Cremation Rumination

What happens to the mercury in fillings during cremation?  Are there adsorbents for heavy metals which the crematories can periodically “mine” for accumulated gold, silver and mercury?

These thoughts occurred to me once while I was dining on fast-food, and watching the distorted optics of hot gasses eminating from the chimney of a nearby crematory. Come to think of it, I never did eat there again.