Effect of curing method and thermocycling on flexural strength and microhardness of a new composite resin with alkaline filler

Abstract

Background: Cention N has been introduced as an alternative material for amalgam. The purpose
was to investigate the flexural strength and microhardness of this material in self‑cure and dual‑cure
modes before and after thermocycling.
Materials and Methods: In this experimental study, 40 samples of Cention N were prepared
in order to determine and compare the microhardness. Half of the samples were set by self‑cure
method and the other half with dual‑cure method. The Vickers microhardness test was performed
once after 24 h and again after 10000 thermocyclings. Three‑point flexural test was used to
determine and compare the flexural strength of 52 rod‑shaped samples. Half of the samples were
set by self‑cure method and the other half with dual‑cure method. Among 26 samples in each group,
13 samples were randomly selected and three‑point flexural test was performed after 24 h and
for another 13 samples after 10,000 thermocyclings. Data were analyzed using two‑way ANOVA
and paired samples t‑test (P < 0.05).
Results: There was a statistically significant difference between the mean of microhardness
values in two curing methods (P < 0.001) and in two storage conditions (P < 0.001). The mean
of dual‑cure microhardness (100.99 ± 7.22) was higher than that of self‑cure (64.61 ± 12.51)
and the mean value associated with pre‑thermocycling (89.75 ± 15.84) was higher than that
of the post‑thermocycling (76.44 ± 23.56). There was no statistically significant difference
between the mean flexural strength in the two curing methods (self‑cure [72.85 ± 16.26],
dual cure [79.87 ± 23.07]; [P > 0.05]). However, the mean flexural strength without
thermocycling (85.98 ± 21.74) was higher than that of the thermocycled group (64.24 ± 6.40) (P < 0.001).
Conclusion: The microhardness of Cention N in dual‑cure mode was higher than that of self‑cure
mode, but the flexural strength of dual‑cure was not significantly different from that of self‑cure.
Thermocycling had a significant effect on the microhardness and flexural strength.
Key Words: Aging, composite resins, flexural strength, hardness, self‑curing of dental resins