Hydrochloric Acid Cyclic Exposure Effect on Microleakage of Resin Cements

Objectives: To evaluate microleakage of different resin cements after immersion of zirconia-reinforced lithium silicate crowns (ZLS) in hydrochloric acid solution (HCl).
Methods: Thirty extracted non-carious human molars were prepared for full coverage porcelain crowns. Teeth were randomized into three groups, one for each resin cement tested: Rely-X UniCem (3M, ESPE), Variolink Esthetic Dual-cure (Ivoclar Vivadent) and Panavia 21 (Kuraray America Inc.). ZLS crowns were designed and milled from Celtra Duo blocks using CEREC CAD/CAM system and then cemented to the prepared teeth using the assigned cement according to the manufacturers’ guidelines. Samples were thermal cycled between water temperatures of 5°C and 55°C for 5,000 cycles with a 15 second dwell-time after each temperature. In order to mimic one year of clinical time in a patient’s mouth, samples were subjected to 91 one hour cycles in HCl (pH 2) followed by one hour in artificial saliva. After the 91 cycles were completed, the samples were submerged in 50% silver nitrate solution for 24 hours followed by a developer solution for eight hours. The samples were embedded in clear epoxy resin and sectioned in a buccolingual direction at 0.5 mm. Sections were analyzed by a stereomicroscope at a magnification of 10X. Proportion of microleakage was calculated by dividing the total length of the dye penetration by the total length of the restoration. Data were analyzed with the Kruskal-Wallis test.
Results: There was no statistically significant difference in median microleakage among the three cements tested (p >.05). Panavia 21 showed the highest median microleakage score (59.22%) followed by Rely-X UniCem (55.2%) and Variolink Esthetic (44.47%).
Conclusions: Within the limitations of this study, no proven evidence showed a statistically significant difference in microleakage among the tested resin cements when used in ZLS crowns immersed in hydrochloric acid.