Hygroscopic/Hydrolytic Kinetics of Two Bulk-fill Resin Composite Restorative Materials Stored in Different Media: An inVitro Comparative Study

Objectives: The aim of this study was to determine the effect of different storage media
on Sorption/solubility kinetics of two bulk-fill resin composites, Venus bulk fill flowable resin
composite (VF) and Sonic Fill bulk fill resin composite (SF), stored in different media (alkaline
water Aw, 75% ethyl alcohol EA and lemon juice LJ).
Materials and Methods: One hundred and twenty disc specimens were fabricated and divided
into two main groups (n=60) involve two bulk-fill resin composites, depending on their low
viscosity. The specimens in each group were divided into three subgroups according to the storage
media (n=20) i.e. alkaline drinking water, 75% ethyl alcohol and lemon juice. All specimens were
desiccated before storage to obtain a constant mass (m1) and volume (V) in mm3. Specimens were
subjected to 4 weeks immersion, then dried and reweighed again to obtain (m2). The specimens were
desiccated again to obtain constant mass (m3). Sorption and solubility’s properties’ in water were
calculated according to proposed formula by ISO 4049- 2009.
Results: Two-way ANOVA indicated significant difference in sorption and solubility kinetics
for both factors, resin composites and immersion media (p<0.05). Tukey’s test showed that VF
significantly absorb fluids than SF, regardless the storage media. The mean weight changes in the
VF resin composite showed increasing fluid sorption after storage in AW, EA and LJ. There were
significant differences between either AW or EA and LJ. For SF, fluid sorption is increased from
AW, followed by EA and LJ. Solubility of VF was significantly higher than SF, when stored in
each immersion medium. The mean weight loss in the VF resin composite showed insignificant
increasing solubility after immersion in AW , LJ and EA. The mean weight loss for SF revealed
increasing solubility after immersion in AW, LJ and EA. VF revealed higher significant fluid
solubility when stored in water, than in EA or LJ. EA cause significantly higher solubility of SF
resin composite, than AW or LJ storage media,
Conclusions: Within the conditions of this in-vitro study, the following conclusions were
drawn: The sorption and solubility behaviour of the resin composites is material dependent, as Venus
flow bulk-fill resin composite tested in this study showed higher fluids sorption/solubility tendency
than that of Sonicfill bulk-fill resin composite. Regarding to the storage media, pH of the solutions
seems to have an influence on the sorption/solubility behavior of composite resin materials. Both
acidic and alkaline media increase sorption/solubility behaviour of the resin composites.