The Dent-Liner
Volume 4 Issue 3
Summer 2000
A BULLETIN DEALING WITH ISSUES FOR DENTAL HEALTH PROFESSIONALS
| Inside This Issue |
| 1. Exakto-Form Model Resin Profiled |
| 2. Wear Study of Attachments |
| 3. Q and A on Compatible Implant Parts |
| 4. New Product from Bredent, page 2 |
Wear Study of Precision Attachments
B io mechanical considera- tions such as loading
and force distribution on to implants and roots effectuates controversy
regarding the best retention mechanism (rigid or stress breaking) and the
best retention device for over denture connection (single anchors
or bar splits). Findings indicate that the retention choice be selected
according to the specific clinical and individual needs of the patient.
It has been noted that preservation of root structure can prevent or a
least delay ridge atrophy. Over denture literature describes the concepts
back to Dr. Ledger of the U.K. 1856. A further study by M.Wichmann, and
W. Kunze compares the wear of prefabricated precision attachments.
The aim of this laboratory study was to measure the effect on the forces
required to engage and disengage prefabricated precision attachments. Five
different types or prefabricated attachments were selected for testing,
Three attachments (Bredent SG, mini SG and PreciVertix) had removable plastic
inserts. Two conventional attachments consisted of metal female and male
components. Five specimens of each type were exposed to continuous stress
of 10000 cycles of engaging and disengaging using an axial line of draw.
The retentive forces were measured simultaneously at each loading cycle.
A solution representing the electrolyte component of saliva was flowing
over the female and male components to remove the abraded material. During
the first 1000 loading cycles the retentive force of the conventional metal
attachments decreased from an initial 7 Newton's to 3 respectively 4 Newton's.
During the next 9000 loading cycles the retentive forces decreased
steadily to a mean value of 3 Newton's. By comparison, all attachments
with plastic female inserts showed nearly no decrease in retentive force
during 10000 loading cycles. Depending on the type of plastic insert the
retentive force was between 2 Newton's and 30 Newton's. In conclusion the
conventional metal attachments showed significant wear and an extensive
loss of retention. In contrast to this, attachments with plastic inserts
showed only negligible amounts of wear and the most consistent retentive
force. Furthermore the study included wear-induced loss of retention in
attachment-retained dentures poses a major clinical problem. To counteract
this unwanted effect, most prefabricated precision attachments can be activated
to restore wear-induced loss of friction. This is achieved by design elements
such as resilient metal tongues, partially or completely slotted male components,
set screws, or replaceable plastic wearing parts. The aim of this comparative
study was to assess thewear behavior of different prefabricated attachments
and the effectiveness of activation in restoring wear-induced loss of friction
and retention. Attachments of various designs were subjected to alternating
load cycles in a wear simulator. Five specimens of attachments were
subjected to the wear test. Theses consisted of a total of four consecutive
cycles of 10000 respectively 5000 separating and joining movements each.
At baseline, each attachment was activated to have a retentive force of
7 Newton's. In each of the four consecutive cycles, the attachments
with metallic surfaces showed a rapid loss of friction of approximately
60 to 70 % even after forced activation to retentive forces between 15
and 20 Newton's, the same rapid loss of friction was found. The attachments
with plastic inserts by contrast showed only negligible reductions in the
required engaging / disengaging forces even after 10000 wear cycles. Although
there was only little loss of friction in the attachments with plastic
inserts, activation or replacement of the plastic insert was effective
to restore friction to the level present in the beginning of each load
cycle. Source: www.zahnheilkunde and Peter T. Pontsa,
R.D.T.
 |
Exakto-Form Model Resin Profiled
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Exakto-From comes in a set
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6 x 50 gram each of components A & B
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Standard colour is green
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Colour conentrates are available in blue, red, yellow, white, black and
brown.
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For details call us at 1-800-250-5111 or e-mail us atinfo@dent-line.com.
|
 |
T his model resin was developed by Bredent as a dual
component model material, based on polyurethane, for fabricating extremely
precise dental models. Because of its very low viscosity, it is easily
poured into the impression without trapping air bubbles. This cost effective
model resin features absolutely precise reproduction of surfaces, dimensional
stability and unequaled precision of fit, with no expansion whatsoever
and is exact to .175 shrinkage. The hardened resin can be sawed, drilled,
and trimmed easily. Components A and B are mixed together to produce a
light green colored model. There are also color concentrates available.
Exakto-Form comes in a set of 6 x 50 gram each of component A and B. Also
available is Exakto-Form insulating liquid for easy separation from silicone
impression materials. For more informatiion, please call Dent-Line at
1-800-250-5111
or e-mail us at info@dent-line.com.
Q and A on Compatible Implant Parts
Q. The Replace TM
4.3 mm series platform is 0.3 mm wider than the Bredent VKS-oc-rs
4 mm platform abutment. Is there a clinical disadvantage?
A. No. The VKS-oc-rs abutment is slightly
smaller when screwed down. Titanium being rather soft, it is possible to
rubber wheel the edge smooth on an analogue before placing the abutment.
Tissue will form over the joint and cover it.
Q. I want to use Replace TM to a direct
implant over denture abut ment. But the implants are too angled for the
O rings. What can I do?
A. By using Bredent VKS-oc-rs replacement
abutments, they can accept deviations up to 15 degrees to the planned angle
of insertion. The retention sleeves give three different frictions if required.
Q. My patient has a 0.5mm ( or .06 mm) platform
and I want to use direct to over denture abutments. What's available?
A. The VKS-oc-rs abutments are available
for 0.5 and 0.6 mm platforms. Although 0.6 mm are not generally used for
that purpose, it can be utilised if necessary.
Q. Can the VKS-oc-rs compatible abutments
designed for Replace TM implant be used on the Steri-Oss 0.5 and 0.6 mm
implant platform?
A. Yes.
Q. Are there any competitive components
compatible with Replace TM, Steri-Oss, Branemark or 3i?
A. Yes the Bredent VKS-oc-rs
replacement abutment components fit 0.4, 0.5, and 0.6 mm hex platforms,
with the advantage of multi retentive load bearing replacement sleeves.
For info call Dent-line at 1-800-250-5111
New Bredent Product
New milling burs have been developed for non precious metals. They
will be available in 1.5 and 2.3 mm sets. Contact Dent-Line of Canada at
1-800-250-5111.
The Dent-liner; Vol. 4, No. 3
Publisher: Peter T. Pontsa RDT
Editor: A. Van Breemen BA
E-Mail: info@dent-line.com
