at what temperature bones get burned?

Answer 1

Cremation takes a tempture of around 1100 degrees.

Answer 2

Not that this is botany...

I read a book by Dr. Maples (dead now, but he was at the University of Florida) called Dead Men Do Tell Tales. He said that bones generally warp and deform in fire, sometimes even at extremely high temperatures.

Cremation burns up the flesh and dries out the bones, but the cremains (actual term!) are pounded into dust in most crematoriums so it's not so...bony. Teeth often don't burn. Also, metal doesn't really burn, so you might find tooth fillings or surgical screws, things like that. The metal often melts, but doesn't burn.

I'd go with the 1100 degrees, sounds about right. But bones don't burn up completely--they leave ash. Burning doesn't consume material completely.