Aren't you using the publish operation to insert those content objects? If you're using this operation, clearing caches would be done automatically. Or do these content objects already exist and are you creating additional node assignments?
To respond to your question my extension is inserting objects inside one of my root folders, its not creating extra node assignements.
Actually i had hard time finding documentation about inserting an object from an extension, i had to browse contribution to take code as exemple but i didn't know if i used the right procedure but now that you say that the right EZP insert function is auto clearing the cache, i am shure i didn't use the right one because mine doesn't.
What is the "right" function to handle such operations ? I mean the built in ezp function that insert an object somewhere and clear parent's cache automatically ?
After creating node assignments for your object, you should call the publish operation, as mentioned in this thread: http://ez.no/community/forum/general/publish_object_with_php:
There are other forum threads about programmatically creating content objects, like http://ez.no/community/forum/developer/importing_update_entry_if_it_already_exists, but they're quite hard to find with the search function.