Database tables created using ore.push will have the prefix ORE$. Normally, these are automatically cleaned up when the R session ends or the ORE db connection terminated (unless you save the ore.frame objects in an ORE datastore).
In-database models from Oracle Data Mining (ODM) as created from ore.odmSVM will also normally be deleted automatically and the end of the R session or ORE db connection termination. You should not attempt to remove DM$ tables as they are part of the in-database model. If you do delete any of these, their corresponding models will be corrupted/invalid.
You can invoke
SELECT name FROM dm_user_models;
to see the list of models in the database for your schema.
You can drop ODM models using the following in SQL*Plus or SQL Dev:
Lots of thanks goes to Mark Hornick, Senior Manager, Oracle Advanced Analytics for his constant support in ORE implementation in my project.