CT APPLIANCE
Fig. 1
Each virtual implant placement software
system has its own design requirements for the CT appliance (Fig.1) and is specific
to each software provider. Regardless of the CT appliance requirements and
virtual implant placement software used, the appliance should represent the
tooth position and dimension of the proposed final restoration with a well
adapted basal surface. Restoration of a edentulous arch will require the
same process as if a traditional full denture were the treatment goal and
the finished denture being used as a CT appliance or duplicated to the
software purveyors CT appliance specifications.
Fig. 2
Some advocate utilizing a preexisting denture and just add fiducial
markers. In theory this can be accomplished but one should consider
the disadvantages to this practice. Old and worn dentures are often ill
fitting, poorly adapted to the soft tissue and no longer represent the
ideal vertical dimension resulting in a poorly fitting
surgical guide.
Since the implant placement should be driven by the final restorations
position and dimensions it is best to start with a mock up of the ideal
restoration as the CT appliance (Fig.2).
Fig. 3
The appliance serves a dual purpose in some instances; CT appliance and
surgical guide (Fig.3). Once the scan is taken, the finished virtual plan, CT
appliance and the model the CT appliance was fabricated on are forwarded
to the software providers dedicated conversion facility. Others
electronically duplicate the CT appliance from the CT scan data and add
drill guide bushings in the appropriate position according to the virtual
implant placement plan.
Fig. 4
Fabricating the CT appliance may require the addition of fiducial
markers (Fig.1) such as gutta percha, cold cure acrylic mixed with barium
sulfate or
Biocryl X (Great Lakes Orthodontics) into the periphery of the
appliance while others demand the addition of prefabricated CT plates
(SICAT). CT appliances for fully and partially edentulous cases may also
be crafted with denture teeth made of barium sulfate containing acrylic
(Fig.4) while the base is plain acrylic. Others postulate the base be made
of acrylic containing 10 percent barium sulfate and the denture teeth
contain 20 percent barium sulfate.
Materialise
BioHorizons®
Biomet 3i
Nobel Biocare
SICAT
Image Fig. 3 courtesy of
Nobel Biocare®
Image Fig. 4 courtesy of
SICAT