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Installing the OC attachment on root caps |
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The OC attachment is an excellent choice for custom root
cap cases. The overdenture case above requires two
custom root caps with attachments on top. |
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The root cap posts are waxed up and the universal patrix
is placed using the VKS Paralleling Mandrel. When placed
correctly, the patrix is attached by waxing around the
cap. |
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This shows the final waxup of the root cap and the
attachment. The entire waxup is cast in one piece. This
gives the restoration greater strength while saving time
and money. |
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After casting, finish the patrix by polishing lightly.
Overpolishing will cause the attachment to lose
retention. The blocking out disc is then placed on the
attachment, under the ball. The blocking out disc aids
in blocking out and ensures the matrix sits parallel and
stable on the patrix. |
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The yellow matrix is snapped into the metal housing
using the insertion pin. It is recommended to use the
yellow matrix with medium friction. For reduced and
increased friction, use the green or red matrix
respectively. |
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Prior to finishing, apply liquid silicone to the root
cap or patrix. This will block out the undercuts and
prevent acrylic from spreading underneath the attachment
in the final restoration. |
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The metal housing with integrated plastic matrix is
snapped onto the patrix, on top of the blocking out
disc. This should be done while the silicone is still
soft. |
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This is the finished denture viewed from the fitting
surface. To change the matrix, the matrix must be
destroyed with a round-head bur and pried out. A new
matrix is snapped in using the insertion pin. |
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Installing the OC attachment on distal extensions |
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The copings for the crowns are waxed up using standard
techniques. It is recommended to double abut to give
added strength for the OC patrix. It is also highly
recommended to wax a lingual rest shelf for a lingual
arm. |
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The OC patrix is waxed onto the copings with the VKS
Paralleling Mandrel. The use of a surveyor to parallel
the patrices is necessary. The patrix should be placed
as close to the tissue as possible to increase
stablility and minimize torque. |
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As seen above, the backing of the patrix can be reduced
in height and length to allow optimum placement. |
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After casting and fitting on the model, polish the
attachment lightly. If the attachment is not polished,
residue and oxide may wear the matrices prematurely. The
ball should not be ground upon or highly polished as it
would lose retention and damage the attachment. |
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The yellow matrix is snapped into the metal housing
using the insertion pin. It is recommended to use the
yellow matrix with medium friction. For reduced and
increased friction, use the green or red matrix
respectively. |
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To create the overcasting, the model needs to be
duplicated with the yellow matrix in place. Block out
frame and the area between disc and the ridge. No wax
should be on the matrix when it is duplicated. |
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The case is duplicated using silicone duplicating
material. Above shows the refractory model of the case.
The refractory model is a duplicate model made in
investment. Notice the refractory "dummy" of the yellow
matrix. It is important not to scratch or damage the
refractory matrix or any of the areas that will be waxed
over. |
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The chrome cobalt overframe is waxed as required. Waxing
over the refractory matrix will create the housing for
the attachment matrices. A lingual arm should be
incorporated into the framework for partials. Bredent
retention beads or crystals could be placed on the wax
framework to create a more retentive surface for the
acrylic. The entire model & wax-up is then invested.
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The framework is then cast and fitted. A light deplating
of the chrome cobalt framework casting is usually
required to clean and polish the interior of the
attachment metal housing. If a higher electro-polish of
the framework is required, it is necessary to block out
the housing interior with a drop of wax to prevent
overpolishing. Overpolishing could result in loss of
friction. |
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To place the matrix into the framework, simply use the
insertion pin and push the matrix into place. No acrylic
is required to hold the matrix in place. To change the
friction of the attachment, a small bur is used to tear
the old matrix out of the housing and the new matrix is
placed as usual. |
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This shows the finished frame with the yellow matrix
inserted. No acrylic is needed to hold the matrix in
place. The matrix is held in the framework by the
undercuts on its sides. |
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The above picture shows the finsihed frame snapped onto
the attachment. As with all attachments, the patients
need to know that the appliance should not be inserted
by biting into place - it needs to be inserted via hand
pressure. Biting any attachment into place causes
extreme forces that wear down the attachments
prematurely. |
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Installing the OC attachment on a bar |
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The bar is inserted using a bar mandrel to keep the bar
parallel with the path of insertion. A parallel bar is
recommended but a tapered bar will work as well. |
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If necessary, the top and bottom of the bar can be
adjusted to conform to the shape of the tissue area and
to allow room for the attachment on top. |
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The Universal Patrix is placed on top of the bar using
the VKS Paralleling Mandrel. The use of a surveyor to
parallel the mandrel is necessary. The patrix is
attached to the bar using wax. |
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After casting and fitting on the model, polish the
attachment lightly. If the attachment is not polished,
residue and oxide may wear the matrices prematurely.
Overpolishing would cause the ball to lose retention. |
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Place the blocking out disc under the ball and press the
yellow matrix over it. The model needs to be duplicated
with the yellow matrix in place. Block out the case and
duplicate as described in the procedure for distal
extensions above. |
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Above shows the refractory model of the case. The
refractory model is a duplicate model made in
investment. Notice the refractory "dummy" of the yellow
matrix. It is important not to scratch or damage the
refractory matrix or any of the areas that will be waxed
over. |
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The chrome cobalt overframe is waxed normally. Waxing
over the refractory matrix will create the housing for
the attachment matrices. Bredent retention beads or
crystals could be utilized to create a more retentive
surface for the acrylic. The entire model & wax-up is
then invested. |
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Finish the chrome cobalt and insert the matrix as
described in the procedure for distal extensions above. |
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All
measurements are in millimeters.
