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Statement of the problem: Despite their outstanding esthetic characteristics, the adequacy of implant-supported all-ceramic crowns under occlusal loads in the posterior segment of the jaw remains questionable. Aim of the study: Evaluation of the fracture resistance of different CAD/CAM fabricated implant-supported all-ceramic monolithic posterior crowns cemented on ready and custom made zirconia abutments. Materials and methods: 30 internal connection titanium dummy implants were embedded in epoxy resin and randomly divided into three groups (n=10 each) according to the crown material used; Group I: Polycrystalline ceramic (Katana Zirconia), Group II: Hybrid ceramic (Vita Enamic) and Group III: Lithium disilicate glass ceramic (IPS e.max CAD).All crowns were CAD/CAM fabricated as monolithic maxillary right first premolar.In each group, five crowns were cemented on ready made zirconia abutments (subgroup A) while the other five were cemented on custom made zirconia abutments (subgroup B). All samples were thermocycled (5o to 55o,10 seconds dwell time) then compressively loaded under axial static load till fracture using a universal testing machine with a loadcell of 5 kN at a cross-head speed of 1mm/min. The load required to fracture was recorded in Newton and failure modes were visually analyzed. Statistical analyses were performed by Two-way ANOVA and Tukey’s post-hoc test.( P ≤ 0.05)Results: Fracture resistance of implant-supported all-ceramic monolithic posterior crowns was statistically significantly affected by the ceramic crown material and abutment type (P |
