Hossam Mohammed Mokhtar , Manal Rafei Hassan Abo-Eittah And Mohammed Moustafa Shalaby,

ABSTRACT
Purpose : To Determine The Effect Of Material Type And Restoration Thickness On The Fracture Resistance Of Posterior Occlusal Veneers Made From Polymer Infiltrate Glass Ceramic And Lithium Disilicate. Methods : Twenty Extracted Mandibular Second Molars Were Collected . Occlusal Surface Was Prepared With The Aid Of Triple Wheel Stone For Standard Preparation In The Enamel Surface And Scanned For CAD/CAM Fabrication. They Were Fabricated Of Lithium Disilicate (E Max) And Polymer Infiltrate Glass Ceramic (Vita Enamic) With Thicknesses Of 1 Mm And 1.5 Mm (N=10) Then Cemented With Self Adhesive Resin Cement. All Samples Were Vertically Loaded Till Fracture With Universal Machine Test For Recording Fracture Resistance Values. Strength Values Were Statistically Analyzed With Two Ways ANOVA (significance Level 0.05)Results : Fracture Resistance Mean Values For Samples Of IPS E.max CAD 1 Mm (II-L 1), 1.5 Mm (II-L2), Vita Enamic 1 Mm (IP-1), 1.5 Mm (IP-2) Were 1421.2?233.8 N, 1614.1?242.4N, 1539.3?282.5 N, 2079.8?237 N Respectivly. Statistical Analyses Revealed That, Significantdifference Was Found Between Different Thicknesses For Vita Enamic Sub-groups. Vita Enamic Showed Higher Significant Strength Value Than E Max In Samples With Higher Thickness Of 1.5 Mm.Conclusion : Occlusal Veneer Of Both Thicknesses Found To Be Toralable For Occlusal Masticatory Forces With Satisfactory Acceptance. All Tested Occlusal Veneer With Both Materials Proved To Withstand Normal And Parafunctional Masticatory Forces. Occlusal Veneers Fabricated From Vita Enamic Have Higher Significant Fracture Resistance Than Occlusal Veneer Made Of Lithium Disilicat