titanium (Ti) /tītā′nē·əm/ [Gk, Titan, mythic giant] , a chemical element. Its atomic number is 22; its atomic mass is 47.88. An alloy of titanium is used in the manufacture of orthopedic prostheses and dental implants. Titanium dioxide is the active ingredient in a number of topical ointments and lotions. Titanium dioxide is one of the whitest substances known and is used as a base pigment in many sunscreens.