الفهرس 
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Abstract
Abstract Objective: The purpose of this study was to evaluate the impact of pre-heatedtemperature of two types resin cements on the color stability of lithium disilicate and zirconia restorations. Materials and methods: Eighty intact human maxillary premolars were divided into two main groups (n=40) according to the restorative material used. group E (IPS e.max Press); teeth restored with monolithic lithium disilicate restorations and group Z (Blu Zirkon); teeth restored with monolithic zirconia restorations. Each main group was subdivided randomly into two subgroups (n=20) according to the type of resin cement used. group L (G-CEM LinkForce); adhesive dual cure resin cement and group P (Panavia SA Cement Plus); self-adhesive dual cure resin cement. Each subgroup then subdivided into two subgroups (n=10) according to the pre-heated resin cement temperatures. group r (room temperature) ; resin cements at 25°C and group h (pre-heated); resin cement at 54°C. CAD/CAM was used for standardization of natural teeth preparation. A spectrophotometer was used for color standardization for each tooth. CIEL*a*b* values were measured by a spectrophotometer (24 hours after cementation) and after artificial aging with; 240000 cycles of dynamic chewing simulation and 10000 thermal cycles and 18 hours coffee immersion. L*a*b* individual difference and ΔE color difference were calculated and compared. Results: There was statistically significant differences between the two temperatures degree of the pre-heated resin cement on the effect of color stability after artificial aging. As well as there was statistically significant differences in color stability between IPS e.max Press and Blu Zirkon restorations and also between the adhesive and self-adhesive resin cements. Conclusions: Elevated pre-heated temperature of resin cements increased the color stability of these cements after artificial aging. IPS e.max Press monolithic restorations was more color stable than Blu Zirkon monolithic restorations. Moreover, both resin cements used in this study expressed discoloration after artificial aging referring that the color stability of self-adhesive resin cement was higher than that of adhesive resin cement.