When you're getting (Saving changes is not permitted. The changes that you have made require the following tables to be dropped and re-created.
You have either made changes to a table that can't be re-created .......) this error when Alter your table..etc.
FIXED:
1 .Microsoft Sql Server Management Studio ->Options -> Designers ->
Prevent saving changes that require the table re-creation
UnCHECK its.