Effect of Different Marginal Cement Space Thickness on the Retention of Monolithic Zirconium Crown Using Different Luting Agents
Aim: The objective of this study done in vitro was to compare and assess the effects of various marginal cement gap thicknesses on retention of zirconium with using various luting agents. Materials and Method: A 48 freshly first premolar teeth of comparable shape and size. Teeth were prepared by one operator with the aid of modified dental surveyor to receive a monolithic zirconia crown restoration according to the guidelines recommended for KATANATM zirconia. The prepared teeth then based on the setting of marginal cement space thickness, they were separated into two main groups (n=24), Group Aa: zero μm cement space around the margin, Group : 25μm cement space around the margin and additional space 80 μm starting 1 mm above the margin for both groups. Each group then divided into 3 subgroup (N=8) according to luting used: (A1, B1) using RelyX U200 self-adhesive cement ,(A2,B2) using RelyX Ultimate adhesive cement and (A3,B3) using Riva Luting Plus RMGIC . Samples were subjected to tensile test, dislodgment force recorded in MPa. Statistical analyses: Two-way ANOVA test and Post hoc Bonferroni test significance at level of 0.05 was used. Result: showed that the highest mean retentive stress value was recorded with subgroup B3 (9.208),followed by B2(6.683),A3(6.057), A2(5.200),B1(5.046) ,A1(4.049). Concerning the failure-mode the majority of samples revealed adhesive failure between teeth and cement. Conclusion: With in limitation of this study, using 25 um marginal cement space thickness result in statically significant increase in retention value for all types of luting agent used.