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Background and Aim : Due to the importance of polymerization of resin cements on the longevity of indirect restorations, this study aimed to evaluate the effect of various thicknesses of  IPS e.max Press  porcelain on the amount of polymerization of light cured choice 2 resin  cement  by FTIR method.
Methods and Materials: In this experimental study, 40 porcelain disks (IPS e.max Press, (Ivacolar Vivadent, Liechtenstein) with a diameter of 10 and thicknesses of, 0.5, 1, And 1.5 mm (n = 10) were prepared using wax removal method. Resin cement Choice 2 (Bisco Inc, USA) with A2 color once before curing and wants after curing with  LED (LEDemetronll, Ker, USA) mv / cm2 1200 the samples were placed in an FTIR machine and the polymerization percentage was recorded. Data were analyzed using ANOVA.
Results:  The light cured Choice 2 resin cement  polymerization in four groups showed that the highest polymerization was related to 1.5 mm thickness (72.5% ± 0.41% ) and the least of them was for  0.5 mm thickness ( 68.7% ± 0.88%) ANOVA test showed that this difference between groups were not statistically significant (p <0.2).
Conclusion: Selective thicknesses of porcelain IPS e.max Press in this study did not have  affect on  polymerization of choice2 cement.
Key words: dental Porcelain,  Polymerization, resin cement, ips e max press