Go to the pharmacy and buy some Chlorhexidine - its a surgical scrub...what doctors use to wash their hands, or else some Betadyne. Put a little bit on a soft bristle tooth brush and gently scrub the shell of the tortoise to remove those white specks. Then rinse him off. I don't see the dent you're talking about, but the white specks show up well in these latest pictures. Also, in the picture of the plastron, I think I'm seeing the beginning of shell rot. You'll need to rub some athlete's foot cream into those spots.