Challenges & Solutions
KAT Implant System was designed to overcome multiple challenges associated
with conventional screw retained and locking taper connection systems.
This new design had to be supported by extensive tests in order to be
approved by the FDA for marketing. The following is the description
of challenges we faced designing the system and the solutions we offer.
Challenge: Length of the post, rotational play between the abutment and the implant
Some external locking taper implants have a
hex positioned at a proximal end. The hex is used to
screw the implant into the osteotomy and to provide indexing means.
Hex increases the length of an implant post which necessitates deeper
implant placement and hinders occlusal and peripheral abutment reduction.
A rotational play between internal and external hexes is always present
due to manufacturing tolerances.
Solution: It is critical to keep
the length of the implant post to a minimum without compromising the
security of locking taper connection. Vertical groves were incorporated
into the implant taper post to allow secure implant placement and
to keep the length of a post to a minimum. Key was incorporated into
the abutment to provide rotation-free engagement with the implant.
Due to a patent pending combination of implant post vertical grooves
and abutment key, KAT implant system allows for as much occlusal reduction
as traditional external and internal connection implant systems while
providing unprecedented accuracy of implant indexing in horizontal
plane.
Challenge: Locking taper, or any kind of tapered/conical
connection, is not a predictable connection when it comes to conventional
implant level impression techniques
A smaller gap between abutment and implant, that conical connection
implant systems exhibit when compared to “flat to flat” connection
systems, is a positive development. All implants and abutments are
machined to a certain tolerance, usually ± .0005" (±12.5
microns) in critical areas. Conical surfaces slide against each other
if subjected to a clamping force. This sliding action is what contributes
to the smaller gap between two components, even though the "flat
to flat” and "conical fit” parts are machined to
the same tolerance. Smaller angles of the mating parts correspond
to a greater sliding distance and a smaller gap (at least theoretically).
Bicon®1 Implant manufacturer reports 0.25mm average sliding distance
for abutments with 3.0mm post, while manufacturers of conical fit
systems privately acknowledge some sliding, but, to our knowledge,
do not officially report it. While the sliding fit of the components
is beneficial for gap reduction, it can not be viewed as a positive
factor when current implant level impression technique is considered.
That’s where tolerances to which the parts are machined to
should be studied in more detail. Computer models of two mating parts
corresponding to the size of a Bicon implant and abutment were created
at KAT Implants, LLC facility. It was noticed that if the abutment
was at the upper limit of the ± .0005" tolerance and
the implant was at a lower limit of the tolerance, the length of
the assembly was over 0.4mm longer than the assembly where the opposite
limit tolerances (lower limit for an abutment and higher limit for
an implant) were used. A gain of 6 microns in diameter resulted in
additional length of 100 microns. Since the impression copings and
implant analogs are machined to the same tolerances as the implants,
it is easy to see why the sliding fit of the parts, and the magnification
of length discrepancies associated with it, are detrimental to the
fit of the final prosthesis.
Solution: There is only one realistic
possibility (machining the parts to 0 tolerance is unfortunately not
a possibility) to address the problem of a sliding engagement. The
final abutment has to be used in place of a pick-up coping. Then,
the dimensions of the implant analog become irrelevant. All KAT abutments
have an integrated retainer to act as a pick-up coping. A unique impression
technique was also developed to meet the challenge of a sliding fit
engagement. Patent pending Pick-up Abutment™ and Pick-up Abutment™ impression
technique also allows for a much more accurate fabrication of screw
retained prostheses.
Challenge: Hammering action to engage the locking taper connection is not predictable, may damage components and may be objectionable to the patient
Current locking taper systems, such as Bicon1,
rely on hammering action to engage locking taper connection between
abutment and implant. This hammering action is difficult to calibrate
due to variations in speed, weight of hammer, distance between the
hammer and the tapping instrument and the angle of force. All of
these variables may result in less than optimal engagement between
the system components.
Solution: A threaded bore of
the implant post and specially designed instruments allow for an
accurate (within 10 microns) and reproducible fit of the implant
abutments and healing abutments. Only 15Ncm of force is needed
to fully engage the locking taper connection. Removal of the abutments
is also accomplished with threaded tools, no twisting with forceps
or reverse hammering is needed.
1 Bicon is a registered trademark of Bicon, Inc.
