Objective:To investigate the mechanical properties of different classifications of
composites indicated for posterior application as functions of the storage
condition and of the energy dose.Material and Methods:Specimens (8x2x2 mm) were obtained according to the factors: I) Composites (3M
ESPE): Filtek P60, Filtek Z350XT, and Filtek Silorane; II) Syringe storage
conditions: room temperature, aged, oven, refrigerator, and freezer; and III)
Energy dose: 24 J/cm2 and 48 J/cm2. After photoactivation,
the specimens were stored at 37ºC for 24 h. After storage, a three-point bending
test was carried out in a universal testing machine at 0.5 mm/min. Flexural
strength (S) and flexural modulus (E) were calculated. Data were analyzed by
three-way ANOVA and Tukey's test (α=0.05).Results:Different storage conditions significantly affected the silorane composite for S;
conversely, no effects were noted in terms of E. The accelerated aging protocol
significantly increased the S of Filtek P60 and Filtek Silorane, whereas storage
in the oven significantly decreased the S for all of the composites tested. Filtek
P60 was the only composite not affected by the lower storage temperatures tested
for S, whereas for the silorane this parameter was impacted at the same
conditions. The factor "dose" was not statistically significant.Conclusions:The syringe storage at different temperature conditions proved to influence mostly
the flexural strength, a clinically important characteristic considering the
posterior indication of the materials tested. The silorane composite should not be
stored at lower temperatures.
The purpose of this study was to evaluate the impact of replacing P90 primer with simplified adhesive systems (with a conventional, two-step adhesive or a self-etching, one-step adhesive) on bond strength to dentin in Class I restorations. The interfaces were also analyzed using confocal microscopy by adding a fluorophore to the adhesive components and SEM using silver nitrate for nanoleakage investigation. X-ray diffraction (XRD) characterized the chemical interaction of the adhesives. Failure mode and nanoleakage varied among groups. Characteristic micromorphology and higher nanoleakage were noted for silorane combinations. On the other hand, no signs of phase crystallization in the silorane adhesive combinations were noted. Replacing the silorane primer with simplified adhesives proved successful as the modified systems provided bonding to dentin comparable to that of the unmodified silorane systems. However, the dedicated adhesive exhibited signs of degradation immediately after application, which may impact the longevity of restorations in short periods.
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