Curing depth of a silorane-based resin composite

Resumo

The silorane-based resin appears aiming to minimize
the effects of polymerization shrinkage, but other properties must
be studied. Objective: To evaluate the polymerization depth of two
composites with different organic matrix. Material and methods:
80 cylindrical specimens were prepared using a metallic matrix,
with three layers (top, middle and bottom), 1 mm high and 5 mm
in diameter. The specimens were divided into eight groups (n = 10)
according to the composite resins: Filtek P90 (3M/ESPE); Filtek Z250
(3M/ESPE), light-cured with a LED device with different irradiance and
times (600mW/cm2 x 40s, 1000mW/cm2 x 40s, 1000mW/cm2 x 20s;
1400mW/cm2 x 20s). The irradiance was controlled by placing plastic
rings coupled to the device’s tip. Immediately after polymerization,
the specimens’ layers were separated and five Knoop microhardness
readings (initial hardness) were performed on each one of the four
layers (0, 1, 2, and 3 mm). After 7 day storage in water at 37ºC,
new readings were performed (final microhardness). The data were
analyzed by four-way ANOVA (resin, energy density, depth and time)
and Tukey test (α = 0.05). Results: The microhardness decreased
with the depth increasing both in the initial and 7 day readings. The
hardness increased with the highest power densities. The resin P90
had lower hardness values. Conclusion: The silorane-based resin
showed Knoop microhardness values significant smaller than those of
methacrylate-based resin in almost all evaluated parameters. However,
both presented similar behaviors in relation to the curing depth.