Is nonstick cookware safe to use after overheating
Based on a search of sources covering health risks around Teflon (PTFE) cookware, nobody has found any evidence that cooking with previously overheated cookware is dangerous to your health.  Breathing the fumes during overheating is bad for you, and cookware that has been overheated may cease to be nonstick, even though it looks OK:


  Teflon™ nonstick coatings will not begin to deteriorate in appearance
  or performance until the temperature of the cookware reaches about
  500°F (260°C). The coating will not show significant decomposition
  unless temperatures exceed about 660°F (349°C).


... in other words, the nonstick starts to fail before there's visible damage.