Abstract: An improved reusable respirator mask apparatus is provided. The apparatus comprises a gasket, body and head and neck strap. The gasket is configured to provide comfort to a user, maintain a reliable airtight seal and allow a user to wear glasses while also using the mask. Further the mask is configured to receive multiple types of filter media, provide minimal rebreathing, be easily cleanable and allow visual communication of a user's facial expression.

Abstract: A calcium phosphate self-setting cement is invented by using diffusion controlled solid liquid heterogeneous reaction between tetracalcium phosphate (Ca4(PO4)2O, TTCP) fine powder and solution of di-potassium hydrogen phosphate (K2HPO4). Fine powders of tetracalcium phosphate is introduced into the di-potassium hydrogen phosphate solution and homogenized well to form a cement paste. The cement paste was allowed to set at room temperature (25±5° C.). In the cement paste calcium is leached from the tetracalcium phosphate (TTCP) fine particles as Ca(OH)2 into the aqueous phase. Leaching of calcium continues until the Ca/P ratio changes from 2 to 1.67, which corresponds to hydroxyapatite. Calcium hydroxide thus formed reacts with the phosphate ions (p043?) that exist in the liquid phase, and the reaction leads to in-situ precipitation of hydroxyapatite as the reaction product, which leads to interparticle entanglement in the cement paste, thereby forming self-setting bone cement.