Mustafa M. Abdullah, Manal R. Hassan And Raiesa M. Mohammed,

ABSTRACT
Objective: The Purpose Of This Study Was To Assess Fracture Resistance Of Endocrown Constructed Of Two Different Materials Namely IPS E.max And Hybrid Ceramic Compared To Conventional Post And Core And IPS E.max Full Coverage Crown. Materials And Methods : Thirty Sound Extracted Human Permanent Mandibular Molars (N =30) Were Endodontically Treated. Standardized Preparations Were Done With 3-mm Intracoronal Extensions Into The Pulp Chamber And Divided Into 3groups Of Each (n=10). Group I : Specimens Involved Endodontically Treated Mandibular Molars Restored With Glass Fiber Posts Cemented With Rely X Cement, Composite Cores Were Built Up And IPS E.max Press Full Coverage Crowns (control Group) .Group II: Involved Endodontically Treated Mandibular Molars Restored With IPS E.max Press Endocrown. Group III: Specimens Involved Endodontically Treated Mandibular Molars Restored With Hybrid Ceramic Vita Enamic Endocrown. Each Group Of II And III Subdivided Into Sub-groups According To Ferrule Preparation GPIa (n=5) With Ferrule And GPIIb(n=5) Without Ferrule. Specimens Were Subjected To Fatigue By Cyclic Loading 150,000 Cycles In Order To Simulate A Clinical Service Time Of 1years And Were Mounted In A Universal Testing Machine(instron) And Then They Subjected To Vertical Compression Load Until Failure. 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 Highest Fracture Resistance Mean Value Was Recorded For Vita Enamic Endocrown With Ferrule Group (1405.69�34.7 N) While The Lowest Fracture Resistance Mean Value Was Recorded For Vita-enamic Endocrown Without Ferrule Group (847.04�45.54 N). Difference Between Control Group And Vita Enamic Endocrown With Ferrule Group While Without Ferrule The Difference Was Significant (p<0.05) Conclusion: Endocrowns Preparation With 1mm Ferrule And Vita Enamic Material Can Be The Best Of Choice To Achieve A Higher Fracture Resistance In High Stress Bearing Areas. KEY WORDS: Endocrown, Endodontically Treated Molars Reinforced With Post And Core, IPS E.max Crown, Hybrid Ceramics Vita Enamic.