Containment systems and methods safely and permanently encapsulate a sharp portion of a sharp medical instrument (e.g. a hypodermic needle). The containment system includes a cap or other container having a rim defining an open end configured to receive the sharp portion therein and an ingress port configured to permit injection of a liquid hardenable solution into the container to encapsulate the sharp portion. The method of use includes inserting the sharp metal instrument into the container, and injecting a liquid hardenable solution into the container through the ingress port to encapsulate the sharp portion of the medical instrument. The hardenable solution then hardens, encapsulating the sharp portion of the medical instrument. The liquid hardenable solution is injected by a base or base unit configured to receive the container and to inject the solution through the ingress port.