Objectives: This research aimed to evaluate the influence of different vonlay preparation designs on fracture resistance in comparison with full coverage ceramic crown (as a control group) Methods: Thirty fresh extracted upper four teeth were collected from the orthodontic clinic in Minia and Nahda university. Teeth were divided according to the design of vonlay preparation into three groups. In Group (A); the control group the teeth were prepared to receive full coverage lithium-disilicate

more »

... ns (n=10), Group (B); teeth were prepared to receive bonded partial restoration (vonlay) involving functional cusp (n=10), and Group (C); teeth were prepared to receive bonded partial restoration (vonlay) without involving functional cusp (n=10). Then, by using a universal testing machine, samples were loaded along the long axis of the teeth until they fractured, and the maximum breaking load was recorded, as well as fracture patterns were noted. All samples were exposed to thermo-mechanical aging before testing. Results: preparation design of vonlay influences the fracture resistance of restoration.