Ahmed G. Abdelnabi, Shams W. Amged And Cherif A. Mohsen,

ABSTRACT
Objective The Purpose Of This Study Was To Assess Fracture Strength And Colour Change Of Different Constructed Thicknesses Of Two Different Materials Namely IPS E.max Press And IPS E.max CAD.

Materials and Methods: Thirty Sound Extracted Human Permanent Premolar Teeth (N =30, N = 15 Per Group) Were Occlusaly Sectioned To Expose Underlying Yellow Dentin And Create A Smooth Uniform Surface. Standardized Preparations Of Thirty Disc Of Lithium Disilicate HT A3 Were Studied; They Were Divided Into Two Groups (15 Samples For Each) According To The Process Of Fabrication Into IPS E.max CAD And IPS E.max Press. Each Group Was Subdivided Into Three Groups According To Thickness 0.5mm, 1mm And 1.5mm (5 Samples For Each). Each Sample Was Cemented To Its Represented Tooth Using Adhesive Resin Cement Universal (A2 Shade) And Preserved In Distilled Water For 3 Days. A Digital Spectrophotometer (vita Esayshade) Was Used And CIE LAB Parameters Were Measured And The Average Values Of The Color Differences (?E) Were Calculated. The Samples Then Subjected To Vertical Compression Load Until Failure Using A Universal Testing Machine. Data Were Collected, Tabulated And Statically Analyzed. One Way ANOVA Followed By Pair-wise Tukey?s Post-hoc Tests Were Performed To Detect Significance Between Groups. Student T-test Was Done Between Subgroups. Result: The Results Showed That IPS E.max Press Recorded Higher Color Change (3.436) Than IPS E.max CAD (2.751). Concerned Fracture Resistance Highest Mean Value Was Recorded For The IPS E.max CAD (850.6N) That Higher Than IPS E.max Press (687.133N). (p�0.05). For Both Groups Of Monolithic Lithium Disilicate Glass-ceramic Material With 1.5mm Thickness Recorded Higher Fracture Strength Than Those Monolithic Lithium Disilicate Glass-ceramic Material With 1mm And 0.5mm. Conclusion: IPS E.max CAD Advocated Lower Color Change Compared With IPS E.max Press. And Concerning Fracture Strength, The IPS E.max CAD Advocated Higher Fracture Strength Compared With IPS E.max Press.