Step-by-Step Implant Cementation
Guidance and Alternate Technique
Chandur Wadhwani, DDS
One cause of
local tissue inflammation associated with dental implants that has recently
come to light is dental cement. Cements, while often used in the attachment of
the coronal restoration to the implant fixture, have been directly linked with
peri-implant diseases and have been blamed for bone loss and implant failure
(Figures 1 and 2).1-3 One aspect of the disease process that is
especially concerning is the time between restoring the implant and the disease
process—on average three years pass before dentists discover a problem, with a
range of four months to beyond nine years (Figures 3 and 4).4
and dentists alike should be aware of the differences between implants and
teeth. Because their peri-implant biology is not the same, the appropriate
cementation techniques, suitable cement selections, and even the procedures for
the clean-up of excess cement are different. The authors recognize that a
comprehensive review of the attachment apparatus and cement properties is
beyond the scope of this discussion5; the article will briefly
highlight these issues and offer solutions to overcome the attendant problems.6
consider implants to be similar to teeth, but they differ in many important
ways.7-9 A weak adhesion exists between soft tissue connective
tissues and implant surfaces, for example, whereas teeth have a more robustly
developed attachment system. This is
related in part to the role of the connective tissue, which adheres rather than attaches to the surfaces of a dental implant.10 The
clinician should be aware of the fact that the weaker soft tissue adhesion seen
with implants is more susceptible to complications caused by excess cement and
the hydrostatic force of cement being pushed into the tissues during crown
often do not understand that only a very limited amount of cement is needed to
fix a restoration to an implant abutment (Figure 5). A recent survey of over
400 dentists showed that many dentists placed in excess of 20 times more cement
into the crown than was required.11 This overload of cement means
that 95% are extruded out at the restorative margin, which is frequently found subgingivally,
making cement removal virtually impossible.
The solution is
to limit the amount of cement that is placed in the crown. For comparative
purposes, it may be helpful to equate the amount of cement needed to everyday,
well-known subjects. For example, “The
space provided for cement on the inside of the crown is the same thickness as a
layer of nail polish.” This layer is often about 50 micrometers thick, which is
about the thickness of a human hair. A technique has been developed using a
spacer and some fast-setting dental impression material to make a chair-side
copy abutment (CCA) that can be used to coat the inside of the crown with close
to the 50 um needed.6
The crown is
painted internally with a water-soluble lubricant. This allows polytetrafluoroethylene
(PTFE) plumbers tape, which is 50 um thick, to be adapted to the inside of
the crown using a dry brush (Figures 6 and 7). The adaptation is completed by
the operator, who gently pushes the abutment into the crown and then carefully
removes it. The inside of the crown is inspected to confirm that the PTFE is
well formed (Figure 8).
The CCA is then
fabricated. Using a fast-setting impression or bite registration material, the
inside of the crown is filled and even overfilled until a “handle” is produced
(Figure 9). (Hint: A fine-tip nozzle is ideal for use in this process.) The CCA is removed, as is the PTFE, and the
inside of the crown is cleaned (important!) to remove the lubricating agent
(Figure 10). This produces the CCA,
which is 50 um smaller than the
inside of the crown. At this stage, the
CCA is inspected and compared to the actual abutment so the author is assured
of the proper orientation (Figure 11).
The CCA is now
ready for use. The abutment is placed in the patient’s mouth, checked for
proper seating, and its screw is torqued to the appropriate Ncm value. The
crown is now ready to be cemented. The crown can be loaded with any amount of
cement desired—the CCA will subsequently be pushed into the crown, and the
excess cement will be extruded chairside and easily removed (Figures 12 and 13). This is done extraorally.
Advantages of the CCA
The use of
inappropriate or excessive amounts of cement in the placement of implant
restorations can result in clinical complications. A fast, inexpensive, simple
technique, the aforementioned CCA approach limits excess cement to an absolute
minimum, and makes cleanup quicker and easier. The CCA can be used for custom,
stock and even multiple abutments (Figures 14 and 15). The CCA is an
improvement over use of the actual abutment, or laboratory abutments which, in
the authors’ experience, do not provide quite enough cement space to assure
suitable amounts of cement for problem-free crown retention. The CCA produces
the ideal amount.
practice, Bellevue, WA.
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