Hi Andrew,
Active Directory depens upon the NTDS.dit file.
Entire NTDS.dit is backed up even in incrementals.
But also you would require the other files too.
You will have first to restore the FULL backup then restore the incrementals in order.
What kind of incremental you use differential or cumulative
If its differential then u will have to restore all the incrementals in order.
if its cumulative then only the most latest incremental after the Full backup would be required.