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Technique For Use
Effective local anesthetic should be given as the preparation will extend subgingivally.
Occlusal reduction is carried out to obtain clearance of approximately 1.5 mm (fig. 3). |
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Figure 3.
If a rubber dam has been placed, the preparation can be compared with the occlusal height of the neighboring teeth.
The mesial and distal contact points are cleared and a smooth taper from occlusal to gingival should be obtained that
is free of ledges or shoulders (fig. 2).
Figure 2.
All caries are removed and the line angles rounded off. Often half or more of the tooth preparation is completed simply by caries removal.
It is possible to lose a large amount of the clinical crown, yet still be able to fit a stainless steel crown.
Stainless steel crowns
are not close fitting,
therefore the preparation
does not have to be precise.
The gingival finishing
line should be a feather
edge with no ledges or
steps detectable. A reasonable
taper mesially and distally
will help to achieve this. If a step or ledge is present (fig.
3), the clinician will have difficulty seating the crown and may
be tempted to trim it unnecessarily.
Figure 3.
No preparation is usually needed on the buccal or lingual surfaces of primary molars except where there is a pronounced mesio-buccal convexity
as seen on some primary first molars. The stainless steel crowns are flexible enough to spring over minor contours.
When multiple crowns are to be placed in the same quadrant, the adjacent proximal surfaces of the teeth being prepared should be reduced
slightly more than usual. This will make multiple crown placement easier.
The finishing line should be approximately 1 mm below the gingival margin.
The correct size crown
is selected by measuring
the mesio-distal width
between the contact points
of the neighboring teeth
with calipers. If teeth
are missing, the mesio-distal
width of the matching
tooth in the opposite
arch can be measured.
It is advisable to choose
the smallest crown that
will fit. If the crown
is too large it is very
time consuming to adjust
it to obtain good retention.
When fitting a crown for a second primary molar, where the first permanent molar has not yet erupted, care must be taken when measuring
the available mesio-distal dimension for the crown. If the stainless steel crown encroaches on the space needed for eruption of the permanent molar,
its eruption path may be distorted.
To seat the crown on a prepared tooth it is placed lingually and rolled over the preparation to the buccal margin.
A crown will often make an audible "click" as it springs into place over the gingival undercut area. Firm pressure is usually needed to seat the crown.
The marginal gingiva will blanch somewhat with a well fitting crown as it seats. The crown margin should be located approximately 1 mm subgingivally both
to give retention and a good cement seal (fig. 4).
Figure 4.
If excess gingival blanching is seen the crown will need to be trimmed. It may be helpful to scribe a line on the crown along the gingival contour with a sharp explorer.
The crown can then be trimmed to 1 mm below the scribe line.
The occlusion should be checked and the crown removed with a sharp excavator.
Trimming can be done with crown scissors (fig. 5) (3M 801-202) or with an abrasive wheel. Some operators consider the latter to give a better result
than cutting with crown scissors.
Figure 5.
After trimming, the crown will have a larger cervical opening. It must be crimped to regain its retentive contour.
3M™ ESPE™ Crimping Pliers
(800421) (fig. 6) are
recommended for ease
and efficiency in crimping
stainless steel crowns;
however, conventional
orthodontic pliers can
also be used.
Figure 6.
Once the adjustments
are completed, the crown
margins should be thinned
slightly and smoothed
with a large "heatless" stone.
Final polishing can be
done with a rubber wheel.
The crown is now ready
to be cemented. Resin-modified
glass ionomer, polycarboxylate
or zinc phosphate cements
can be used. 3M™ ESPE™
RelyX™ Luting Plus Cement
is recommended as an
easy to use fluoride
releasing cement.
Stainless steel crowns are not a tight fit except at the margin, so a larger than normal volume of cement should be mixed (fig. 7).
Figure 7.
As the crown is seated over the tooth, excess cement should be seen to flow out from the margins. If excess cement is absent from the margins, it is an indication of an
inadequate volume of cement which may lead to early failure of the crown. Excess cement is removed with a scaler or explorer, and knotted dental floss is used interproximally.
Finally the crown is checked for occlusion. The primary dentition has great ability to adjust to a slightly opened bite of 1mm or so over a few days with no adverse effect.
The patient should be advised that there may be some temporary gingival discomfort when the local anesthetic wears off.
Stainless steel crowns can be adapted as useful space maintainers by soldering a loop of stainless steel wire to the buccal and lingual surfaces. Once space maintenance is completed,
the soldered wire loop can be removed leaving the stainless steel crown in place until the primary molar is shed. The alternative of using an orthodontic band and soldered wire loop
as a space maintainer may give rise to secondary caries if the cement beneath the band washes out.
Placement of 3M™ ESPE™
Stainless Steel Crowns
is an economical and
reliable treatment for
primary molars giving
excellent long-term function
and patient comfort.
The placement technique
is quickly mastered.
Crowns can often be fitted
in less time than would
be needed to complete
some conventional multi-surface
restorations.
Please
refer to product instructions
for more detailed information
as well as precautionary and
warranty information when using
3M™ ESPE™ materials.
Copyright © 2011 3M. All rights reserved
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