Abstract: A unidirectional plunger device for a syringe includes a base member and a ratchet mechanism. The base member is configured to attach to the proximal end of the syringe body such that the ratchet mechanism engages the plunger of the syringe. The ratchet mechanism may include a pawl configured to engage teeth on a plunger rod of the plunger. The ratchet mechanism is desirably configured to permit distal movement of the plunger while resisting proximal movement of the plunger. The unidirectional plunger device may be a retrofit that can be attached to (e.g., clipped onto) an existing syringe design. The device may be used in conjunction with a two-barrel syringe for dispensing a two-part curable composition, such as calcium phosphate bone cement or epoxy resin.