Nothing has indicated he can unsummon anyone on an individual level, it also makes no sense that kabutoro would sacrifice freaking pein just to get itachi back under his control or actually risk defeat by hand of the uchiha brothers.
If he could unsummon individual ones, he could've easily just done it when itachi arrived, captured sasuke and then use anko to resummon itachi.

Speaking of anko, that cave doesn't look too big and they blasted the hell out of it...