Sorption and solubility characteristics of self-adhesive resin cements

The aim of this in vitro study was to evaluate some sorption characteristics [sorption (S), solubility (SL) and the percentages of mass change (M(g)%), solubility (SL%) as well as sorbed liquid (S%)] of self-adhesive resin cements when immersed in distilled water and lactic acid.

A disc-shaped specimen of each self-adhesive resin cements [G-Cem (GC), SmartCem™ 2 (SC2), RelyX™ U100 (R1), RelyX™ Unicem 2 (RU2)] were prepared in a split-Teflon mold and irradiated by an Optilux 501 light cure at 580mW/cm(2) for 40s in eight overlapping sections each side. The volume of each specimen was calculated and placed inside a desiccator containing anhydrous calcium chloride, then weighed on an analytical electronic balance. Two independent groups were established according to the immersion media or liquids (distilled water and 0.01M lactic acid) maintained at 37°C for the time intervals: 1, 6, 12, 24, 48 and 168h, where the sorption (S) property (μg/mm(3)) was calculated. However, the SL, M(g)%, SL% and S% were measured after 168h of immersion. The data were statistically analyzed by repeated measures ANOVA, one-way ANOVA and post hoc Tukey's test (p<0.05).

Analysis of variance revealed highly significant differences between the materials for the sorption and solubility values examined with some exceptions (p<0.05). However, independent samples T-test expressed significant differences of all the sorption values between both water and lactic acid media for the resin cements with some border significances (p>0.05). The highest liquid's sorption was exhibited by GC material after immersion in lactic acid for 168h period followed by SC2 (37.83 and 34.15μg/mm(3), respectively), while the lowest sorption was presented by RU2 cement after 1h immersion period in water (3.89μg/mm(3)). Stereomicroscope showed homogenous surface topography in RU2 and R1 samples, while some striated cracks and microvoids were observed in GC and SC2 materials, respectively. The SL values followed this order: RU2

Knowing the best self-adhesive cement that can provide less sorption and solubility values will help the dentist to choose the most suitable luting material for indirect restorations.