Rana Abdel Hameed El Gazar, Mohamad Seddik Mohamad Kamel And Eman Fahmy Ado Elfetoh .,

ABSTRACT
Background: Tooth Bleaching Has Become Popular In Dentistry Since It Has Been Shown To Be An Effective And Noninvasive Treatment. The Bleaching Agent Is Applied In Intimate Contact With The Teeth, With Potentially Associated Restorations, It Has Been Speculated That This Process Could Cause Negative Alterations In Oral Substrates

Purpose: To Evaluate In-office Light-activated Bleaching On Translucency Of Hybrid Ceramic By Measuring Transmittance And Absorption Of Light By Spectrophotometer.

Materials and Methods: Twenty Specimens Were Prepared In (3M2-T) Shade And Were Cut From CAD/CAM Blocks Of Hybrid Ceramic. The Study Will Consist Of Twenty Specimens Of Hybrid Ceramic And These Specimens Will Be Randomly Divided Into 2 Groups. The Translucency Of The Samples Of Group I Act As A Controlled Group Which Were Not Received32% Hydrogen Peroxide Bleaching Agent Was Measured By Spectrophotometer. Samples Of Group II Received 3 Times Applications Of The Bleaching Agent. Each Cycle Ranges 15-20 Min. Then Exposed To A LED Power Bleach System For Three Cycles � 15 Min Each With 10 Min Resting Time. New Translucency Evaluation By The Spectrophotometry In The Same Way For Samples Of Group II.

Results: In This Study, A Comparison Of The Groups Using Independent T-test Revealed Statistically Significant Differences In Translucency Values Before And After Bleaching (P<0.001). After Bleaching, We Can Observe A Decrease In The Absorption Of Light. Also, There Was An Increase In Transmittance Of Light In Group II Samples When Compared With Samples Of Group I. This Is Proved That Bleaching Caused A Highly Significant Change In Translucency Values Of Hybrid Ceramic. Conclusion: In Conclusion, Statistically Significant Differences Among The Translucency Changes Of All Test Groups Were Found After Exposing Them To The Bleaching Agent.