PART SELECTION (cementable) TITANIUM ABUTMENT
There are four key determinants in choosing a stock titanium abutment for a cementable
porcelain fused to metal or full gold restoration. If a stock abutment
can not be used because of excessive tissue thickness above the implant
or angulation correction in excess of 25 degrees for example, a custom abutment
can be fabricated through traditional
wax and cast or
CAD CAM technology.
1. Tissue height

Collar height
Most stock abutments are machined with a collar or finish line already
and various collar heights are available from many manufacturers.
Placement of the margin on the abutment for the final restoration should be around
1.5mm below the crest of the tissue on the facial side of the abutment.
Placing the margin deeper will make the removal of excess cement or bonding
agents difficult. Any incomplete cleaning might lead to tissue inflammation
and possible implant failure. Placement of the margin less than 1.5mm
might lead to abutment exposure due to tissue recession over the
lifetime of the implant.
2. Emergence profile

Emergence profiles
Some implant manufacturers offer healing abutments in different flare
diameters. Biomet 3i for example offers healing abutments for their
implants that flare from the original platform diameter to up to 7.5mm diameter.
This information sometimes gets lost when the restorative dentist utilizes
a impression coping of a different diameter flare than the healing abutment.
3. Angulation

Pre angled abutment
Miss aligned implants can be compensated with pre angled stock abutments.
Most implant manufacturers offer pre angled abutments with a correction
of 10 to 25 degrees, depending on implant brand.
4. Anti rotational feature position

Fig. 1
The relationship of the indexing feature (hex, tri lobe, octagon a.o.)
of the implant to the angulation it was placed in is the key factor
in determining which preangled abutment to choose because preangled
abutments are angled towards or away, in relation to a pre determined
aspect of the antirotational feature (hex, tri lobe, octagon a.o.)
of the abutment.
For example; if the antirotational feature of the abutment is a hex,
the angulation of the abutment is machined either towards or
away from the flat side of the hex or the point of the hex.

Fig. 2
The interplay of the antirotational feature of the implant (Fig. 1 and Fig. 2) and
the angle it was placed in, in relation to the preangled abutment
angulation to its own antirotational feature makes the selection
of the proper abutment a challenging task. Some manufacturers offer
try in abutment kits to simplify this task. The more positions
the antirotational feature allows, the easier the selection process
will be. A tri lobe (NobelReplace, Camlog a. o.) feature will allow
only three positions whereas a dodecagon (Biomet 3i Certain®) allows
12 positions for angled abutments. If the position of the antirotational
feature of the implant is not in sync with its angled position a
custom abutment needs to be fabricated through traditional
wax up
or CAD CAM technology.