7/30/2019 Retention Fracture Resistance
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duced a negative that was used as a
mould for all samples.
The prepared denture teeth were in-
serted in this mould and the base was fil-
led with PalaXpress cold-curing acrylic
(Heraeus Kulzer/Hanau, Germany) and
then polymerised in a pressure pot at 2
bar and 45 C for 30 minutes.
Ten samples from all the different
sample groups of 20 were randomly se-
lected and artificially aged. The samples
were aged using 10000 thermocycles of
5C to 55C.All samples were then tested in a
universal testing machine (Zwick/Ulm,
Germany) with a feed rate of 0.5 mm/
min. The force application was the same
as previously published and completed
studies at an angle of 45 [3], whereby
the incisal edge was used as the contact
point for the indenter. Placement of
polyethylene foil between the indenter
and denture tooth was intended to dis-
tribute the force uniformly (see Fig. 1).
3 Results
All samples tested fractured at the
junction between the denture base and
acrylic tooth in the cervical area, i.e. the
actual tooth fractured and the interface
between the cold-curing acrylic and
denture tooth withstood the loading. In
order to check this fact, 3 samples with
unprepared teeth were tested and in this
case the acrylic tooth loosened from the
base with a load of approx. 60 N.
After preparation with a channel
cutter and conditioning with the bond-
ing agent recommended by the manu-
facturer, the Mondial teeth exhibited an
initial mean fracture resistance of
570.12 N ( 46.47) and when aged a
mean fracture resistance of 378.10 N (
60.84). This corresponds to a loss of re-
sistance of about 34%; the difference
was highly significant p = 0.000 (Mann-
Whitney U test, significance level p
