AIM: To report our experience with the retrieval of
cold welded gingival former.
INTRODUCTION: Cold welding of gingival former
is a rare mechanical complication.1
Cold welding
of a well osseointegrated dental implant can give
sleepless nights to a practitioner. Retrieval without
damaging the threads of an implant is a difficult task.
CASE REPORT: This case report describes how a
cold welded gingival former was retrieved without
damaging the threads of an implant.
CONCLUSION: To minimize the incidence of cold
welded gingival former adequate precautions should
be taken. Adequate knowledge of various retrieval
modes is imperative to overcome the challenge.
Key words: cold welding, preload, complications, gingival former
Cold welded gingival former is a rare mechanical
complication. Etiology and retrieval techniques for
the same are barely mentioned in any literature.
Retrieval without damaging the internal threads
of the implants is quiet a difficult task.1
In the previously reported cases, when retrieved
cold welded cover screws were inspected, dried
blood was always present around the threads
of the coverscrews. Blood and bone debris that
remained around the threads of the implant were
considered as the main reason for the cold welding.
The fibrin in the blood acts as glue and binds the
two parts together. Dried blood bone or any other
debris can wedge in between the threads and can
affect the seating of the gingival former.1,2,3
Various methods have been tried for retrieving
the coverscrew by clinicians,The same methods
can also be applied to gingival formers. Some of
them are: 1,3,4
Precautions to be taken to avoid coldwelding:1,2,3
A 44 years old male patient reported to the
department of Prosthodontics for prosthetic
rehabilitation of an implant placed in the lower
right second premolar. The implant was placed 4 months prior to his visit. Implant dimension was
3.75*11.5mm. radiographic examination showed
a complete osseointegrated fixture.
During prosthetic phase hex driver was engaged
into the gingival former of the implant and
unscrewing of gingival former was attempted
multiple times. Since it did not loosen a manual
ratchet was used to retrieve the gingival former
by applying reverse torque of greater than
35Ncm. Friction slot of gingival former was worn
out because of repeated trial. The drilling of the
gingival former had a high risk of damaging the
internal threads of the implant. So drilling the
body of gingival former was aborted.
Using a high speed handpiece extensions were
made on the gingival formers from the center
to both end with carbide bur. The flat end of a
cement mixing spatula was engaged and turned
the gingival former in an anticlockwise direction
still no change happened. Lower anterior forceps
with fine beaks were used to hold gingival former
firm apical pressure was applied followed by
anticlockwise movement until the gingival former
was retrieved. The implant threads were well
preserved. Thorough betadine irrigation was done.
A new gingival former was placed.
Cold welding is defined as an increase in loosening
torque with respect to tightening torque and it has been suggested that this might occur and
result in a lack of retrievability which is inherent
in the 3 component system of the hex design.5
The connection between the gingivalformer and
implant is termed as screwjoint.6
Tightening of
screw creates tension in the screw. Preload is the
initial load created by the application of a torque
and causes elongation of the screw. Preload leads
to an over clamping force between the healing cap
and the implant. Large magnitudes of the preload
have been seen to cause plastic deformation
or permanent change in the material at which
point the screw is no longer retrievable which is
sometimes referred to as cold welding. different
companies provide different torque wrench which
is not completely accurate and components may
corrode after autoclaving many times, which in turn
may increase the torque applied to the screw joint.
Therefore, advocated position for autoclaving of
hand torque wrenches are open (broken) position.7
This situation is one of the rare mechanical
complication. The assumed reason is wedging
of the dried blood between the screw and implant
components. Other possibilities could be a defect
in the screw itself. Several techniques have been
tried by clinicians. Preparation of healing cap as
conventional abutment and fabrication of crown
over it is a logical solution.7
However different techniques may be used in
conjunction to successfully retrieve the gingival
former. In the presented clinical situation, gingival
former couldn’t be retrieved by reverse torque or
drilling through the screw.
Though a notch was created over the gingival
former to retrieve it using a cement spatula, it
was not successful. Hence extraction forceps with fine beaks were used to turn it anticlockwise. This
technique is cost effective, simple and applicable
to all available dental implant system. This can
be incorporated where the retrievability of the
coldwelded gingival formers are difficult. However
there is a possibility of applying injudicious force
while removing it and care should be taken not to
disturb the osseointegrated implant.
Cold welding of gingival former is a rare complications. To minimize the incidence of coldwelded gingival former adequate precautions should be taken knowledge of various retrieval schemes will also come handy in such situations. There is no universally applied technique to retrieve a coldwelded gingival former. Its more of a trial and error approach to save the situation.