Comparison Study of Water Absorption of Four Luting Cements

Objective: To evaluate and compare the water absorption and hygroscopic expansion of resin modified glass-ionomer (RMGI) and composite resin (CR) luting cements. Methods: Four materials, two RMGI (Rely X and Fuji Plus) and two CR (Panavia F, Variolink II) luting cements were used. The specimens were immersed in distilled water at 37ºC. Five discoid specimens of each material were weighed at regular intervals (baseline, 24 hours, 2 days, 3 days, 5 days, 7 days, 14 days, 30 days and 90 days). The water absorption was calculated according to the ISO document 4049. Another five specimens of each material were packed into cavities in Perspex. The surfaces of the specimens were finished flush with their Perspex holders and a baseline profile taken. The dimensional change was determined by profiling the surfaces of the specimens after 7 days, 30 days and 90 days: and comparing them with the baseline reading. Results: The water absorption for the CR cements at 90 days ranged from 28.4µg/mm³ to 30.5µg/mm³; while for the RMGI cements, it ranged from 90.6µg/mm³ to 103.6µg/mm³. The water absorption were significantly different when analysed using one-way ANOVA (p<0.05) and Tukey's pairwise test. Profiles of the CR luting cements indicated that the material had shrunk at day 7 but reverted to baseline by day 90. RMGI luting cements swelled after water immersion at day 7 and 90. The dimensional change was tested using one-way ANOVA (p<0.05) and Tukey's pairwise test. The results at day 7 and day 90 were statistically significant when tested with ANOVA (p<0.05). However, the dimensional changes showed by the specific CR and RMGI cements were not significantly different from each other when tested with Tukey's pairwise test. Conclusion: RMGI and CR luting cements absorbed water and showed a change in dimension following water immersion.