Chainset compatibility

Paulkingk Posts: 689
edited January 2013 in MTB workshop & tech
Hi guys i wand to put a External BB Chainset on my winter bike. It currently has a square taper unit. Will a shimano 9 speed chainset work with 10 gears on the back and a ten speed chain or will i have to get 10 speed chainrings? Are the dimensions of a hollowtech 9 speed chainset any different to the 10 speed ones?