Mohy El Din Mahmoud Osama, Ahmed Hassanein Khalil And Lamia Sayed Kheirallah,

ABSTRACT
Statement Of Problem. The Recent Development Of Polymer-based Computer-aided Design And Computer-aided Manufactured (CAD/CAM) Milling Blocks (Cerasmart Hybrid Ceramics) And The Limited Availability Of Independent Studies On These Materials Make It Pertinent To Evaluate Their Properties And Identify Their Potential Strengths And Limitations. Purpose. The Aim Of This Study Was To Investigate The Effect Of Different Bonding Protocols On The Fracture Resistance Of Cerasmart Crowns Cemented Either With: Rely X Ultimate Resin Cement (total Etch Adhesive Bonding System) , Rely X Unicem Resin Cement (self Adhesive Bonding System). Materials And Methods. 24 Maxillary Human Canine Teeth Were Prepared Using CNC Milling Machine To Receive 24 Hybrid Ceramic Crowns That Were Fabricated From Cerasmart Blocks. The Crowns Were Divided Into 2 Groups (N=12each) According To The Adhesive Luting Systems. Group (A): Using Rely XUnicem Resin Cement (self-adhesive System). Group (B): Rely X Ultimate Resin Cement (total-etch System). The Crowns Were Subjected To Cyclic Loading And Fracture Resistance Test Was Done Using Universal Testing Machine (Instron). Data Were Statistically Analyzed Using Several Steps. Initially, Descriptive Statistics For Each Group Results. Student T-test Was Done Between Both Groups. Statistical Analysis Was Performed Using Grapg-Pad Instat Statistics Software For Windows (www.graphpad.com). Results. It Was Found That Total Etch Group Recorded Higher Fracture Resistance Mean Value (553.68�94.71 N) Than Self-adhesive Group Value (341.07�58.16 N). The Difference Between Both Cement Approaches Groups Was Statistically Significant As Indicated By T-test (t = 4.18, P Value = .0004 < 0.05) .

Conclusions: Bonded Cerasmart Restorations With Total-etch System Offer Superior Fracture Resistance Values Than Restorations With Self-adhesive System. The Bonding Protocol Drastically Affects The Fracture Resistance And Mode Of Failure Of Hybrid Ceramic Restorations. Total Etch Bonding Protocol Resulted In Higher Rate Of Unrepairable Failure Modes For Bonded Cerasmart Restorations, When Compared With Self Etch Bonding Protocol.