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DISCUSSION
In this study, the zirconia abutment assemblies were analyzed
in static and linear conditions. Figure 5 details the
comparison between a zirconia abutment with geometry
not optimized for zirconia and an otherwise identical zirconia
abutment with connection geometry optimized for
zirconia. The mating surface factors of safety for both
abutments are nearly identical. However, when the abutment
connection geometry contacts the implant connection
geometry, the minimum factor of safety drops to 0.903 on
the non-optimized zirconia abutment, compared to 2.125
on the Inclusive ® All-Zirconia Custom Abutment from
Glidewell Laboratories. The Inclusive All-Zirconia Custom
Abutment achieves the higher factor of safety by optimizing
the connection geometry for the material properties of the
zirconia. Specifically, the connection height is reduced to
minimize the potential transmission of tensile loads, sharp
corners are removed from the connection, and the implant
mating surface is undercut to provide clearance.
The shanks of zirconia abutments screws are smaller compared
to those used for titanium abutments. The smallerdiameter
shanks stretch more and generate higher preload
in the screw from the same amount of torque. This increased
The Inclusive All-Zirconia
Custom Abutment achieves
the higher factor of safety by
optimizing the connection
geometry for the material
properties of the zirconia.
Increased preload improves
the performance of the
connection between the
implant and abutment,
inhibiting risk of the screw
loosening over time.
preload improves the performance of the connection between
the implant and abutment, inhibiting risk of the screw
loosening over time.
The fracture toughness of fully sintered zirconia is about
13 MPa(m ½ ) compared to titanium alloys, which are about
75 MPa(m ½ ). This makes zirconia vulnerable to cracks
and faults. The manufacturing process for zirconia abutments
requires very precise, repeatable machinery and a
well-controlled sintering process to produce abutments that
fit and perform well.
CONCLUSION
Zirconia is an engineering ceramic with great potential for
implant abutments. Zirconia has good esthetics and high
compressive strength, but lower tensile strength and fracture
toughness relative to titanium. Because of this, zirconia
abutments have to be designed with these material properties
in mind. The material properties of zirconia require a
specially designed prosthetic connection to minimize the
potential for breakage.
– Optimizing the Design of Zirconia Implant Abutments: A Finite Element Analysis – 25