A. BEHRENS, B. BURGER, and H. HAUPTMANN, 3M ESPE, Seefeld, Germany
Objectives: The objective was to show
that copings out of colored LavaTM Y-TZP-ZrO2 (3M ESPE) with
a reduced wall thickness of 0,3 mm have sufficient fracture strength for the
anterior region in order to allow the clinician a less invasive preparation. By
fractographic analysis the fracture mode of the copings was ensured to be
similar to clinically occurring fracture modes.
Methods: A total of 48 coping were
produced out of colored Y-TZP-ZrO2. 24 copings were prepared from a
tangential and 24 from a champher preparation and each of these were further splitted
in subgroups of 12 for the fabrication of wall thicknesses of 0,3 mm and 0,5
mm. The copings were cemented with glass ionomer cement (Ketac CemTM)
on brass dies and fracture strength has been subsequently determined in a universal
testing machine (Zwick). The load was applied by an indented punch via a tin
foil to ensure a load distribution similar to veneered copings. Fractography was
done with scanning electron microscopy.
Fracture
strength (N)
|
Wall
thickness
|
Tangential
preparation
|
Champher
preparation
|
|
|
Mean
(SD)
|
Min
|
Max
|
Mean
(SD)
|
Min
|
Max
|
|
0,3
mm
|
908
(115)
|
714
|
1185
|
913
(106)
|
729
|
1095
|
|
0,5
mm
|
1476
(192)
|
1075
|
1672
|
1333
(107)
|
1180
|
1527
|
Results: There is no significant
difference (Kruskal-Wallis test, Dunn's post test, p>0.05) of the fracture
strength for copings fabricated with tangential or champher preparation but
with the same wall thickness. However, there is a significant strength reduction
between wall thickness of 0,5 and 0,3 mm (Kruskal-Wallis test, Dunn's post
test, p<0.001).
Conclusion: The fracture strength of Y-TZP-ZrO2
copings with a wall thickness of 0,3 mm is three times higher compared to the
expected chewing forces in the anterior region.
|