival margin of the preparation
gap will be present while condensing; amalgam will extrude through opening creating an overhang
- if daylight, gingiva, or RD is visible between band and margin, it is NOT sealed
if rubber dam or gingiva is caught between the band and gingival margin of the prep
will leave open, unsealed marginal gap
if band does not completely seal the gingival margin of the prep
will create an amalgam overhang if not carved away
if the matrix band does not completely seal the gingival margin of the prep, what can be be done to correct it?
- different wedging technique
- different matrix band
- "buttering" wedge with warm compound
if wedge is placed improperly, it may leave
- margin unsealed
- matrix band unstable and may dislodge
- matrix improperly contoured
if band is not tall enough occlusogingivally to allow for overpacking of the amalgam
- insufficient occlusal height of amalgam, poor anatomical result
- fracture of MR upon band removal or carving
- correction by using a wider band
if band is placed upside down on tooth
- will be difficult to seal gingival margin
- poor anatomical contours
if band becomes loose or dislodges during condensation...
remove it and start over
- internal fractures of amalgam
rubber dam clamps to be used with matrix bands
- wingless clamp
- flat, pronged, W3
NOT "A" clamp - has downward projecting prongs, makes clamp sit higher on the tooth and interferes with matrix placement
danger of restoring adjacent surfaces at the same time
overbulking the contours of the one restored without a contact present
restoring multiple teeth in one area of the mouth at the same time
- saves multiple anesthetic injections
- saves multiple RD applications
if restoring a quadrant, prep and restore
every other tooth to maintain uncut adjacent tooth
if two adjacent proximal surfaces are prepared...
restore one first, then the other
- do not apply two matrix bands
restore the ____ prep first to maintain open proximal contacts for the second one
smallest (B-L width)
after matrix is placed on smallest prep to be restored, what should be done to to the adjacent proximal box?
pack cotton pellets in there to provide some resistance against displacement of the matrix band during condensation
before restoring the second tooth, what must be done?
carve the first restoration to establish proper proximal contour
when are liners and varnish placed in Class II amalgams?
prior to placing the matrix band
- avoids inadvertent application to the matrix band
- avoids pooling at cavosurface margins
bonding agents are placed in Class II amalgams
AFTER matrix band placement to prevent contamination, and so they do not set up before amalgam is placed
when should gross carving of the occlusal surface begin?
while the matrix band is still on and you are waiting for the amalgam to set enough to safely remove the band
what is the explorer used for in class II amalgam restoration?
removing excess amalgam bulk from the matrix band and MR area
if matrix band is removed too soon
amalgam may fracture upon removal
if matrix band is removed too late
amalgam may get too hard to carve
wedges should be removed
before removing matrix band
do NOT attempt matrix band removal before
removing excess bulk from MR, proximal margins, and matrix band
- may fracture upon removal
steps to matrix band removal
1. stabilize matrix with thumb, while loosening the set-screw and the rotating spindle with the other
2. once retainer is loose, gently pull the retainer occlusally to remove it, leaving band on tooth
3. stabilize MR of the restoration with a large conden
while stabilizing the marginal ridge with a large condenser
gently tease the band out of the restored contact area
pull band
facially or lingually, rather than occlusally to remove
- fingers/hemostat may be used
immediately after matrix band removal start carving ____
the hardest-to-reach areas/margins before the amalgam sets
- gingival margin
- buccal and lingual margins of the proximal box
what should be used to remove flash on the gingival margin?
carver
if amalgam sets, what can be used to carve the gingival margin?
perio scalers
#12 blade
usually, lingual embrasure will be ____ than buccal
wider
in normal occlusion, occlusal height should be
at same level as adjacent MR
ridge should be
concave in the center from BL
Class II restoration, what surface should be carved LAST?
occlusal
how do we check proximal contact
floss should "snap" through contact and not shred