Do epoxide rings react with bases?
Do epoxied rings react with bases


Yes, they can be opened, e.g. with alkoxides.


  what is the mechanism?




In principle, this is a $S_N2$ reaction, with the typical approach of the nucleophile from the back side. The difference to a non-epoxide case is that removal of the leaving group (bond breaking, ring opening) is facilitated by the ring strain. 

But the general rules for the reactivity of alkyl-substituted centres in $S_N2$ nevertheless apply: the higher the substitution, the lower the rate. This is attributed to the steric hindrance of the respective centre.

Note that the regioselectivity is different under acidic conditions!