Abstract: A dental syringe safety sheath having a modified duckbill valve for minimizing cross-contamination between dental patients is provided. The sheath includes a generally tubular body member having a nozzle engaging portion and a discharge portion. The nozzle engaging portion is configured to substantially fit over and cover the nozzle of a dental syringe having a discharge orifice. The discharge portion defines a fluid passageway having an inlet adjacent the discharge orifice and outlet downstream therefrom. The fluid passageway progressively narrows in cross-section between the inlet and the outlet to form a substantially wedge-shaped cavity terminating in a slit disposed between a pair of opposing sealing lips. The cross-section of the sealing lips between the ends of the slit is wider than the corresponding cross-section of the sealing lips at the lip margins.