Nested Dictionaries: memory usage question

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C#

.NET

Hello.

Assumed we have an instance in the safe (managed by GC) code:
Dictionary<Guid, Dictionary<int, SomeClass>> dictionary;

Would it be "enough properly", please,
to call the dictionary.Clear() to rebuild (refill) it,
or it should be called for the nested (no more needed, allocated by new) items too ? :)

The count of the outer dictionary's entries averages 100,
the entries' count of the inner dictionaries can exceed 10000
and it can be rebuilt (refilled) by an user's mouse click at any time...

...should I dispose and reconstruct the objects explicitly too ?

Thank you !

--
/the value type corrected/edit