Volume 4 Issue 3
A BULLETIN DEALING WITH ISSUES FOR DENTAL HEALTH
Wear Study of Precision Attachments
Bio 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
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.
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,
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
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
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.
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 firstname.lastname@example.org.
Exakto-Form Model Resin Profiled
- Exakto-From comes in a set
- 6 x 50 gram each of components A & B
- Standard colour is green
- Colour conentrates are available in blue, red,
yellow, white, black and brown.
- For details call us at 1-800-250-5111 or
e-mail us email@example.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
A. No. The VKS-oc-rs abutment is
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
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
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
for Replace TM implant be used on the Steri-Oss 0.5 and 0.6 mm implant
Q. Are there any competitive components
compatible with Replace TM, Steri-Oss, Branemark or 3i?
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