Are metal partials found by airport metal detectors?

Not usually. By and large, partial dentures with metal frameworks fabricated in the us rarely cause issues with airport security. Once in a while, however, a patient with such partials may be asked to step aside for screening with a metal-detecting wand.
Not likely. I have never heard of dental restorations triggering the alarms, but if you want to avoid the delay or any embarassment, consider putting your partials in a case in your carry-on.